Add openfst to external, as used by GoogleTTSandroid-sdk-support_r11android-cts-4.2_r2android-cts-4.2_r1android-cts-4.1_r4android-cts-4.1_r2android-cts-4.1_r1android-4.2_r1android-4.2.2_r1.2android-4.2.2_r1.1android-4.2.2_r1android-4.2.1_r1.2android-4.2.1_r1.1android-4.2.1_r1android-4.1.2_r2.1android-4.1.2_r2android-4.1.2_r1android-4.1.1_r6.1android-4.1.1_r6android-4.1.1_r5android-4.1.1_r4android-4.1.1_r3android-4.1.1_r2android-4.1.1_r1.1android-4.1.1_r1tools_r22tools_r21jb-releasejb-mr1.1-releasejb-mr1.1-dev-plus-aospjb-mr1.1-devjb-mr1-releasejb-mr1-dev-plus-aospjb-mr1-devjb-mr0-releasejb-dev

Moved from GoogleTTS

Change-Id: I6bc6bdadaa53bd0f810b88443339f6d899502cc8

171 files changed, 46943 insertions, 0 deletions

diff --git a/src/include/fst/accumulator.h b/src/include/fst/accumulator.h
new file mode 100644
index 0000000..fcb960c
--- /dev/null
+++ b/src/include/fst/accumulator.h
@@ -0,0 +1,745 @@
+// accumulator.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Classes to accumulate arc weights. Useful for weight lookahead.
+
+#ifndef FST_LIB_ACCUMULATOR_H__
+#define FST_LIB_ACCUMULATOR_H__
+
+#include <algorithm>
+#include <functional>
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <vector>
+using std::vector;
+
+#include <fst/arcfilter.h>
+#include <fst/arcsort.h>
+#include <fst/dfs-visit.h>
+#include <fst/expanded-fst.h>
+#include <fst/replace.h>
+
+namespace fst {
+
+// This class accumulates arc weights using the semiring Plus().
+template <class A>
+class DefaultAccumulator {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  DefaultAccumulator() {}
+
+  DefaultAccumulator(const DefaultAccumulator<A> &acc) {}
+
+  void Init(const Fst<A>& fst, bool copy = false) {}
+
+  void SetState(StateId) {}
+
+  Weight Sum(Weight w, Weight v) {
+    return Plus(w, v);
+  }
+
+  template <class ArcIterator>
+  Weight Sum(Weight w, ArcIterator *aiter, ssize_t begin,
+             ssize_t end) {
+    Weight sum = w;
+    aiter->Seek(begin);
+    for (ssize_t pos = begin; pos < end; aiter->Next(), ++pos)
+      sum = Plus(sum, aiter->Value().weight);
+    return sum;
+  }
+
+  bool Error() const { return false; }
+
+ private:
+  void operator=(const DefaultAccumulator<A> &);   // Disallow
+};
+
+
+// This class accumulates arc weights using the log semiring Plus()
+// assuming an arc weight has a WeightConvert specialization to
+// and from log64 weights.
+template <class A>
+class LogAccumulator {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  LogAccumulator() {}
+
+  LogAccumulator(const LogAccumulator<A> &acc) {}
+
+  void Init(const Fst<A>& fst, bool copy = false) {}
+
+  void SetState(StateId) {}
+
+  Weight Sum(Weight w, Weight v) {
+    return LogPlus(w, v);
+  }
+
+  template <class ArcIterator>
+  Weight Sum(Weight w, ArcIterator *aiter, ssize_t begin,
+             ssize_t end) {
+    Weight sum = w;
+    aiter->Seek(begin);
+    for (ssize_t pos = begin; pos < end; aiter->Next(), ++pos)
+      sum = LogPlus(sum, aiter->Value().weight);
+    return sum;
+  }
+
+  bool Error() const { return false; }
+
+ private:
+  double LogPosExp(double x) { return log(1.0F + exp(-x)); }
+
+  Weight LogPlus(Weight w, Weight v) {
+    double f1 = to_log_weight_(w).Value();
+    double f2 = to_log_weight_(v).Value();
+    if (f1 > f2)
+      return to_weight_(f2 - LogPosExp(f1 - f2));
+    else
+      return to_weight_(f1 - LogPosExp(f2 - f1));
+  }
+
+  WeightConvert<Weight, Log64Weight> to_log_weight_;
+  WeightConvert<Log64Weight, Weight> to_weight_;
+
+  void operator=(const LogAccumulator<A> &);   // Disallow
+};
+
+
+// Stores shareable data for fast log accumulator copies.
+class FastLogAccumulatorData {
+ public:
+  FastLogAccumulatorData() {}
+
+  vector<double> *Weights() { return &weights_; }
+  vector<ssize_t> *WeightPositions() { return &weight_positions_; }
+  double *WeightEnd() { return &(weights_[weights_.size() - 1]); };
+  int RefCount() const { return ref_count_.count(); }
+  int IncrRefCount() { return ref_count_.Incr(); }
+  int DecrRefCount() { return ref_count_.Decr(); }
+
+ private:
+  // Cummulative weight per state for all states s.t. # of arcs >
+  // arc_limit_ with arcs in order. Special first element per state
+  // being Log64Weight::Zero();
+  vector<double> weights_;
+  // Maps from state to corresponding beginning weight position in
+  // weights_. Position -1 means no pre-computed weights for that
+  // state.
+  vector<ssize_t> weight_positions_;
+  RefCounter ref_count_;                  // Reference count.
+
+  DISALLOW_COPY_AND_ASSIGN(FastLogAccumulatorData);
+};
+
+
+// This class accumulates arc weights using the log semiring Plus()
+// assuming an arc weight has a WeightConvert specialization to and
+// from log64 weights. The member function Init(fst) has to be called
+// to setup pre-computed weight information.
+template <class A>
+class FastLogAccumulator {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  explicit FastLogAccumulator(ssize_t arc_limit = 20, ssize_t arc_period = 10)
+      : arc_limit_(arc_limit),
+        arc_period_(arc_period),
+        data_(new FastLogAccumulatorData()),
+        error_(false) {}
+
+  FastLogAccumulator(const FastLogAccumulator<A> &acc)
+      : arc_limit_(acc.arc_limit_),
+        arc_period_(acc.arc_period_),
+        data_(acc.data_),
+        error_(acc.error_) {
+    data_->IncrRefCount();
+  }
+
+  ~FastLogAccumulator() {
+    if (!data_->DecrRefCount())
+      delete data_;
+  }
+
+  void SetState(StateId s) {
+    vector<double> &weights = *data_->Weights();
+    vector<ssize_t> &weight_positions = *data_->WeightPositions();
+
+    if (weight_positions.size() <= s) {
+      FSTERROR() << "FastLogAccumulator::SetState: invalid state id.";
+      error_ = true;
+      return;
+    }
+
+    ssize_t pos = weight_positions[s];
+    if (pos >= 0)
+      state_weights_ = &(weights[pos]);
+    else
+      state_weights_ = 0;
+  }
+
+  Weight Sum(Weight w, Weight v) {
+    return LogPlus(w, v);
+  }
+
+  template <class ArcIterator>
+  Weight Sum(Weight w, ArcIterator *aiter, ssize_t begin,
+             ssize_t end) {
+    if (error_) return Weight::NoWeight();
+    Weight sum = w;
+    // Finds begin and end of pre-stored weights
+    ssize_t index_begin = -1, index_end = -1;
+    ssize_t stored_begin = end, stored_end = end;
+    if (state_weights_ != 0) {
+      index_begin = begin > 0 ? (begin - 1)/ arc_period_ + 1 : 0;
+      index_end = end / arc_period_;
+      stored_begin = index_begin * arc_period_;
+      stored_end = index_end * arc_period_;
+    }
+    // Computes sum before pre-stored weights
+    if (begin < stored_begin) {
+      ssize_t pos_end = min(stored_begin, end);
+      aiter->Seek(begin);
+      for (ssize_t pos = begin; pos < pos_end; aiter->Next(), ++pos)
+        sum = LogPlus(sum, aiter->Value().weight);
+    }
+    // Computes sum between pre-stored weights
+    if (stored_begin < stored_end) {
+      sum = LogPlus(sum, LogMinus(state_weights_[index_end],
+                                  state_weights_[index_begin]));
+    }
+    // Computes sum after pre-stored weights
+    if (stored_end < end) {
+      ssize_t pos_start = max(stored_begin, stored_end);
+      aiter->Seek(pos_start);
+      for (ssize_t pos = pos_start; pos < end; aiter->Next(), ++pos)
+        sum = LogPlus(sum, aiter->Value().weight);
+    }
+    return sum;
+  }
+
+  template <class F>
+  void Init(const F &fst, bool copy = false) {
+    if (copy)
+      return;
+    vector<double> &weights = *data_->Weights();
+    vector<ssize_t> &weight_positions = *data_->WeightPositions();
+    if (!weights.empty() || arc_limit_ < arc_period_) {
+      FSTERROR() << "FastLogAccumulator: initialization error.";
+      error_ = true;
+      return;
+    }
+    weight_positions.reserve(CountStates(fst));
+
+    ssize_t weight_position = 0;
+    for(StateIterator<F> siter(fst); !siter.Done(); siter.Next()) {
+      StateId s = siter.Value();
+      if (fst.NumArcs(s) >= arc_limit_) {
+        double sum = FloatLimits<double>::kPosInfinity;
+        weight_positions.push_back(weight_position);
+        weights.push_back(sum);
+        ++weight_position;
+        ssize_t narcs = 0;
+        for(ArcIterator<F> aiter(fst, s); !aiter.Done(); aiter.Next()) {
+          const A &arc = aiter.Value();
+          sum = LogPlus(sum, arc.weight);
+          // Stores cumulative weight distribution per arc_period_.
+          if (++narcs % arc_period_ == 0) {
+            weights.push_back(sum);
+            ++weight_position;
+          }
+        }
+      } else {
+        weight_positions.push_back(-1);
+      }
+    }
+  }
+
+  bool Error() const { return error_; }
+
+ private:
+  double LogPosExp(double x) {
+    return x == FloatLimits<double>::kPosInfinity ?
+        0.0 : log(1.0F + exp(-x));
+  }
+
+  double LogMinusExp(double x) {
+    return x == FloatLimits<double>::kPosInfinity ?
+        0.0 : log(1.0F - exp(-x));
+  }
+
+  Weight LogPlus(Weight w, Weight v) {
+    double f1 = to_log_weight_(w).Value();
+    double f2 = to_log_weight_(v).Value();
+    if (f1 > f2)
+      return to_weight_(f2 - LogPosExp(f1 - f2));
+    else
+      return to_weight_(f1 - LogPosExp(f2 - f1));
+  }
+
+  double LogPlus(double f1, Weight v) {
+    double f2 = to_log_weight_(v).Value();
+    if (f1 == FloatLimits<double>::kPosInfinity)
+      return f2;
+    else if (f1 > f2)
+      return f2 - LogPosExp(f1 - f2);
+    else
+      return f1 - LogPosExp(f2 - f1);
+  }
+
+  Weight LogMinus(double f1, double f2) {
+    if (f1 >= f2) {
+      FSTERROR() << "FastLogAcumulator::LogMinus: f1 >= f2 with f1 = " << f1
+                 << " and f2 = " << f2;
+      error_ = true;
+      return Weight::NoWeight();
+    }
+    if (f2 == FloatLimits<double>::kPosInfinity)
+      return to_weight_(f1);
+    else
+      return to_weight_(f1 - LogMinusExp(f2 - f1));
+  }
+
+  WeightConvert<Weight, Log64Weight> to_log_weight_;
+  WeightConvert<Log64Weight, Weight> to_weight_;
+
+  ssize_t arc_limit_;     // Minimum # of arcs to pre-compute state
+  ssize_t arc_period_;    // Save cumulative weights per 'arc_period_'.
+  bool init_;             // Cumulative weights initialized?
+  FastLogAccumulatorData *data_;
+  double *state_weights_;
+  bool error_;
+
+  void operator=(const FastLogAccumulator<A> &);   // Disallow
+};
+
+
+// Stores shareable data for cache log accumulator copies.
+// All copies share the same cache.
+template <class A>
+class CacheLogAccumulatorData {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  CacheLogAccumulatorData(bool gc, size_t gc_limit)
+      : cache_gc_(gc), cache_limit_(gc_limit), cache_size_(0) {}
+
+  ~CacheLogAccumulatorData() {
+    for(typename unordered_map<StateId, CacheState>::iterator it = cache_.begin();
+        it != cache_.end();
+        ++it)
+      delete it->second.weights;
+  }
+
+  bool CacheDisabled() const { return cache_gc_ && cache_limit_ == 0; }
+
+  vector<double> *GetWeights(StateId s) {
+    typename unordered_map<StateId, CacheState>::iterator it = cache_.find(s);
+    if (it != cache_.end()) {
+      it->second.recent = true;
+      return it->second.weights;
+    } else {
+      return 0;
+    }
+  }
+
+  void AddWeights(StateId s, vector<double> *weights) {
+    if (cache_gc_ && cache_size_ >= cache_limit_)
+      GC(false);
+    cache_.insert(make_pair(s, CacheState(weights, true)));
+    if (cache_gc_)
+      cache_size_ += weights->capacity() * sizeof(double);
+  }
+
+  int RefCount() const { return ref_count_.count(); }
+  int IncrRefCount() { return ref_count_.Incr(); }
+  int DecrRefCount() { return ref_count_.Decr(); }
+
+ private:
+  // Cached information for a given state.
+  struct CacheState {
+    vector<double>* weights;  // Accumulated weights for this state.
+    bool recent;              // Has this state been accessed since last GC?
+
+    CacheState(vector<double> *w, bool r) : weights(w), recent(r) {}
+  };
+
+  // Garbage collect: Delete from cache states that have not been
+  // accessed since the last GC ('free_recent = false') until
+  // 'cache_size_' is 2/3 of 'cache_limit_'. If it does not free enough
+  // memory, start deleting recently accessed states.
+  void GC(bool free_recent) {
+    size_t cache_target = (2 * cache_limit_)/3 + 1;
+    typename unordered_map<StateId, CacheState>::iterator it = cache_.begin();
+    while (it != cache_.end() && cache_size_ > cache_target) {
+      CacheState &cs = it->second;
+      if (free_recent || !cs.recent) {
+        cache_size_ -= cs.weights->capacity() * sizeof(double);
+        delete cs.weights;
+        cache_.erase(it++);
+      } else {
+        cs.recent = false;
+        ++it;
+      }
+    }
+    if (!free_recent && cache_size_ > cache_target)
+      GC(true);
+  }
+
+  unordered_map<StateId, CacheState> cache_;  // Cache
+  bool cache_gc_;                        // Enable garbage collection
+  size_t cache_limit_;                   // # of bytes cached
+  size_t cache_size_;                    // # of bytes allowed before GC
+  RefCounter ref_count_;
+
+  DISALLOW_COPY_AND_ASSIGN(CacheLogAccumulatorData);
+};
+
+// This class accumulates arc weights using the log semiring Plus()
+//  has a WeightConvert specialization to and from log64 weights.  It
+//  is similar to the FastLogAccumator. However here, the accumulated
+//  weights are pre-computed and stored only for the states that are
+//  visited. The member function Init(fst) has to be called to setup
+//  this accumulator.
+template <class A>
+class CacheLogAccumulator {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  explicit CacheLogAccumulator(ssize_t arc_limit = 10, bool gc = false,
+                               size_t gc_limit = 10 * 1024 * 1024)
+      : arc_limit_(arc_limit), fst_(0), data_(
+          new CacheLogAccumulatorData<A>(gc, gc_limit)), s_(kNoStateId),
+        error_(false) {}
+
+  CacheLogAccumulator(const CacheLogAccumulator<A> &acc)
+      : arc_limit_(acc.arc_limit_), fst_(acc.fst_ ? acc.fst_->Copy() : 0),
+        data_(acc.data_), s_(kNoStateId), error_(acc.error_) {
+    data_->IncrRefCount();
+  }
+
+  ~CacheLogAccumulator() {
+    if (fst_)
+      delete fst_;
+    if (!data_->DecrRefCount())
+      delete data_;
+  }
+
+  // Arg 'arc_limit' specifies minimum # of arcs to pre-compute state.
+  void Init(const Fst<A> &fst, bool copy = false) {
+    if (copy) {
+      delete fst_;
+    } else if (fst_) {
+      FSTERROR() << "CacheLogAccumulator: initialization error.";
+      error_ = true;
+      return;
+    }
+    fst_ = fst.Copy();
+  }
+
+  void SetState(StateId s, int depth = 0) {
+    if (s == s_)
+      return;
+    s_ = s;
+
+    if (data_->CacheDisabled() || error_) {
+      weights_ = 0;
+      return;
+    }
+
+    if (!fst_) {
+      FSTERROR() << "CacheLogAccumulator::SetState: incorrectly initialized.";
+      error_ = true;
+      weights_ = 0;
+      return;
+    }
+
+    weights_ = data_->GetWeights(s);
+    if ((weights_ == 0) && (fst_->NumArcs(s) >= arc_limit_)) {
+      weights_ = new vector<double>;
+      weights_->reserve(fst_->NumArcs(s) + 1);
+      weights_->push_back(FloatLimits<double>::kPosInfinity);
+      data_->AddWeights(s, weights_);
+    }
+  }
+
+  Weight Sum(Weight w, Weight v) {
+    return LogPlus(w, v);
+  }
+
+  template <class Iterator>
+  Weight Sum(Weight w, Iterator *aiter, ssize_t begin,
+             ssize_t end) {
+    if (weights_ == 0) {
+      Weight sum = w;
+      aiter->Seek(begin);
+      for (ssize_t pos = begin; pos < end; aiter->Next(), ++pos)
+        sum = LogPlus(sum, aiter->Value().weight);
+      return sum;
+    } else {
+      if (weights_->size() <= end)
+        for (aiter->Seek(weights_->size() - 1);
+             weights_->size() <= end;
+             aiter->Next())
+          weights_->push_back(LogPlus(weights_->back(),
+                                      aiter->Value().weight));
+      return LogPlus(w, LogMinus((*weights_)[end], (*weights_)[begin]));
+    }
+  }
+
+  template <class Iterator>
+  size_t LowerBound(double w, Iterator *aiter) {
+    if (weights_ != 0) {
+      return lower_bound(weights_->begin() + 1,
+                         weights_->end(),
+                         w,
+                         std::greater<double>())
+          - weights_->begin() - 1;
+    } else {
+      size_t n = 0;
+      double x =  FloatLimits<double>::kPosInfinity;
+      for(aiter->Reset(); !aiter->Done(); aiter->Next(), ++n) {
+        x = LogPlus(x, aiter->Value().weight);
+        if (x < w) break;
+      }
+      return n;
+    }
+  }
+
+  bool Error() const { return error_; }
+
+ private:
+  double LogPosExp(double x) {
+    return x == FloatLimits<double>::kPosInfinity ?
+        0.0 : log(1.0F + exp(-x));
+  }
+
+  double LogMinusExp(double x) {
+    return x == FloatLimits<double>::kPosInfinity ?
+        0.0 : log(1.0F - exp(-x));
+  }
+
+  Weight LogPlus(Weight w, Weight v) {
+    double f1 = to_log_weight_(w).Value();
+    double f2 = to_log_weight_(v).Value();
+    if (f1 > f2)
+      return to_weight_(f2 - LogPosExp(f1 - f2));
+    else
+      return to_weight_(f1 - LogPosExp(f2 - f1));
+  }
+
+  double LogPlus(double f1, Weight v) {
+    double f2 = to_log_weight_(v).Value();
+    if (f1 == FloatLimits<double>::kPosInfinity)
+      return f2;
+    else if (f1 > f2)
+      return f2 - LogPosExp(f1 - f2);
+    else
+      return f1 - LogPosExp(f2 - f1);
+  }
+
+  Weight LogMinus(double f1, double f2) {
+    if (f1 >= f2) {
+      FSTERROR() << "CacheLogAcumulator::LogMinus: f1 >= f2 with f1 = " << f1
+                 << " and f2 = " << f2;
+      error_ = true;
+      return Weight::NoWeight();
+    }
+    if (f2 == FloatLimits<double>::kPosInfinity)
+      return to_weight_(f1);
+    else
+      return to_weight_(f1 - LogMinusExp(f2 - f1));
+  }
+
+  WeightConvert<Weight, Log64Weight> to_log_weight_;
+  WeightConvert<Log64Weight, Weight> to_weight_;
+
+  ssize_t arc_limit_;                    // Minimum # of arcs to cache a state
+  vector<double> *weights_;              // Accumulated weights for cur. state
+  const Fst<A>* fst_;                    // Input fst
+  CacheLogAccumulatorData<A> *data_;     // Cache data
+  StateId s_;                            // Current state
+  bool error_;
+
+  void operator=(const CacheLogAccumulator<A> &);   // Disallow
+};
+
+
+// Stores shareable data for replace accumulator copies.
+template <class Accumulator, class T>
+class ReplaceAccumulatorData {
+ public:
+  typedef typename Accumulator::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef T StateTable;
+  typedef typename T::StateTuple StateTuple;
+
+  ReplaceAccumulatorData() : state_table_(0) {}
+
+  ReplaceAccumulatorData(const vector<Accumulator*> &accumulators)
+      : state_table_(0), accumulators_(accumulators) {}
+
+  ~ReplaceAccumulatorData() {
+    for (size_t i = 0; i < fst_array_.size(); ++i)
+      delete fst_array_[i];
+    for (size_t i = 0; i < accumulators_.size(); ++i)
+      delete accumulators_[i];
+  }
+
+  void Init(const vector<pair<Label, const Fst<Arc>*> > &fst_tuples,
+       const StateTable *state_table) {
+    state_table_ = state_table;
+    accumulators_.resize(fst_tuples.size());
+    for (size_t i = 0; i < accumulators_.size(); ++i) {
+      if (!accumulators_[i])
+        accumulators_[i] = new Accumulator;
+      accumulators_[i]->Init(*(fst_tuples[i].second));
+      fst_array_.push_back(fst_tuples[i].second->Copy());
+    }
+  }
+
+  const StateTuple &GetTuple(StateId s) const {
+    return state_table_->Tuple(s);
+  }
+
+  Accumulator *GetAccumulator(size_t i) { return accumulators_[i]; }
+
+  const Fst<Arc> *GetFst(size_t i) const { return fst_array_[i]; }
+
+  int RefCount() const { return ref_count_.count(); }
+  int IncrRefCount() { return ref_count_.Incr(); }
+  int DecrRefCount() { return ref_count_.Decr(); }
+
+ private:
+  const T * state_table_;
+  vector<Accumulator*> accumulators_;
+  vector<const Fst<Arc>*> fst_array_;
+  RefCounter ref_count_;
+
+  DISALLOW_COPY_AND_ASSIGN(ReplaceAccumulatorData);
+};
+
+// This class accumulates weights in a ReplaceFst.  The 'Init' method
+// takes as input the argument used to build the ReplaceFst and the
+// ReplaceFst state table. It uses accumulators of type 'Accumulator'
+// in the underlying FSTs.
+template <class Accumulator,
+          class T = DefaultReplaceStateTable<typename Accumulator::Arc> >
+class ReplaceAccumulator {
+ public:
+  typedef typename Accumulator::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+  typedef T StateTable;
+  typedef typename T::StateTuple StateTuple;
+
+  ReplaceAccumulator()
+      : init_(false), data_(new ReplaceAccumulatorData<Accumulator, T>()),
+        error_(false) {}
+
+  ReplaceAccumulator(const vector<Accumulator*> &accumulators)
+      : init_(false),
+        data_(new ReplaceAccumulatorData<Accumulator, T>(accumulators)),
+        error_(false) {}
+
+  ReplaceAccumulator(const ReplaceAccumulator<Accumulator, T> &acc)
+      : init_(acc.init_), data_(acc.data_), error_(acc.error_) {
+    if (!init_)
+      FSTERROR() << "ReplaceAccumulator: can't copy unintialized accumulator";
+    data_->IncrRefCount();
+  }
+
+  ~ReplaceAccumulator() {
+     if (!data_->DecrRefCount())
+      delete data_;
+  }
+
+  // Does not take ownership of the state table, the state table
+  // is own by the ReplaceFst
+  void Init(const vector<pair<Label, const Fst<Arc>*> > &fst_tuples,
+            const StateTable *state_table) {
+    init_ = true;
+    data_->Init(fst_tuples, state_table);
+  }
+
+  void SetState(StateId s) {
+    if (!init_) {
+      FSTERROR() << "ReplaceAccumulator::SetState: incorrectly initialized.";
+      error_ = true;
+      return;
+    }
+    StateTuple tuple = data_->GetTuple(s);
+    fst_id_ = tuple.fst_id - 1;  // Replace FST ID is 1-based
+    data_->GetAccumulator(fst_id_)->SetState(tuple.fst_state);
+    if ((tuple.prefix_id != 0) &&
+        (data_->GetFst(fst_id_)->Final(tuple.fst_state) != Weight::Zero())) {
+      offset_ = 1;
+      offset_weight_ = data_->GetFst(fst_id_)->Final(tuple.fst_state);
+    } else {
+      offset_ = 0;
+      offset_weight_ = Weight::Zero();
+    }
+  }
+
+  Weight Sum(Weight w, Weight v) {
+    if (error_) return Weight::NoWeight();
+    return data_->GetAccumulator(fst_id_)->Sum(w, v);
+  }
+
+  template <class ArcIterator>
+  Weight Sum(Weight w, ArcIterator *aiter, ssize_t begin,
+             ssize_t end) {
+    if (error_) return Weight::NoWeight();
+    Weight sum = begin == end ? Weight::Zero()
+        : data_->GetAccumulator(fst_id_)->Sum(
+            w, aiter, begin ? begin - offset_ : 0, end - offset_);
+    if (begin == 0 && end != 0 && offset_ > 0)
+      sum = Sum(offset_weight_, sum);
+    return sum;
+  }
+
+  bool Error() const { return error_; }
+
+ private:
+  bool init_;
+  ReplaceAccumulatorData<Accumulator, T> *data_;
+  Label fst_id_;
+  size_t offset_;
+  Weight offset_weight_;
+  bool error_;
+
+  void operator=(const ReplaceAccumulator<Accumulator, T> &);   // Disallow
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_ACCUMULATOR_H__
diff --git a/src/include/fst/add-on.h b/src/include/fst/add-on.h
new file mode 100644
index 0000000..ee21a93
--- /dev/null
+++ b/src/include/fst/add-on.h
@@ -0,0 +1,306 @@
+// add-on.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Fst implementation class to attach an arbitrary object with a
+// read/write method to an FST and its file rep. The FST is given a
+// new type name.
+
+#ifndef FST_LIB_ADD_ON_FST_H__
+#define FST_LIB_ADD_ON_FST_H__
+
+#include <stddef.h>
+#include <string>
+
+#include <fst/fst.h>
+
+
+namespace fst {
+
+// Identifies stream data as an add-on fst.
+static const int32 kAddOnMagicNumber = 446681434;
+
+
+//
+// Some useful add-on objects.
+//
+
+// Nothing to save.
+class NullAddOn {
+ public:
+  NullAddOn() {}
+
+  static NullAddOn *Read(istream &istrm) {
+    return new NullAddOn();
+  };
+
+  bool Write(ostream &ostrm) const { return true; }
+
+  int RefCount() const { return ref_count_.count(); }
+  int IncrRefCount() { return ref_count_.Incr(); }
+  int DecrRefCount() { return ref_count_.Decr(); }
+
+ private:
+  RefCounter ref_count_;
+
+  DISALLOW_COPY_AND_ASSIGN(NullAddOn);
+};
+
+
+// Create a new add-on from a pair of add-ons.
+template <class A1, class A2>
+class AddOnPair {
+ public:
+  // Argument reference count incremented.
+  AddOnPair(A1 *a1, A2 *a2)
+      : a1_(a1), a2_(a2) {
+    if (a1_)
+      a1_->IncrRefCount();
+    if (a2_)
+      a2_->IncrRefCount();
+  }
+
+  ~AddOnPair() {
+    if (a1_ && !a1_->DecrRefCount())
+      delete a1_;
+    if (a2_ && !a2_->DecrRefCount())
+      delete a2_;
+  }
+
+  A1 *First() const { return a1_; }
+  A2 *Second() const { return a2_; }
+
+  static AddOnPair<A1, A2> *Read(istream &istrm) {
+    A1 *a1 = 0;
+    bool have_addon1 = false;
+    ReadType(istrm, &have_addon1);
+    if (have_addon1)
+      a1 = A1::Read(istrm);
+
+    A2 *a2 = 0;
+    bool have_addon2 = false;
+    ReadType(istrm, &have_addon2);
+    if (have_addon2)
+      a2 = A2::Read(istrm);
+
+    AddOnPair<A1, A2> *a = new AddOnPair<A1, A2>(a1, a2);
+    if (a1)
+      a1->DecrRefCount();
+    if (a2)
+      a2->DecrRefCount();
+    return a;
+  };
+
+  bool Write(ostream &ostrm) const {
+    bool have_addon1 = a1_;
+    WriteType(ostrm, have_addon1);
+    if (have_addon1)
+      a1_->Write(ostrm);
+    bool have_addon2 = a2_;
+    WriteType(ostrm, have_addon2);
+    if (have_addon2)
+      a2_->Write(ostrm);
+    return true;
+  }
+
+  int RefCount() const { return ref_count_.count(); }
+
+  int IncrRefCount() {
+    return ref_count_.Incr();
+  }
+
+  int DecrRefCount() {
+    return ref_count_.Decr();
+  }
+
+ private:
+  A1 *a1_;
+  A2 *a2_;
+  RefCounter ref_count_;
+
+  DISALLOW_COPY_AND_ASSIGN(AddOnPair);
+};
+
+
+// Add to an Fst F a type T object. T must have a 'T* Read(istream &)',
+// a 'bool Write(ostream &)' method, and 'int RecCount(), 'int IncrRefCount()'
+// and 'int DecrRefCount()' methods (e.g. 'MatcherData' in matcher-fst.h).
+// The result is a new Fst implemenation with type name 'type'.
+template<class F, class T>
+class AddOnImpl : public FstImpl<typename F::Arc> {
+ public:
+  typedef typename F::Arc Arc;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  using FstImpl<Arc>::SetType;
+  using FstImpl<Arc>::SetProperties;
+  using FstImpl<Arc>::WriteHeader;
+
+  // If 't' is non-zero, its reference count is incremented.
+  AddOnImpl(const F &fst, const string &type, T *t = 0)
+      : fst_(fst), t_(t) {
+    SetType(type);
+    SetProperties(fst_.Properties(kFstProperties, false));
+    if (t_)
+      t_->IncrRefCount();
+  }
+
+  // If 't' is non-zero, its reference count is incremented.
+  AddOnImpl(const Fst<Arc> &fst, const string &type, T *t = 0)
+      : fst_(fst), t_(t) {
+    SetType(type);
+    SetProperties(fst_.Properties(kFstProperties, false));
+    if (t_)
+      t_->IncrRefCount();
+  }
+
+  AddOnImpl(const AddOnImpl<F, T> &impl)
+      : fst_(impl.fst_), t_(impl.t_) {
+    SetType(impl.Type());
+    SetProperties(fst_.Properties(kCopyProperties, false));
+    if (t_)
+      t_->IncrRefCount();
+  }
+
+  ~AddOnImpl() {
+    if (t_ && !t_->DecrRefCount())
+      delete t_;
+  }
+
+  StateId Start() const { return fst_.Start(); }
+  Weight Final(StateId s) const { return fst_.Final(s); }
+  size_t NumArcs(StateId s) const { return fst_.NumArcs(s); }
+
+  size_t NumInputEpsilons(StateId s) const {
+    return fst_.NumInputEpsilons(s);
+  }
+
+  size_t NumOutputEpsilons(StateId s) const {
+    return fst_.NumOutputEpsilons(s);
+  }
+
+  size_t NumStates() const { return fst_.NumStates(); }
+
+  static AddOnImpl<F, T> *Read(istream &strm, const FstReadOptions &opts) {
+    FstReadOptions nopts(opts);
+    FstHeader hdr;
+    if (!nopts.header) {
+      hdr.Read(strm, nopts.source);
+      nopts.header = &hdr;
+    }
+    AddOnImpl<F, T> *impl = new AddOnImpl<F, T>(nopts.header->FstType());
+    if (!impl->ReadHeader(strm, nopts, kMinFileVersion, &hdr))
+      return 0;
+    delete impl;       // Used here only for checking types.
+
+    int32 magic_number = 0;
+    ReadType(strm, &magic_number);   // Ensures this is an add-on Fst.
+    if (magic_number != kAddOnMagicNumber) {
+      LOG(ERROR) << "AddOnImpl::Read: Bad add-on header: " << nopts.source;
+      return 0;
+    }
+
+    FstReadOptions fopts(opts);
+    fopts.header = 0;  // Contained header was written out.
+    F *fst = F::Read(strm, fopts);
+    if (!fst)
+      return 0;
+
+    T *t = 0;
+    bool have_addon = false;
+    ReadType(strm, &have_addon);
+    if (have_addon) {   // Read add-on object if present.
+      t = T::Read(strm);
+      if (!t)
+        return 0;
+    }
+    impl = new AddOnImpl<F, T>(*fst, nopts.header->FstType(), t);
+    delete fst;
+    if (t)
+      t->DecrRefCount();
+    return impl;
+  }
+
+  bool Write(ostream &strm, const FstWriteOptions &opts) const {
+    FstHeader hdr;
+    FstWriteOptions nopts(opts);
+    nopts.write_isymbols = false;  // Let contained FST hold any symbols.
+    nopts.write_osymbols = false;
+    WriteHeader(strm, nopts, kFileVersion, &hdr);
+    WriteType(strm, kAddOnMagicNumber);  // Ensures this is an add-on Fst.
+    FstWriteOptions fopts(opts);
+    fopts.write_header = true;     // Force writing contained header.
+    if (!fst_.Write(strm, fopts))
+      return false;
+    bool have_addon = t_;
+    WriteType(strm, have_addon);
+    if (have_addon)                // Write add-on object if present.
+      t_->Write(strm);
+    return true;
+  }
+
+  void InitStateIterator(StateIteratorData<Arc> *data) const {
+    fst_.InitStateIterator(data);
+  }
+
+  void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) const {
+    fst_.InitArcIterator(s, data);
+  }
+
+  F &GetFst() { return fst_; }
+
+  const F &GetFst() const { return fst_; }
+
+  T *GetAddOn() const { return t_; }
+
+  // If 't' is non-zero, its reference count is incremented.
+  void SetAddOn(T *t) {
+    if (t == t_)
+      return;
+    if (t_ && !t_->DecrRefCount())
+      delete t_;
+    t_ = t;
+    if (t_)
+      t_->IncrRefCount();
+  }
+
+ private:
+  explicit AddOnImpl(const string &type) : t_(0) {
+    SetType(type);
+    SetProperties(kExpanded);
+  }
+
+  // Current file format version
+  static const int kFileVersion = 1;
+  // Minimum file format version supported
+  static const int kMinFileVersion = 1;
+
+  F fst_;
+  T *t_;
+
+  void operator=(const AddOnImpl<F, T> &fst);  // Disallow
+};
+
+template <class F, class T> const int AddOnImpl<F, T>::kFileVersion;
+template <class F, class T> const int AddOnImpl<F, T>::kMinFileVersion;
+
+
+}  // namespace fst
+
+#endif  // FST_LIB_ADD_ON_FST_H__
diff --git a/src/include/fst/arc-map.h b/src/include/fst/arc-map.h
new file mode 100644
index 0000000..3055f71
--- /dev/null
+++ b/src/include/fst/arc-map.h
@@ -0,0 +1,1146 @@
+// arc-map.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to map over/transform arcs e.g., change semirings or
+// implement project/invert. Consider using when operation does
+// not change the number of arcs (except possibly superfinal arcs).
+
+#ifndef FST_LIB_ARC_MAP_H__
+#define FST_LIB_ARC_MAP_H__
+
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <string>
+#include <utility>
+using std::pair; using std::make_pair;
+
+#include <fst/cache.h>
+#include <fst/mutable-fst.h>
+
+
+namespace fst {
+
+// This determines how final weights are mapped.
+enum MapFinalAction {
+  // A final weight is mapped into a final weight. An error
+  // is raised if this is not possible.
+  MAP_NO_SUPERFINAL,
+
+  // A final weight is mapped to an arc to the superfinal state
+  // when the result cannot be represented as a final weight.
+  // The superfinal state will be added only if it is needed.
+  MAP_ALLOW_SUPERFINAL,
+
+  // A final weight is mapped to an arc to the superfinal state
+  // unless the result can be represented as a final weight of weight
+  // Zero(). The superfinal state is always added (if the input is
+  // not the empty Fst).
+  MAP_REQUIRE_SUPERFINAL
+};
+
+// This determines how symbol tables are mapped.
+enum MapSymbolsAction {
+  // Symbols should be cleared in the result by the map.
+  MAP_CLEAR_SYMBOLS,
+
+  // Symbols should be copied from the input FST by the map.
+  MAP_COPY_SYMBOLS,
+
+  // Symbols should not be modified in the result by the map itself.
+  // (They may set by the mapper).
+  MAP_NOOP_SYMBOLS
+};
+
+// ArcMapper Interface - class determinies how arcs and final weights
+// are mapped. Useful for implementing operations that do not change
+// the number of arcs (expect possibly superfinal arcs).
+//
+// class ArcMapper {
+//  public:
+//   typedef A FromArc;
+//   typedef B ToArc;
+//
+//   // Maps an arc type A to arc type B.
+//   B operator()(const A &arc);
+//   // Specifies final action the mapper requires (see above).
+//   // The mapper will be passed final weights as arcs of the
+//   // form A(0, 0, weight, kNoStateId).
+//   MapFinalAction FinalAction() const;
+//   // Specifies input symbol table action the mapper requires (see above).
+//   MapSymbolsAction InputSymbolsAction() const;
+//   // Specifies output symbol table action the mapper requires (see above).
+//   MapSymbolsAction OutputSymbolsAction() const;
+//   // This specifies the known properties of an Fst mapped by this
+//   // mapper. It takes as argument the input Fst's known properties.
+//   uint64 Properties(uint64 props) const;
+// };
+//
+// The ArcMap functions and classes below will use the FinalAction()
+// method of the mapper to determine how to treat final weights,
+// e.g. whether to add a superfinal state. They will use the Properties()
+// method to set the result Fst properties.
+//
+// We include a various map versions below. One dimension of
+// variation is whether the mapping mutates its input, writes to a
+// new result Fst, or is an on-the-fly Fst. Another dimension is how
+// we pass the mapper. We allow passing the mapper by pointer
+// for cases that we need to change the state of the user's mapper.
+// This is the case with the encode mapper, which is reused during
+// decoding. We also include map versions that pass the mapper
+// by value or const reference when this suffices.
+
+
+// Maps an arc type A using a mapper function object C, passed
+// by pointer.  This version modifies its Fst input.
+template<class A, class C>
+void ArcMap(MutableFst<A> *fst, C* mapper) {
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  if (mapper->InputSymbolsAction() == MAP_CLEAR_SYMBOLS)
+    fst->SetInputSymbols(0);
+
+  if (mapper->OutputSymbolsAction() == MAP_CLEAR_SYMBOLS)
+    fst->SetOutputSymbols(0);
+
+  if (fst->Start() == kNoStateId)
+    return;
+
+  uint64 props = fst->Properties(kFstProperties, false);
+
+  MapFinalAction final_action = mapper->FinalAction();
+  StateId superfinal = kNoStateId;
+  if (final_action == MAP_REQUIRE_SUPERFINAL) {
+    superfinal = fst->AddState();
+    fst->SetFinal(superfinal, Weight::One());
+  }
+
+  for (StateId s = 0; s < fst->NumStates(); ++s) {
+    for (MutableArcIterator< MutableFst<A> > aiter(fst, s);
+         !aiter.Done(); aiter.Next()) {
+      const A &arc = aiter.Value();
+      aiter.SetValue((*mapper)(arc));
+    }
+
+    switch (final_action) {
+      case MAP_NO_SUPERFINAL:
+      default: {
+        A final_arc = (*mapper)(A(0, 0, fst->Final(s), kNoStateId));
+        if (final_arc.ilabel != 0 || final_arc.olabel != 0) {
+          FSTERROR() << "ArcMap: non-zero arc labels for superfinal arc";
+          fst->SetProperties(kError, kError);
+        }
+
+        fst->SetFinal(s, final_arc.weight);
+        break;
+      }
+      case MAP_ALLOW_SUPERFINAL: {
+        if (s != superfinal) {
+          A final_arc = (*mapper)(A(0, 0, fst->Final(s), kNoStateId));
+          if (final_arc.ilabel != 0 || final_arc.olabel != 0) {
+            // Add a superfinal state if not already done.
+            if (superfinal == kNoStateId) {
+              superfinal = fst->AddState();
+              fst->SetFinal(superfinal, Weight::One());
+            }
+            final_arc.nextstate = superfinal;
+            fst->AddArc(s, final_arc);
+            fst->SetFinal(s, Weight::Zero());
+          } else {
+            fst->SetFinal(s, final_arc.weight);
+          }
+          break;
+        }
+      }
+      case MAP_REQUIRE_SUPERFINAL: {
+        if (s != superfinal) {
+          A final_arc = (*mapper)(A(0, 0, fst->Final(s), kNoStateId));
+          if (final_arc.ilabel != 0 || final_arc.olabel != 0 ||
+              final_arc.weight != Weight::Zero())
+            fst->AddArc(s, A(final_arc.ilabel, final_arc.olabel,
+                             final_arc.weight, superfinal));
+            fst->SetFinal(s, Weight::Zero());
+        }
+        break;
+      }
+    }
+  }
+  fst->SetProperties(mapper->Properties(props), kFstProperties);
+}
+
+
+// Maps an arc type A using a mapper function object C, passed
+// by value.  This version modifies its Fst input.
+template<class A, class C>
+void ArcMap(MutableFst<A> *fst, C mapper) {
+  ArcMap(fst, &mapper);
+}
+
+
+// Maps an arc type A to an arc type B using mapper function
+// object C, passed by pointer. This version writes the mapped
+// input Fst to an output MutableFst.
+template<class A, class B, class C>
+void ArcMap(const Fst<A> &ifst, MutableFst<B> *ofst, C* mapper) {
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  ofst->DeleteStates();
+
+  if (mapper->InputSymbolsAction() == MAP_COPY_SYMBOLS)
+    ofst->SetInputSymbols(ifst.InputSymbols());
+  else if (mapper->InputSymbolsAction() == MAP_CLEAR_SYMBOLS)
+    ofst->SetInputSymbols(0);
+
+  if (mapper->OutputSymbolsAction() == MAP_COPY_SYMBOLS)
+    ofst->SetOutputSymbols(ifst.OutputSymbols());
+  else if (mapper->OutputSymbolsAction() == MAP_CLEAR_SYMBOLS)
+    ofst->SetOutputSymbols(0);
+
+  uint64 iprops = ifst.Properties(kCopyProperties, false);
+
+  if (ifst.Start() == kNoStateId) {
+    if (iprops & kError) ofst->SetProperties(kError, kError);
+    return;
+  }
+
+  MapFinalAction final_action = mapper->FinalAction();
+  if (ifst.Properties(kExpanded, false)) {
+    ofst->ReserveStates(CountStates(ifst) +
+                        final_action == MAP_NO_SUPERFINAL ? 0 : 1);
+  }
+
+  // Add all states.
+  for (StateIterator< Fst<A> > siter(ifst); !siter.Done(); siter.Next())
+    ofst->AddState();
+
+  StateId superfinal = kNoStateId;
+  if (final_action == MAP_REQUIRE_SUPERFINAL) {
+    superfinal = ofst->AddState();
+    ofst->SetFinal(superfinal, B::Weight::One());
+  }
+  for (StateIterator< Fst<A> > siter(ifst); !siter.Done(); siter.Next()) {
+    StateId s = siter.Value();
+    if (s == ifst.Start())
+      ofst->SetStart(s);
+
+    ofst->ReserveArcs(s, ifst.NumArcs(s));
+    for (ArcIterator< Fst<A> > aiter(ifst, s); !aiter.Done(); aiter.Next())
+      ofst->AddArc(s, (*mapper)(aiter.Value()));
+
+    switch (final_action) {
+      case MAP_NO_SUPERFINAL:
+      default: {
+        B final_arc = (*mapper)(A(0, 0, ifst.Final(s), kNoStateId));
+        if (final_arc.ilabel != 0 || final_arc.olabel != 0) {
+          FSTERROR() << "ArcMap: non-zero arc labels for superfinal arc";
+          ofst->SetProperties(kError, kError);
+        }
+        ofst->SetFinal(s, final_arc.weight);
+        break;
+      }
+      case MAP_ALLOW_SUPERFINAL: {
+        B final_arc = (*mapper)(A(0, 0, ifst.Final(s), kNoStateId));
+        if (final_arc.ilabel != 0 || final_arc.olabel != 0) {
+            // Add a superfinal state if not already done.
+          if (superfinal == kNoStateId) {
+            superfinal = ofst->AddState();
+            ofst->SetFinal(superfinal, B::Weight::One());
+          }
+          final_arc.nextstate = superfinal;
+          ofst->AddArc(s, final_arc);
+          ofst->SetFinal(s, B::Weight::Zero());
+        } else {
+          ofst->SetFinal(s, final_arc.weight);
+        }
+        break;
+      }
+      case MAP_REQUIRE_SUPERFINAL: {
+        B final_arc = (*mapper)(A(0, 0, ifst.Final(s), kNoStateId));
+        if (final_arc.ilabel != 0 || final_arc.olabel != 0 ||
+            final_arc.weight != B::Weight::Zero())
+          ofst->AddArc(s, B(final_arc.ilabel, final_arc.olabel,
+                            final_arc.weight, superfinal));
+        ofst->SetFinal(s, B::Weight::Zero());
+        break;
+      }
+    }
+  }
+  uint64 oprops = ofst->Properties(kFstProperties, false);
+  ofst->SetProperties(mapper->Properties(iprops) | oprops, kFstProperties);
+}
+
+// Maps an arc type A to an arc type B using mapper function
+// object C, passed by value. This version writes the mapped input
+// Fst to an output MutableFst.
+template<class A, class B, class C>
+void ArcMap(const Fst<A> &ifst, MutableFst<B> *ofst, C mapper) {
+  ArcMap(ifst, ofst, &mapper);
+}
+
+
+struct ArcMapFstOptions : public CacheOptions {
+  // ArcMapFst default caching behaviour is to do no caching. Most
+  // mappers are cheap and therefore we save memory by not doing
+  // caching.
+  ArcMapFstOptions() : CacheOptions(true, 0) {}
+  ArcMapFstOptions(const CacheOptions& opts) : CacheOptions(opts) {}
+};
+
+
+template <class A, class B, class C> class ArcMapFst;
+
+// Implementation of delayed ArcMapFst.
+template <class A, class B, class C>
+class ArcMapFstImpl : public CacheImpl<B> {
+ public:
+  using FstImpl<B>::SetType;
+  using FstImpl<B>::SetProperties;
+  using FstImpl<B>::SetInputSymbols;
+  using FstImpl<B>::SetOutputSymbols;
+
+  using VectorFstBaseImpl<typename CacheImpl<B>::State>::NumStates;
+
+  using CacheImpl<B>::PushArc;
+  using CacheImpl<B>::HasArcs;
+  using CacheImpl<B>::HasFinal;
+  using CacheImpl<B>::HasStart;
+  using CacheImpl<B>::SetArcs;
+  using CacheImpl<B>::SetFinal;
+  using CacheImpl<B>::SetStart;
+
+  friend class StateIterator< ArcMapFst<A, B, C> >;
+
+  typedef B Arc;
+  typedef typename B::Weight Weight;
+  typedef typename B::StateId StateId;
+
+  ArcMapFstImpl(const Fst<A> &fst, const C &mapper,
+                 const ArcMapFstOptions& opts)
+      : CacheImpl<B>(opts),
+        fst_(fst.Copy()),
+        mapper_(new C(mapper)),
+        own_mapper_(true),
+        superfinal_(kNoStateId),
+        nstates_(0) {
+    Init();
+  }
+
+  ArcMapFstImpl(const Fst<A> &fst, C *mapper,
+                 const ArcMapFstOptions& opts)
+      : CacheImpl<B>(opts),
+        fst_(fst.Copy()),
+        mapper_(mapper),
+        own_mapper_(false),
+        superfinal_(kNoStateId),
+        nstates_(0) {
+    Init();
+  }
+
+  ArcMapFstImpl(const ArcMapFstImpl<A, B, C> &impl)
+      : CacheImpl<B>(impl),
+        fst_(impl.fst_->Copy(true)),
+        mapper_(new C(*impl.mapper_)),
+        own_mapper_(true),
+        superfinal_(kNoStateId),
+        nstates_(0) {
+    Init();
+  }
+
+  ~ArcMapFstImpl() {
+    delete fst_;
+    if (own_mapper_) delete mapper_;
+  }
+
+  StateId Start() {
+    if (!HasStart())
+      SetStart(FindOState(fst_->Start()));
+    return CacheImpl<B>::Start();
+  }
+
+  Weight Final(StateId s) {
+    if (!HasFinal(s)) {
+      switch (final_action_) {
+        case MAP_NO_SUPERFINAL:
+        default: {
+          B final_arc = (*mapper_)(A(0, 0, fst_->Final(FindIState(s)),
+                                        kNoStateId));
+          if (final_arc.ilabel != 0 || final_arc.olabel != 0) {
+            FSTERROR() << "ArcMapFst: non-zero arc labels for superfinal arc";
+            SetProperties(kError, kError);
+          }
+          SetFinal(s, final_arc.weight);
+          break;
+        }
+        case MAP_ALLOW_SUPERFINAL: {
+          if (s == superfinal_) {
+            SetFinal(s, Weight::One());
+          } else {
+            B final_arc = (*mapper_)(A(0, 0, fst_->Final(FindIState(s)),
+                                          kNoStateId));
+            if (final_arc.ilabel == 0 && final_arc.olabel == 0)
+              SetFinal(s, final_arc.weight);
+            else
+              SetFinal(s, Weight::Zero());
+          }
+          break;
+        }
+        case MAP_REQUIRE_SUPERFINAL: {
+          SetFinal(s, s == superfinal_ ? Weight::One() : Weight::Zero());
+          break;
+        }
+      }
+    }
+    return CacheImpl<B>::Final(s);
+  }
+
+  size_t NumArcs(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<B>::NumArcs(s);
+  }
+
+  size_t NumInputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<B>::NumInputEpsilons(s);
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<B>::NumOutputEpsilons(s);
+  }
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if ((mask & kError) && (fst_->Properties(kError, false) ||
+                            (mapper_->Properties(0) & kError)))
+      SetProperties(kError, kError);
+    return FstImpl<Arc>::Properties(mask);
+  }
+
+  void InitArcIterator(StateId s, ArcIteratorData<B> *data) {
+    if (!HasArcs(s))
+      Expand(s);
+    CacheImpl<B>::InitArcIterator(s, data);
+  }
+
+  void Expand(StateId s) {
+    // Add exiting arcs.
+    if (s == superfinal_) { SetArcs(s); return; }
+
+    for (ArcIterator< Fst<A> > aiter(*fst_, FindIState(s));
+         !aiter.Done(); aiter.Next()) {
+      A aarc(aiter.Value());
+      aarc.nextstate = FindOState(aarc.nextstate);
+      const B& barc = (*mapper_)(aarc);
+      PushArc(s, barc);
+    }
+
+    // Check for superfinal arcs.
+    if (!HasFinal(s) || Final(s) == Weight::Zero())
+      switch (final_action_) {
+        case MAP_NO_SUPERFINAL:
+        default:
+          break;
+        case MAP_ALLOW_SUPERFINAL: {
+          B final_arc = (*mapper_)(A(0, 0, fst_->Final(FindIState(s)),
+                                        kNoStateId));
+          if (final_arc.ilabel != 0 || final_arc.olabel != 0) {
+            if (superfinal_ == kNoStateId)
+              superfinal_ = nstates_++;
+            final_arc.nextstate = superfinal_;
+            PushArc(s, final_arc);
+          }
+          break;
+        }
+      case MAP_REQUIRE_SUPERFINAL: {
+        B final_arc = (*mapper_)(A(0, 0, fst_->Final(FindIState(s)),
+                                      kNoStateId));
+        if (final_arc.ilabel != 0 || final_arc.olabel != 0 ||
+            final_arc.weight != B::Weight::Zero())
+          PushArc(s, B(final_arc.ilabel, final_arc.olabel,
+                      final_arc.weight, superfinal_));
+        break;
+      }
+    }
+    SetArcs(s);
+  }
+
+ private:
+  void Init() {
+    SetType("map");
+
+    if (mapper_->InputSymbolsAction() == MAP_COPY_SYMBOLS)
+      SetInputSymbols(fst_->InputSymbols());
+    else if (mapper_->InputSymbolsAction() == MAP_CLEAR_SYMBOLS)
+      SetInputSymbols(0);
+
+    if (mapper_->OutputSymbolsAction() == MAP_COPY_SYMBOLS)
+      SetOutputSymbols(fst_->OutputSymbols());
+    else if (mapper_->OutputSymbolsAction() == MAP_CLEAR_SYMBOLS)
+      SetOutputSymbols(0);
+
+    if (fst_->Start() == kNoStateId) {
+      final_action_ = MAP_NO_SUPERFINAL;
+      SetProperties(kNullProperties);
+    } else {
+      final_action_ = mapper_->FinalAction();
+      uint64 props = fst_->Properties(kCopyProperties, false);
+      SetProperties(mapper_->Properties(props));
+      if (final_action_ == MAP_REQUIRE_SUPERFINAL)
+        superfinal_ = 0;
+    }
+  }
+
+  // Maps from output state to input state.
+  StateId FindIState(StateId s) {
+    if (superfinal_ == kNoStateId || s < superfinal_)
+      return s;
+    else
+      return s - 1;
+  }
+
+  // Maps from input state to output state.
+  StateId FindOState(StateId is) {
+    StateId os;
+    if (superfinal_ == kNoStateId || is < superfinal_)
+      os = is;
+    else
+      os = is + 1;
+
+    if (os >= nstates_)
+      nstates_ = os + 1;
+
+    return os;
+  }
+
+
+  const Fst<A> *fst_;
+  C*   mapper_;
+  bool own_mapper_;
+  MapFinalAction final_action_;
+
+  StateId superfinal_;
+  StateId nstates_;
+
+  void operator=(const ArcMapFstImpl<A, B, C> &);  // disallow
+};
+
+
+// Maps an arc type A to an arc type B using Mapper function object
+// C. This version is a delayed Fst.
+template <class A, class B, class C>
+class ArcMapFst : public ImplToFst< ArcMapFstImpl<A, B, C> > {
+ public:
+  friend class ArcIterator< ArcMapFst<A, B, C> >;
+  friend class StateIterator< ArcMapFst<A, B, C> >;
+
+  typedef B Arc;
+  typedef typename B::Weight Weight;
+  typedef typename B::StateId StateId;
+  typedef CacheState<B> State;
+  typedef ArcMapFstImpl<A, B, C> Impl;
+
+  ArcMapFst(const Fst<A> &fst, const C &mapper, const ArcMapFstOptions& opts)
+      : ImplToFst<Impl>(new Impl(fst, mapper, opts)) {}
+
+  ArcMapFst(const Fst<A> &fst, C* mapper, const ArcMapFstOptions& opts)
+      : ImplToFst<Impl>(new Impl(fst, mapper, opts)) {}
+
+  ArcMapFst(const Fst<A> &fst, const C &mapper)
+      : ImplToFst<Impl>(new Impl(fst, mapper, ArcMapFstOptions())) {}
+
+  ArcMapFst(const Fst<A> &fst, C* mapper)
+      : ImplToFst<Impl>(new Impl(fst, mapper, ArcMapFstOptions())) {}
+
+  // See Fst<>::Copy() for doc.
+  ArcMapFst(const ArcMapFst<A, B, C> &fst, bool safe = false)
+    : ImplToFst<Impl>(fst, safe) {}
+
+  // Get a copy of this ArcMapFst. See Fst<>::Copy() for further doc.
+  virtual ArcMapFst<A, B, C> *Copy(bool safe = false) const {
+    return new ArcMapFst<A, B, C>(*this, safe);
+  }
+
+  virtual inline void InitStateIterator(StateIteratorData<B> *data) const;
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<B> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+ private:
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const ArcMapFst<A, B, C> &fst);  // disallow
+};
+
+
+// Specialization for ArcMapFst.
+template<class A, class B, class C>
+class StateIterator< ArcMapFst<A, B, C> > : public StateIteratorBase<B> {
+ public:
+  typedef typename B::StateId StateId;
+
+  explicit StateIterator(const ArcMapFst<A, B, C> &fst)
+      : impl_(fst.GetImpl()), siter_(*impl_->fst_), s_(0),
+        superfinal_(impl_->final_action_ == MAP_REQUIRE_SUPERFINAL)
+  { CheckSuperfinal(); }
+
+  bool Done() const { return siter_.Done() && !superfinal_; }
+
+  StateId Value() const { return s_; }
+
+  void Next() {
+    ++s_;
+    if (!siter_.Done()) {
+      siter_.Next();
+      CheckSuperfinal();
+    }
+    else if (superfinal_)
+      superfinal_ = false;
+  }
+
+  void Reset() {
+    s_ = 0;
+    siter_.Reset();
+    superfinal_ = impl_->final_action_ == MAP_REQUIRE_SUPERFINAL;
+    CheckSuperfinal();
+  }
+
+ private:
+  // This allows base-class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  bool Done_() const { return Done(); }
+  StateId Value_() const { return Value(); }
+  void Next_() { Next(); }
+  void Reset_() { Reset(); }
+
+  void CheckSuperfinal() {
+    if (impl_->final_action_ != MAP_ALLOW_SUPERFINAL || superfinal_)
+      return;
+    if (!siter_.Done()) {
+      B final_arc = (*impl_->mapper_)(A(0, 0, impl_->fst_->Final(s_),
+                                           kNoStateId));
+      if (final_arc.ilabel != 0 || final_arc.olabel != 0)
+        superfinal_ = true;
+    }
+  }
+
+  const ArcMapFstImpl<A, B, C> *impl_;
+  StateIterator< Fst<A> > siter_;
+  StateId s_;
+  bool superfinal_;    // true if there is a superfinal state and not done
+
+  DISALLOW_COPY_AND_ASSIGN(StateIterator);
+};
+
+
+// Specialization for ArcMapFst.
+template <class A, class B, class C>
+class ArcIterator< ArcMapFst<A, B, C> >
+    : public CacheArcIterator< ArcMapFst<A, B, C> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const ArcMapFst<A, B, C> &fst, StateId s)
+      : CacheArcIterator< ArcMapFst<A, B, C> >(fst.GetImpl(), s) {
+    if (!fst.GetImpl()->HasArcs(s))
+      fst.GetImpl()->Expand(s);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+template <class A, class B, class C> inline
+void ArcMapFst<A, B, C>::InitStateIterator(StateIteratorData<B> *data)
+    const {
+  data->base = new StateIterator< ArcMapFst<A, B, C> >(*this);
+}
+
+
+//
+// Utility Mappers
+//
+
+// Mapper that returns its input.
+template <class A>
+struct IdentityArcMapper {
+  typedef A FromArc;
+  typedef A ToArc;
+
+  A operator()(const A &arc) const { return arc; }
+
+  MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS;}
+
+  uint64 Properties(uint64 props) const { return props; }
+};
+
+
+// Mapper that returns its input with final states redirected to
+// a single super-final state.
+template <class A>
+struct SuperFinalMapper {
+  typedef A FromArc;
+  typedef A ToArc;
+
+  A operator()(const A &arc) const { return arc; }
+
+  MapFinalAction FinalAction() const { return MAP_REQUIRE_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS;}
+
+  uint64 Properties(uint64 props) const {
+    return props & kAddSuperFinalProperties;
+  }
+};
+
+
+// Mapper that leaves labels and nextstate unchanged and constructs a new weight
+// from the underlying value of the arc weight.  Requires that there is a
+// WeightConvert class specialization that converts the weights.
+template <class A, class B>
+class WeightConvertMapper {
+ public:
+  typedef A FromArc;
+  typedef B ToArc;
+  typedef typename FromArc::Weight FromWeight;
+  typedef typename ToArc::Weight ToWeight;
+
+  ToArc operator()(const FromArc &arc) const {
+    return ToArc(arc.ilabel, arc.olabel,
+                 convert_weight_(arc.weight), arc.nextstate);
+  }
+
+  MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS;}
+
+  uint64 Properties(uint64 props) const { return props; }
+
+ private:
+  WeightConvert<FromWeight, ToWeight> convert_weight_;
+};
+
+// Non-precision-changing weight conversions.
+// Consider using more efficient Cast (fst.h) instead.
+typedef WeightConvertMapper<StdArc, LogArc> StdToLogMapper;
+typedef WeightConvertMapper<LogArc, StdArc> LogToStdMapper;
+
+// Precision-changing weight conversions.
+typedef WeightConvertMapper<StdArc, Log64Arc> StdToLog64Mapper;
+typedef WeightConvertMapper<LogArc, Log64Arc> LogToLog64Mapper;
+typedef WeightConvertMapper<Log64Arc, StdArc> Log64ToStdMapper;
+typedef WeightConvertMapper<Log64Arc, LogArc> Log64ToLogMapper;
+
+// Mapper from A to GallicArc<A>.
+template <class A, StringType S = STRING_LEFT>
+struct ToGallicMapper {
+  typedef A FromArc;
+  typedef GallicArc<A, S> ToArc;
+
+  typedef StringWeight<typename A::Label, S> SW;
+  typedef typename A::Weight AW;
+  typedef typename GallicArc<A, S>::Weight GW;
+
+  ToArc operator()(const A &arc) const {
+    // 'Super-final' arc.
+    if (arc.nextstate == kNoStateId && arc.weight != AW::Zero())
+      return ToArc(0, 0, GW(SW::One(), arc.weight), kNoStateId);
+    // 'Super-non-final' arc.
+    else if (arc.nextstate == kNoStateId)
+      return ToArc(0, 0, GW(SW::Zero(), arc.weight), kNoStateId);
+    // Epsilon label.
+    else if (arc.olabel == 0)
+      return ToArc(arc.ilabel, arc.ilabel,
+                   GW(SW::One(), arc.weight), arc.nextstate);
+    // Regular label.
+    else
+      return ToArc(arc.ilabel, arc.ilabel,
+                   GW(SW(arc.olabel), arc.weight), arc.nextstate);
+  }
+
+  MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_CLEAR_SYMBOLS;}
+
+  uint64 Properties(uint64 props) const {
+    return ProjectProperties(props, true) & kWeightInvariantProperties;
+  }
+};
+
+
+// Mapper from GallicArc<A> to A.
+template <class A, StringType S = STRING_LEFT>
+struct FromGallicMapper {
+  typedef GallicArc<A, S> FromArc;
+  typedef A ToArc;
+
+  typedef typename A::Label Label;
+  typedef StringWeight<Label, S> SW;
+  typedef typename A::Weight AW;
+  typedef typename GallicArc<A, S>::Weight GW;
+
+  FromGallicMapper(Label superfinal_label = 0)
+      : superfinal_label_(superfinal_label), error_(false) {}
+
+  A operator()(const FromArc &arc) const {
+    // 'Super-non-final' arc.
+    if (arc.nextstate == kNoStateId && arc.weight == GW::Zero())
+      return A(arc.ilabel, 0, AW::Zero(), kNoStateId);
+
+    SW w1 = arc.weight.Value1();
+    AW w2 = arc.weight.Value2();
+    StringWeightIterator<Label, S> iter1(w1);
+
+    Label l = w1.Size() == 1 ? iter1.Value() : 0;
+
+    if (l == kStringInfinity || l == kStringBad ||
+        arc.ilabel != arc.olabel || w1.Size() > 1) {
+      FSTERROR() << "FromGallicMapper: unrepesentable weight";
+      error_ = true;
+    }
+
+    if (arc.ilabel == 0 && l != 0 && arc.nextstate == kNoStateId)
+      return A(superfinal_label_, l, w2, arc.nextstate);
+    else
+      return A(arc.ilabel, l, w2, arc.nextstate);
+  }
+
+  MapFinalAction FinalAction() const { return MAP_ALLOW_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_CLEAR_SYMBOLS;}
+
+  uint64 Properties(uint64 inprops) const {
+    uint64 outprops = inprops & kOLabelInvariantProperties &
+        kWeightInvariantProperties & kAddSuperFinalProperties;
+    if (error_)
+      outprops |= kError;
+    return outprops;
+  }
+
+ private:
+  Label superfinal_label_;
+  mutable bool error_;
+};
+
+
+// Mapper from GallicArc<A> to A.
+template <class A, StringType S = STRING_LEFT>
+struct GallicToNewSymbolsMapper {
+  typedef GallicArc<A, S> FromArc;
+  typedef A ToArc;
+
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef StringWeight<Label, S> SW;
+  typedef typename A::Weight AW;
+  typedef typename GallicArc<A, S>::Weight GW;
+
+  GallicToNewSymbolsMapper(MutableFst<ToArc> *fst)
+      : fst_(fst), lmax_(0), osymbols_(fst->OutputSymbols()),
+        isymbols_(0), error_(false) {
+    fst_->DeleteStates();
+    state_ = fst_->AddState();
+    fst_->SetStart(state_);
+    fst_->SetFinal(state_, AW::One());
+    if (osymbols_) {
+      string name = osymbols_->Name() + "_from_gallic";
+      fst_->SetInputSymbols(new SymbolTable(name));
+      isymbols_ = fst_->MutableInputSymbols();
+      isymbols_->AddSymbol(osymbols_->Find((int64) 0), 0);
+    } else {
+      fst_->SetInputSymbols(0);
+    }
+  }
+
+  A operator()(const FromArc &arc) {
+    // 'Super-non-final' arc.
+    if (arc.nextstate == kNoStateId && arc.weight == GW::Zero())
+      return A(arc.ilabel, 0, AW::Zero(), kNoStateId);
+
+    SW w1 = arc.weight.Value1();
+    AW w2 = arc.weight.Value2();
+    Label l;
+
+    if (w1.Size() == 0) {
+      l = 0;
+    } else {
+      typename Map::iterator miter = map_.find(w1);
+      if (miter != map_.end()) {
+        l = (*miter).second;
+      } else {
+        l = ++lmax_;
+        map_.insert(pair<const SW, Label>(w1, l));
+        StringWeightIterator<Label, S> iter1(w1);
+        StateId n;
+        string s;
+        for(size_t i = 0, p = state_;
+            i < w1.Size();
+            ++i, iter1.Next(), p = n) {
+          n = i == w1.Size() - 1 ? state_ : fst_->AddState();
+          fst_->AddArc(p, ToArc(i ? 0 : l, iter1.Value(), AW::One(), n));
+          if (isymbols_) {
+            if (i) s = s + "_";
+            s = s + osymbols_->Find(iter1.Value());
+          }
+        }
+        if (isymbols_)
+          isymbols_->AddSymbol(s, l);
+      }
+    }
+
+    if (l == kStringInfinity || l == kStringBad || arc.ilabel != arc.olabel) {
+      FSTERROR() << "GallicToNewSymbolMapper: unrepesentable weight";
+      error_ = true;
+    }
+
+    return A(arc.ilabel, l, w2, arc.nextstate);
+  }
+
+  MapFinalAction FinalAction() const { return MAP_ALLOW_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_CLEAR_SYMBOLS; }
+
+  uint64 Properties(uint64 inprops) const {
+    uint64 outprops = inprops & kOLabelInvariantProperties &
+        kWeightInvariantProperties & kAddSuperFinalProperties;
+    if (error_)
+      outprops |= kError;
+    return outprops;
+  }
+
+ private:
+  class StringKey {
+   public:
+    size_t operator()(const SW &x) const {
+      return x.Hash();
+    }
+  };
+
+  typedef unordered_map<SW, Label, StringKey> Map;
+
+  MutableFst<ToArc> *fst_;
+  Map map_;
+  Label lmax_;
+  StateId state_;
+  const SymbolTable *osymbols_;
+  SymbolTable *isymbols_;
+  mutable bool error_;
+
+  DISALLOW_COPY_AND_ASSIGN(GallicToNewSymbolsMapper);
+};
+
+
+// Mapper to add a constant to all weights.
+template <class A>
+struct PlusMapper {
+  typedef A FromArc;
+  typedef A ToArc;
+  typedef typename A::Weight Weight;
+
+  explicit PlusMapper(Weight w) : weight_(w) {}
+
+  A operator()(const A &arc) const {
+    if (arc.weight == Weight::Zero())
+      return arc;
+    Weight w = Plus(arc.weight, weight_);
+    return A(arc.ilabel, arc.olabel, w, arc.nextstate);
+  }
+
+  MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS;}
+
+  uint64 Properties(uint64 props) const {
+    return props & kWeightInvariantProperties;
+  }
+
+ private:
+
+
+
+  Weight weight_;
+};
+
+
+// Mapper to (right) multiply a constant to all weights.
+template <class A>
+struct TimesMapper {
+  typedef A FromArc;
+  typedef A ToArc;
+  typedef typename A::Weight Weight;
+
+  explicit TimesMapper(Weight w) : weight_(w) {}
+
+  A operator()(const A &arc) const {
+    if (arc.weight == Weight::Zero())
+      return arc;
+    Weight w = Times(arc.weight, weight_);
+    return A(arc.ilabel, arc.olabel, w, arc.nextstate);
+  }
+
+  MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS;}
+
+  uint64 Properties(uint64 props) const {
+    return props & kWeightInvariantProperties;
+  }
+
+ private:
+  Weight weight_;
+};
+
+
+// Mapper to reciprocate all non-Zero() weights.
+template <class A>
+struct InvertWeightMapper {
+  typedef A FromArc;
+  typedef A ToArc;
+  typedef typename A::Weight Weight;
+
+  A operator()(const A &arc) const {
+    if (arc.weight == Weight::Zero())
+      return arc;
+    Weight w = Divide(Weight::One(), arc.weight);
+    return A(arc.ilabel, arc.olabel, w, arc.nextstate);
+  }
+
+  MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS;}
+
+  uint64 Properties(uint64 props) const {
+    return props & kWeightInvariantProperties;
+  }
+};
+
+
+// Mapper to map all non-Zero() weights to One().
+template <class A, class B = A>
+struct RmWeightMapper {
+  typedef A FromArc;
+  typedef B ToArc;
+  typedef typename FromArc::Weight FromWeight;
+  typedef typename ToArc::Weight ToWeight;
+
+  B operator()(const A &arc) const {
+    ToWeight w = arc.weight != FromWeight::Zero() ?
+                   ToWeight::One() : ToWeight::Zero();
+    return B(arc.ilabel, arc.olabel, w, arc.nextstate);
+  }
+
+  MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS;}
+
+  uint64 Properties(uint64 props) const {
+    return (props & kWeightInvariantProperties) | kUnweighted;
+  }
+};
+
+
+// Mapper to quantize all weights.
+template <class A, class B = A>
+struct QuantizeMapper {
+  typedef A FromArc;
+  typedef B ToArc;
+  typedef typename FromArc::Weight FromWeight;
+  typedef typename ToArc::Weight ToWeight;
+
+  QuantizeMapper() : delta_(kDelta) {}
+
+  explicit QuantizeMapper(float d) : delta_(d) {}
+
+  B operator()(const A &arc) const {
+    ToWeight w = arc.weight.Quantize(delta_);
+    return B(arc.ilabel, arc.olabel, w, arc.nextstate);
+  }
+
+  MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS;}
+
+  uint64 Properties(uint64 props) const {
+    return props & kWeightInvariantProperties;
+  }
+
+ private:
+  float delta_;
+};
+
+
+// Mapper from A to B under the assumption:
+//    B::Weight = A::Weight::ReverseWeight
+//    B::Label == A::Label
+//    B::StateId == A::StateId
+// The weight is reversed, while the label and nextstate preserved
+// in the mapping.
+template <class A, class B>
+struct ReverseWeightMapper {
+  typedef A FromArc;
+  typedef B ToArc;
+
+  B operator()(const A &arc) const {
+    return B(arc.ilabel, arc.olabel, arc.weight.Reverse(), arc.nextstate);
+  }
+
+  MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS;}
+
+  uint64 Properties(uint64 props) const { return props; }
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_ARC_MAP_H__
diff --git a/src/include/fst/arc.h b/src/include/fst/arc.h
new file mode 100644
index 0000000..56086c9
--- /dev/null
+++ b/src/include/fst/arc.h
@@ -0,0 +1,306 @@
+// arc.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+//
+// Commonly used Fst arc types.
+
+#ifndef FST_LIB_ARC_H__
+#define FST_LIB_ARC_H__
+
+#include <string>
+
+
+#include <fst/expectation-weight.h>
+#include <fst/float-weight.h>
+#include <fst/lexicographic-weight.h>
+#include <fst/power-weight.h>
+#include <fst/product-weight.h>
+#include <fst/signed-log-weight.h>
+#include <fst/sparse-power-weight.h>
+#include <iostream>
+#include <fstream>
+#include <fst/string-weight.h>
+
+
+namespace fst {
+
+template <class W>
+class ArcTpl {
+ public:
+  typedef W Weight;
+  typedef int Label;
+  typedef int StateId;
+
+  ArcTpl(Label i, Label o, const Weight& w, StateId s)
+      : ilabel(i), olabel(o), weight(w), nextstate(s) {}
+
+  ArcTpl() {}
+
+  static const string &Type(void) {
+    static const string type =
+        (Weight::Type() == "tropical") ? "standard" : Weight::Type();
+    return type;
+  }
+
+  Label ilabel;
+  Label olabel;
+  Weight weight;
+  StateId nextstate;
+};
+
+typedef ArcTpl<TropicalWeight> StdArc;
+typedef ArcTpl<LogWeight> LogArc;
+typedef ArcTpl<Log64Weight> Log64Arc;
+typedef ArcTpl<SignedLogWeight> SignedLogArc;
+typedef ArcTpl<SignedLog64Weight> SignedLog64Arc;
+typedef ArcTpl<MinMaxWeight> MinMaxArc;
+
+
+// Arc with integer labels and state Ids and string weights.
+template <StringType S = STRING_LEFT>
+class StringArc {
+ public:
+  typedef int Label;
+  typedef StringWeight<int, S> Weight;
+  typedef int StateId;
+
+  StringArc(Label i, Label o, Weight w, StateId s)
+      : ilabel(i), olabel(o), weight(w), nextstate(s) {}
+
+  StringArc() {}
+
+  static const string &Type() {  // Arc type name
+    static const string type =
+        S == STRING_LEFT ? "standard_string" :
+        (S == STRING_RIGHT ? "right_standard_string" :
+         (S == STRING_LEFT_RESTRICT ? "restricted_string" :
+          "right_restricted_string"));
+    return type;
+  }
+
+  Label ilabel;       // Transition input label
+  Label olabel;       // Transition output label
+  Weight weight;      // Transition weight
+  StateId nextstate;  // Transition destination state
+};
+
+
+// Arc with label and state Id type the same as template arg and with
+// weights over the Gallic semiring w.r.t the output labels and weights of A.
+template <class A, StringType S = STRING_LEFT>
+struct GallicArc {
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef GallicWeight<Label, typename A::Weight, S> Weight;
+
+  GallicArc() {}
+
+  GallicArc(Label i, Label o, Weight w, StateId s)
+      : ilabel(i), olabel(o), weight(w), nextstate(s) {}
+
+  GallicArc(const A &arc)
+      : ilabel(arc.ilabel), olabel(arc.ilabel),
+        weight(arc.olabel, arc.weight), nextstate(arc.nextstate) {}
+
+  static const string &Type() {  // Arc type name
+    static const string type =
+        (S == STRING_LEFT ? "gallic_" :
+         (S == STRING_RIGHT ? "right_gallic_" :
+          (S == STRING_LEFT_RESTRICT ? "restricted_gallic_" :
+           "right_restricted_gallic_"))) + A::Type();
+    return type;
+  }
+
+  Label ilabel;       // Transition input label
+  Label olabel;       // Transition output label
+  Weight weight;      // Transition weight
+  StateId nextstate;  // Transition destination state
+};
+
+
+// Arc with the reverse of the weight found in its template arg.
+template <class A> struct ReverseArc {
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::Weight AWeight;
+  typedef typename AWeight::ReverseWeight Weight;
+  typedef typename A::StateId StateId;
+
+  ReverseArc(Label i, Label o, Weight w, StateId s)
+      : ilabel(i), olabel(o), weight(w), nextstate(s) {}
+
+  ReverseArc() {}
+
+  static const string &Type() {  // Arc type name
+    static const string type = "reverse_" + Arc::Type();
+    return type;
+  }
+
+  Label ilabel;       // Transition input label
+  Label olabel;       // Transition output label
+  Weight weight;      // Transition weight
+  StateId nextstate;  // Transition destination state
+};
+
+
+// Arc with integer labels and state Ids and lexicographic weights.
+template<class W1, class W2>
+struct LexicographicArc {
+  typedef int Label;
+  typedef LexicographicWeight<W1, W2> Weight;
+  typedef int StateId;
+
+  LexicographicArc(Label i, Label o, Weight w, StateId s)
+      : ilabel(i), olabel(o), weight(w), nextstate(s) {}
+
+  LexicographicArc() {}
+
+  static const string &Type() {  // Arc type name
+    static const string type = Weight::Type();
+    return type;
+  }
+
+  Label ilabel;       // Transition input label
+  Label olabel;       // Transition output label
+  Weight weight;      // Transition weight
+  StateId nextstate;  // Transition destination state
+};
+
+
+// Arc with integer labels and state Ids and product weights.
+template<class W1, class W2>
+struct ProductArc {
+  typedef int Label;
+  typedef ProductWeight<W1, W2> Weight;
+  typedef int StateId;
+
+  ProductArc(Label i, Label o, Weight w, StateId s)
+      : ilabel(i), olabel(o), weight(w), nextstate(s) {}
+
+  ProductArc() {}
+
+  static const string &Type() {  // Arc type name
+    static const string type = Weight::Type();
+    return type;
+  }
+
+  Label ilabel;       // Transition input label
+  Label olabel;       // Transition output label
+  Weight weight;      // Transition weight
+  StateId nextstate;  // Transition destination state
+};
+
+
+// Arc with label and state Id type the same as first template arg and with
+// weights over the n-th cartesian power of the weight type of the
+// template arg.
+template <class A, unsigned int n>
+struct PowerArc {
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef PowerWeight<typename A::Weight, n> Weight;
+
+  PowerArc() {}
+
+  PowerArc(Label i, Label o, Weight w, StateId s)
+      : ilabel(i), olabel(o), weight(w), nextstate(s) {}
+
+  static const string &Type() {  // Arc type name
+    static string type;
+    if (type.empty()) {
+      string power;
+      Int64ToStr(n, &power);
+      type = A::Type() + "_^" + power;
+    }
+    return type;
+  }
+
+  Label ilabel;       // Transition input label
+  Label olabel;       // Transition output label
+  Weight weight;      // Transition weight
+  StateId nextstate;  // Transition destination state
+};
+
+
+// Arc with label and state Id type the same as first template arg and with
+// weights over the arbitrary cartesian power of the weight type.
+template <class A, class K = int>
+struct SparsePowerArc {
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef SparsePowerWeight<typename A::Weight, K> Weight;
+
+  SparsePowerArc() {}
+
+  SparsePowerArc(Label i, Label o, Weight w, StateId s)
+      : ilabel(i), olabel(o), weight(w), nextstate(s) {}
+
+  static const string &Type() {  // Arc type name
+    static string type;
+    if (type.empty()) { type = A::Type() + "_^n"; }
+    if(sizeof(K) != sizeof(uint32)) {
+      string size;
+      Int64ToStr(8 * sizeof(K), &size);
+      type += "_" + size;
+    }
+    return type;
+  }
+
+  Label ilabel;       // Transition input label
+  Label olabel;       // Transition output label
+  Weight weight;      // Transition weight
+  StateId nextstate;  // Transition destination state
+};
+
+
+// Arc with label and state Id type the same as first template arg and with
+// expectation weight over the first template arg weight type and the
+// second template arg.
+template <class A, class X2>
+struct ExpectationArc {
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight X1;
+  typedef ExpectationWeight<X1, X2> Weight;
+
+  ExpectationArc() {}
+
+  ExpectationArc(Label i, Label o, Weight w, StateId s)
+      : ilabel(i), olabel(o), weight(w), nextstate(s) {}
+
+  static const string &Type() {  // Arc type name
+    static string type;
+    if (type.empty()) {
+      type = "expectation_" + A::Type() + "_" + X2::Type();
+    }
+    return type;
+  }
+
+  Label ilabel;       // Transition input label
+  Label olabel;       // Transition output label
+  Weight weight;      // Transition weight
+  StateId nextstate;  // Transition destination state
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_ARC_H__
diff --git a/src/include/fst/arcfilter.h b/src/include/fst/arcfilter.h
new file mode 100644
index 0000000..179dc2c
--- /dev/null
+++ b/src/include/fst/arcfilter.h
@@ -0,0 +1,99 @@
+// arcfilter.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Function objects to restrict which arcs are traversed in an FST.
+
+#ifndef FST_LIB_ARCFILTER_H__
+#define FST_LIB_ARCFILTER_H__
+
+
+#include <fst/fst.h>
+#include <fst/util.h>
+
+
+namespace fst {
+
+// True for all arcs.
+template <class A>
+class AnyArcFilter {
+public:
+  bool operator()(const A &arc) const { return true; }
+};
+
+
+// True for (input/output) epsilon arcs.
+template <class A>
+class EpsilonArcFilter {
+public:
+  bool operator()(const A &arc) const {
+    return arc.ilabel == 0 && arc.olabel == 0;
+  }
+};
+
+
+// True for input epsilon arcs.
+template <class A>
+class InputEpsilonArcFilter {
+public:
+  bool operator()(const A &arc) const {
+    return arc.ilabel == 0;
+  }
+};
+
+
+// True for output epsilon arcs.
+template <class A>
+class OutputEpsilonArcFilter {
+public:
+  bool operator()(const A &arc) const {
+    return arc.olabel == 0;
+  }
+};
+
+
+// True if specified labels match (don't match) when keep_match is
+// true (false).
+template <class A>
+class MultiLabelArcFilter {
+public:
+  typedef typename A::Label Label;
+
+  MultiLabelArcFilter(bool match_input = true, bool keep_match = true)
+    :  match_input_(match_input),
+       keep_match_(keep_match) {}
+
+
+  bool operator()(const A &arc) const {
+    Label label = match_input_ ? arc.ilabel : arc.olabel;
+    bool match = labels_.Find(label) != labels_.End();
+    return keep_match_ ? match : !match;
+  }
+
+  void AddLabel(Label label) {
+    labels_.Insert(label);
+  }
+
+private:
+  CompactSet<Label, kNoLabel> labels_;
+  bool match_input_;
+  bool keep_match_;
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_ARCFILTER_H__
diff --git a/src/include/fst/arcsort.h b/src/include/fst/arcsort.h
new file mode 100644
index 0000000..38f4f95
--- /dev/null
+++ b/src/include/fst/arcsort.h
@@ -0,0 +1,203 @@
+// arcsort.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Functions and classes to sort arcs in an FST.
+
+#ifndef FST_LIB_ARCSORT_H__
+#define FST_LIB_ARCSORT_H__
+
+#include <algorithm>
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+#include <fst/state-map.h>
+#include <fst/test-properties.h>
+
+
+namespace fst {
+
+template <class Arc, class Compare>
+class ArcSortMapper {
+ public:
+  typedef Arc FromArc;
+  typedef Arc ToArc;
+
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+
+  ArcSortMapper(const Fst<Arc> &fst, const Compare &comp)
+      : fst_(fst), comp_(comp), i_(0) {}
+
+  // Allows updating Fst argument; pass only if changed.
+  ArcSortMapper(const ArcSortMapper<Arc, Compare> &mapper,
+                const Fst<Arc> *fst = 0)
+      : fst_(fst ? *fst : mapper.fst_), comp_(mapper.comp_), i_(0) {}
+
+  StateId Start() { return fst_.Start(); }
+  Weight Final(StateId s) const { return fst_.Final(s); }
+
+  void SetState(StateId s) {
+    i_ = 0;
+    arcs_.clear();
+    arcs_.reserve(fst_.NumArcs(s));
+    for (ArcIterator< Fst<Arc> > aiter(fst_, s); !aiter.Done(); aiter.Next())
+      arcs_.push_back(aiter.Value());
+    sort(arcs_.begin(), arcs_.end(), comp_);
+  }
+
+  bool Done() const { return i_ >= arcs_.size(); }
+  const Arc &Value() const { return arcs_[i_]; }
+  void Next() { ++i_; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+  uint64 Properties(uint64 props) const { return comp_.Properties(props); }
+
+ private:
+  const Fst<Arc> &fst_;
+  const Compare &comp_;
+  vector<Arc> arcs_;
+  ssize_t i_;               // current arc position
+
+  void operator=(const ArcSortMapper<Arc, Compare> &);  // disallow
+};
+
+
+// Sorts the arcs in an FST according to function object 'comp' of
+// type Compare. This version modifies its input.  Comparison function
+// objects ILabelCompare and OLabelCompare are provived by the
+// library. In general, Compare must meet the requirements for an STL
+// sort comparision function object. It must also have a member
+// Properties(uint64) that specifies the known properties of the
+// sorted FST; it takes as argument the input FST's known properties
+// before the sort.
+//
+// Complexity:
+// - Time: O(V D log D)
+// - Space: O(D)
+// where V = # of states and D = maximum out-degree.
+template<class Arc, class Compare>
+void ArcSort(MutableFst<Arc> *fst, Compare comp) {
+  ArcSortMapper<Arc, Compare> mapper(*fst, comp);
+  StateMap(fst, mapper);
+}
+
+typedef CacheOptions ArcSortFstOptions;
+
+// Sorts the arcs in an FST according to function object 'comp' of
+// type Compare. This version is a delayed Fst.  Comparsion function
+// objects ILabelCompare and OLabelCompare are provided by the
+// library. In general, Compare must meet the requirements for an STL
+// comparision function object (e.g. as used for STL sort). It must
+// also have a member Properties(uint64) that specifies the known
+// properties of the sorted FST; it takes as argument the input FST's
+// known properties.
+//
+// Complexity:
+// - Time: O(v d log d)
+// - Space: O(d)
+// where v = # of states visited, d = maximum out-degree of states
+// visited. Constant time and space to visit an input state is assumed
+// and exclusive of caching.
+template <class A, class C>
+class ArcSortFst : public StateMapFst<A, A, ArcSortMapper<A, C> > {
+ public:
+  typedef A Arc;
+ typedef ArcSortMapper<A, C> M;
+
+  ArcSortFst(const Fst<A> &fst, const C &comp)
+      : StateMapFst<A, A, M>(fst, ArcSortMapper<A, C>(fst, comp)) {}
+
+  ArcSortFst(const Fst<A> &fst, const C &comp, const ArcSortFstOptions &opts)
+      : StateMapFst<A, A, M>(fst, ArcSortMapper<A, C>(fst, comp), opts) {}
+
+  // See Fst<>::Copy() for doc.
+  ArcSortFst(const ArcSortFst<A, C> &fst, bool safe = false)
+      : StateMapFst<A, A, M>(fst, safe) {}
+
+  // Get a copy of this ArcSortFst. See Fst<>::Copy() for further doc.
+  virtual ArcSortFst<A, C> *Copy(bool safe = false) const {
+    return new ArcSortFst(*this, safe);
+  }
+};
+
+
+// Specialization for ArcSortFst.
+template <class A, class C>
+class StateIterator< ArcSortFst<A, C> >
+    : public StateIterator< StateMapFst<A, A,  ArcSortMapper<A, C> > > {
+ public:
+  explicit StateIterator(const ArcSortFst<A, C> &fst)
+      : StateIterator< StateMapFst<A, A,  ArcSortMapper<A, C> > >(fst) {}
+};
+
+
+// Specialization for ArcSortFst.
+template <class A, class C>
+class ArcIterator< ArcSortFst<A, C> >
+    : public ArcIterator< StateMapFst<A, A,  ArcSortMapper<A, C> > > {
+ public:
+  ArcIterator(const ArcSortFst<A, C> &fst, typename A::StateId s)
+      : ArcIterator< StateMapFst<A, A,  ArcSortMapper<A, C> > >(fst, s) {}
+};
+
+
+// Compare class for comparing input labels of arcs.
+template<class A> class ILabelCompare {
+ public:
+  bool operator() (A arc1, A arc2) const {
+    return arc1.ilabel < arc2.ilabel;
+  }
+
+  uint64 Properties(uint64 props) const {
+    return (props & kArcSortProperties) | kILabelSorted |
+        (props & kAcceptor ? kOLabelSorted : 0);
+  }
+};
+
+
+// Compare class for comparing output labels of arcs.
+template<class A> class OLabelCompare {
+ public:
+  bool operator() (const A &arc1, const A &arc2) const {
+    return arc1.olabel < arc2.olabel;
+  }
+
+  uint64 Properties(uint64 props) const {
+    return (props & kArcSortProperties) | kOLabelSorted |
+        (props & kAcceptor ? kILabelSorted : 0);
+  }
+};
+
+
+// Useful aliases when using StdArc.
+template<class C> class StdArcSortFst : public ArcSortFst<StdArc, C> {
+ public:
+  typedef StdArc Arc;
+  typedef C Compare;
+};
+
+typedef ILabelCompare<StdArc> StdILabelCompare;
+
+typedef OLabelCompare<StdArc> StdOLabelCompare;
+
+}  // namespace fst
+
+#endif  // FST_LIB_ARCSORT_H__
diff --git a/src/include/fst/bi-table.h b/src/include/fst/bi-table.h
new file mode 100644
index 0000000..dbb436c
--- /dev/null
+++ b/src/include/fst/bi-table.h
@@ -0,0 +1,396 @@
+// bi-table.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Classes for representing a bijective mapping between an arbitrary entry
+// of type T and a signed integral ID.
+
+#ifndef FST_LIB_BI_TABLE_H__
+#define FST_LIB_BI_TABLE_H__
+
+#include <deque>
+#include <vector>
+using std::vector;
+
+namespace fst {
+
+// BI TABLES - these determine a bijective mapping between an
+// arbitrary entry of type T and an signed integral ID of type I. The IDs are
+// allocated starting from 0 in order.
+//
+// template <class I, class T>
+// class BiTable {
+//  public:
+//
+//   // Required constructors.
+//   BiTable();
+//
+//   // Lookup integer ID from entry. If it doesn't exist, then add it.
+//   I FindId(const T &entry);
+//   // Lookup entry from integer ID.
+//   const T &FindEntry(I) const;
+//   // # of stored entries.
+//   I Size() const;
+// };
+
+// An implementation using a hash map for the entry to ID mapping.
+// The  entry T must have == defined and the default constructor
+// must produce an entry that will never be seen. H is the hash function.
+template <class I, class T, class H>
+class HashBiTable {
+ public:
+
+  HashBiTable() {
+    T empty_entry;
+  }
+
+  I FindId(const T &entry) {
+    I &id_ref = entry2id_[entry];
+    if (id_ref == 0) {  // T not found; store and assign it a new ID.
+      id2entry_.push_back(entry);
+      id_ref = id2entry_.size();
+    }
+    return id_ref - 1;  // NB: id_ref = ID + 1
+  }
+
+  const T &FindEntry(I s) const {
+    return id2entry_[s];
+  }
+
+  I Size() const { return id2entry_.size(); }
+
+ private:
+  unordered_map<T, I, H> entry2id_;
+  vector<T> id2entry_;
+
+  DISALLOW_COPY_AND_ASSIGN(HashBiTable);
+};
+
+
+// An implementation using a hash set for the entry to ID
+// mapping.  The hash set holds 'keys' which are either the ID
+// or kCurrentKey.  These keys can be mapped to entrys either by
+// looking up in the entry vector or, if kCurrentKey, in current_entry_
+// member. The hash and key equality functions map to entries first.
+// The  entry T must have == defined and the default constructor
+// must produce a entry that will never be seen. H is the hash
+// function.
+template <class I, class T, class H>
+class CompactHashBiTable {
+ public:
+  friend class HashFunc;
+  friend class HashEqual;
+
+  CompactHashBiTable()
+      : hash_func_(*this),
+        hash_equal_(*this),
+        keys_(0, hash_func_, hash_equal_) {
+  }
+
+  // Reserves space for table_size elements.
+  explicit CompactHashBiTable(size_t table_size)
+      : hash_func_(*this),
+        hash_equal_(*this),
+        keys_(table_size, hash_func_, hash_equal_) {
+    id2entry_.reserve(table_size);
+  }
+
+  I FindId(const T &entry) {
+    current_entry_ = &entry;
+    typename KeyHashSet::const_iterator it = keys_.find(kCurrentKey);
+    if (it == keys_.end()) {
+      I key = id2entry_.size();
+      id2entry_.push_back(entry);
+      keys_.insert(key);
+      return key;
+    } else {
+      return *it;
+    }
+  }
+
+  const T &FindEntry(I s) const { return id2entry_[s]; }
+  I Size() const { return id2entry_.size(); }
+
+ private:
+  static const I kEmptyKey;    // -1
+  static const I kCurrentKey;  // -2
+
+  class HashFunc {
+   public:
+    HashFunc(const CompactHashBiTable &ht) : ht_(&ht) {}
+
+    size_t operator()(I k) const { return hf(ht_->Key2T(k)); }
+   private:
+    const CompactHashBiTable *ht_;
+    H hf;
+  };
+
+  class HashEqual {
+   public:
+    HashEqual(const CompactHashBiTable &ht) : ht_(&ht) {}
+
+    bool operator()(I k1, I k2) const {
+      return ht_->Key2T(k1) == ht_->Key2T(k2);
+    }
+   private:
+    const CompactHashBiTable *ht_;
+  };
+
+  typedef unordered_set<I, HashFunc, HashEqual> KeyHashSet;
+
+  const T &Key2T(I k) const {
+    if (k == kEmptyKey)
+      return empty_entry_;
+    else if (k == kCurrentKey)
+      return *current_entry_;
+    else
+      return id2entry_[k];
+  }
+
+  HashFunc hash_func_;
+  HashEqual hash_equal_;
+  KeyHashSet keys_;
+  vector<T> id2entry_;
+  const T empty_entry_;
+  const T *current_entry_;
+
+  DISALLOW_COPY_AND_ASSIGN(CompactHashBiTable);
+};
+
+template <class I, class T, class H>
+const I CompactHashBiTable<I, T, H>::kEmptyKey = -1;
+
+template <class I, class T, class H>
+const I CompactHashBiTable<I, T, H>::kCurrentKey = -2;
+
+
+// An implementation using a vector for the entry to ID mapping.
+// It is passed a function object FP that should fingerprint entries
+// uniquely to an integer that can used as a vector index. Normally,
+// VectorBiTable constructs the FP object.  The user can instead
+// pass in this object; in that case, VectorBiTable takes its
+// ownership.
+template <class I, class T, class FP>
+class VectorBiTable {
+ public:
+  explicit VectorBiTable(FP *fp = 0) : fp_(fp ? fp : new FP()) {}
+
+  ~VectorBiTable() { delete fp_; }
+
+  I FindId(const T &entry) {
+    ssize_t fp = (*fp_)(entry);
+    if (fp >= fp2id_.size())
+      fp2id_.resize(fp + 1);
+    I &id_ref = fp2id_[fp];
+    if (id_ref == 0) {  // T not found; store and assign it a new ID.
+      id2entry_.push_back(entry);
+      id_ref = id2entry_.size();
+    }
+    return id_ref - 1;  // NB: id_ref = ID + 1
+  }
+
+  const T &FindEntry(I s) const { return id2entry_[s]; }
+
+  I Size() const { return id2entry_.size(); }
+
+  const FP &Fingerprint() const { return *fp_; }
+
+ private:
+  FP *fp_;
+  vector<I> fp2id_;
+  vector<T> id2entry_;
+
+  DISALLOW_COPY_AND_ASSIGN(VectorBiTable);
+};
+
+
+// An implementation using a vector and a compact hash table. The
+// selecting functor S returns true for entries to be hashed in the
+// vector.  The fingerprinting functor FP returns a unique fingerprint
+// for each entry to be hashed in the vector (these need to be
+// suitable for indexing in a vector).  The hash functor H is used when
+// hashing entry into the compact hash table.
+template <class I, class T, class S, class FP, class H>
+class VectorHashBiTable {
+ public:
+  friend class HashFunc;
+  friend class HashEqual;
+
+  VectorHashBiTable(S *s, FP *fp, H *h,
+                       size_t vector_size = 0,
+                       size_t entry_size = 0)
+      : selector_(s),
+        fp_(fp),
+        h_(h),
+        hash_func_(*this),
+        hash_equal_(*this),
+        keys_(0, hash_func_, hash_equal_) {
+    if (vector_size)
+      fp2id_.reserve(vector_size);
+    if (entry_size)
+      id2entry_.reserve(entry_size);
+  }
+
+  ~VectorHashBiTable() {
+    delete selector_;
+    delete fp_;
+    delete h_;
+  }
+
+  I FindId(const T &entry) {
+    if ((*selector_)(entry)) {  // Use the vector if 'selector_(entry) == true'
+      uint64 fp = (*fp_)(entry);
+      if (fp2id_.size() <= fp)
+        fp2id_.resize(fp + 1, 0);
+      if (fp2id_[fp] == 0) {
+        id2entry_.push_back(entry);
+        fp2id_[fp] = id2entry_.size();
+      }
+      return fp2id_[fp] - 1;  // NB: assoc_value = ID + 1
+    } else {  // Use the hash table otherwise.
+      current_entry_ = &entry;
+      typename KeyHashSet::const_iterator it = keys_.find(kCurrentKey);
+      if (it == keys_.end()) {
+        I key = id2entry_.size();
+        id2entry_.push_back(entry);
+        keys_.insert(key);
+        return key;
+      } else {
+        return *it;
+      }
+    }
+  }
+
+  const T &FindEntry(I s) const {
+    return id2entry_[s];
+  }
+
+  I Size() const { return id2entry_.size(); }
+
+  const S &Selector() const { return *selector_; }
+
+  const FP &Fingerprint() const { return *fp_; }
+
+  const H &Hash() const { return *h_; }
+
+ private:
+  static const I kEmptyKey;
+  static const I kCurrentKey;
+
+  class HashFunc {
+   public:
+    HashFunc(const VectorHashBiTable &ht) : ht_(&ht) {}
+
+    size_t operator()(I k) const { return (*(ht_->h_))(ht_->Key2Entry(k)); }
+   private:
+    const VectorHashBiTable *ht_;
+  };
+
+  class HashEqual {
+   public:
+    HashEqual(const VectorHashBiTable &ht) : ht_(&ht) {}
+
+    bool operator()(I k1, I k2) const {
+      return ht_->Key2Entry(k1) == ht_->Key2Entry(k2);
+    }
+   private:
+    const VectorHashBiTable *ht_;
+  };
+
+  typedef unordered_set<I, HashFunc, HashEqual> KeyHashSet;
+
+  const T &Key2Entry(I k) const {
+    if (k == kEmptyKey)
+      return empty_entry_;
+    else if (k == kCurrentKey)
+      return *current_entry_;
+    else
+      return id2entry_[k];
+  }
+
+
+  S *selector_;  // Returns true if entry hashed into vector
+  FP *fp_;       // Fingerprint used when hashing entry into vector
+  H *h_;         // Hash function used when hashing entry into hash_set
+
+  vector<T> id2entry_;  // Maps state IDs to entry
+  vector<I> fp2id_;        // Maps entry fingerprints to IDs
+
+  // Compact implementation of the hash table mapping entrys to
+  // state IDs using the hash function 'h_'
+  HashFunc hash_func_;
+  HashEqual hash_equal_;
+  KeyHashSet keys_;
+  const T empty_entry_;
+  const T *current_entry_;
+
+  DISALLOW_COPY_AND_ASSIGN(VectorHashBiTable);
+};
+
+template <class I, class T, class S, class FP, class H>
+const I VectorHashBiTable<I, T, S, FP, H>::kEmptyKey = -1;
+
+template <class I, class T, class S, class FP, class H>
+const I VectorHashBiTable<I, T, S, FP, H>::kCurrentKey = -2;
+
+
+// An implementation using a hash map for the entry to ID
+// mapping. This version permits erasing of s.  The  entry T
+// must have == defined and its default constructor must produce a
+// entry that will never be seen. F is the hash function.
+template <class I, class T, class F>
+class ErasableBiTable {
+ public:
+  ErasableBiTable() : first_(0) {}
+
+  I FindId(const T &entry) {
+    I &id_ref = entry2id_[entry];
+    if (id_ref == 0) {  // T not found; store and assign it a new ID.
+      id2entry_.push_back(entry);
+      id_ref = id2entry_.size() + first_;
+    }
+    return id_ref - 1;  // NB: id_ref = ID + 1
+  }
+
+  const T &FindEntry(I s) const { return id2entry_[s - first_]; }
+
+  I Size() const { return id2entry_.size(); }
+
+  void Erase(I s) {
+    T &entry = id2entry_[s - first_];
+    typename unordered_map<T, I, F>::iterator it =
+        entry2id_.find(entry);
+    entry2id_.erase(it);
+    id2entry_[s - first_] = empty_entry_;
+    while (!id2entry_.empty() && id2entry_.front() == empty_entry_) {
+      id2entry_.pop_front();
+      ++first_;
+    }
+  }
+
+ private:
+  unordered_map<T, I, F> entry2id_;
+  deque<T> id2entry_;
+  const T empty_entry_;
+  I first_;        // I of first element in the deque;
+
+  DISALLOW_COPY_AND_ASSIGN(ErasableBiTable);
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_BI_TABLE_H__
diff --git a/src/include/fst/cache.h b/src/include/fst/cache.h
new file mode 100644
index 0000000..a6a92d4
--- /dev/null
+++ b/src/include/fst/cache.h
@@ -0,0 +1,738 @@
+// cache.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// An Fst implementation that caches FST elements of a delayed
+// computation.
+
+#ifndef FST_LIB_CACHE_H__
+#define FST_LIB_CACHE_H__
+
+#include <vector>
+using std::vector;
+#include <list>
+
+#include <fst/vector-fst.h>
+
+
+DECLARE_bool(fst_default_cache_gc);
+DECLARE_int64(fst_default_cache_gc_limit);
+
+namespace fst {
+
+struct CacheOptions {
+  bool gc;          // enable GC
+  size_t gc_limit;  // # of bytes allowed before GC
+
+  CacheOptions(bool g, size_t l) : gc(g), gc_limit(l) {}
+  CacheOptions()
+      : gc(FLAGS_fst_default_cache_gc),
+        gc_limit(FLAGS_fst_default_cache_gc_limit) {}
+};
+
+// A CacheStateAllocator allocates and frees CacheStates
+// template <class S>
+// struct CacheStateAllocator {
+//   S *Allocate(StateId s);
+//   void Free(S *state, StateId s);
+// };
+//
+
+// A simple allocator class, can be overridden as needed,
+// maintains a single entry cache.
+template <class S>
+struct DefaultCacheStateAllocator {
+  typedef typename S::Arc::StateId StateId;
+
+  DefaultCacheStateAllocator() : mru_(NULL) { }
+
+  ~DefaultCacheStateAllocator() {
+    delete mru_;
+  }
+
+  S *Allocate(StateId s) {
+    if (mru_) {
+      S *state = mru_;
+      mru_ = NULL;
+      state->Reset();
+      return state;
+    }
+    return new S();
+  }
+
+  void Free(S *state, StateId s) {
+    if (mru_) {
+      delete mru_;
+    }
+    mru_ = state;
+  }
+
+ private:
+  S *mru_;
+};
+
+// VectorState but additionally has a flags data member (see
+// CacheState below). This class is used to cache FST elements with
+// the flags used to indicate what has been cached. Use HasStart()
+// HasFinal(), and HasArcs() to determine if cached and SetStart(),
+// SetFinal(), AddArc(), (or PushArc() and SetArcs()) to cache. Note you
+// must set the final weight even if the state is non-final to mark it as
+// cached. If the 'gc' option is 'false', cached items have the extent
+// of the FST - minimizing computation. If the 'gc' option is 'true',
+// garbage collection of states (not in use in an arc iterator) is
+// performed, in a rough approximation of LRU order, when 'gc_limit'
+// bytes is reached - controlling memory use. When 'gc_limit' is 0,
+// special optimizations apply - minimizing memory use.
+
+template <class S, class C = DefaultCacheStateAllocator<S> >
+class CacheBaseImpl : public VectorFstBaseImpl<S> {
+ public:
+  typedef S State;
+  typedef C Allocator;
+  typedef typename State::Arc Arc;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  using FstImpl<Arc>::Type;
+  using FstImpl<Arc>::Properties;
+  using FstImpl<Arc>::SetProperties;
+  using VectorFstBaseImpl<State>::NumStates;
+  using VectorFstBaseImpl<State>::AddState;
+  using VectorFstBaseImpl<State>::SetState;
+
+  explicit CacheBaseImpl(C *allocator = 0)
+      : cache_start_(false), nknown_states_(0), min_unexpanded_state_id_(0),
+        cache_first_state_id_(kNoStateId), cache_first_state_(0),
+        cache_gc_(FLAGS_fst_default_cache_gc),  cache_size_(0),
+        cache_limit_(FLAGS_fst_default_cache_gc_limit > kMinCacheLimit ||
+                     FLAGS_fst_default_cache_gc_limit == 0 ?
+                     FLAGS_fst_default_cache_gc_limit : kMinCacheLimit) {
+          allocator_ = allocator ? allocator : new C();
+        }
+
+  explicit CacheBaseImpl(const CacheOptions &opts, C *allocator = 0)
+      : cache_start_(false), nknown_states_(0),
+        min_unexpanded_state_id_(0), cache_first_state_id_(kNoStateId),
+        cache_first_state_(0), cache_gc_(opts.gc), cache_size_(0),
+        cache_limit_(opts.gc_limit > kMinCacheLimit || opts.gc_limit == 0 ?
+                     opts.gc_limit : kMinCacheLimit) {
+          allocator_ = allocator ? allocator : new C();
+        }
+
+  // Preserve gc parameters, but initially cache nothing.
+  CacheBaseImpl(const CacheBaseImpl &impl)
+    : cache_start_(false), nknown_states_(0),
+      min_unexpanded_state_id_(0), cache_first_state_id_(kNoStateId),
+      cache_first_state_(0), cache_gc_(impl.cache_gc_), cache_size_(0),
+      cache_limit_(impl.cache_limit_) {
+        allocator_ = new C();
+      }
+
+  ~CacheBaseImpl() {
+    allocator_->Free(cache_first_state_, cache_first_state_id_);
+    delete allocator_;
+  }
+
+  // Gets a state from its ID; state must exist.
+  const S *GetState(StateId s) const {
+    if (s == cache_first_state_id_)
+      return cache_first_state_;
+    else
+      return VectorFstBaseImpl<S>::GetState(s);
+  }
+
+  // Gets a state from its ID; state must exist.
+  S *GetState(StateId s) {
+    if (s == cache_first_state_id_)
+      return cache_first_state_;
+    else
+      return VectorFstBaseImpl<S>::GetState(s);
+  }
+
+  // Gets a state from its ID; return 0 if it doesn't exist.
+  const S *CheckState(StateId s) const {
+    if (s == cache_first_state_id_)
+      return cache_first_state_;
+    else if (s < NumStates())
+      return VectorFstBaseImpl<S>::GetState(s);
+    else
+      return 0;
+  }
+
+  // Gets a state from its ID; add it if necessary.
+  S *ExtendState(StateId s) {
+    if (s == cache_first_state_id_) {
+      return cache_first_state_;                   // Return 1st cached state
+    } else if (cache_limit_ == 0 && cache_first_state_id_ == kNoStateId) {
+      cache_first_state_id_ = s;                   // Remember 1st cached state
+      cache_first_state_ = allocator_->Allocate(s);
+      return cache_first_state_;
+    } else if (cache_first_state_id_ != kNoStateId &&
+               cache_first_state_->ref_count == 0) {
+      // With Default allocator, the Free and Allocate will reuse the same S*.
+      allocator_->Free(cache_first_state_, cache_first_state_id_);
+      cache_first_state_id_ = s;
+      cache_first_state_ = allocator_->Allocate(s);
+      return cache_first_state_;                   // Return 1st cached state
+    } else {
+      while (NumStates() <= s)                     // Add state to main cache
+        AddState(0);
+      if (!VectorFstBaseImpl<S>::GetState(s)) {
+        SetState(s, allocator_->Allocate(s));
+        if (cache_first_state_id_ != kNoStateId) {  // Forget 1st cached state
+          while (NumStates() <= cache_first_state_id_)
+            AddState(0);
+          SetState(cache_first_state_id_, cache_first_state_);
+          if (cache_gc_) {
+            cache_states_.push_back(cache_first_state_id_);
+            cache_size_ += sizeof(S) +
+                           cache_first_state_->arcs.capacity() * sizeof(Arc);
+          }
+          cache_limit_ = kMinCacheLimit;
+          cache_first_state_id_ = kNoStateId;
+          cache_first_state_ = 0;
+        }
+        if (cache_gc_) {
+          cache_states_.push_back(s);
+          cache_size_ += sizeof(S);
+          if (cache_size_ > cache_limit_)
+            GC(s, false);
+        }
+      }
+      S *state = VectorFstBaseImpl<S>::GetState(s);
+      return state;
+    }
+  }
+
+  void SetStart(StateId s) {
+    VectorFstBaseImpl<S>::SetStart(s);
+    cache_start_ = true;
+    if (s >= nknown_states_)
+      nknown_states_ = s + 1;
+  }
+
+  void SetFinal(StateId s, Weight w) {
+    S *state = ExtendState(s);
+    state->final = w;
+    state->flags |= kCacheFinal | kCacheRecent | kCacheModified;
+  }
+
+  // AddArc adds a single arc to state s and does incremental cache
+  // book-keeping.  For efficiency, prefer PushArc and SetArcs below
+  // when possible.
+  void AddArc(StateId s, const Arc &arc) {
+    S *state = ExtendState(s);
+    state->arcs.push_back(arc);
+    if (arc.ilabel == 0) {
+      ++state->niepsilons;
+    }
+    if (arc.olabel == 0) {
+      ++state->noepsilons;
+    }
+    const Arc *parc = state->arcs.empty() ? 0 : &(state->arcs.back());
+    SetProperties(AddArcProperties(Properties(), s, arc, parc));
+    state->flags |= kCacheModified;
+    if (cache_gc_ && s != cache_first_state_id_) {
+      cache_size_ += sizeof(Arc);
+      if (cache_size_ > cache_limit_)
+        GC(s, false);
+    }
+  }
+
+  // Adds a single arc to state s but delays cache book-keeping.
+  // SetArcs must be called when all PushArc calls at a state are
+  // complete.  Do not mix with calls to AddArc.
+  void PushArc(StateId s, const Arc &arc) {
+    S *state = ExtendState(s);
+    state->arcs.push_back(arc);
+  }
+
+  // Marks arcs of state s as cached and does cache book-keeping after all
+  // calls to PushArc have been completed.  Do not mix with calls to AddArc.
+  void SetArcs(StateId s) {
+    S *state = ExtendState(s);
+    vector<Arc> &arcs = state->arcs;
+    state->niepsilons = state->noepsilons = 0;
+    for (size_t a = 0; a < arcs.size(); ++a) {
+      const Arc &arc = arcs[a];
+      if (arc.nextstate >= nknown_states_)
+        nknown_states_ = arc.nextstate + 1;
+      if (arc.ilabel == 0)
+        ++state->niepsilons;
+      if (arc.olabel == 0)
+        ++state->noepsilons;
+    }
+    ExpandedState(s);
+    state->flags |= kCacheArcs | kCacheRecent | kCacheModified;
+    if (cache_gc_ && s != cache_first_state_id_) {
+      cache_size_ += arcs.capacity() * sizeof(Arc);
+      if (cache_size_ > cache_limit_)
+        GC(s, false);
+    }
+  };
+
+  void ReserveArcs(StateId s, size_t n) {
+    S *state = ExtendState(s);
+    state->arcs.reserve(n);
+  }
+
+  void DeleteArcs(StateId s, size_t n) {
+    S *state = ExtendState(s);
+    const vector<Arc> &arcs = GetState(s)->arcs;
+    for (size_t i = 0; i < n; ++i) {
+      size_t j = arcs.size() - i - 1;
+      if (arcs[j].ilabel == 0)
+        --GetState(s)->niepsilons;
+      if (arcs[j].olabel == 0)
+        --GetState(s)->noepsilons;
+    }
+    state->arcs.resize(arcs.size() - n);
+    SetProperties(DeleteArcsProperties(Properties()));
+    state->flags |= kCacheModified;
+  }
+
+  void DeleteArcs(StateId s) {
+    S *state = ExtendState(s);
+    state->niepsilons = 0;
+    state->noepsilons = 0;
+    state->arcs.clear();
+    SetProperties(DeleteArcsProperties(Properties()));
+    state->flags |= kCacheModified;
+  }
+
+  // Is the start state cached?
+  bool HasStart() const {
+    if (!cache_start_ && Properties(kError))
+      cache_start_ = true;
+    return cache_start_;
+  }
+
+  // Is the final weight of state s cached?
+  bool HasFinal(StateId s) const {
+    const S *state = CheckState(s);
+    if (state && state->flags & kCacheFinal) {
+      state->flags |= kCacheRecent;
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  // Are arcs of state s cached?
+  bool HasArcs(StateId s) const {
+    const S *state = CheckState(s);
+    if (state && state->flags & kCacheArcs) {
+      state->flags |= kCacheRecent;
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  Weight Final(StateId s) const {
+    const S *state = GetState(s);
+    return state->final;
+  }
+
+  size_t NumArcs(StateId s) const {
+    const S *state = GetState(s);
+    return state->arcs.size();
+  }
+
+  size_t NumInputEpsilons(StateId s) const {
+    const S *state = GetState(s);
+    return state->niepsilons;
+  }
+
+  size_t NumOutputEpsilons(StateId s) const {
+    const S *state = GetState(s);
+    return state->noepsilons;
+  }
+
+  // Provides information needed for generic arc iterator.
+  void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) const {
+    const S *state = GetState(s);
+    data->base = 0;
+    data->narcs = state->arcs.size();
+    data->arcs = data->narcs > 0 ? &(state->arcs[0]) : 0;
+    data->ref_count = &(state->ref_count);
+    ++(*data->ref_count);
+  }
+
+  // Number of known states.
+  StateId NumKnownStates() const { return nknown_states_; }
+
+  // Update number of known states taking in account the existence of state s.
+  void UpdateNumKnownStates(StateId s) {
+    if (s >= nknown_states_)
+      nknown_states_ = s + 1;
+  }
+
+  // Find the mininum never-expanded state Id
+  StateId MinUnexpandedState() const {
+    while (min_unexpanded_state_id_ < expanded_states_.size() &&
+          expanded_states_[min_unexpanded_state_id_])
+      ++min_unexpanded_state_id_;
+    return min_unexpanded_state_id_;
+  }
+
+  // Removes from cache_states_ and uncaches (not referenced-counted)
+  // states that have not been accessed since the last GC until
+  // cache_limit_/3 bytes are uncached.  If that fails to free enough,
+  // recurs uncaching recently visited states as well. If still
+  // unable to free enough memory, then widens cache_limit_.
+  void GC(StateId current, bool free_recent) {
+    if (!cache_gc_)
+      return;
+    VLOG(2) << "CacheImpl: Enter GC: object = " << Type() << "(" << this
+            << "), free recently cached = " << free_recent
+            << ", cache size = " << cache_size_
+            << ", cache limit = " << cache_limit_ << "\n";
+    typename list<StateId>::iterator siter = cache_states_.begin();
+
+    size_t cache_target = (2 * cache_limit_)/3 + 1;
+    while (siter != cache_states_.end()) {
+      StateId s = *siter;
+      S* state = VectorFstBaseImpl<S>::GetState(s);
+      if (cache_size_ > cache_target && state->ref_count == 0 &&
+          (free_recent || !(state->flags & kCacheRecent)) && s != current) {
+        cache_size_ -= sizeof(S) + state->arcs.capacity() * sizeof(Arc);
+        allocator_->Free(state, s);
+        SetState(s, 0);
+        cache_states_.erase(siter++);
+      } else {
+        state->flags &= ~kCacheRecent;
+        ++siter;
+      }
+    }
+    if (!free_recent && cache_size_ > cache_target) {
+      GC(current, true);
+    } else {
+      while (cache_size_ > cache_target) {
+        cache_limit_ *= 2;
+        cache_target *= 2;
+      }
+    }
+    VLOG(2) << "CacheImpl: Exit GC: object = " << Type() << "(" << this
+            << "), free recently cached = " << free_recent
+            << ", cache size = " << cache_size_
+            << ", cache limit = " << cache_limit_ << "\n";
+  }
+
+  void ExpandedState(StateId s) {
+    if (s < min_unexpanded_state_id_)
+      return;
+    while (expanded_states_.size() <= s)
+      expanded_states_.push_back(false);
+    expanded_states_[s] = true;
+  }
+
+  // Caching on/off switch, limit and size accessors.
+  bool GetCacheGc() const { return cache_gc_; }
+  size_t GetCacheLimit() const { return cache_limit_; }
+  size_t GetCacheSize() const { return cache_size_; }
+
+ private:
+  static const size_t kMinCacheLimit = 8096;  // Minimum (non-zero) cache limit
+  static const uint32 kCacheFinal =  0x0001;  // Final weight has been cached
+  static const uint32 kCacheArcs =   0x0002;  // Arcs have been cached
+  static const uint32 kCacheRecent = 0x0004;  // Mark as visited since GC
+
+ public:
+  static const uint32 kCacheModified = 0x0008;  // Mark state as modified
+  static const uint32 kCacheFlags = kCacheFinal | kCacheArcs | kCacheRecent
+                                    | kCacheModified;
+
+ protected:
+  C *allocator_;                             // used to allocate new states
+
+ private:
+  mutable bool cache_start_;                 // Is the start state cached?
+  StateId nknown_states_;                    // # of known states
+  vector<bool> expanded_states_;             // states that have been expanded
+  mutable StateId min_unexpanded_state_id_;  // minimum never-expanded state Id
+  StateId cache_first_state_id_;             // First cached state id
+  S *cache_first_state_;                     // First cached state
+  list<StateId> cache_states_;               // list of currently cached states
+  bool cache_gc_;                            // enable GC
+  size_t cache_size_;                        // # of bytes cached
+  size_t cache_limit_;                       // # of bytes allowed before GC
+
+  void operator=(const CacheBaseImpl<S> &impl);    // disallow
+};
+
+template <class S, class C> const uint32 CacheBaseImpl<S, C>::kCacheFinal;
+template <class S, class C> const uint32 CacheBaseImpl<S, C>::kCacheArcs;
+template <class S, class C> const uint32 CacheBaseImpl<S, C>::kCacheRecent;
+template <class S, class C> const uint32 CacheBaseImpl<S, C>::kCacheModified;
+template <class S, class C> const size_t CacheBaseImpl<S, C>::kMinCacheLimit;
+
+// Arcs implemented by an STL vector per state. Similar to VectorState
+// but adds flags and ref count to keep track of what has been cached.
+template <class A>
+struct CacheState {
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  CacheState() :  final(Weight::Zero()), flags(0), ref_count(0) {}
+
+  void Reset() {
+    flags = 0;
+    ref_count = 0;
+    arcs.resize(0);
+  }
+
+  Weight final;              // Final weight
+  vector<A> arcs;            // Arcs represenation
+  size_t niepsilons;         // # of input epsilons
+  size_t noepsilons;         // # of output epsilons
+  mutable uint32 flags;
+  mutable int ref_count;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(CacheState);
+};
+
+// A CacheBaseImpl with a commonly used CacheState.
+template <class A>
+class CacheImpl : public CacheBaseImpl< CacheState<A> > {
+ public:
+  typedef CacheState<A> State;
+
+  CacheImpl() {}
+
+  explicit CacheImpl(const CacheOptions &opts)
+      : CacheBaseImpl< CacheState<A> >(opts) {}
+
+  CacheImpl(const CacheImpl<State> &impl) : CacheBaseImpl<State>(impl) {}
+
+ private:
+  void operator=(const CacheImpl<State> &impl);    // disallow
+};
+
+
+// Use this to make a state iterator for a CacheBaseImpl-derived Fst,
+// which must have type 'State' defined.  Note this iterator only
+// returns those states reachable from the initial state, so consider
+// implementing a class-specific one.
+template <class F>
+class CacheStateIterator : public StateIteratorBase<typename F::Arc> {
+ public:
+  typedef typename F::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename F::State State;
+  typedef CacheBaseImpl<State> Impl;
+
+  CacheStateIterator(const F &fst, Impl *impl)
+      : fst_(fst), impl_(impl), s_(0) {}
+
+  bool Done() const {
+    if (s_ < impl_->NumKnownStates())
+      return false;
+    fst_.Start();  // force start state
+    if (s_ < impl_->NumKnownStates())
+      return false;
+    for (StateId u = impl_->MinUnexpandedState();
+         u < impl_->NumKnownStates();
+         u = impl_->MinUnexpandedState()) {
+      // force state expansion
+      ArcIterator<F> aiter(fst_, u);
+      aiter.SetFlags(kArcValueFlags, kArcValueFlags | kArcNoCache);
+      for (; !aiter.Done(); aiter.Next())
+        impl_->UpdateNumKnownStates(aiter.Value().nextstate);
+      impl_->ExpandedState(u);
+      if (s_ < impl_->NumKnownStates())
+        return false;
+    }
+    return true;
+  }
+
+  StateId Value() const { return s_; }
+
+  void Next() { ++s_; }
+
+  void Reset() { s_ = 0; }
+
+ private:
+  // This allows base class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual bool Done_() const { return Done(); }
+  virtual StateId Value_() const { return Value(); }
+  virtual void Next_() { Next(); }
+  virtual void Reset_() { Reset(); }
+
+  const F &fst_;
+  Impl *impl_;
+  StateId s_;
+};
+
+
+// Use this to make an arc iterator for a CacheBaseImpl-derived Fst,
+// which must have types 'Arc' and 'State' defined.
+template <class F,
+          class C = DefaultCacheStateAllocator<CacheState<typename F::Arc> > >
+class CacheArcIterator {
+ public:
+  typedef typename F::Arc Arc;
+  typedef typename F::State State;
+  typedef typename Arc::StateId StateId;
+  typedef CacheBaseImpl<State, C> Impl;
+
+  CacheArcIterator(Impl *impl, StateId s) : i_(0) {
+    state_ = impl->ExtendState(s);
+    ++state_->ref_count;
+  }
+
+  ~CacheArcIterator() { --state_->ref_count;  }
+
+  bool Done() const { return i_ >= state_->arcs.size(); }
+
+  const Arc& Value() const { return state_->arcs[i_]; }
+
+  void Next() { ++i_; }
+
+  size_t Position() const { return i_; }
+
+  void Reset() { i_ = 0; }
+
+  void Seek(size_t a) { i_ = a; }
+
+  uint32 Flags() const {
+    return kArcValueFlags;
+  }
+
+  void SetFlags(uint32 flags, uint32 mask) {}
+
+ private:
+  const State *state_;
+  size_t i_;
+
+  DISALLOW_COPY_AND_ASSIGN(CacheArcIterator);
+};
+
+// Use this to make a mutable arc iterator for a CacheBaseImpl-derived Fst,
+// which must have types 'Arc' and 'State' defined.
+template <class F,
+          class C = DefaultCacheStateAllocator<CacheState<typename F::Arc> > >
+class CacheMutableArcIterator
+    : public MutableArcIteratorBase<typename F::Arc> {
+ public:
+  typedef typename F::State State;
+  typedef typename F::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef CacheBaseImpl<State, C> Impl;
+
+  // You will need to call MutateCheck() in the constructor.
+  CacheMutableArcIterator(Impl *impl, StateId s) : i_(0), s_(s), impl_(impl) {
+    state_ = impl_->ExtendState(s_);
+    ++state_->ref_count;
+  };
+
+  ~CacheMutableArcIterator() {
+    --state_->ref_count;
+  }
+
+  bool Done() const { return i_ >= state_->arcs.size(); }
+
+  const Arc& Value() const { return state_->arcs[i_]; }
+
+  void Next() { ++i_; }
+
+  size_t Position() const { return i_; }
+
+  void Reset() { i_ = 0; }
+
+  void Seek(size_t a) { i_ = a; }
+
+  void SetValue(const Arc& arc) {
+    state_->flags |= CacheBaseImpl<State, C>::kCacheModified;
+    uint64 properties = impl_->Properties();
+    Arc& oarc = state_->arcs[i_];
+    if (oarc.ilabel != oarc.olabel)
+      properties &= ~kNotAcceptor;
+    if (oarc.ilabel == 0) {
+      --state_->niepsilons;
+      properties &= ~kIEpsilons;
+      if (oarc.olabel == 0)
+        properties &= ~kEpsilons;
+    }
+    if (oarc.olabel == 0) {
+      --state_->noepsilons;
+      properties &= ~kOEpsilons;
+    }
+    if (oarc.weight != Weight::Zero() && oarc.weight != Weight::One())
+      properties &= ~kWeighted;
+    oarc = arc;
+    if (arc.ilabel != arc.olabel) {
+      properties |= kNotAcceptor;
+      properties &= ~kAcceptor;
+    }
+    if (arc.ilabel == 0) {
+      ++state_->niepsilons;
+      properties |= kIEpsilons;
+      properties &= ~kNoIEpsilons;
+      if (arc.olabel == 0) {
+        properties |= kEpsilons;
+        properties &= ~kNoEpsilons;
+      }
+    }
+    if (arc.olabel == 0) {
+      ++state_->noepsilons;
+      properties |= kOEpsilons;
+      properties &= ~kNoOEpsilons;
+    }
+    if (arc.weight != Weight::Zero() && arc.weight != Weight::One()) {
+      properties |= kWeighted;
+      properties &= ~kUnweighted;
+    }
+    properties &= kSetArcProperties | kAcceptor | kNotAcceptor |
+        kEpsilons | kNoEpsilons | kIEpsilons | kNoIEpsilons |
+        kOEpsilons | kNoOEpsilons | kWeighted | kUnweighted;
+    impl_->SetProperties(properties);
+  }
+
+  uint32 Flags() const {
+    return kArcValueFlags;
+  }
+
+  void SetFlags(uint32 f, uint32 m) {}
+
+ private:
+  virtual bool Done_() const { return Done(); }
+  virtual const Arc& Value_() const { return Value(); }
+  virtual void Next_() { Next(); }
+  virtual size_t Position_() const { return Position(); }
+  virtual void Reset_() { Reset(); }
+  virtual void Seek_(size_t a) { Seek(a); }
+  virtual void SetValue_(const Arc &a) { SetValue(a); }
+  uint32 Flags_() const { return Flags(); }
+  void SetFlags_(uint32 f, uint32 m) { SetFlags(f, m); }
+
+  size_t i_;
+  StateId s_;
+  Impl *impl_;
+  State *state_;
+
+  DISALLOW_COPY_AND_ASSIGN(CacheMutableArcIterator);
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_CACHE_H__
diff --git a/src/include/fst/closure.h b/src/include/fst/closure.h
new file mode 100644
index 0000000..541562b
--- /dev/null
+++ b/src/include/fst/closure.h
@@ -0,0 +1,155 @@
+// closure.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Functions and classes to compute the concatenative closure of an Fst.
+
+#ifndef FST_LIB_CLOSURE_H__
+#define FST_LIB_CLOSURE_H__
+
+#include <vector>
+using std::vector;
+#include <algorithm>
+
+#include <fst/mutable-fst.h>
+#include <fst/rational.h>
+
+
+namespace fst {
+
+// Computes the concatenative closure. This version modifies its
+// MutableFst input. If FST transduces string x to y with weight a,
+// then the closure transduces x to y with weight a, xx to yy with
+// weight Times(a, a), xxx to yyy with with Times(Times(a, a), a),
+// etc. If closure_type == CLOSURE_STAR, then the empty string is
+// transduced to itself with weight Weight::One() as well.
+//
+// Complexity:
+// - Time: O(V)
+// - Space: O(V)
+// where V = # of states.
+template<class Arc>
+void Closure(MutableFst<Arc> *fst, ClosureType closure_type) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  uint64 props = fst->Properties(kFstProperties, false);
+  StateId start = fst->Start();
+  for (StateIterator< MutableFst<Arc> > siter(*fst);
+       !siter.Done();
+       siter.Next()) {
+    StateId s = siter.Value();
+    Weight final = fst->Final(s);
+    if (final != Weight::Zero())
+      fst->AddArc(s, Arc(0, 0, final, start));
+  }
+  if (closure_type == CLOSURE_STAR) {
+    fst->ReserveStates(fst->NumStates() + 1);
+    StateId nstart = fst->AddState();
+    fst->SetStart(nstart);
+    fst->SetFinal(nstart, Weight::One());
+    if (start != kNoLabel)
+      fst->AddArc(nstart, Arc(0, 0, Weight::One(), start));
+  }
+  fst->SetProperties(ClosureProperties(props, closure_type == CLOSURE_STAR),
+                     kFstProperties);
+}
+
+// Computes the concatenative closure. This version modifies its
+// RationalFst input.
+template<class Arc>
+void Closure(RationalFst<Arc> *fst, ClosureType closure_type) {
+  fst->GetImpl()->AddClosure(closure_type);
+}
+
+
+struct ClosureFstOptions : RationalFstOptions {
+  ClosureType type;
+
+  ClosureFstOptions(const RationalFstOptions &opts, ClosureType t)
+      : RationalFstOptions(opts), type(t) {}
+  explicit ClosureFstOptions(ClosureType t) : type(t) {}
+  ClosureFstOptions() : type(CLOSURE_STAR) {}
+};
+
+
+// Computes the concatenative closure. This version is a delayed
+// Fst. If FST transduces string x to y with weight a, then the
+// closure transduces x to y with weight a, xx to yy with weight
+// Times(a, a), xxx to yyy with weight Times(Times(a, a), a), etc. If
+// closure_type == CLOSURE_STAR, then The empty string is transduced
+// to itself with weight Weight::One() as well.
+//
+// Complexity:
+// - Time: O(v)
+// - Space: O(v)
+// where v = # of states visited. Constant time and space to visit an
+// input state or arc is assumed and exclusive of caching.
+template <class A>
+class ClosureFst : public RationalFst<A> {
+ public:
+  using ImplToFst< RationalFstImpl<A> >::GetImpl;
+
+  typedef A Arc;
+
+  ClosureFst(const Fst<A> &fst, ClosureType closure_type) {
+    GetImpl()->InitClosure(fst, closure_type);
+  }
+
+  ClosureFst(const Fst<A> &fst, const ClosureFstOptions &opts)
+      : RationalFst<A>(opts) {
+    GetImpl()->InitClosure(fst, opts.type);
+  }
+
+  // See Fst<>::Copy() for doc.
+  ClosureFst(const ClosureFst<A> &fst, bool safe = false)
+      : RationalFst<A>(fst, safe) {}
+
+  // Get a copy of this ClosureFst. See Fst<>::Copy() for further doc.
+  virtual ClosureFst<A> *Copy(bool safe = false) const {
+    return new ClosureFst<A>(*this, safe);
+  }
+};
+
+
+// Specialization for ClosureFst.
+template <class A>
+class StateIterator< ClosureFst<A> > : public StateIterator< RationalFst<A> > {
+ public:
+  explicit StateIterator(const ClosureFst<A> &fst)
+      : StateIterator< RationalFst<A> >(fst) {}
+};
+
+
+// Specialization for ClosureFst.
+template <class A>
+class ArcIterator< ClosureFst<A> > : public ArcIterator< RationalFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const ClosureFst<A> &fst, StateId s)
+      : ArcIterator< RationalFst<A> >(fst, s) {}
+};
+
+
+// Useful alias when using StdArc.
+typedef ClosureFst<StdArc> StdClosureFst;
+
+}  // namespace fst
+
+#endif  // FST_LIB_CLOSURE_H__
diff --git a/src/include/fst/compact-fst.h b/src/include/fst/compact-fst.h
new file mode 100644
index 0000000..efa567a
--- /dev/null
+++ b/src/include/fst/compact-fst.h
@@ -0,0 +1,1307 @@
+// compact-fst.h
+
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// FST Class for memory-efficient representation of common types of
+// FSTs: linear automata, acceptors, unweighted FSTs, ...
+
+#ifndef FST_LIB_COMPACT_FST_H__
+#define FST_LIB_COMPACT_FST_H__
+
+#include <iterator>
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+#include <fst/expanded-fst.h>
+#include <fst/fst-decl.h>  // For optional argument declarations
+#include <fst/matcher.h>
+#include <fst/test-properties.h>
+#include <fst/util.h>
+
+
+namespace fst {
+
+struct CompactFstOptions : public CacheOptions {
+  // CompactFst default caching behaviour is to do no caching. Most
+  // compactors are cheap and therefore we save memory by not doing
+  // caching.
+  CompactFstOptions() : CacheOptions(true, 0) {}
+  CompactFstOptions(const CacheOptions &opts) : CacheOptions(opts) {}
+};
+
+// Compactor Interface - class determinies how arcs and final weights
+// are compacted and expanded.
+//
+// Final weights are treated as transitions to the superfinal state,
+// i.e. ilabel = olabel = kNoLabel and nextstate = kNoStateId.
+//
+// There are two types of compactors:
+//
+// * Fixed out-degree compactors: 'compactor.Size()' returns a
+// positive integer 's'. An FST can be compacted by this compactor
+// only if each state has exactly 's' outgoing transitions (counting a
+// non-Zero() final weight as a transition). A typical example is a
+// compactor for string FSTs, i.e. 's == 1'.
+//
+// * Variable out-degree compactors: 'compactor.Size() == -1'. There
+// are no out-degree restrictions for these compactors.
+//
+//
+// class Compactor {
+//  public:
+//   // Element is the type of the compacted transitions.
+//   typedef ... Element;
+//   // Return the compacted representation of a transition 'arc'
+//   // at a state 's'.
+//   Element Compact(StateId s, const Arc &arc);
+//   // Return the transition at state 's' represented by the compacted
+//   // transition 'e'.
+//   Arc Expand(StateId s, const Element &e);
+//   // Return -1 for variable out-degree compactors, and the mandatory
+//   // out-degree otherwise.
+//   ssize_t Size();
+//   // Test whether 'fst' can be compacted by this compactor.
+//   bool Compatible(const Fst<A> &fst);
+//   // Return the properties that are always true for an fst
+//   // compacted using this compactor
+//   uint64 Properties();
+//   // Return a string identifying the type of compactor.
+//   static const string &Type();
+//   // Write a compactor to a file.
+//   bool Write(ostream &strm);
+//   // Read a compactor from a file.
+//   static Compactor *Read(istream &strm);
+//   // Default constructor (optional, see comment below).
+//   Compactor();
+// };
+//
+// The default constructor is only required for FST_REGISTER to work
+// (i.e. enabling Convert() and the command-line utilities to work
+// with this new compactor). However, a default constructor always
+// needs to be specify for this code to compile, but one can have it
+// simply raised an error when called:
+//
+// Compactor::Compactor() {
+//   FSTERROR() << "Compactor: no default constructor";
+// }
+
+
+// Implementation data for Compact Fst, which can shared between otherwise
+// independent copies.
+//
+// The implementation contains two arrays: 'states_' and 'compacts_'.
+//
+// For fixed out-degree compactors, the 'states_' array is unallocated.
+// The 'compacts_' contains the compacted transitions. Its size is
+// 'ncompacts_'. The outgoing transitions at a given state are stored
+// consecutively. For a given state 's', its 'compactor.Size()' outgoing
+// transitions (including superfinal transition when 's' is final), are
+// stored in position ['s*compactor.Size()', '(s+1)*compactor_.Size()').
+//
+// For variable out-degree compactors, the states_ array has size
+// 'nstates_ + 1' and contains pointers to positions into 'compacts_'.
+// For a given state 's', the compacted transitions of 's' are
+// stored in positions [ 'states_[s]', 'states_[s + 1]' ) in 'compacts_'.
+// By convention, 'states_[nstates_] == ncompacts_'.
+//
+// In both cases, the superfinal transitons (when 's' is final, i.e.
+// 'Final(s) != Weight::Zero()') is stored first.
+//
+// The unsigned type U is used to represent indices into the compacts_
+// array.
+template <class E, class U>
+class CompactFstData {
+  public:
+  typedef E CompactElement;
+  typedef U Unsigned;
+
+  CompactFstData()
+      : states_(0),
+        compacts_(0),
+        nstates_(0),
+        ncompacts_(0),
+        narcs_(0),
+        start_(kNoStateId),
+        error_(false) {}
+
+  template <class A, class Compactor>
+  CompactFstData(const Fst<A> &fst, const Compactor &compactor);
+
+  template <class Iterator, class Compactor>
+  CompactFstData(const Iterator &begin, const Iterator &end,
+                 const Compactor &compactor);
+
+  ~CompactFstData() {
+    delete[] states_;
+    delete[] compacts_;
+  }
+
+  template <class Compactor>
+  static CompactFstData<E, U> *Read(istream &strm,
+                                       const FstReadOptions &opts,
+                                       const FstHeader &hdr,
+                                       const Compactor &compactor);
+
+  bool Write(ostream &strm, const FstWriteOptions &opts) const;
+
+  Unsigned States(ssize_t i) const { return states_[i]; }
+  const CompactElement &Compacts(size_t i) const { return compacts_[i]; }
+  size_t NumStates() const { return nstates_; }
+  size_t NumCompacts() const { return ncompacts_; }
+  size_t NumArcs() const { return narcs_; }
+  ssize_t Start() const { return start_; }
+
+  int RefCount() const { return ref_count_.count(); }
+  int IncrRefCount() { return ref_count_.Incr(); }
+  int DecrRefCount() { return ref_count_.Decr(); }
+
+  bool Error() const { return error_; }
+
+ private:
+  // Byte alignment for states and arcs in file format (version 1 only)
+  static const int kFileAlign = 16;
+
+  Unsigned *states_;
+  CompactElement *compacts_;
+  size_t nstates_;
+  size_t ncompacts_;
+  size_t narcs_;
+  ssize_t start_;
+  RefCounter ref_count_;
+  bool error_;
+};
+
+template <class E, class U>
+const int CompactFstData<E, U>::kFileAlign;
+
+
+template <class E, class U>
+template <class A, class C>
+CompactFstData<E, U>::CompactFstData(const Fst<A> &fst, const C &compactor)
+    : states_(0),
+      compacts_(0),
+      nstates_(0),
+      ncompacts_(0),
+      narcs_(0),
+      start_(kNoStateId),
+      error_(false) {
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+  start_ = fst.Start();
+  // Count # of states and arcs.
+  StateId nfinals = 0;
+  for (StateIterator< Fst<A> > siter(fst);
+       !siter.Done();
+       siter.Next()) {
+    ++nstates_;
+    StateId s = siter.Value();
+    for (ArcIterator< Fst<A> > aiter(fst, s);
+         !aiter.Done();
+         aiter.Next())
+      ++narcs_;
+    if (fst.Final(s) != Weight::Zero()) ++nfinals;
+  }
+  if (compactor.Size() == -1) {
+    states_ = new Unsigned[nstates_ + 1];
+    ncompacts_ = narcs_ + nfinals;
+    compacts_ = new CompactElement[ncompacts_];
+    states_[nstates_] = ncompacts_;
+  } else {
+    states_ = 0;
+    ncompacts_ = nstates_ * compactor.Size();
+    if ((narcs_ + nfinals) != ncompacts_) {
+      FSTERROR() << "CompactFstData: compactor incompatible with fst";
+      error_ = true;
+      return;
+    }
+    compacts_ = new CompactElement[ncompacts_];
+  }
+  size_t pos = 0, fpos = 0;
+  for (StateId s = 0; s < nstates_; ++s) {
+    fpos = pos;
+    if (compactor.Size() == -1)
+      states_[s] = pos;
+    if (fst.Final(s) != Weight::Zero())
+      compacts_[pos++] = compactor.Compact(s, A(kNoLabel, kNoLabel,
+                                                fst.Final(s), kNoStateId));
+    for (ArcIterator< Fst<A> > aiter(fst, s);
+         !aiter.Done();
+         aiter.Next()) {
+      compacts_[pos++] = compactor.Compact(s, aiter.Value());
+    }
+    if ((compactor.Size() != -1) && ((pos - fpos) != compactor.Size())) {
+      FSTERROR() << "CompactFstData: compactor incompatible with fst";
+      error_ = true;
+      return;
+    }
+  }
+  if (pos != ncompacts_) {
+    FSTERROR() << "CompactFstData: compactor incompatible with fst";
+    error_ = true;
+    return;
+  }
+}
+
+template <class E, class U>
+template <class Iterator, class C>
+CompactFstData<E, U>::CompactFstData(const Iterator &begin,
+                                     const Iterator &end,
+                                     const C &compactor)
+    : states_(0),
+      compacts_(0),
+      nstates_(0),
+      ncompacts_(0),
+      narcs_(0),
+      start_(kNoStateId),
+      error_(false) {
+  typedef typename C::Arc Arc;
+  typedef typename Arc::Weight Weight;
+  if (compactor.Size() != -1) {
+    ncompacts_ = distance(begin, end);
+    if (compactor.Size() == 1) {
+      // For strings, allow implicit final weight.
+      // Empty input is the empty string.
+      if (ncompacts_ == 0) {
+        ++ncompacts_;
+      } else {
+        Arc arc = compactor.Expand(ncompacts_ - 1,
+                                      *(begin + (ncompacts_ - 1)));
+        if (arc.ilabel != kNoLabel)
+          ++ncompacts_;
+      }
+    }
+    if (ncompacts_ % compactor.Size()) {
+      FSTERROR() << "CompactFstData: size of input container incompatible"
+                 << " with compactor";
+      error_ = true;
+      return;
+    }
+    if (ncompacts_ == 0)
+      return;
+    start_ = 0;
+    nstates_ = ncompacts_ / compactor.Size();
+    compacts_ = new CompactElement[ncompacts_];
+    size_t i = 0;
+    Iterator it = begin;
+    for(; it != end; ++it, ++i){
+      compacts_[i] = *it;
+      if (compactor.Expand(i, *it).ilabel != kNoLabel)
+        ++narcs_;
+    }
+    if (i < ncompacts_)
+      compacts_[i] = compactor.Compact(i, Arc(kNoLabel, kNoLabel,
+                                              Weight::One(), kNoStateId));
+  } else {
+    if (distance(begin, end) == 0)
+      return;
+    // Count # of states, arcs and compacts.
+    Iterator it = begin;
+    for(size_t i = 0; it != end; ++it, ++i) {
+      Arc arc = compactor.Expand(i, *it);
+      if (arc.ilabel != kNoLabel) {
+        ++narcs_;
+        ++ncompacts_;
+      } else {
+        ++nstates_;
+        if (arc.weight != Weight::Zero())
+          ++ncompacts_;
+      }
+    }
+    start_ = 0;
+    compacts_ = new CompactElement[ncompacts_];
+    states_ = new Unsigned[nstates_ + 1];
+    states_[nstates_] = ncompacts_;
+    size_t i = 0, s = 0;
+    for(it = begin; it != end; ++it) {
+      Arc arc = compactor.Expand(i, *it);
+      if (arc.ilabel != kNoLabel) {
+        compacts_[i++] = *it;
+      } else {
+        states_[s++] = i;
+        if (arc.weight != Weight::Zero())
+          compacts_[i++] = *it;
+      }
+    }
+    if ((s != nstates_) || (i != ncompacts_)) {
+      FSTERROR() << "CompactFstData: ill-formed input container";
+      error_ = true;
+      return;
+    }
+  }
+}
+
+template <class E, class U>
+template <class C>
+CompactFstData<E, U> *CompactFstData<E, U>::Read(
+    istream &strm,
+    const FstReadOptions &opts,
+    const FstHeader &hdr,
+    const C &compactor) {
+  CompactFstData<E, U> *data = new CompactFstData<E, U>();
+  data->start_ = hdr.Start();
+  data->nstates_ = hdr.NumStates();
+  data->narcs_ = hdr.NumArcs();
+
+  if (compactor.Size() == -1) {
+    data->states_ = new Unsigned[data->nstates_ + 1];
+    if ((hdr.GetFlags() & FstHeader::IS_ALIGNED) &&
+        !AlignInput(strm, kFileAlign)) {
+      LOG(ERROR) << "CompactFst::Read: Alignment failed: " << opts.source;
+      delete data;
+      return 0;
+    }
+    // TODO: memory map this
+    size_t b = (data->nstates_ + 1) * sizeof(Unsigned);
+    strm.read(reinterpret_cast<char *>(data->states_), b);
+    if (!strm) {
+      LOG(ERROR) << "CompactFst::Read: Read failed: " << opts.source;
+      delete data;
+      return 0;
+    }
+  } else {
+    data->states_ = 0;
+  }
+  data->ncompacts_ = compactor.Size() == -1
+      ? data->states_[data->nstates_]
+      : data->nstates_ * compactor.Size();
+  data->compacts_ = new CompactElement[data->ncompacts_];
+  // TODO: memory map this
+  size_t b = data->ncompacts_ * sizeof(CompactElement);
+  if ((hdr.GetFlags() & FstHeader::IS_ALIGNED) &&
+      !AlignInput(strm, kFileAlign)) {
+    LOG(ERROR) << "CompactFst::Read: Alignment failed: " << opts.source;
+    delete data;
+    return 0;
+  }
+  strm.read(reinterpret_cast<char *>(data->compacts_), b);
+  if (!strm) {
+    LOG(ERROR) << "CompactFst::Read: Read failed: " << opts.source;
+    delete data;
+    return 0;
+  }
+  return data;
+}
+
+template<class E, class U>
+bool CompactFstData<E, U>::Write(ostream &strm,
+                                 const FstWriteOptions &opts) const {
+  if (states_) {
+    if (opts.align && !AlignOutput(strm, kFileAlign)) {
+      LOG(ERROR) << "CompactFst::Write: Alignment failed: " << opts.source;
+      return false;
+    }
+    strm.write(reinterpret_cast<char *>(states_),
+               (nstates_ + 1) * sizeof(Unsigned));
+  }
+  if (opts.align && !AlignOutput(strm, kFileAlign)) {
+    LOG(ERROR) << "CompactFst::Write: Alignment failed: " << opts.source;
+    return false;
+  }
+  strm.write(reinterpret_cast<char *>(compacts_),
+             ncompacts_ * sizeof(CompactElement));
+
+  strm.flush();
+  if (!strm) {
+    LOG(ERROR) << "CompactFst::Write: Write failed: " << opts.source;
+    return false;
+  }
+  return true;
+}
+
+template <class A, class C, class U> class CompactFst;
+template <class F, class G> void Cast(const F &, G *);
+
+// Implementation class for CompactFst, which contains CompactFstData
+// and Fst cache.
+template <class A, class C, class U>
+class CompactFstImpl : public CacheImpl<A> {
+ public:
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::Properties;
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+  using FstImpl<A>::WriteHeader;
+
+  using CacheImpl<A>::PushArc;
+  using CacheImpl<A>::HasArcs;
+  using CacheImpl<A>::HasFinal;
+  using CacheImpl<A>::HasStart;
+  using CacheImpl<A>::SetArcs;
+  using CacheImpl<A>::SetFinal;
+  using CacheImpl<A>::SetStart;
+
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef C Compactor;
+  typedef typename C::Element CompactElement;
+  typedef U Unsigned;
+
+  CompactFstImpl()
+      :  CacheImpl<A>(CompactFstOptions()),
+         compactor_(0),
+         own_compactor_(false),
+         data_(0) {
+    string type = "compact";
+    if (sizeof(U) != sizeof(uint32)) {
+      string size;
+      Int64ToStr(8 * sizeof(U), &size);
+      type += size;
+    }
+    type += "_";
+    type += C::Type();
+    SetType(type);
+    SetProperties(kNullProperties | kStaticProperties);
+  }
+
+  CompactFstImpl(const Fst<Arc> &fst, const C &compactor,
+                 const CompactFstOptions &opts)
+      : CacheImpl<A>(opts),
+        compactor_(new C(compactor)),
+        own_compactor_(true),
+        data_(0) {
+    Init(fst);
+  }
+
+  CompactFstImpl(const Fst<Arc> &fst, C *compactor,
+                 const CompactFstOptions &opts)
+      : CacheImpl<A>(opts),
+        compactor_(compactor),
+        own_compactor_(false),
+        data_(0) {
+    Init(fst);
+  }
+
+  template <class Iterator>
+  CompactFstImpl(const Iterator &b, const Iterator &e, const C &compactor,
+                 const CompactFstOptions &opts)
+      : CacheImpl<A>(opts),
+        compactor_(new C(compactor)),
+        own_compactor_(true),
+        data_(0) {
+    Init(b, e);
+  }
+
+  template <class Iterator>
+  CompactFstImpl(const Iterator &b, const Iterator &e, C *compactor,
+                 const CompactFstOptions &opts)
+      : CacheImpl<A>(opts),
+        compactor_(compactor),
+        own_compactor_(false),
+        data_(0) {
+    Init(b, e);
+  }
+
+  CompactFstImpl(const CompactFstImpl<A, C, U> &impl)
+      : CacheImpl<A>(impl),
+        compactor_(new C(*impl.compactor_)),
+        own_compactor_(true),
+        data_(impl.data_) {
+    if (data_)
+      data_->IncrRefCount();
+    SetType(impl.Type());
+    SetProperties(impl.Properties());
+    SetInputSymbols(impl.InputSymbols());
+    SetOutputSymbols(impl.OutputSymbols());
+  }
+
+  ~CompactFstImpl(){
+    if (own_compactor_)
+      delete compactor_;
+    if (data_ && !data_->DecrRefCount())
+      delete data_;
+  }
+
+  StateId Start() {
+    if (!HasStart()) {
+      SetStart(data_->Start());
+    }
+    return CacheImpl<A>::Start();
+  }
+
+  Weight Final(StateId s) {
+    if (!HasFinal(s)) {
+      Arc arc(kNoLabel, kNoLabel, Weight::Zero(), kNoStateId);
+      if ((compactor_->Size() != -1) ||
+          (data_->States(s) != data_->States(s + 1)))
+        arc = ComputeArc(s,
+                         compactor_->Size() == -1
+                         ? data_->States(s)
+                         : s * compactor_->Size());
+      SetFinal(s, arc.ilabel == kNoLabel ? arc.weight : Weight::Zero());
+    }
+    return CacheImpl<A>::Final(s);
+  }
+
+  StateId NumStates() const {
+    if (Properties(kError)) return 0;
+    return data_->NumStates();
+  }
+
+  size_t NumArcs(StateId s) {
+    if (HasArcs(s))
+      return CacheImpl<A>::NumArcs(s);
+    Unsigned i, num_arcs;
+    if (compactor_->Size() == -1) {
+      i = data_->States(s);
+      num_arcs = data_->States(s + 1) - i;
+    } else {
+      i =  s * compactor_->Size();
+      num_arcs = compactor_->Size();
+    }
+    if (num_arcs > 0) {
+      const A &arc = ComputeArc(s, i, kArcILabelValue);
+      if (arc.ilabel == kNoStateId) {
+        --num_arcs;
+      }
+    }
+    return num_arcs;
+  }
+
+  size_t NumInputEpsilons(StateId s) {
+    if (!HasArcs(s) && !Properties(kILabelSorted))
+      Expand(s);
+    if (HasArcs(s))
+      return CacheImpl<A>::NumInputEpsilons(s);
+    return CountEpsilons(s, false);
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    if (!HasArcs(s) && !Properties(kOLabelSorted))
+      Expand(s);
+    if (HasArcs(s))
+      return CacheImpl<A>::NumOutputEpsilons(s);
+    return CountEpsilons(s, true);
+  }
+
+  size_t CountEpsilons(StateId s, bool output_epsilons) {
+    size_t begin =  compactor_->Size() == -1 ?
+        data_->States(s) : s * compactor_->Size();
+    size_t end = compactor_->Size() == -1 ?
+        data_->States(s + 1) : (s + 1) * compactor_->Size();
+    size_t num_eps = 0;
+    for (size_t i = begin; i < end; ++i) {
+      const A &arc = ComputeArc(
+          s, i, output_epsilons ? kArcOLabelValue : kArcILabelValue);
+      const typename A::Label &label =
+          (output_epsilons ? arc.olabel : arc.ilabel);
+      if (label == kNoLabel)
+        continue;
+      else if (label > 0)
+        break;
+      ++num_eps;
+    }
+    return num_eps;
+  }
+
+  static CompactFstImpl<A, C, U> *Read(istream &strm,
+                                       const FstReadOptions &opts) {
+    CompactFstImpl<A, C, U> *impl = new CompactFstImpl<A, C, U>();
+    FstHeader hdr;
+    if (!impl->ReadHeader(strm, opts, kMinFileVersion, &hdr)) {
+      delete impl;
+      return 0;
+    }
+
+    // Ensures compatibility
+    if (hdr.Version() == kAlignedFileVersion)
+      hdr.SetFlags(hdr.GetFlags() | FstHeader::IS_ALIGNED);
+
+    impl->compactor_ = C::Read(strm);
+    if (!impl->compactor_) {
+      delete impl;
+      return 0;
+    }
+    impl->own_compactor_ = true;
+    impl->data_ = CompactFstData<CompactElement, U>::Read(strm, opts, hdr,
+                                                          *impl->compactor_);
+    if (!impl->data_) {
+      delete impl;
+      return 0;
+    }
+    return impl;
+  }
+
+  bool Write(ostream &strm, const FstWriteOptions &opts) const {
+    FstHeader hdr;
+    hdr.SetStart(data_->Start());
+    hdr.SetNumStates(data_->NumStates());
+    hdr.SetNumArcs(data_->NumArcs());
+
+    // Ensures compatibility
+    int file_version = opts.align ? kAlignedFileVersion : kFileVersion;
+    WriteHeader(strm, opts, file_version, &hdr);
+
+    compactor_->Write(strm);
+    return data_->Write(strm, opts);
+  }
+
+  // Provide information needed for generic state iterator
+  void InitStateIterator(StateIteratorData<A> *data) const {
+    data->base = 0;
+    data->nstates = data_->NumStates();
+  }
+
+  void InitArcIterator(StateId s, ArcIteratorData<A> *data) {
+    if (!HasArcs(s))
+      Expand(s);
+    CacheImpl<A>::InitArcIterator(s, data);
+  }
+
+  Arc ComputeArc(StateId s, Unsigned i, uint32 f = kArcValueFlags) const {
+    return compactor_->Expand(s, data_->Compacts(i), f);
+  }
+
+  void Expand(StateId s) {
+    size_t begin =  compactor_->Size() == -1 ?
+        data_->States(s) : s * compactor_->Size();
+    size_t end = compactor_->Size() == -1 ?
+        data_->States(s + 1) : (s + 1) * compactor_->Size();
+    for (size_t i = begin; i < end; ++i) {
+      const Arc &arc = ComputeArc(s, i);
+      if (arc.ilabel == kNoLabel) continue;
+      PushArc(s, arc);
+    }
+    SetArcs(s);
+  }
+
+  template <class Iterator>
+  void SetCompactElements(const Iterator &b, const Iterator &e) {
+    if (data_ && !data_->DecrRefCount())
+      delete data_;
+    data_ = new CompactFstData<CompactElement, U>(b, e, *compactor_);
+  }
+
+  C *GetCompactor() const { return compactor_; }
+  CompactFstData<CompactElement, U> *Data() const { return data_; }
+
+ protected:
+  template <class B, class D>
+  explicit CompactFstImpl(const CompactFstImpl<B, D, U> &impl)
+      : CacheImpl<A>(CacheOptions(impl.GetCacheGc(), impl.GetCacheLimit())),
+        compactor_(new C(*impl.GetCompactor())),
+        own_compactor_(true),
+        data_(impl.Data()) {
+    if (data_)
+      data_->IncrRefCount();
+    SetType(impl.Type());
+    SetProperties(impl.Properties());
+    SetInputSymbols(impl.InputSymbols());
+    SetOutputSymbols(impl.OutputSymbols());
+  }
+
+ private:
+  void Init(const Fst<Arc> &fst) {
+    string type = "compact";
+    if (sizeof(U) != sizeof(uint32)) {
+      string size;
+      Int64ToStr(8 * sizeof(U), &size);
+      type += size;
+    }
+    type += "_";
+    type += compactor_->Type();
+    SetType(type);
+    SetInputSymbols(fst.InputSymbols());
+    SetOutputSymbols(fst.OutputSymbols());
+    data_ = new CompactFstData<CompactElement, U>(fst, *compactor_);
+    if (data_->Error())
+      SetProperties(kError, kError);
+    uint64 copy_properties = fst.Properties(kCopyProperties, true);
+    if ((copy_properties & kError) || !compactor_->Compatible(fst)) {
+      FSTERROR() << "CompactFstImpl: input fst incompatible with compactor";
+      SetProperties(kError, kError);
+      return;
+    }
+    SetProperties(copy_properties | kStaticProperties);
+  }
+
+  template <class Iterator>
+  void Init(const Iterator &b, const Iterator &e) {
+    string type = "compact";
+    if (sizeof(U) != sizeof(uint32)) {
+      string size;
+      Int64ToStr(8 * sizeof(U), &size);
+      type += size;
+    }
+    type += "_";
+    type += compactor_->Type();
+    SetType(type);
+    SetProperties(kStaticProperties | compactor_->Properties());
+    data_ = new CompactFstData<CompactElement, U>(b, e, *compactor_);
+    if (data_->Error())
+      SetProperties(kError, kError);
+  }
+
+  // Properties always true of this Fst class
+  static const uint64 kStaticProperties = kExpanded;
+  // Current unaligned file format version
+  static const int kFileVersion = 2;
+  // Current aligned file format version
+  static const int kAlignedFileVersion = 1;
+  // Minimum file format version supported
+  static const int kMinFileVersion = 1;
+
+  C *compactor_;
+  bool own_compactor_;
+  CompactFstData<CompactElement, U> *data_;
+};
+
+template <class A, class C, class U>
+const uint64 CompactFstImpl<A, C, U>::kStaticProperties;
+template <class A, class C, class U>
+const int CompactFstImpl<A, C, U>::kFileVersion;
+template <class A, class C, class U>
+const int CompactFstImpl<A, C, U>::kAlignedFileVersion;
+template <class A, class C, class U>
+const int CompactFstImpl<A, C, U>::kMinFileVersion;
+
+
+// CompactFst.  This class attaches interface to implementation and
+// handles reference counting, delegating most methods to
+// ImplToExpandedFst. The unsigned type U is used to represent indices
+// into the compact arc array (uint32 by default, declared in
+// fst-decl.h).
+template <class A, class C, class U>
+class CompactFst : public ImplToExpandedFst< CompactFstImpl<A, C, U> > {
+ public:
+  friend class StateIterator< CompactFst<A, C, U> >;
+  friend class ArcIterator< CompactFst<A, C, U> >;
+  template <class F, class G> void friend Cast(const F &, G *);
+
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef CompactFstImpl<A, C, U> Impl;
+  typedef CacheState<A> State;
+  typedef U Unsigned;
+
+  CompactFst() : ImplToExpandedFst<Impl>(new Impl()) {}
+
+  explicit CompactFst(const Fst<A> &fst, const C &compactor = C(),
+                      const CompactFstOptions &opts = CompactFstOptions())
+      : ImplToExpandedFst<Impl>(new Impl(fst, compactor, opts)) {}
+
+  CompactFst(const Fst<A> &fst, C *compactor,
+             const CompactFstOptions &opts = CompactFstOptions())
+      : ImplToExpandedFst<Impl>(new Impl(fst, compactor, opts)) {}
+
+  // The following 2 constructors take as input two iterators delimiting
+  // a set of (already) compacted transitions, starting with the
+  // transitions out of the initial state. The format of the input
+  // differs for fixed out-degree and variable out-degree compactors.
+  //
+  // - For fixed out-degree compactors, the final weight (encoded as a
+  // compacted transition) needs to be given only for final
+  // states. All strings (compactor of size 1) will be assume to be
+  // terminated by a final state even when the final state is not
+  // implicitely given.
+  //
+  // - For variable out-degree compactors, the final weight (encoded
+  // as a compacted transition) needs to be given for all states and
+  // must appeared first in the list (for state s, final weight of s,
+  // followed by outgoing transitons in s).
+  //
+  // These 2 constructors allows the direct construction of a CompactFst
+  // without first creating a more memory hungry 'regular' FST. This
+  // is useful when memory usage is severely constrained.
+  template <class Iterator>
+  explicit CompactFst(const Iterator &begin, const Iterator &end,
+                      const C &compactor = C(),
+                      const CompactFstOptions &opts = CompactFstOptions())
+      : ImplToExpandedFst<Impl>(new Impl(begin, end, compactor, opts)) {}
+
+  template <class Iterator>
+  CompactFst(const Iterator &begin, const Iterator &end,
+             C *compactor, const CompactFstOptions &opts = CompactFstOptions())
+      : ImplToExpandedFst<Impl>(new Impl(begin, end, compactor, opts)) {}
+
+  // See Fst<>::Copy() for doc.
+  CompactFst(const CompactFst<A, C, U> &fst, bool safe = false)
+      : ImplToExpandedFst<Impl>(fst, safe) {}
+
+  // Get a copy of this CompactFst. See Fst<>::Copy() for further doc.
+  virtual CompactFst<A, C, U> *Copy(bool safe = false) const {
+    return new CompactFst<A, C, U>(*this, safe);
+  }
+
+  // Read a CompactFst from an input stream; return NULL on error
+  static CompactFst<A, C, U> *Read(istream &strm, const FstReadOptions &opts) {
+    Impl* impl = Impl::Read(strm, opts);
+    return impl ? new CompactFst<A, C, U>(impl) : 0;
+  }
+
+  // Read a CompactFst from a file; return NULL on error
+  // Empty filename reads from standard input
+  static CompactFst<A, C, U> *Read(const string &filename) {
+    Impl* impl = ImplToExpandedFst<Impl>::Read(filename);
+    return impl ? new CompactFst<A, C, U>(impl) : 0;
+  }
+
+  virtual bool Write(ostream &strm, const FstWriteOptions &opts) const {
+    return GetImpl()->Write(strm, opts);
+  }
+
+  virtual bool Write(const string &filename) const {
+    return Fst<A>::WriteFile(filename);
+  }
+
+  virtual void InitStateIterator(StateIteratorData<A> *data) const {
+    GetImpl()->InitStateIterator(data);
+  }
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<A> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+  virtual MatcherBase<A> *InitMatcher(MatchType match_type) const {
+    return new SortedMatcher<CompactFst<A, C, U> >(*this, match_type);
+  }
+
+  template <class Iterator>
+  void SetCompactElements(const Iterator &b, const Iterator &e) {
+    GetImpl()->SetCompactElements(b, e);
+  }
+
+ private:
+  CompactFst(Impl *impl) : ImplToExpandedFst<Impl>(impl) {}
+
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl, ExpandedFst<A> >::GetImpl(); }
+
+  void SetImpl(Impl *impl, bool own_impl = false) {
+    ImplToFst< Impl, ExpandedFst<A> >::SetImpl(impl, own_impl);
+  }
+
+  void operator=(const CompactFst<A, C, U> &fst);  // disallow
+};
+
+
+// Specialization for CompactFst; see generic version in fst.h
+// for sample usage (but use the CompactFst type!). This version
+// should inline.
+template <class A, class C, class U>
+class StateIterator< CompactFst<A, C, U> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  explicit StateIterator(const CompactFst<A, C, U> &fst)
+      : nstates_(fst.GetImpl()->NumStates()), s_(0) {}
+
+  bool Done() const { return s_ >= nstates_; }
+
+  StateId Value() const { return s_; }
+
+  void Next() { ++s_; }
+
+  void Reset() { s_ = 0; }
+
+ private:
+  StateId nstates_;
+  StateId s_;
+
+  DISALLOW_COPY_AND_ASSIGN(StateIterator);
+};
+
+// Specialization for CompactFst.
+// Never caches, always iterates over the underlying compact elements.
+template <class A, class C, class U>
+class ArcIterator< CompactFst<A, C, U> > {
+ public:
+  typedef typename A::StateId StateId;
+  typedef typename C::Element CompactElement;
+
+  ArcIterator(const CompactFst<A, C, U> &fst, StateId s)
+      : compactor_(fst.GetImpl()->GetCompactor()), state_(s), compacts_(0),
+        pos_(0), flags_(kArcValueFlags) {
+
+    const CompactFstData<CompactElement, U> *data = fst.GetImpl()->Data();
+    size_t offset;
+    if (compactor_->Size() == -1) {  // Variable out-degree compactor
+      offset = data->States(s);
+      num_arcs_ = data->States(s + 1) - offset;
+    } else {  // Fixed out-degree compactor
+      offset =  s * compactor_->Size();
+      num_arcs_ = compactor_->Size();
+    }
+    if (num_arcs_ > 0) {
+      compacts_ = &(data->Compacts(offset));
+      arc_ = compactor_->Expand(s, *compacts_, kArcILabelValue);
+      if (arc_.ilabel == kNoStateId) {
+        ++compacts_;
+        --num_arcs_;
+      }
+    }
+  }
+
+  ~ArcIterator() {}
+
+  bool Done() const { return pos_ >= num_arcs_; }
+
+  const A& Value() const {
+    arc_ = compactor_->Expand(state_, compacts_[pos_], flags_);
+    return arc_;
+  }
+
+  void Next() { ++pos_; }
+
+  size_t Position() const { return pos_; }
+
+  void Reset() { pos_ = 0;  }
+
+  void Seek(size_t pos) { pos_ = pos; }
+
+  uint32 Flags() const { return flags_; }
+
+  void SetFlags(uint32 f, uint32 m) {
+    flags_ &= ~m;
+    flags_ |= (f & kArcValueFlags);
+  }
+
+ private:
+  C *compactor_;
+  StateId state_;
+  const CompactElement *compacts_;
+  size_t pos_;
+  size_t num_arcs_;
+  mutable A arc_;
+  uint32 flags_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+// // Specialization for CompactFst.
+// // This is an optionally caching arc iterator.
+// // TODO(allauzen): implements the kArcValueFlags, the current
+// // implementation only implements the kArcNoCache flag.
+// template <class A, class C, class U>
+// class ArcIterator< CompactFst<A, C, U> > {
+//  public:
+//   typedef typename A::StateId StateId;
+
+//   ArcIterator(const CompactFst<A, C, U> &fst, StateId s)
+//       : fst_(fst), state_(s), pos_(0), num_arcs_(0), offset_(0),
+//         flags_(kArcValueFlags) {
+//     cache_data_.ref_count = 0;
+
+//     if (fst_.GetImpl()->HasArcs(state_)) {
+//       fst_.GetImpl()->InitArcIterator(s, &cache_data_);
+//       num_arcs_ = cache_data_.narcs;
+//       return;
+//     }
+
+//     const C *compactor = fst_.GetImpl()->GetCompactor();
+//     const CompactFstData<A, C, U> *data = fst_.GetImpl()->Data();
+//     if (compactor->Size() == -1) {  // Variable out-degree compactor
+//       offset_ = data->States(s);
+//       num_arcs_ = data->States(s + 1) - offset_;
+//     } else {  // Fixed out-degree compactor
+//       offset_ =  s * compactor->Size();
+//       num_arcs_ = compactor->Size();
+//     }
+//     if (num_arcs_ > 0) {
+//       const A &arc = fst_.GetImpl()->ComputeArc(s, offset_);
+//       if (arc.ilabel == kNoStateId) {
+//         ++offset_;
+//         --num_arcs_;
+//       }
+//     }
+//   }
+
+
+//   ~ArcIterator() {
+//     if (cache_data_.ref_count)
+//       --(*cache_data_.ref_count);
+//   }
+
+//   bool Done() const { return pos_ >= num_arcs_; }
+
+//   const A& Value() const {
+//     if (cache_data_.ref_count == 0) {
+//       if (flags_ & kArcNoCache) {
+//         arc_ = fst_.GetImpl()->ComputeArc(state_, pos_ + offset_);
+//         return arc_;
+//       } else {
+//         fst_.GetImpl()->InitArcIterator(state_, &cache_data_);
+//       }
+//     }
+//     return cache_data_.arcs[pos_];
+//   }
+
+//   void Next() { ++pos_; }
+
+//   size_t Position() const { return pos_; }
+
+//   void Reset() { pos_ = 0;  }
+
+//   void Seek(size_t pos) { pos_ = pos; }
+
+//   uint32 Flags() const { return flags_; }
+
+//   void SetFlags(uint32 f, uint32 m) {
+//     flags_ &= ~m;
+//     flags_ |= f;
+
+//     if (!(flags_ & kArcNoCache) && cache_data_.ref_count == 0)
+//       fst_.GetImpl()->InitArcIterator(state_, &cache_data_);
+//   }
+
+//  private:
+//   mutable const CompactFst<A, C, U> &fst_;
+//   StateId state_;
+//   size_t pos_;
+//   size_t num_arcs_;
+//   size_t offset_;
+//   uint32 flags_;
+//   mutable A arc_;
+//   mutable ArcIteratorData<A> cache_data_;
+
+//   DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+// };
+
+
+//
+// Utility Compactors
+//
+
+// Compactor for unweighted string FSTs
+template <class A>
+class StringCompactor {
+ public:
+  typedef A Arc;
+  typedef typename A::Label Element;
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  Element Compact(StateId s, const A &arc) const { return arc.ilabel; }
+
+  Arc Expand(StateId s, const Element &p, uint32 f = kArcValueFlags) const {
+    return Arc(p, p, Weight::One(), p != kNoLabel ? s + 1 : kNoStateId);
+  }
+
+  ssize_t Size() const { return 1; }
+
+  uint64 Properties() const {
+    return kString | kAcceptor | kUnweighted;
+  }
+
+  bool Compatible(const Fst<A> &fst) const {
+    uint64 props = Properties();
+    return fst.Properties(props, true) == props;
+  }
+
+  static const string &Type() {
+    static const string type = "string";
+    return type;
+  }
+
+  bool Write(ostream &strm) const { return true; }
+
+  static StringCompactor *Read(istream &strm) {
+    return new StringCompactor;
+  }
+};
+
+
+// Compactor for weighted string FSTs
+template <class A>
+class WeightedStringCompactor {
+ public:
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+  typedef pair<Label, Weight> Element;
+
+  Element Compact(StateId s, const A &arc) const {
+    return make_pair(arc.ilabel, arc.weight);
+  }
+
+  Arc Expand(StateId s, const Element &p, uint32 f = kArcValueFlags) const {
+    return Arc(p.first, p.first, p.second,
+               p.first != kNoLabel ? s + 1 : kNoStateId);
+  }
+
+  ssize_t Size() const { return 1;}
+
+  uint64 Properties() const {
+    return kString | kAcceptor;
+  }
+
+  bool Compatible(const Fst<A> &fst) const {
+    uint64 props = Properties();
+    return fst.Properties(props, true) == props;
+  }
+
+  static const string &Type() {
+    static const string type = "weighted_string";
+    return type;
+  }
+
+  bool Write(ostream &strm) const { return true; }
+
+  static WeightedStringCompactor *Read(istream &strm) {
+    return new WeightedStringCompactor;
+  }
+};
+
+
+// Compactor for unweighted acceptor FSTs
+template <class A>
+class UnweightedAcceptorCompactor {
+ public:
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+  typedef pair<Label, StateId> Element;
+
+  Element Compact(StateId s, const A &arc) const {
+    return make_pair(arc.ilabel, arc.nextstate);
+  }
+
+  Arc Expand(StateId s, const Element &p, uint32 f = kArcValueFlags) const {
+    return Arc(p.first, p.first, Weight::One(), p.second);
+  }
+
+  ssize_t Size() const { return -1;}
+
+  uint64 Properties() const {
+    return kAcceptor | kUnweighted;
+  }
+
+  bool Compatible(const Fst<A> &fst) const {
+    uint64 props = Properties();
+    return fst.Properties(props, true) == props;
+  }
+
+  static const string &Type() {
+    static const string type = "unweighted_acceptor";
+    return type;
+  }
+
+  bool Write(ostream &strm) const { return true; }
+
+  static UnweightedAcceptorCompactor *Read(istream &istrm) {
+    return new UnweightedAcceptorCompactor;
+  }
+};
+
+
+// Compactor for weighted acceptor FSTs
+template <class A>
+class AcceptorCompactor {
+ public:
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+  typedef pair< pair<Label, Weight>, StateId > Element;
+
+  Element Compact(StateId s, const A &arc) const {
+    return make_pair(make_pair(arc.ilabel, arc.weight), arc.nextstate);
+  }
+
+  Arc Expand(StateId s, const Element &p, uint32 f = kArcValueFlags) const {
+    return Arc(p.first.first, p.first.first, p.first.second, p.second);
+  }
+
+  ssize_t Size() const { return -1;}
+
+  uint64 Properties() const {
+    return kAcceptor;
+  }
+
+  bool Compatible(const Fst<A> &fst) const {
+    uint64 props = Properties();
+    return fst.Properties(props, true) == props;
+  }
+
+  static const string &Type() {
+    static const string type = "acceptor";
+    return type;
+  }
+
+  bool Write(ostream &strm) const { return true; }
+
+  static AcceptorCompactor *Read(istream &strm) {
+    return new AcceptorCompactor;
+  }
+};
+
+
+// Compactor for unweighted FSTs
+template <class A>
+class UnweightedCompactor {
+ public:
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+  typedef pair< pair<Label, Label>, StateId > Element;
+
+  Element Compact(StateId s, const A &arc) const {
+    return make_pair(make_pair(arc.ilabel, arc.olabel), arc.nextstate);
+  }
+
+  Arc Expand(StateId s, const Element &p, uint32 f = kArcValueFlags) const {
+    return Arc(p.first.first, p.first.second, Weight::One(), p.second);
+  }
+
+  ssize_t Size() const { return -1; }
+
+  uint64 Properties() const {
+    return kUnweighted;
+  }
+
+  bool Compatible(const Fst<A> &fst) const {
+    uint64 props = Properties();
+    return fst.Properties(props, true) == props;
+  }
+
+  static const string &Type() {
+    static const string type = "unweighted";
+    return type;
+  }
+
+  bool Write(ostream &strm) const { return true; }
+
+  static UnweightedCompactor *Read(istream &strm) {
+    return new UnweightedCompactor;
+  }
+};
+
+
+// Uselful aliases when using StdArc
+typedef CompactFst< StdArc, StringCompactor<StdArc> >
+StdCompactStringFst;
+typedef CompactFst< StdArc, WeightedStringCompactor<StdArc> >
+StdCompactWeightedStringFst;
+typedef CompactFst<StdArc, AcceptorCompactor<StdArc> >
+StdCompactAcceptorFst;
+typedef CompactFst<StdArc, UnweightedCompactor<StdArc> >
+StdCompactUnweightedFst;
+typedef CompactFst<StdArc, UnweightedAcceptorCompactor<StdArc> >
+StdCompactUnweightedAcceptorFst;
+
+}  // namespace fst
+
+#endif // FST_LIB_COMPACT_FST_H__
diff --git a/src/include/fst/compat.h b/src/include/fst/compat.h
new file mode 100644
index 0000000..034b57e
--- /dev/null
+++ b/src/include/fst/compat.h
@@ -0,0 +1,152 @@
+// compat.h
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Google compatibility declarations and inline definitions.
+
+#ifndef FST_LIB_COMPAT_H__
+#define FST_LIB_COMPAT_H__
+
+#include <dlfcn.h>
+
+#include <climits>
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+#include <string>
+#include <vector>
+
+// Makes copy constructor and operator= private
+#define DISALLOW_COPY_AND_ASSIGN(type)    \
+  type(const type&);                      \
+  void operator=(const type&)
+
+#include <fst/config.h>
+#include <fst/types.h>
+#include <fst/lock.h>
+#include <fst/flags.h>
+#include <fst/log.h>
+
+#ifdef HAVE_ICU
+#include <fst/icu.h>
+#endif
+
+using std::cin;
+using std::cout;
+using std::cerr;
+using std::endl;
+using std::string;
+
+void FailedNewHandler();
+
+namespace fst {
+
+using namespace std;
+
+void SplitToVector(char *line, const char *delim,
+                   std::vector<char *> *vec, bool omit_empty_strings);
+
+// Downcasting
+template<typename To, typename From>
+inline To down_cast(From* f) {
+  return static_cast<To>(f);
+}
+
+// Bitcasting
+template <class Dest, class Source>
+inline Dest bit_cast(const Source& source) {
+  // Compile time assertion: sizeof(Dest) == sizeof(Source)
+  // A compile error here means your Dest and Source have different sizes.
+  typedef char VerifySizesAreEqual [sizeof(Dest) == sizeof(Source) ? 1 :
+                                    -1];
+  Dest dest;
+  memcpy(&dest, &source, sizeof(dest));
+  return dest;
+}
+
+// Check sums
+class CheckSummer {
+ public:
+  CheckSummer() : count_(0) {
+    check_sum_.resize(kCheckSumLength, '\0');
+  }
+
+  void Reset() {
+    count_ = 0;
+    for (int i = 0; i < kCheckSumLength; ++i)
+      check_sum_[0] = '\0';
+  }
+
+  void Update(void const *data, int size) {
+    const char *p = reinterpret_cast<const char *>(data);
+    for (int i = 0; i < size; ++i)
+      check_sum_[(count_++) % kCheckSumLength] ^= p[i];
+  }
+
+  void Update(string const &data) {
+    for (int i = 0; i < data.size(); ++i)
+      check_sum_[(count_++) % kCheckSumLength] ^= data[i];
+  }
+
+  string Digest() {
+    return check_sum_;
+  }
+
+ private:
+  static const int kCheckSumLength = 32;
+  int count_;
+  string check_sum_;
+
+  DISALLOW_COPY_AND_ASSIGN(CheckSummer);
+};
+
+// Define the UTF8 string conversion function to throw an error
+// when the ICU Library is missing or disabled.
+#ifndef HAVE_ICU
+
+template <class Label>
+bool UTF8StringToLabels(const string&, std::vector<Label>*) {
+  LOG(ERROR) << "UTF8StringToLabels: ICU Library required for UTF8 handling";
+  return false;
+}
+
+template <class Label>
+bool LabelsToUTF8String(const std::vector<Label>&, string*) {
+  LOG(ERROR) << "LabelsToUTF8String: ICU Library required for UTF8 handling";
+  return false;
+}
+
+#endif  // HAVE_ICU
+
+}  // namespace fst
+
+
+// Define missing hash functions if needed
+#ifndef HAVE_STD__TR1__HASH_LONG_LONG_UNSIGNED_
+namespace std {
+namespace tr1 {
+
+template <class T> class hash;
+
+template<> struct hash<uint64> {
+  size_t operator()(uint64 x) const { return x; }
+};
+
+}
+}
+#endif  // HAVE_STD__TR1__HASH_LONG_LONG_UNSIGNED_
+
+#endif  // FST_LIB_COMPAT_H__
diff --git a/src/include/fst/complement.h b/src/include/fst/complement.h
new file mode 100644
index 0000000..dacf396
--- /dev/null
+++ b/src/include/fst/complement.h
@@ -0,0 +1,338 @@
+// complement.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to complement an Fst.
+
+#ifndef FST_LIB_COMPLEMENT_H__
+#define FST_LIB_COMPLEMENT_H__
+
+#include <algorithm>
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/fst.h>
+#include <fst/test-properties.h>
+
+
+namespace fst {
+
+template <class A> class ComplementFst;
+
+// Implementation of delayed ComplementFst. The algorithm used
+// completes the (deterministic) FSA and then exchanges final and
+// non-final states.  Completion, i.e. ensuring that all labels can be
+// read from every state, is accomplished by using RHO labels, which
+// match all labels that are otherwise not found leaving a state. The
+// first state in the output is reserved to be a new state that is the
+// destination of all RHO labels. Each remaining output state s
+// corresponds to input state s - 1. The first arc in the output at
+// these states is the rho label, the remaining arcs correspond to the
+// input arcs.
+template <class A>
+class ComplementFstImpl : public FstImpl<A> {
+ public:
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+
+  friend class StateIterator< ComplementFst<A> >;
+  friend class ArcIterator< ComplementFst<A> >;
+
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  explicit ComplementFstImpl(const Fst<A> &fst) : fst_(fst.Copy()) {
+    SetType("complement");
+    uint64 props = fst.Properties(kILabelSorted, false);
+    SetProperties(ComplementProperties(props), kCopyProperties);
+    SetInputSymbols(fst.InputSymbols());
+    SetOutputSymbols(fst.OutputSymbols());
+  }
+
+  ComplementFstImpl(const ComplementFstImpl<A> &impl)
+      : fst_(impl.fst_->Copy()) {
+    SetType("complement");
+    SetProperties(impl.Properties(), kCopyProperties);
+    SetInputSymbols(impl.InputSymbols());
+    SetOutputSymbols(impl.OutputSymbols());
+  }
+
+  ~ComplementFstImpl() { delete fst_; }
+
+  StateId Start() const {
+    if (Properties(kError))
+      return kNoStateId;
+
+    StateId start = fst_->Start();
+    if (start != kNoStateId)
+      return start + 1;
+    else
+      return 0;
+  }
+
+  // Exchange final and non-final states; make rho destination state final.
+  Weight Final(StateId s) const {
+    if (s == 0 || fst_->Final(s - 1) == Weight::Zero())
+      return Weight::One();
+    else
+      return Weight::Zero();
+  }
+
+  size_t NumArcs(StateId s) const {
+    if (s == 0)
+      return 1;
+    else
+      return fst_->NumArcs(s - 1) + 1;
+  }
+
+  size_t NumInputEpsilons(StateId s) const {
+    return s == 0 ? 0 : fst_->NumInputEpsilons(s - 1);
+  }
+
+  size_t NumOutputEpsilons(StateId s) const {
+    return s == 0 ? 0 : fst_->NumOutputEpsilons(s - 1);
+  }
+
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if ((mask & kError) && fst_->Properties(kError, false))
+      SetProperties(kError, kError);
+    return FstImpl<Arc>::Properties(mask);
+  }
+
+
+ private:
+  const Fst<A> *fst_;
+
+  void operator=(const ComplementFstImpl<A> &fst);  // Disallow
+};
+
+
+// Complements an automaton. This is a library-internal operation that
+// introduces a (negative) 'rho' label; use Difference/DifferenceFst in
+// user code, which will not see this label. This version is a delayed Fst.
+//
+// This class attaches interface to implementation and handles
+// reference counting, delegating most methods to ImplToFst.
+template <class A>
+class ComplementFst : public ImplToFst< ComplementFstImpl<A> > {
+ public:
+  friend class StateIterator< ComplementFst<A> >;
+  friend class ArcIterator< ComplementFst<A> >;
+
+  using ImplToFst< ComplementFstImpl<A> >::GetImpl;
+
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef ComplementFstImpl<A> Impl;
+
+  explicit ComplementFst(const Fst<A> &fst)
+      : ImplToFst<Impl>(new Impl(fst)) {
+    uint64 props = kUnweighted | kNoEpsilons | kIDeterministic | kAcceptor;
+    if (fst.Properties(props, true) != props) {
+      FSTERROR() << "ComplementFst: argument not an unweighted "
+                 << "epsilon-free deterministic acceptor";
+      GetImpl()->SetProperties(kError, kError);
+    }
+  }
+
+  // See Fst<>::Copy() for doc.
+  ComplementFst(const ComplementFst<A> &fst, bool safe = false)
+      : ImplToFst<Impl>(fst, safe) {}
+
+  // Get a copy of this ComplementFst. See Fst<>::Copy() for further doc.
+  virtual ComplementFst<A> *Copy(bool safe = false) const {
+    return new ComplementFst<A>(*this, safe);
+  }
+
+  virtual inline void InitStateIterator(StateIteratorData<A> *data) const;
+
+  virtual inline void InitArcIterator(StateId s,
+                                      ArcIteratorData<A> *data) const;
+
+  // Label that represents the rho transition.
+  // We use a negative value, which is thus private to the library and
+  // which will preserve FST label sort order.
+  static const Label kRhoLabel = -2;
+ private:
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const ComplementFst<A> &fst);  // disallow
+};
+
+template <class A> const typename A::Label ComplementFst<A>::kRhoLabel;
+
+
+// Specialization for ComplementFst.
+template <class A>
+class StateIterator< ComplementFst<A> > : public StateIteratorBase<A> {
+ public:
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+
+  explicit StateIterator(const ComplementFst<A> &fst)
+      : siter_(*fst.GetImpl()->fst_), s_(0) {
+  }
+
+  bool Done() const { return s_ > 0 && siter_.Done(); }
+
+  StateId Value() const { return s_; }
+
+  void Next() {
+    if (s_ != 0)
+      siter_.Next();
+    ++s_;
+  }
+
+  void Reset() {
+    siter_.Reset();
+    s_ = 0;
+  }
+
+ private:
+  // This allows base class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual bool Done_() const { return Done(); }
+  virtual StateId Value_() const { return Value(); }
+  virtual void Next_() { Next(); }
+  virtual void Reset_() { Reset(); }
+
+  StateIterator< Fst<A> > siter_;
+  StateId s_;
+
+  DISALLOW_COPY_AND_ASSIGN(StateIterator);
+};
+
+
+// Specialization for ComplementFst.
+template <class A>
+class ArcIterator< ComplementFst<A> > : public ArcIteratorBase<A> {
+ public:
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+
+  ArcIterator(const ComplementFst<A> &fst, StateId s)
+      : aiter_(0), s_(s), pos_(0) {
+    if (s_ != 0)
+      aiter_ = new ArcIterator< Fst<A> >(*fst.GetImpl()->fst_, s - 1);
+  }
+
+  virtual ~ArcIterator() { delete aiter_; }
+
+  bool Done() const {
+    if (s_ != 0)
+      return pos_ > 0 && aiter_->Done();
+    else
+      return pos_ > 0;
+  }
+
+  // Adds the rho label to the rho destination state.
+  const A& Value() const {
+    if (pos_ == 0) {
+      arc_.ilabel = arc_.olabel = ComplementFst<A>::kRhoLabel;
+      arc_.weight = Weight::One();
+      arc_.nextstate = 0;
+    } else {
+      arc_ = aiter_->Value();
+      ++arc_.nextstate;
+    }
+    return arc_;
+  }
+
+  void Next() {
+    if (s_ != 0 && pos_ > 0)
+      aiter_->Next();
+    ++pos_;
+  }
+
+  size_t Position() const {
+    return pos_;
+  }
+
+  void Reset() {
+    if (s_ != 0)
+      aiter_->Reset();
+    pos_ = 0;
+  }
+
+  void Seek(size_t a) {
+    if (s_ != 0) {
+      if (a == 0) {
+        aiter_->Reset();
+      } else {
+        aiter_->Seek(a - 1);
+      }
+    }
+    pos_ = a;
+  }
+
+  uint32 Flags() const {
+    return kArcValueFlags;
+  }
+
+  void SetFlags(uint32 f, uint32 m) {}
+
+ private:
+  // This allows base class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual bool Done_() const { return Done(); }
+  virtual const A& Value_() const { return Value(); }
+  virtual void Next_() { Next(); }
+  virtual size_t Position_() const { return Position(); }
+  virtual void Reset_() { Reset(); }
+  virtual void Seek_(size_t a) { Seek(a); }
+  uint32 Flags_() const { return Flags(); }
+  void SetFlags_(uint32 f, uint32 m) { SetFlags(f, m); }
+
+  ArcIterator< Fst<A> > *aiter_;
+  StateId s_;
+  size_t pos_;
+  mutable A arc_;
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+
+template <class A> inline void
+ComplementFst<A>::InitStateIterator(StateIteratorData<A> *data) const {
+  data->base = new StateIterator< ComplementFst<A> >(*this);
+}
+
+template <class A> inline void
+ComplementFst<A>::InitArcIterator(StateId s, ArcIteratorData<A> *data) const {
+  data->base = new ArcIterator< ComplementFst<A> >(*this, s);
+}
+
+
+// Useful alias when using StdArc.
+typedef ComplementFst<StdArc> StdComplementFst;
+
+}  // namespace fst
+
+#endif  // FST_LIB_COMPLEMENT_H__
diff --git a/src/include/fst/compose-filter.h b/src/include/fst/compose-filter.h
new file mode 100644
index 0000000..6bf7736
--- /dev/null
+++ b/src/include/fst/compose-filter.h
@@ -0,0 +1,542 @@
+// compose-filter.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Classes for filtering the composition matches, e.g. for correct epsilon
+// handling.
+
+#ifndef FST_LIB_COMPOSE_FILTER_H__
+#define FST_LIB_COMPOSE_FILTER_H__
+
+#include <fst/fst.h>
+#include <fst/fst-decl.h>  // For optional argument declarations
+#include <fst/matcher.h>
+
+
+namespace fst {
+
+
+// COMPOSITION FILTER STATE - this represents the state of
+// the composition filter. It has the form:
+//
+// class FilterState {
+//  public:
+//   // Required constructors
+//   FilterState();
+//   FilterState(const FilterState &f);
+//   // An invalid filter state.
+//   static const FilterState NoState();
+//   // Maps state to integer for hashing.
+//   size_t Hash() const;
+//   // Equality of filter states.
+//   bool operator==(const FilterState &f) const;
+//   // Inequality of filter states.
+//   bool operator!=(const FilterState &f) const;
+//   // Assignment to filter states.
+//   FilterState& operator=(const FilterState& f);
+// };
+
+
+// Filter state that is a signed integral type.
+template <typename T>
+class IntegerFilterState {
+ public:
+  IntegerFilterState() : state_(kNoStateId) {}
+  explicit IntegerFilterState(T s) : state_(s) {}
+
+  static const IntegerFilterState NoState() { return IntegerFilterState(); }
+
+  size_t Hash() const { return static_cast<size_t>(state_); }
+
+  bool operator==(const IntegerFilterState &f) const {
+    return state_ == f.state_;
+  }
+
+  bool operator!=(const IntegerFilterState &f) const {
+    return state_ != f.state_;
+  }
+
+  T GetState() const { return state_; }
+
+  void SetState(T state) { state_ = state; }
+
+private:
+  T state_;
+};
+
+typedef IntegerFilterState<signed char> CharFilterState;
+typedef IntegerFilterState<short> ShortFilterState;
+typedef IntegerFilterState<int> IntFilterState;
+
+
+// Filter state that is a weight (class).
+template <class W>
+class WeightFilterState {
+ public:
+  WeightFilterState() : weight_(W::Zero()) {}
+  explicit WeightFilterState(W w) : weight_(w) {}
+
+  static const WeightFilterState NoState() { return WeightFilterState(); }
+
+  size_t Hash() const { return weight_.Hash(); }
+
+  bool operator==(const WeightFilterState &f) const {
+    return weight_ == f.weight_;
+  }
+
+  bool operator!=(const WeightFilterState &f) const {
+    return weight_ != f.weight_;
+  }
+
+  W GetWeight() const { return weight_; }
+
+  void SetWeight(W w) { weight_ = w; }
+
+private:
+  W weight_;
+};
+
+
+// Filter state that is the combination of two filter states.
+template <class F1, class F2>
+class PairFilterState {
+ public:
+  PairFilterState() : f1_(F1::NoState()), f2_(F2::NoState()) {}
+
+  PairFilterState(const F1 &f1, const F2 &f2) : f1_(f1), f2_(f2) {}
+
+  static const PairFilterState NoState() { return PairFilterState(); }
+
+  size_t Hash() const {
+    size_t h1 = f1_.Hash();
+    size_t h2 = f2_.Hash();
+    const int lshift = 5;
+    const int rshift = CHAR_BIT * sizeof(size_t) - 5;
+    return h1 << lshift ^ h1 >> rshift ^ h2;
+  }
+
+  bool operator==(const PairFilterState &f) const {
+    return f1_ == f.f1_ && f2_ == f.f2_;
+  }
+
+  bool operator!=(const PairFilterState &f) const {
+    return f1_ != f.f1_ || f2_ != f.f2_;
+  }
+
+  const F1 &GetState1() const { return f1_; }
+  const F2 &GetState2() const { return f2_; }
+
+  void SetState(const F1 &f1, const F2 &f2) {
+    f1_ = f1;
+    f2_ = f2;
+  }
+
+private:
+  F1 f1_;
+  F2 f2_;
+};
+
+
+// COMPOSITION FILTERS - these determine which matches are allowed to
+// proceed. The filter's state is represented by the type
+// ComposeFilter::FilterState. The basic filters handle correct
+// epsilon matching.  Their interface is:
+//
+// template <class M1, class M2>
+// class ComposeFilter {
+//  public:
+//   typedef typename M1::FST1 FST1;
+//   typedef typename M1::FST2 FST2;
+//   typedef typename FST1::Arc Arc;
+//   typedef ... FilterState;
+//   typedef ... Matcher1;
+//   typedef ... Matcher2;
+//
+//   // Required constructors.
+//   ComposeFilter(const FST1 &fst1, const FST2 &fst2,
+//   //            M1 *matcher1 = 0, M2 *matcher2 = 0);
+//   // If safe=true, the copy is thread-safe. See Fst<>::Copy()
+//   // for further doc.
+//   ComposeFilter(const ComposeFilter<M1, M2> &filter,
+//   //            bool safe = false);
+//   // Return start state of filter.
+//   FilterState Start() const;
+//   // Specifies current composition state.
+//   void SetState(StateId s1, StateId s2, const FilterState &f);
+//
+//   // Apply filter at current composition state to these transitions.
+//   // If an arc label to be matched is kNolabel, then that side
+//   // does not consume a symbol. Returns the new filter state or,
+//   // if disallowed, FilterState::NoState(). The filter is permitted to
+//   // modify its inputs, e.g. for optimizations.
+//   FilterState FilterArc(Arc *arc1, Arc *arc2) const;
+
+//   // Apply filter at current composition state to these final weights
+//   // (cf. superfinal transitions). The filter may modify its inputs,
+//   // e.g. for optimizations.
+//   void FilterFinal(Weight *final1, Weight *final2) const;
+//
+//   // Return resp matchers. Ownership stays with filter. These
+//   // methods allow the filter to access and possibly modify
+//   // the composition matchers (useful e.g. with lookahead).
+//   Matcher1 *GetMatcher1();
+//   Matcher2 *GetMatcher2();
+//
+//   // This specifies how the filter affects the composition result
+//   // properties. It takes as argument the properties that would
+//   // apply with a trivial composition fitler.
+//   uint64 Properties(uint64 props) const;
+// };
+
+// This filter requires epsilons on FST1 to be read before epsilons on FST2.
+template <class M1, class M2>
+class SequenceComposeFilter {
+ public:
+  typedef typename M1::FST FST1;
+  typedef typename M2::FST FST2;
+  typedef typename FST1::Arc Arc;
+  typedef CharFilterState FilterState;
+  typedef M1 Matcher1;
+  typedef M2 Matcher2;
+
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  SequenceComposeFilter(const FST1 &fst1, const FST2 &fst2,
+                        M1 *matcher1 = 0, M2 *matcher2 = 0)
+      : matcher1_(matcher1 ? matcher1 : new M1(fst1, MATCH_OUTPUT)),
+        matcher2_(matcher2 ? matcher2 : new M2(fst2, MATCH_INPUT)),
+        fst1_(matcher1_->GetFst()),
+        s1_(kNoStateId),
+        s2_(kNoStateId),
+        f_(kNoStateId) {}
+
+  SequenceComposeFilter(const SequenceComposeFilter<M1, M2> &filter,
+                        bool safe = false)
+      : matcher1_(filter.matcher1_->Copy(safe)),
+        matcher2_(filter.matcher2_->Copy(safe)),
+        fst1_(matcher1_->GetFst()),
+        s1_(kNoStateId),
+        s2_(kNoStateId),
+        f_(kNoStateId) {}
+
+  ~SequenceComposeFilter() {
+    delete matcher1_;
+    delete matcher2_;
+  }
+
+  FilterState Start() const { return FilterState(0); }
+
+  void SetState(StateId s1, StateId s2, const FilterState &f) {
+    if (s1_ == s1 && s2_ == s2 && f == f_)
+      return;
+    s1_ = s1;
+    s2_ = s2;
+    f_ = f;
+    size_t na1 = internal::NumArcs(fst1_, s1);
+    size_t ne1 = internal::NumOutputEpsilons(fst1_, s1);
+    bool fin1 = internal::Final(fst1_, s1) != Weight::Zero();
+    alleps1_ = na1 == ne1 && !fin1;
+    noeps1_ = ne1 == 0;
+  }
+
+  FilterState FilterArc(Arc *arc1, Arc *arc2) const {
+    if (arc1->olabel == kNoLabel)
+      return alleps1_ ? FilterState::NoState() :
+        noeps1_ ? FilterState(0) : FilterState(1);
+    else if (arc2->ilabel == kNoLabel)
+      return f_ != FilterState(0) ? FilterState::NoState() : FilterState(0);
+    else
+      return arc1->olabel == 0 ? FilterState::NoState() : FilterState(0);
+  }
+
+  void FilterFinal(Weight *, Weight *) const {}
+
+  // Return resp matchers. Ownership stays with filter.
+  Matcher1 *GetMatcher1() { return matcher1_; }
+  Matcher2 *GetMatcher2() { return matcher2_; }
+
+  uint64 Properties(uint64 props) const { return props; }
+
+ private:
+  Matcher1 *matcher1_;
+  Matcher2 *matcher2_;
+  const FST1 &fst1_;
+  StateId s1_;     // Current fst1_ state;
+  StateId s2_;     // Current fst2_ state;
+  FilterState f_;  // Current filter state
+  bool alleps1_;   // Only epsilons (and non-final) leaving s1_?
+  bool noeps1_;    // No epsilons leaving s1_?
+
+  void operator=(const SequenceComposeFilter<M1, M2> &);  // disallow
+};
+
+
+// This filter requires epsilons on FST2 to be read before epsilons on FST1.
+template <class M1, class M2>
+class AltSequenceComposeFilter {
+ public:
+  typedef typename M1::FST FST1;
+  typedef typename M2::FST FST2;
+  typedef typename FST1::Arc Arc;
+  typedef CharFilterState FilterState;
+  typedef M1 Matcher1;
+  typedef M2 Matcher2;
+
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  AltSequenceComposeFilter(const FST1 &fst1, const FST2 &fst2,
+                        M1 *matcher1 = 0, M2 *matcher2 = 0)
+      : matcher1_(matcher1 ? matcher1 : new M1(fst1, MATCH_OUTPUT)),
+        matcher2_(matcher2 ? matcher2 : new M2(fst2, MATCH_INPUT)),
+        fst2_(matcher2_->GetFst()),
+        s1_(kNoStateId),
+        s2_(kNoStateId),
+        f_(kNoStateId) {}
+
+  AltSequenceComposeFilter(const AltSequenceComposeFilter<M1, M2> &filter,
+                           bool safe = false)
+      : matcher1_(filter.matcher1_->Copy(safe)),
+        matcher2_(filter.matcher2_->Copy(safe)),
+        fst2_(matcher2_->GetFst()),
+        s1_(kNoStateId),
+        s2_(kNoStateId),
+        f_(kNoStateId) {}
+
+  ~AltSequenceComposeFilter() {
+    delete matcher1_;
+    delete matcher2_;
+  }
+
+  FilterState Start() const { return FilterState(0); }
+
+  void SetState(StateId s1, StateId s2, const FilterState &f) {
+    if (s1_ == s1 && s2_ == s2 && f == f_)
+      return;
+    s1_ = s1;
+    s2_ = s2;
+    f_ = f;
+    size_t na2 = internal::NumArcs(fst2_, s2);
+    size_t ne2 = internal::NumInputEpsilons(fst2_, s2);
+    bool fin2 = internal::Final(fst2_, s2) != Weight::Zero();
+    alleps2_ = na2 == ne2 && !fin2;
+    noeps2_ = ne2 == 0;
+  }
+
+  FilterState FilterArc(Arc *arc1, Arc *arc2) const {
+    if (arc2->ilabel == kNoLabel)
+      return alleps2_ ? FilterState::NoState() :
+        noeps2_ ? FilterState(0) : FilterState(1);
+    else if (arc1->olabel == kNoLabel)
+      return f_ == FilterState(1) ? FilterState::NoState() : FilterState(0);
+    else
+      return arc1->olabel == 0 ? FilterState::NoState() : FilterState(0);
+  }
+
+  void FilterFinal(Weight *, Weight *) const {}
+
+  // Return resp matchers. Ownership stays with filter.
+  Matcher1 *GetMatcher1() { return matcher1_; }
+  Matcher2 *GetMatcher2() { return matcher2_; }
+
+  uint64 Properties(uint64 props) const { return props; }
+
+ private:
+  Matcher1 *matcher1_;
+  Matcher2 *matcher2_;
+  const FST2 &fst2_;
+  StateId s1_;     // Current fst1_ state;
+  StateId s2_;     // Current fst2_ state;
+  FilterState f_;  // Current filter state
+  bool alleps2_;   // Only epsilons (and non-final) leaving s2_?
+  bool noeps2_;    // No epsilons leaving s2_?
+
+void operator=(const AltSequenceComposeFilter<M1, M2> &);  // disallow
+};
+
+
+// This filter requires epsilons on FST1 to be matched with epsilons on FST2
+// whenever possible.
+template <class M1, class M2>
+class MatchComposeFilter {
+ public:
+  typedef typename M1::FST FST1;
+  typedef typename M2::FST FST2;
+  typedef typename FST1::Arc Arc;
+  typedef CharFilterState FilterState;
+  typedef M1 Matcher1;
+  typedef M2 Matcher2;
+
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  MatchComposeFilter(const FST1 &fst1, const FST2 &fst2,
+                     M1 *matcher1 = 0, M2 *matcher2 = 0)
+      : matcher1_(matcher1 ? matcher1 : new M1(fst1, MATCH_OUTPUT)),
+        matcher2_(matcher2 ? matcher2 : new M2(fst2, MATCH_INPUT)),
+        fst1_(matcher1_->GetFst()),
+        fst2_(matcher2_->GetFst()),
+        s1_(kNoStateId),
+        s2_(kNoStateId),
+        f_(kNoStateId) {}
+
+  MatchComposeFilter(const MatchComposeFilter<M1, M2> &filter,
+                     bool safe = false)
+      : matcher1_(filter.matcher1_->Copy(safe)),
+        matcher2_(filter.matcher2_->Copy(safe)),
+        fst1_(matcher1_->GetFst()),
+        fst2_(matcher2_->GetFst()),
+        s1_(kNoStateId),
+        s2_(kNoStateId),
+        f_(kNoStateId) {}
+
+  ~MatchComposeFilter() {
+    delete matcher1_;
+    delete matcher2_;
+  }
+
+  FilterState Start() const { return FilterState(0); }
+
+  void SetState(StateId s1, StateId s2, const FilterState &f) {
+    if (s1_ == s1 && s2_ == s2 && f == f_)
+      return;
+    s1_ = s1;
+    s2_ = s2;
+    f_ = f;
+    size_t na1 = internal::NumArcs(fst1_, s1);
+    size_t ne1 = internal::NumOutputEpsilons(fst1_, s1);
+    bool f1 = internal::Final(fst1_, s1) != Weight::Zero();
+    alleps1_ = na1 == ne1 && !f1;
+    noeps1_ = ne1 == 0;
+    size_t na2 = internal::NumArcs(fst2_, s2);
+    size_t ne2 = internal::NumInputEpsilons(fst2_, s2);
+    bool f2 = internal::Final(fst2_, s2) != Weight::Zero();
+    alleps2_ = na2 == ne2 && !f2;
+    noeps2_ = ne2 == 0;
+  }
+
+  FilterState FilterArc(Arc *arc1, Arc *arc2) const {
+    if (arc2->ilabel == kNoLabel)  // Epsilon on Fst1
+      return f_ == FilterState(0) ?
+          (noeps2_ ? FilterState(0) :
+           (alleps2_ ? FilterState::NoState(): FilterState(1))) :
+          (f_ == FilterState(1) ? FilterState(1) : FilterState::NoState());
+    else if (arc1->olabel == kNoLabel)  // Epsilon on Fst2
+      return f_ == FilterState(0) ?
+          (noeps1_ ? FilterState(0) :
+           (alleps1_ ? FilterState::NoState() : FilterState(2))) :
+          (f_ == FilterState(2) ? FilterState(2) : FilterState::NoState());
+    else if (arc1->olabel == 0)  // Epsilon on both
+      return f_ == FilterState(0) ? FilterState(0) : FilterState::NoState();
+    else  // Both are non-epsilons
+      return FilterState(0);
+  }
+
+  void FilterFinal(Weight *, Weight *) const {}
+
+  // Return resp matchers. Ownership stays with filter.
+  Matcher1 *GetMatcher1() { return matcher1_; }
+  Matcher2 *GetMatcher2() { return matcher2_; }
+
+  uint64 Properties(uint64 props) const { return props; }
+
+ private:
+  Matcher1 *matcher1_;
+  Matcher2 *matcher2_;
+  const FST1 &fst1_;
+  const FST2 &fst2_;
+  StateId s1_;              // Current fst1_ state;
+  StateId s2_;              // Current fst2_ state;
+  FilterState f_;           // Current filter state ID
+  bool alleps1_, alleps2_;  // Only epsilons (and non-final) leaving s1, s2?
+  bool noeps1_, noeps2_;    // No epsilons leaving s1, s2?
+
+  void operator=(const MatchComposeFilter<M1, M2> &);  // disallow
+};
+
+
+// This filter works with the MultiEpsMatcher to determine if
+// 'multi-epsilons' are preserved in the composition output
+// (rather than rewritten as 0) and ensures correct properties.
+template <class F>
+class MultiEpsFilter {
+ public:
+  typedef typename F::FST1 FST1;
+  typedef typename F::FST2 FST2;
+  typedef typename F::Arc Arc;
+  typedef typename F::Matcher1 Matcher1;
+  typedef typename F::Matcher2 Matcher2;
+  typedef typename F::FilterState FilterState;
+  typedef MultiEpsFilter<F> Filter;
+
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  MultiEpsFilter(const FST1 &fst1, const FST2 &fst2,
+                 Matcher1 *matcher1 = 0,  Matcher2 *matcher2 = 0,
+                 bool keep_multi_eps = false)
+      : filter_(fst1, fst2, matcher1, matcher2),
+        keep_multi_eps_(keep_multi_eps) {}
+
+  MultiEpsFilter(const Filter &filter, bool safe = false)
+      : filter_(filter.filter_, safe),
+        keep_multi_eps_(filter.keep_multi_eps_) {}
+
+  FilterState Start() const { return filter_.Start(); }
+
+  void SetState(StateId s1, StateId s2, const FilterState &f) {
+    return filter_.SetState(s1, s2, f);
+  }
+
+  FilterState FilterArc(Arc *arc1, Arc *arc2) const {
+    FilterState f = filter_.FilterArc(arc1, arc2);
+    if (keep_multi_eps_) {
+      if (arc1->olabel == kNoLabel)
+        arc1->ilabel = arc2->ilabel;
+      if (arc2->ilabel == kNoLabel)
+        arc2->olabel = arc1->olabel;
+    }
+    return f;
+  }
+
+  void FilterFinal(Weight *w1, Weight *w2) const {
+    return filter_.FilterFinal(w1, w2);
+  }
+
+  // Return resp matchers. Ownership stays with filter.
+  Matcher1 *GetMatcher1() { return filter_.GetMatcher1(); }
+  Matcher2 *GetMatcher2() { return filter_.GetMatcher2(); }
+
+  uint64 Properties(uint64 iprops) const {
+    uint64 oprops = filter_.Properties(iprops);
+    return oprops & kILabelInvariantProperties & kOLabelInvariantProperties;
+  }
+
+ private:
+  F filter_;
+  bool keep_multi_eps_;
+};
+
+}  // namespace fst
+
+
+#endif  // FST_LIB_COMPOSE_FILTER_H__
diff --git a/src/include/fst/compose.h b/src/include/fst/compose.h
new file mode 100644
index 0000000..c0bf4b1
--- /dev/null
+++ b/src/include/fst/compose.h
@@ -0,0 +1,673 @@
+// compose.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to compute the composition of two FSTs
+
+#ifndef FST_LIB_COMPOSE_H__
+#define FST_LIB_COMPOSE_H__
+
+#include <algorithm>
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+#include <fst/compose-filter.h>
+#include <fst/lookahead-filter.h>
+#include <fst/matcher.h>
+#include <fst/state-table.h>
+#include <fst/test-properties.h>
+
+
+namespace fst {
+
+// Delayed composition options templated on the arc type, the matcher,
+// the composition filter, and the composition state table.  By
+// default, the matchers, filter, and state table are constructed by
+// composition. If set below, the user can instead pass in these
+// objects; in that case, ComposeFst takes their ownership. This
+// version controls composition implemented between generic Fst<Arc>
+// types and a shared matcher type M for Fst<Arc>. This should be
+// adequate for most applications, giving a reasonable tradeoff
+// between efficiency and code sharing (but see ComposeFstImplOptions).
+template <class A,
+          class M = Matcher<Fst<A> >,
+          class F = SequenceComposeFilter<M>,
+          class T = GenericComposeStateTable<A, typename F::FilterState> >
+struct ComposeFstOptions : public CacheOptions {
+  M *matcher1;      // FST1 matcher (see matcher.h)
+  M *matcher2;      // FST2 matcher
+  F *filter;        // Composition filter (see compose-filter.h)
+  T *state_table;   // Composition state table (see compose-state-table.h)
+
+  explicit ComposeFstOptions(const CacheOptions &opts,
+                             M *mat1 = 0, M *mat2 = 0,
+                             F *filt = 0, T *sttable= 0)
+      : CacheOptions(opts), matcher1(mat1), matcher2(mat2),
+        filter(filt), state_table(sttable) {}
+
+  ComposeFstOptions() : matcher1(0), matcher2(0), filter(0), state_table(0) {}
+};
+
+
+// Delayed composition options templated on the two matcher types, the
+// composition filter, and the composition state table.  By default,
+// the matchers, filter, and state table are constructed by
+// composition. If set below, the user can instead pass in these
+// objects; in that case, ComposeFst takes their ownership. This
+// version controls composition implemented using arbitrary matchers
+// (of the same Arc type but otherwise arbitrary Fst type). The user
+// must ensure the matchers are compatible. These options permit the
+// most efficient use, but shares the least code. This is for advanced
+// use only in the most demanding or specialized applications that can
+// benefit from it (o.w. prefer ComposeFstOptions).
+template <class M1, class M2,
+          class F = SequenceComposeFilter<M1, M2>,
+          class T = GenericComposeStateTable<typename M1::Arc,
+                                             typename F::FilterState> >
+struct ComposeFstImplOptions : public CacheOptions {
+  M1 *matcher1;     // FST1 matcher (see matcher.h)
+  M2 *matcher2;     // FST2 matcher
+  F *filter;        // Composition filter (see compose-filter.h)
+  T *state_table;   // Composition state table (see compose-state-table.h)
+
+  explicit ComposeFstImplOptions(const CacheOptions &opts,
+                                 M1 *mat1 = 0, M2 *mat2 = 0,
+                                 F *filt = 0, T *sttable= 0)
+      : CacheOptions(opts), matcher1(mat1), matcher2(mat2),
+        filter(filt), state_table(sttable) {}
+
+  ComposeFstImplOptions()
+  : matcher1(0), matcher2(0), filter(0), state_table(0) {}
+};
+
+
+// Implementation of delayed composition. This base class is
+// common to the variants with different matchers, composition filters
+// and state tables.
+template <class A>
+class ComposeFstImplBase : public CacheImpl<A> {
+ public:
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::Properties;
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+
+  using CacheBaseImpl< CacheState<A> >::HasStart;
+  using CacheBaseImpl< CacheState<A> >::HasFinal;
+  using CacheBaseImpl< CacheState<A> >::HasArcs;
+  using CacheBaseImpl< CacheState<A> >::SetFinal;
+  using CacheBaseImpl< CacheState<A> >::SetStart;
+
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef CacheState<A> State;
+
+  ComposeFstImplBase(const Fst<A> &fst1, const Fst<A> &fst2,
+                     const CacheOptions &opts)
+      :CacheImpl<A>(opts) {
+    VLOG(2) << "ComposeFst(" << this << "): Begin";
+    SetType("compose");
+
+    if (!CompatSymbols(fst2.InputSymbols(), fst1.OutputSymbols())) {
+      FSTERROR() << "ComposeFst: output symbol table of 1st argument "
+                 << "does not match input symbol table of 2nd argument";
+      SetProperties(kError, kError);
+    }
+
+    SetInputSymbols(fst1.InputSymbols());
+    SetOutputSymbols(fst2.OutputSymbols());
+  }
+
+  ComposeFstImplBase(const ComposeFstImplBase<A> &impl)
+      : CacheImpl<A>(impl) {
+    SetProperties(impl.Properties(), kCopyProperties);
+    SetInputSymbols(impl.InputSymbols());
+    SetOutputSymbols(impl.OutputSymbols());
+  }
+
+  virtual ComposeFstImplBase<A> *Copy() = 0;
+
+  virtual ~ComposeFstImplBase() {}
+
+  StateId Start() {
+    if (!HasStart()) {
+      StateId start = ComputeStart();
+      if (start != kNoStateId) {
+        SetStart(start);
+      }
+    }
+    return CacheImpl<A>::Start();
+  }
+
+  Weight Final(StateId s) {
+    if (!HasFinal(s)) {
+      Weight final = ComputeFinal(s);
+      SetFinal(s, final);
+    }
+    return CacheImpl<A>::Final(s);
+  }
+
+  virtual void Expand(StateId s) = 0;
+
+  size_t NumArcs(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumArcs(s);
+  }
+
+  size_t NumInputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumInputEpsilons(s);
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumOutputEpsilons(s);
+  }
+
+  void InitArcIterator(StateId s, ArcIteratorData<A> *data) {
+    if (!HasArcs(s))
+      Expand(s);
+    CacheImpl<A>::InitArcIterator(s, data);
+  }
+
+ protected:
+  virtual StateId ComputeStart() = 0;
+  virtual Weight ComputeFinal(StateId s) = 0;
+};
+
+
+// Implementaion of delayed composition templated on the matchers (see
+// matcher.h), composition filter (see compose-filter-inl.h) and
+// the composition state table (see compose-state-table.h).
+template <class M1, class M2, class F, class T>
+class ComposeFstImpl : public ComposeFstImplBase<typename M1::Arc> {
+  typedef typename M1::FST FST1;
+  typedef typename M2::FST FST2;
+  typedef typename M1::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+  typedef typename F::FilterState FilterState;
+  typedef typename F::Matcher1 Matcher1;
+  typedef typename F::Matcher2 Matcher2;
+
+  using CacheBaseImpl<CacheState<Arc> >::SetArcs;
+  using FstImpl<Arc>::SetType;
+  using FstImpl<Arc>::SetProperties;
+
+  typedef ComposeStateTuple<StateId, FilterState> StateTuple;
+
+ public:
+  ComposeFstImpl(const FST1 &fst1, const FST2 &fst2,
+                 const ComposeFstImplOptions<M1, M2, F, T> &opts);
+
+  ComposeFstImpl(const ComposeFstImpl<M1, M2, F, T> &impl)
+      : ComposeFstImplBase<Arc>(impl),
+        filter_(new F(*impl.filter_, true)),
+        matcher1_(filter_->GetMatcher1()),
+        matcher2_(filter_->GetMatcher2()),
+        fst1_(matcher1_->GetFst()),
+        fst2_(matcher2_->GetFst()),
+        state_table_(new T(*impl.state_table_)),
+        match_type_(impl.match_type_) {}
+
+  ~ComposeFstImpl() {
+    VLOG(2) << "ComposeFst(" << this
+            << "): End: # of visited states: " << state_table_->Size();
+
+    delete filter_;
+    delete state_table_;
+  }
+
+  virtual ComposeFstImpl<M1, M2, F, T> *Copy() {
+    return new ComposeFstImpl<M1, M2, F, T>(*this);
+  }
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if ((mask & kError) &&
+        (fst1_.Properties(kError, false) ||
+         fst2_.Properties(kError, false) ||
+         (matcher1_->Properties(0) & kError) ||
+         (matcher2_->Properties(0) & kError) |
+         (filter_->Properties(0) & kError) ||
+         state_table_->Error())) {
+      SetProperties(kError, kError);
+    }
+    return FstImpl<Arc>::Properties(mask);
+  }
+
+  // Arranges it so that the first arg to OrderedExpand is the Fst
+  // that will be matched on.
+  void Expand(StateId s) {
+    const StateTuple &tuple = state_table_->Tuple(s);
+    StateId s1 = tuple.state_id1;
+    StateId s2 = tuple.state_id2;
+    filter_->SetState(s1, s2, tuple.filter_state);
+    if (match_type_ == MATCH_OUTPUT ||
+        (match_type_ == MATCH_BOTH &&
+         internal::NumArcs(fst1_, s1) > internal::NumArcs(fst2_, s2)))
+      OrderedExpand(s, fst1_, s1, fst2_, s2, matcher1_, false);
+    else
+      OrderedExpand(s, fst2_, s2, fst1_, s1, matcher2_, true);
+  }
+
+ private:
+  // This does that actual matching of labels in the composition. The
+  // arguments are ordered so matching is called on state 'sa' of
+  // 'fsta' for each arc leaving state 'sb' of 'fstb'. The 'match_input' arg
+  // determines whether the input or output label of arcs at 'sb' is
+  // the one to match on.
+  template <class FST, class Matcher>
+  void OrderedExpand(StateId s, const Fst<Arc> &, StateId sa,
+                     const FST &fstb, StateId sb,
+                     Matcher *matchera,  bool match_input) {
+    matchera->SetState(sa);
+
+    // First process non-consuming symbols (e.g., epsilons) on FSTA.
+    Arc loop(match_input ? 0 : kNoLabel, match_input ? kNoLabel : 0,
+           Weight::One(), sb);
+    MatchArc(s, matchera, loop, match_input);
+
+    // Then process matches on FSTB.
+    for (ArcIterator<FST> iterb(fstb, sb); !iterb.Done(); iterb.Next())
+      MatchArc(s, matchera, iterb.Value(), match_input);
+
+    SetArcs(s);
+  }
+
+  // Matches a single transition from 'fstb' against 'fata' at 's'.
+  template <class Matcher>
+  void MatchArc(StateId s, Matcher *matchera,
+                const Arc &arc, bool match_input) {
+    if (matchera->Find(match_input ? arc.olabel : arc.ilabel)) {
+      for (; !matchera->Done(); matchera->Next()) {
+        Arc arca = matchera->Value();
+        Arc arcb = arc;
+        if (match_input) {
+          const FilterState &f = filter_->FilterArc(&arcb, &arca);
+          if (f != FilterState::NoState())
+            AddArc(s, arcb, arca, f);
+        } else {
+          const FilterState &f = filter_->FilterArc(&arca, &arcb);
+          if (f != FilterState::NoState())
+            AddArc(s, arca, arcb, f);
+        }
+      }
+    }
+  }
+
+  // Add a matching transition at 's'.
+   void AddArc(StateId s, const Arc &arc1, const Arc &arc2,
+               const FilterState &f) {
+    StateTuple tuple(arc1.nextstate, arc2.nextstate, f);
+    Arc oarc(arc1.ilabel, arc2.olabel, Times(arc1.weight, arc2.weight),
+           state_table_->FindState(tuple));
+    CacheImpl<Arc>::PushArc(s, oarc);
+  }
+
+  StateId ComputeStart() {
+    StateId s1 = fst1_.Start();
+    if (s1 == kNoStateId)
+      return kNoStateId;
+
+    StateId s2 = fst2_.Start();
+    if (s2 == kNoStateId)
+      return kNoStateId;
+
+    const FilterState &f = filter_->Start();
+    StateTuple tuple(s1, s2, f);
+    return state_table_->FindState(tuple);
+  }
+
+  Weight ComputeFinal(StateId s) {
+    const StateTuple &tuple = state_table_->Tuple(s);
+    StateId s1 = tuple.state_id1;
+    Weight final1 = internal::Final(fst1_, s1);
+    if (final1 == Weight::Zero())
+      return final1;
+
+    StateId s2 = tuple.state_id2;
+    Weight final2 = internal::Final(fst2_, s2);
+    if (final2 == Weight::Zero())
+      return final2;
+
+    filter_->SetState(s1, s2, tuple.filter_state);
+    filter_->FilterFinal(&final1, &final2);
+    return Times(final1, final2);
+  }
+
+  F *filter_;
+  Matcher1 *matcher1_;
+  Matcher2 *matcher2_;
+  const FST1 &fst1_;
+  const FST2 &fst2_;
+  T *state_table_;
+
+  MatchType match_type_;
+
+  void operator=(const ComposeFstImpl<M1, M2, F, T> &);  // disallow
+};
+
+template <class M1, class M2, class F, class T> inline
+ComposeFstImpl<M1, M2, F, T>::ComposeFstImpl(
+    const FST1 &fst1, const FST2 &fst2,
+    const ComposeFstImplOptions<M1, M2, F, T> &opts)
+    : ComposeFstImplBase<Arc>(fst1, fst2, opts),
+      filter_(opts.filter ? opts.filter :
+              new F(fst1, fst2, opts.matcher1, opts.matcher2)),
+      matcher1_(filter_->GetMatcher1()),
+      matcher2_(filter_->GetMatcher2()),
+      fst1_(matcher1_->GetFst()),
+      fst2_(matcher2_->GetFst()),
+      state_table_(opts.state_table ? opts.state_table :
+                   new T(fst1_, fst2_)) {
+  MatchType type1 = matcher1_->Type(false);
+  MatchType type2 = matcher2_->Type(false);
+  if (type1 == MATCH_OUTPUT && type2  == MATCH_INPUT) {
+    match_type_ = MATCH_BOTH;
+  } else if (type1 == MATCH_OUTPUT) {
+    match_type_ = MATCH_OUTPUT;
+  } else if (type2 == MATCH_INPUT) {
+    match_type_ = MATCH_INPUT;
+  } else if (matcher1_->Type(true) == MATCH_OUTPUT) {
+    match_type_ = MATCH_OUTPUT;
+  } else if (matcher2_->Type(true) == MATCH_INPUT) {
+    match_type_ = MATCH_INPUT;
+  } else {
+    FSTERROR() << "ComposeFst: 1st argument cannot match on output labels "
+               << "and 2nd argument cannot match on input labels (sort?).";
+    SetProperties(kError, kError);
+  }
+  uint64 fprops1 = fst1.Properties(kFstProperties, false);
+  uint64 fprops2 = fst2.Properties(kFstProperties, false);
+  uint64 mprops1 = matcher1_->Properties(fprops1);
+  uint64 mprops2 = matcher2_->Properties(fprops2);
+  uint64 cprops = ComposeProperties(mprops1, mprops2);
+  SetProperties(filter_->Properties(cprops), kCopyProperties);
+  if (state_table_->Error()) SetProperties(kError, kError);
+  VLOG(2) << "ComposeFst(" << this << "): Initialized";
+}
+
+
+// Computes the composition of two transducers. This version is a
+// delayed Fst. If FST1 transduces string x to y with weight a and FST2
+// transduces y to z with weight b, then their composition transduces
+// string x to z with weight Times(x, z).
+//
+// The output labels of the first transducer or the input labels of
+// the second transducer must be sorted (with the default matcher).
+// The weights need to form a commutative semiring (valid for
+// TropicalWeight and LogWeight).
+//
+// Complexity:
+// Assuming the first FST is unsorted and the second is sorted:
+// - Time: O(v1 v2 d1 (log d2 + m2)),
+// - Space: O(v1 v2)
+// where vi = # of states visited, di = maximum out-degree, and mi the
+// maximum multiplicity of the states visited for the ith
+// FST. Constant time and space to visit an input state or arc is
+// assumed and exclusive of caching.
+//
+// Caveats:
+// - ComposeFst does not trim its output (since it is a delayed operation).
+// - The efficiency of composition can be strongly affected by several factors:
+//   - the choice of which tnansducer is sorted - prefer sorting the FST
+//     that has the greater average out-degree.
+//   - the amount of non-determinism
+//   - the presence and location of epsilon transitions - avoid epsilon
+//     transitions on the output side of the first transducer or
+//     the input side of the second transducer or prefer placing
+//     them later in a path since they delay matching and can
+//     introduce non-coaccessible states and transitions.
+//
+// This class attaches interface to implementation and handles
+// reference counting, delegating most methods to ImplToFst.
+template <class A>
+class ComposeFst : public ImplToFst< ComposeFstImplBase<A> > {
+ public:
+  friend class ArcIterator< ComposeFst<A> >;
+  friend class StateIterator< ComposeFst<A> >;
+
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef CacheState<A> State;
+  typedef ComposeFstImplBase<A> Impl;
+
+  using ImplToFst<Impl>::SetImpl;
+
+  // Compose specifying only caching options.
+  ComposeFst(const Fst<A> &fst1, const Fst<A> &fst2,
+             const CacheOptions &opts = CacheOptions())
+      : ImplToFst<Impl>(CreateBase(fst1, fst2, opts)) {}
+
+  // Compose specifying one shared matcher type M.  Requires input
+  // Fsts and matcher FST type (M::FST) be Fst<A>. Recommended for
+  // best code-sharing and matcher compatiblity.
+  template <class M, class F, class T>
+  ComposeFst(const Fst<A> &fst1, const Fst<A> &fst2,
+             const ComposeFstOptions<A, M, F, T> &opts)
+      : ImplToFst<Impl>(CreateBase1(fst1, fst2, opts)) {}
+
+  // Compose specifying two matcher types M1 and M2.  Requires input
+  // Fsts (of the same Arc type but o.w. arbitrary) match the
+  // corresponding matcher FST types (M1::FST, M2::FST). Recommended
+  // only for advanced use in demanding or specialized applications
+  // due to potential code bloat and matcher incompatibilities.
+  template <class M1, class M2, class F, class T>
+  ComposeFst(const typename M1::FST &fst1, const typename M2::FST &fst2,
+             const ComposeFstImplOptions<M1, M2, F, T> &opts)
+      : ImplToFst<Impl>(CreateBase2(fst1, fst2, opts)) {}
+
+  // See Fst<>::Copy() for doc.
+  ComposeFst(const ComposeFst<A> &fst, bool safe = false) {
+    if (safe)
+      SetImpl(fst.GetImpl()->Copy());
+    else
+      SetImpl(fst.GetImpl(), false);
+  }
+
+  // Get a copy of this ComposeFst. See Fst<>::Copy() for further doc.
+  virtual ComposeFst<A> *Copy(bool safe = false) const {
+    return new ComposeFst<A>(*this, safe);
+  }
+
+  virtual inline void InitStateIterator(StateIteratorData<A> *data) const;
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<A> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+ protected:
+  ComposeFst() {}
+
+  // Create compose implementation specifying two matcher types.
+  template <class M1, class M2, class F, class T>
+  static Impl *CreateBase2(
+      const typename M1::FST &fst1, const typename M2::FST &fst2,
+      const ComposeFstImplOptions<M1, M2, F, T> &opts) {
+    Impl *impl = new ComposeFstImpl<M1, M2, F, T>(fst1, fst2, opts);
+    if (!(Weight::Properties() & kCommutative)) {
+      int64 props1 = fst1.Properties(kUnweighted, true);
+      int64 props2 = fst2.Properties(kUnweighted, true);
+      if (!(props1 & kUnweighted) && !(props2 & kUnweighted)) {
+        FSTERROR() << "ComposeFst: Weights must be a commutative semiring: "
+                   << Weight::Type();
+        impl->SetProperties(kError, kError);
+      }
+    }
+    return impl;
+  }
+
+  // Create compose implementation specifying one matcher type.
+  //  Requires input Fsts and matcher FST type (M::FST) be Fst<A>
+  template <class M, class F, class T>
+  static Impl *CreateBase1(const Fst<A> &fst1, const Fst<A> &fst2,
+                           const ComposeFstOptions<A, M, F, T> &opts) {
+    ComposeFstImplOptions<M, M, F, T> nopts(opts, opts.matcher1, opts.matcher2,
+                                            opts.filter, opts.state_table);
+    return CreateBase2(fst1, fst2, nopts);
+  }
+
+  // Create compose implementation specifying no matcher type.
+  static Impl *CreateBase(const Fst<A> &fst1, const Fst<A> &fst2,
+                          const CacheOptions &opts) {
+    switch (LookAheadMatchType(fst1, fst2)) {  // Check for lookahead matchers
+      default:
+      case MATCH_NONE: {     // Default composition (no look-ahead)
+        ComposeFstOptions<Arc> nopts(opts);
+        return CreateBase1(fst1, fst2, nopts);
+      }
+      case MATCH_OUTPUT: {   // Lookahead on fst1
+        typedef typename DefaultLookAhead<Arc, MATCH_OUTPUT>::FstMatcher M;
+        typedef typename DefaultLookAhead<Arc, MATCH_OUTPUT>::ComposeFilter F;
+        ComposeFstOptions<Arc, M, F> nopts(opts);
+        return CreateBase1(fst1, fst2, nopts);
+      }
+      case MATCH_INPUT: {    // Lookahead on fst2
+        typedef typename DefaultLookAhead<Arc, MATCH_INPUT>::FstMatcher M;
+        typedef typename DefaultLookAhead<Arc, MATCH_INPUT>::ComposeFilter F;
+        ComposeFstOptions<Arc, M, F> nopts(opts);
+        return CreateBase1(fst1, fst2, nopts);
+      }
+    }
+  }
+
+ private:
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const ComposeFst<A> &fst);  // disallow
+};
+
+
+// Specialization for ComposeFst.
+template<class A>
+class StateIterator< ComposeFst<A> >
+    : public CacheStateIterator< ComposeFst<A> > {
+ public:
+  explicit StateIterator(const ComposeFst<A> &fst)
+      : CacheStateIterator< ComposeFst<A> >(fst, fst.GetImpl()) {}
+};
+
+
+// Specialization for ComposeFst.
+template <class A>
+class ArcIterator< ComposeFst<A> >
+    : public CacheArcIterator< ComposeFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const ComposeFst<A> &fst, StateId s)
+      : CacheArcIterator< ComposeFst<A> >(fst.GetImpl(), s) {
+    if (!fst.GetImpl()->HasArcs(s))
+      fst.GetImpl()->Expand(s);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+template <class A> inline
+void ComposeFst<A>::InitStateIterator(StateIteratorData<A> *data) const {
+  data->base = new StateIterator< ComposeFst<A> >(*this);
+}
+
+// Useful alias when using StdArc.
+typedef ComposeFst<StdArc> StdComposeFst;
+
+enum ComposeFilter { AUTO_FILTER, SEQUENCE_FILTER, ALT_SEQUENCE_FILTER,
+                     MATCH_FILTER };
+
+struct ComposeOptions {
+  bool connect;  // Connect output
+  ComposeFilter filter_type;  // Which pre-defined filter to use
+
+  ComposeOptions(bool c, ComposeFilter ft = AUTO_FILTER)
+      : connect(c), filter_type(ft) {}
+  ComposeOptions() : connect(true), filter_type(AUTO_FILTER) {}
+};
+
+// Computes the composition of two transducers. This version writes
+// the composed FST into a MurableFst. If FST1 transduces string x to
+// y with weight a and FST2 transduces y to z with weight b, then
+// their composition transduces string x to z with weight
+// Times(x, z).
+//
+// The output labels of the first transducer or the input labels of
+// the second transducer must be sorted.  The weights need to form a
+// commutative semiring (valid for TropicalWeight and LogWeight).
+//
+// Complexity:
+// Assuming the first FST is unsorted and the second is sorted:
+// - Time: O(V1 V2 D1 (log D2 + M2)),
+// - Space: O(V1 V2 D1 M2)
+// where Vi = # of states, Di = maximum out-degree, and Mi is
+// the maximum multiplicity for the ith FST.
+//
+// Caveats:
+// - Compose trims its output.
+// - The efficiency of composition can be strongly affected by several factors:
+//   - the choice of which tnansducer is sorted - prefer sorting the FST
+//     that has the greater average out-degree.
+//   - the amount of non-determinism
+//   - the presence and location of epsilon transitions - avoid epsilon
+//     transitions on the output side of the first transducer or
+//     the input side of the second transducer or prefer placing
+//     them later in a path since they delay matching and can
+//     introduce non-coaccessible states and transitions.
+template<class Arc>
+void Compose(const Fst<Arc> &ifst1, const Fst<Arc> &ifst2,
+             MutableFst<Arc> *ofst,
+             const ComposeOptions &opts = ComposeOptions()) {
+  typedef Matcher< Fst<Arc> > M;
+
+  if (opts.filter_type == AUTO_FILTER) {
+     CacheOptions nopts;
+     nopts.gc_limit = 0;  // Cache only the last state for fastest copy.
+     *ofst = ComposeFst<Arc>(ifst1, ifst2, nopts);
+  } else if (opts.filter_type == SEQUENCE_FILTER) {
+    ComposeFstOptions<Arc> copts;
+    copts.gc_limit = 0;  // Cache only the last state for fastest copy.
+    *ofst = ComposeFst<Arc>(ifst1, ifst2, copts);
+  } else if (opts.filter_type == ALT_SEQUENCE_FILTER) {
+    ComposeFstOptions<Arc, M,  AltSequenceComposeFilter<M> > copts;
+    copts.gc_limit = 0;  // Cache only the last state for fastest copy.
+    *ofst = ComposeFst<Arc>(ifst1, ifst2, copts);
+  } else if (opts.filter_type == MATCH_FILTER) {
+    ComposeFstOptions<Arc, M,  MatchComposeFilter<M> > copts;
+    copts.gc_limit = 0;  // Cache only the last state for fastest copy.
+    *ofst = ComposeFst<Arc>(ifst1, ifst2, copts);
+  }
+
+  if (opts.connect)
+    Connect(ofst);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_COMPOSE_H__
diff --git a/src/include/fst/concat.h b/src/include/fst/concat.h
new file mode 100644
index 0000000..8500d50
--- /dev/null
+++ b/src/include/fst/concat.h
@@ -0,0 +1,246 @@
+// concat.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Functions and classes to compute the concat of two FSTs.
+
+#ifndef FST_LIB_CONCAT_H__
+#define FST_LIB_CONCAT_H__
+
+#include <vector>
+using std::vector;
+#include <algorithm>
+
+#include <fst/mutable-fst.h>
+#include <fst/rational.h>
+
+
+namespace fst {
+
+// Computes the concatenation (product) of two FSTs. If FST1
+// transduces string x to y with weight a and FST2 transduces string w
+// to v with weight b, then their concatenation transduces string xw
+// to yv with Times(a, b).
+//
+// This version modifies its MutableFst argument (in first position).
+//
+// Complexity:
+// - Time: O(V1 + V2 + E2)
+// - Space: O(V1 + V2 + E2)
+// where Vi = # of states and Ei = # of arcs of the ith FST.
+//
+template<class Arc>
+void Concat(MutableFst<Arc> *fst1, const Fst<Arc> &fst2) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  // TODO(riley): restore when voice actions issues fixed
+  // Check that the symbol table are compatible
+  if (!CompatSymbols(fst1->InputSymbols(), fst2.InputSymbols()) ||
+      !CompatSymbols(fst1->OutputSymbols(), fst2.OutputSymbols())) {
+    LOG(ERROR) << "Concat: input/output symbol tables of 1st argument "
+               << "do not match input/output symbol tables of 2nd argument";
+    // fst1->SetProperties(kError, kError);
+    // return;
+  }
+
+  uint64 props1 = fst1->Properties(kFstProperties, false);
+  uint64 props2 = fst2.Properties(kFstProperties, false);
+
+  StateId start1 = fst1->Start();
+  if (start1 == kNoStateId) {
+    if (props2 & kError) fst1->SetProperties(kError, kError);
+    return;
+  }
+
+  StateId numstates1 = fst1->NumStates();
+  if (fst2.Properties(kExpanded, false))
+    fst1->ReserveStates(numstates1 + CountStates(fst2));
+
+  for (StateIterator< Fst<Arc> > siter2(fst2);
+       !siter2.Done();
+       siter2.Next()) {
+    StateId s1 = fst1->AddState();
+    StateId s2 = siter2.Value();
+    fst1->SetFinal(s1, fst2.Final(s2));
+    fst1->ReserveArcs(s1, fst2.NumArcs(s2));
+    for (ArcIterator< Fst<Arc> > aiter(fst2, s2);
+         !aiter.Done();
+         aiter.Next()) {
+      Arc arc = aiter.Value();
+      arc.nextstate += numstates1;
+      fst1->AddArc(s1, arc);
+    }
+  }
+
+  StateId start2 = fst2.Start();
+  for (StateId s1 = 0; s1 < numstates1; ++s1) {
+    Weight final = fst1->Final(s1);
+    if (final != Weight::Zero()) {
+      fst1->SetFinal(s1, Weight::Zero());
+      if (start2 != kNoStateId)
+        fst1->AddArc(s1, Arc(0, 0, final, start2 + numstates1));
+    }
+  }
+  if (start2 != kNoStateId)
+    fst1->SetProperties(ConcatProperties(props1, props2), kFstProperties);
+}
+
+// Computes the concatentation of two FSTs.  This version modifies its
+// MutableFst argument (in second position).
+//
+// Complexity:
+// - Time: O(V1 + E1)
+// - Space: O(V1 + E1)
+// where Vi = # of states and Ei = # of arcs of the ith FST.
+//
+template<class Arc>
+void Concat(const Fst<Arc> &fst1, MutableFst<Arc> *fst2) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  // Check that the symbol table are compatible
+  if (!CompatSymbols(fst1.InputSymbols(), fst2->InputSymbols()) ||
+      !CompatSymbols(fst1.OutputSymbols(), fst2->OutputSymbols())) {
+    LOG(ERROR) << "Concat: input/output symbol tables of 1st argument "
+               << "do not match input/output symbol tables of 2nd argument";
+    // fst2->SetProperties(kError, kError);
+    // return;
+  }
+
+  uint64 props1 = fst1.Properties(kFstProperties, false);
+  uint64 props2 = fst2->Properties(kFstProperties, false);
+
+  StateId start2 = fst2->Start();
+  if (start2 == kNoStateId) {
+    if (props1 & kError) fst2->SetProperties(kError, kError);
+    return;
+  }
+
+  StateId numstates2 = fst2->NumStates();
+  if (fst1.Properties(kExpanded, false))
+    fst2->ReserveStates(numstates2 + CountStates(fst1));
+
+  for (StateIterator< Fst<Arc> > siter(fst1);
+       !siter.Done();
+       siter.Next()) {
+    StateId s1 = siter.Value();
+    StateId s2 = fst2->AddState();
+    Weight final = fst1.Final(s1);
+    fst2->ReserveArcs(s2, fst1.NumArcs(s1) + (final != Weight::Zero() ? 1 : 0));
+    if (final != Weight::Zero())
+      fst2->AddArc(s2, Arc(0, 0, final, start2));
+    for (ArcIterator< Fst<Arc> > aiter(fst1, s1);
+         !aiter.Done();
+         aiter.Next()) {
+      Arc arc = aiter.Value();
+      arc.nextstate += numstates2;
+      fst2->AddArc(s2, arc);
+    }
+  }
+  StateId start1 = fst1.Start();
+  fst2->SetStart(start1 == kNoStateId ? fst2->AddState() : start1 + numstates2);
+  if (start1 != kNoStateId)
+    fst2->SetProperties(ConcatProperties(props1, props2), kFstProperties);
+}
+
+
+// Computes the concatentation of two FSTs. This version modifies its
+// RationalFst input (in first position).
+template<class Arc>
+void Concat(RationalFst<Arc> *fst1, const Fst<Arc> &fst2) {
+  fst1->GetImpl()->AddConcat(fst2, true);
+}
+
+// Computes the concatentation of two FSTs. This version modifies its
+// RationalFst input (in second position).
+template<class Arc>
+void Concat(const Fst<Arc> &fst1, RationalFst<Arc> *fst2) {
+  fst2->GetImpl()->AddConcat(fst1, false);
+}
+
+typedef RationalFstOptions ConcatFstOptions;
+
+
+// Computes the concatenation (product) of two FSTs; this version is a
+// delayed Fst. If FST1 transduces string x to y with weight a and FST2
+// transduces string w to v with weight b, then their concatenation
+// transduces string xw to yv with Times(a, b).
+//
+// Complexity:
+// - Time: O(v1 + e1 + v2 + e2),
+// - Space: O(v1 + v2)
+// where vi = # of states visited and ei = # of arcs visited of the
+// ith FST. Constant time and space to visit an input state or arc is
+// assumed and exclusive of caching.
+template <class A>
+class ConcatFst : public RationalFst<A> {
+ public:
+  using ImplToFst< RationalFstImpl<A> >::GetImpl;
+
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  ConcatFst(const Fst<A> &fst1, const Fst<A> &fst2) {
+    GetImpl()->InitConcat(fst1, fst2);
+  }
+
+  ConcatFst(const Fst<A> &fst1, const Fst<A> &fst2,
+            const ConcatFstOptions &opts) : RationalFst<A>(opts) {
+    GetImpl()->InitConcat(fst1, fst2);
+  }
+
+  // See Fst<>::Copy() for doc.
+  ConcatFst(const ConcatFst<A> &fst, bool safe = false)
+      : RationalFst<A>(fst, safe) {}
+
+  // Get a copy of this ConcatFst. See Fst<>::Copy() for further doc.
+  virtual ConcatFst<A> *Copy(bool safe = false) const {
+    return new ConcatFst<A>(*this, safe);
+  }
+};
+
+
+// Specialization for ConcatFst.
+template <class A>
+class StateIterator< ConcatFst<A> > : public StateIterator< RationalFst<A> > {
+ public:
+  explicit StateIterator(const ConcatFst<A> &fst)
+      : StateIterator< RationalFst<A> >(fst) {}
+};
+
+
+// Specialization for ConcatFst.
+template <class A>
+class ArcIterator< ConcatFst<A> > : public ArcIterator< RationalFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const ConcatFst<A> &fst, StateId s)
+      : ArcIterator< RationalFst<A> >(fst, s) {}
+};
+
+
+// Useful alias when using StdArc.
+typedef ConcatFst<StdArc> StdConcatFst;
+
+}  // namespace fst
+
+#endif  // FST_LIB_CONCAT_H__
diff --git a/src/include/fst/config.h b/src/include/fst/config.h
new file mode 100644
index 0000000..046b49c
--- /dev/null
+++ b/src/include/fst/config.h
@@ -0,0 +1,12 @@
+/* src/include/fst/config.h.  Generated from config.h.in by configure.  */
+// OpenFst config file 
+
+/* Define to 1 if you have the ICU library. */
+/* #undef HAVE_ICU */
+
+/* Define to 1 if the system has the type `std::tr1::hash<long long
+   unsigned>'. */
+#define HAVE_STD__TR1__HASH_LONG_LONG_UNSIGNED_ 1
+
+/* Define to 1 if the system has the type `__gnu_cxx::slist<int>'. */
+#define HAVE___GNU_CXX__SLIST_INT_ 1
diff --git a/src/include/fst/config.h.in b/src/include/fst/config.h.in
new file mode 100644
index 0000000..7815dfc
--- /dev/null
+++ b/src/include/fst/config.h.in
@@ -0,0 +1,11 @@
+// OpenFst config file 
+
+/* Define to 1 if you have the ICU library. */
+#undef HAVE_ICU
+
+/* Define to 1 if the system has the type `std::tr1::hash<long long
+   unsigned>'. */
+#define HAVE_STD__TR1__HASH_LONG_LONG_UNSIGNED_ 1
+
+/* Define to 1 if the system has the type `__gnu_cxx::slist<int>'. */
+#define HAVE___GNU_CXX__SLIST_INT_ 1
diff --git a/src/include/fst/connect.h b/src/include/fst/connect.h
new file mode 100644
index 0000000..427808c
--- /dev/null
+++ b/src/include/fst/connect.h
@@ -0,0 +1,319 @@
+// connect.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Classes and functions to remove unsuccessful paths from an Fst.
+
+#ifndef FST_LIB_CONNECT_H__
+#define FST_LIB_CONNECT_H__
+
+#include <vector>
+using std::vector;
+
+#include <fst/dfs-visit.h>
+#include <fst/union-find.h>
+#include <fst/mutable-fst.h>
+
+
+namespace fst {
+
+// Finds and returns connected components. Use with Visit().
+template <class A>
+class CcVisitor {
+ public:
+  typedef A Arc;
+  typedef typename Arc::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  // cc[i]: connected component number for state i.
+  CcVisitor(vector<StateId> *cc)
+      : comps_(new UnionFind<StateId>(0, kNoStateId)),
+        cc_(cc),
+        nstates_(0) { }
+
+  // comps: connected components equiv classes.
+  CcVisitor(UnionFind<StateId> *comps)
+      : comps_(comps),
+        cc_(0),
+        nstates_(0) { }
+
+  ~CcVisitor() {
+    if (cc_)  // own comps_?
+      delete comps_;
+  }
+
+  void InitVisit(const Fst<A> &fst) { }
+
+  bool InitState(StateId s, StateId root) {
+    ++nstates_;
+    if (comps_->FindSet(s) == kNoStateId)
+      comps_->MakeSet(s);
+    return true;
+  }
+
+  bool WhiteArc(StateId s, const A &arc) {
+    comps_->MakeSet(arc.nextstate);
+    comps_->Union(s, arc.nextstate);
+    return true;
+  }
+
+  bool GreyArc(StateId s, const A &arc) {
+    comps_->Union(s, arc.nextstate);
+    return true;
+  }
+
+  bool BlackArc(StateId s, const A &arc) {
+    comps_->Union(s, arc.nextstate);
+    return true;
+  }
+
+  void FinishState(StateId s) { }
+
+  void FinishVisit() {
+    if (cc_)
+      GetCcVector(cc_);
+  }
+
+  // cc[i]: connected component number for state i.
+  // Returns number of components.
+  int GetCcVector(vector<StateId> *cc) {
+    cc->clear();
+    cc->resize(nstates_, kNoStateId);
+    StateId ncomp = 0;
+    for (StateId i = 0; i < nstates_; ++i) {
+      StateId rep = comps_->FindSet(i);
+      StateId &comp = (*cc)[rep];
+      if (comp == kNoStateId) {
+        comp = ncomp;
+        ++ncomp;
+      }
+      (*cc)[i] = comp;
+    }
+    return ncomp;
+  }
+
+ private:
+  UnionFind<StateId> *comps_;   // Components
+  vector<StateId> *cc_;         // State's cc number
+  StateId nstates_;             // State count
+};
+
+
+// Finds and returns strongly-connected components, accessible and
+// coaccessible states and related properties. Uses Tarjan's single
+// DFS SCC algorithm (see Aho, et al, "Design and Analysis of Computer
+// Algorithms", 189pp). Use with DfsVisit();
+template <class A>
+class SccVisitor {
+ public:
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  // scc[i]: strongly-connected component number for state i.
+  //   SCC numbers will be in topological order for acyclic input.
+  // access[i]: accessibility of state i.
+  // coaccess[i]: coaccessibility of state i.
+  // Any of above can be NULL.
+  // props: related property bits (cyclicity, initial cyclicity,
+  //   accessibility, coaccessibility) set/cleared (o.w. unchanged).
+  SccVisitor(vector<StateId> *scc, vector<bool> *access,
+             vector<bool> *coaccess, uint64 *props)
+      : scc_(scc), access_(access), coaccess_(coaccess), props_(props) {}
+  SccVisitor(uint64 *props)
+      : scc_(0), access_(0), coaccess_(0), props_(props) {}
+
+  void InitVisit(const Fst<A> &fst);
+
+  bool InitState(StateId s, StateId root);
+
+  bool TreeArc(StateId s, const A &arc) { return true; }
+
+  bool BackArc(StateId s, const A &arc) {
+    StateId t = arc.nextstate;
+    if ((*dfnumber_)[t] < (*lowlink_)[s])
+      (*lowlink_)[s] = (*dfnumber_)[t];
+    if ((*coaccess_)[t])
+      (*coaccess_)[s] = true;
+    *props_ |= kCyclic;
+    *props_ &= ~kAcyclic;
+    if (arc.nextstate == start_) {
+      *props_ |= kInitialCyclic;
+      *props_ &= ~kInitialAcyclic;
+    }
+    return true;
+  }
+
+  bool ForwardOrCrossArc(StateId s, const A &arc) {
+    StateId t = arc.nextstate;
+    if ((*dfnumber_)[t] < (*dfnumber_)[s] /* cross edge */ &&
+        (*onstack_)[t] && (*dfnumber_)[t] < (*lowlink_)[s])
+      (*lowlink_)[s] = (*dfnumber_)[t];
+    if ((*coaccess_)[t])
+      (*coaccess_)[s] = true;
+    return true;
+  }
+
+  void FinishState(StateId s, StateId p, const A *);
+
+  void FinishVisit() {
+    // Numbers SCC's in topological order when acyclic.
+    if (scc_)
+      for (StateId i = 0; i < scc_->size(); ++i)
+        (*scc_)[i] = nscc_ - 1 - (*scc_)[i];
+    if (coaccess_internal_)
+      delete coaccess_;
+    delete dfnumber_;
+    delete lowlink_;
+    delete onstack_;
+    delete scc_stack_;
+  }
+
+ private:
+  vector<StateId> *scc_;        // State's scc number
+  vector<bool> *access_;        // State's accessibility
+  vector<bool> *coaccess_;      // State's coaccessibility
+  uint64 *props_;
+  const Fst<A> *fst_;
+  StateId start_;
+  StateId nstates_;             // State count
+  StateId nscc_;                // SCC count
+  bool coaccess_internal_;
+  vector<StateId> *dfnumber_;   // state discovery times
+  vector<StateId> *lowlink_;    // lowlink[s] == dfnumber[s] => SCC root
+  vector<bool> *onstack_;       // is a state on the SCC stack
+  vector<StateId> *scc_stack_;  // SCC stack (w/ random access)
+};
+
+template <class A> inline
+void SccVisitor<A>::InitVisit(const Fst<A> &fst) {
+  if (scc_)
+    scc_->clear();
+  if (access_)
+    access_->clear();
+  if (coaccess_) {
+    coaccess_->clear();
+    coaccess_internal_ = false;
+  } else {
+    coaccess_ = new vector<bool>;
+    coaccess_internal_ = true;
+  }
+  *props_ |= kAcyclic | kInitialAcyclic | kAccessible | kCoAccessible;
+  *props_ &= ~(kCyclic | kInitialCyclic | kNotAccessible | kNotCoAccessible);
+  fst_ = &fst;
+  start_ = fst.Start();
+  nstates_ = 0;
+  nscc_ = 0;
+  dfnumber_ = new vector<StateId>;
+  lowlink_ = new vector<StateId>;
+  onstack_ = new vector<bool>;
+  scc_stack_ = new vector<StateId>;
+}
+
+template <class A> inline
+bool SccVisitor<A>::InitState(StateId s, StateId root) {
+  scc_stack_->push_back(s);
+  while (dfnumber_->size() <= s) {
+    if (scc_)
+      scc_->push_back(-1);
+    if (access_)
+      access_->push_back(false);
+    coaccess_->push_back(false);
+    dfnumber_->push_back(-1);
+    lowlink_->push_back(-1);
+    onstack_->push_back(false);
+  }
+  (*dfnumber_)[s] = nstates_;
+  (*lowlink_)[s] = nstates_;
+  (*onstack_)[s] = true;
+  if (root == start_) {
+    if (access_)
+      (*access_)[s] = true;
+  } else {
+    if (access_)
+      (*access_)[s] = false;
+    *props_ |= kNotAccessible;
+    *props_ &= ~kAccessible;
+  }
+  ++nstates_;
+  return true;
+}
+
+template <class A> inline
+void SccVisitor<A>::FinishState(StateId s, StateId p, const A *) {
+  if (fst_->Final(s) != Weight::Zero())
+    (*coaccess_)[s] = true;
+  if ((*dfnumber_)[s] == (*lowlink_)[s]) {  // root of new SCC
+    bool scc_coaccess = false;
+    size_t i = scc_stack_->size();
+    StateId t;
+    do {
+      t = (*scc_stack_)[--i];
+      if ((*coaccess_)[t])
+        scc_coaccess = true;
+    } while (s != t);
+    do {
+      t = scc_stack_->back();
+      if (scc_)
+        (*scc_)[t] = nscc_;
+      if (scc_coaccess)
+        (*coaccess_)[t] = true;
+      (*onstack_)[t] = false;
+      scc_stack_->pop_back();
+    } while (s != t);
+    if (!scc_coaccess) {
+      *props_ |= kNotCoAccessible;
+      *props_ &= ~kCoAccessible;
+    }
+    ++nscc_;
+  }
+  if (p != kNoStateId) {
+    if ((*coaccess_)[s])
+      (*coaccess_)[p] = true;
+    if ((*lowlink_)[s] < (*lowlink_)[p])
+      (*lowlink_)[p] = (*lowlink_)[s];
+  }
+}
+
+
+// Trims an FST, removing states and arcs that are not on successful
+// paths. This version modifies its input.
+//
+// Complexity:
+// - Time:  O(V + E)
+// - Space: O(V + E)
+// where V = # of states and E = # of arcs.
+template<class Arc>
+void Connect(MutableFst<Arc> *fst) {
+  typedef typename Arc::StateId StateId;
+
+  vector<bool> access;
+  vector<bool> coaccess;
+  uint64 props = 0;
+  SccVisitor<Arc> scc_visitor(0, &access, &coaccess, &props);
+  DfsVisit(*fst, &scc_visitor);
+  vector<StateId> dstates;
+  for (StateId s = 0; s < access.size(); ++s)
+    if (!access[s] || !coaccess[s])
+      dstates.push_back(s);
+  fst->DeleteStates(dstates);
+  fst->SetProperties(kAccessible | kCoAccessible, kAccessible | kCoAccessible);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_CONNECT_H__
diff --git a/src/include/fst/const-fst.h b/src/include/fst/const-fst.h
new file mode 100644
index 0000000..f68e8ed
--- /dev/null
+++ b/src/include/fst/const-fst.h
@@ -0,0 +1,483 @@
+// const-fst.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Simple concrete immutable FST whose states and arcs are each stored
+// in single arrays.
+
+#ifndef FST_LIB_CONST_FST_H__
+#define FST_LIB_CONST_FST_H__
+
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/expanded-fst.h>
+#include <fst/fst-decl.h>  // For optional argument declarations
+#include <fst/test-properties.h>
+#include <fst/util.h>
+
+
+namespace fst {
+
+template <class A, class U> class ConstFst;
+template <class F, class G> void Cast(const F &, G *);
+
+// States and arcs each implemented by single arrays, templated on the
+// Arc definition. The unsigned type U is used to represent indices into
+// the arc array.
+template <class A, class U>
+class ConstFstImpl : public FstImpl<A> {
+ public:
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::Properties;
+
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef U Unsigned;
+
+  ConstFstImpl()
+      : states_(0), arcs_(0), nstates_(0), narcs_(0), start_(kNoStateId) {
+    string type = "const";
+    if (sizeof(U) != sizeof(uint32)) {
+      string size;
+      Int64ToStr(8 * sizeof(U), &size);
+      type += size;
+    }
+    SetType(type);
+    SetProperties(kNullProperties | kStaticProperties);
+  }
+
+  explicit ConstFstImpl(const Fst<A> &fst);
+
+  ~ConstFstImpl() {
+    delete[] states_;
+    delete[] arcs_;
+  }
+
+  StateId Start() const { return start_; }
+
+  Weight Final(StateId s) const { return states_[s].final; }
+
+  StateId NumStates() const { return nstates_; }
+
+  size_t NumArcs(StateId s) const { return states_[s].narcs; }
+
+  size_t NumInputEpsilons(StateId s) const { return states_[s].niepsilons; }
+
+  size_t NumOutputEpsilons(StateId s) const { return states_[s].noepsilons; }
+
+  static ConstFstImpl<A, U> *Read(istream &strm, const FstReadOptions &opts);
+
+  bool Write(ostream &strm, const FstWriteOptions &opts) const;
+
+  A *Arcs(StateId s) { return arcs_ + states_[s].pos; }
+
+  // Provide information needed for generic state iterator
+  void InitStateIterator(StateIteratorData<A> *data) const {
+    data->base = 0;
+    data->nstates = nstates_;
+  }
+
+  // Provide information needed for the generic arc iterator
+  void InitArcIterator(StateId s, ArcIteratorData<A> *data) const {
+    data->base = 0;
+    data->arcs = arcs_ + states_[s].pos;
+    data->narcs = states_[s].narcs;
+    data->ref_count = 0;
+  }
+
+ private:
+  friend class ConstFst<A, U>;  // Allow finding narcs_, nstates_ during Write
+
+  // States implemented by array *states_ below, arcs by (single) *arcs_.
+  struct State {
+    Weight final;                // Final weight
+    Unsigned pos;                // Start of state's arcs in *arcs_
+    Unsigned narcs;              // Number of arcs (per state)
+    Unsigned niepsilons;         // # of input epsilons
+    Unsigned noepsilons;         // # of output epsilons
+    State() : final(Weight::Zero()), niepsilons(0), noepsilons(0) {}
+  };
+
+  // Properties always true of this Fst class
+  static const uint64 kStaticProperties = kExpanded;
+  // Current unaligned file format version. The unaligned version was added and
+  // made the default since the aligned version does not work on pipes.
+  static const int kFileVersion = 2;
+  // Current aligned file format version
+  static const int kAlignedFileVersion = 1;
+  // Minimum file format version supported
+  static const int kMinFileVersion = 1;
+  // Byte alignment for states and arcs in file format (version 1 only)
+  static const int kFileAlign = 16;
+
+  State *states_;                // States represenation
+  A *arcs_;                      // Arcs representation
+  StateId nstates_;              // Number of states
+  size_t narcs_;                 // Number of arcs (per FST)
+  StateId start_;                // Initial state
+
+  DISALLOW_COPY_AND_ASSIGN(ConstFstImpl);
+};
+
+template <class A, class U>
+const uint64 ConstFstImpl<A, U>::kStaticProperties;
+template <class A, class U>
+const int ConstFstImpl<A, U>::kFileVersion;
+template <class A, class U>
+const int ConstFstImpl<A, U>::kAlignedFileVersion;
+template <class A, class U>
+const int ConstFstImpl<A, U>::kMinFileVersion;
+template <class A, class U>
+const int ConstFstImpl<A, U>::kFileAlign;
+
+
+template<class A, class U>
+ConstFstImpl<A, U>::ConstFstImpl(const Fst<A> &fst) : nstates_(0), narcs_(0) {
+  string type = "const";
+  if (sizeof(U) != sizeof(uint32)) {
+    string size;
+    Int64ToStr(sizeof(U) * 8, &size);
+    type += size;
+  }
+  SetType(type);
+  SetInputSymbols(fst.InputSymbols());
+  SetOutputSymbols(fst.OutputSymbols());
+  start_ = fst.Start();
+
+  // Count # of states and arcs.
+  for (StateIterator< Fst<A> > siter(fst);
+       !siter.Done();
+       siter.Next()) {
+    ++nstates_;
+    StateId s = siter.Value();
+    for (ArcIterator< Fst<A> > aiter(fst, s);
+         !aiter.Done();
+         aiter.Next())
+      ++narcs_;
+  }
+  states_ = new State[nstates_];
+  arcs_ = new A[narcs_];
+  size_t pos = 0;
+  for (StateId s = 0; s < nstates_; ++s) {
+    states_[s].final = fst.Final(s);
+    states_[s].pos = pos;
+    states_[s].narcs = 0;
+    states_[s].niepsilons = 0;
+    states_[s].noepsilons = 0;
+    for (ArcIterator< Fst<A> > aiter(fst, s);
+         !aiter.Done();
+         aiter.Next()) {
+      const A &arc = aiter.Value();
+      ++states_[s].narcs;
+      if (arc.ilabel == 0)
+        ++states_[s].niepsilons;
+      if (arc.olabel == 0)
+        ++states_[s].noepsilons;
+      arcs_[pos++] = arc;
+    }
+  }
+  SetProperties(fst.Properties(kCopyProperties, true) | kStaticProperties);
+}
+
+
+template<class A, class U>
+ConstFstImpl<A, U> *ConstFstImpl<A, U>::Read(istream &strm,
+                                             const FstReadOptions &opts) {
+  ConstFstImpl<A, U> *impl = new ConstFstImpl<A, U>;
+  FstHeader hdr;
+  if (!impl->ReadHeader(strm, opts, kMinFileVersion, &hdr)) {
+    delete impl;
+    return 0;
+  }
+  impl->start_ = hdr.Start();
+  impl->nstates_ = hdr.NumStates();
+  impl->narcs_ = hdr.NumArcs();
+  impl->states_ = new State[impl->nstates_];
+  impl->arcs_ = new A[impl->narcs_];
+
+  // Ensures compatibility
+  if (hdr.Version() == kAlignedFileVersion)
+    hdr.SetFlags(hdr.GetFlags() | FstHeader::IS_ALIGNED);
+
+  if ((hdr.GetFlags() & FstHeader::IS_ALIGNED) &&
+      !AlignInput(strm, kFileAlign)) {
+    LOG(ERROR) << "ConstFst::Read: Alignment failed: " << opts.source;
+    delete impl;
+    return 0;
+  }
+  size_t b = impl->nstates_ * sizeof(typename ConstFstImpl<A, U>::State);
+  strm.read(reinterpret_cast<char *>(impl->states_), b);
+  if (!strm) {
+    LOG(ERROR) << "ConstFst::Read: Read failed: " << opts.source;
+    delete impl;
+    return 0;
+  }
+  if ((hdr.GetFlags() & FstHeader::IS_ALIGNED) &&
+      !AlignInput(strm, kFileAlign)) {
+    LOG(ERROR) << "ConstFst::Read: Alignment failed: " << opts.source;
+    delete impl;
+    return 0;
+  }
+  b = impl->narcs_ * sizeof(A);
+  strm.read(reinterpret_cast<char *>(impl->arcs_), b);
+  if (!strm) {
+    LOG(ERROR) << "ConstFst::Read: Read failed: " << opts.source;
+    delete impl;
+    return 0;
+  }
+  return impl;
+}
+
+// Simple concrete immutable FST.  This class attaches interface to
+// implementation and handles reference counting, delegating most
+// methods to ImplToExpandedFst. The unsigned type U is used to
+// represent indices into the arc array (uint32 by default, declared
+// in fst-decl.h).
+template <class A, class U>
+class ConstFst : public ImplToExpandedFst< ConstFstImpl<A, U> > {
+ public:
+  friend class StateIterator< ConstFst<A, U> >;
+  friend class ArcIterator< ConstFst<A, U> >;
+  template <class F, class G> void friend Cast(const F &, G *);
+
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef ConstFstImpl<A, U> Impl;
+  typedef U Unsigned;
+
+  ConstFst() : ImplToExpandedFst<Impl>(new Impl()) {}
+
+  explicit ConstFst(const Fst<A> &fst)
+      : ImplToExpandedFst<Impl>(new Impl(fst)) {}
+
+  ConstFst(const ConstFst<A, U> &fst) : ImplToExpandedFst<Impl>(fst) {}
+
+  // Get a copy of this ConstFst. See Fst<>::Copy() for further doc.
+  virtual ConstFst<A, U> *Copy(bool safe = false) const {
+    return new ConstFst<A, U>(*this);
+  }
+
+  // Read a ConstFst from an input stream; return NULL on error
+  static ConstFst<A, U> *Read(istream &strm, const FstReadOptions &opts) {
+    Impl* impl = Impl::Read(strm, opts);
+    return impl ? new ConstFst<A, U>(impl) : 0;
+  }
+
+  // Read a ConstFst from a file; return NULL on error
+  // Empty filename reads from standard input
+  static ConstFst<A, U> *Read(const string &filename) {
+    Impl* impl = ImplToExpandedFst<Impl>::Read(filename);
+    return impl ? new ConstFst<A, U>(impl) : 0;
+  }
+
+  virtual bool Write(ostream &strm, const FstWriteOptions &opts) const {
+    return WriteFst(*this, strm, opts);
+  }
+
+  virtual bool Write(const string &filename) const {
+    return Fst<A>::WriteFile(filename);
+  }
+
+  template <class F>
+  static bool WriteFst(const F &fst, ostream &strm,
+                       const FstWriteOptions &opts);
+
+  virtual void InitStateIterator(StateIteratorData<Arc> *data) const {
+    GetImpl()->InitStateIterator(data);
+  }
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+ private:
+  explicit ConstFst(Impl *impl) : ImplToExpandedFst<Impl>(impl) {}
+
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl, ExpandedFst<A> >::GetImpl(); }
+
+  void SetImpl(Impl *impl, bool own_impl = true) {
+    ImplToFst< Impl, ExpandedFst<A> >::SetImpl(impl, own_impl);
+  }
+
+  void operator=(const ConstFst<A, U> &fst);  // disallow
+};
+
+// Writes Fst in Const format, potentially with a pass over the machine
+// before writing to compute number of states and arcs.
+//
+template <class A, class U>
+template <class F>
+bool ConstFst<A, U>::WriteFst(const F &fst, ostream &strm,
+                              const FstWriteOptions &opts) {
+  static const int kFileVersion = 2;
+  static const int kAlignedFileVersion = 1;
+  static const int kFileAlign = 16;
+  int file_version = opts.align ? kAlignedFileVersion : kFileVersion;
+  size_t num_arcs = -1, num_states = -1;
+  size_t start_offset = 0;
+  bool update_header = true;
+  if (fst.Type() == ConstFst<A, U>().Type()) {
+    const ConstFst<A, U> *const_fst = static_cast<const ConstFst<A, U> *>(&fst);
+    num_arcs = const_fst->GetImpl()->narcs_;
+    num_states = const_fst->GetImpl()->nstates_;
+    update_header = false;
+  } else if ((start_offset = strm.tellp()) == -1) {
+    // precompute values needed for header when we cannot seek to rewrite it.
+    for (StateIterator<F> siter(fst); !siter.Done(); siter.Next()) {
+      num_arcs += fst.NumArcs(siter.Value());
+      num_states++;
+    }
+    update_header = false;
+  }
+  FstHeader hdr;
+  hdr.SetStart(fst.Start());
+  hdr.SetNumStates(num_states);
+  hdr.SetNumArcs(num_arcs);
+  string type = "const";
+  if (sizeof(U) != sizeof(uint32)) {
+    string size;
+    Int64ToStr(8 * sizeof(U), &size);
+    type += size;
+  }
+  FstImpl<A>::WriteFstHeader(fst, strm, opts, file_version, type, &hdr);
+  if (opts.align && !AlignOutput(strm, kFileAlign)) {
+    LOG(ERROR) << "Could not align file during write after header";
+    return false;
+  }
+  size_t pos = 0, states = 0;
+  typename ConstFstImpl<A, U>::State state;
+  for (StateIterator<F> siter(fst); !siter.Done(); siter.Next()) {
+    state.final = fst.Final(siter.Value());
+    state.pos = pos;
+    state.narcs = fst.NumArcs(siter.Value());
+    state.niepsilons = fst.NumInputEpsilons(siter.Value());
+    state.noepsilons = fst.NumOutputEpsilons(siter.Value());
+    strm.write(reinterpret_cast<const char *>(&state), sizeof(state));
+    pos += state.narcs;
+    states++;
+  }
+  hdr.SetNumStates(states);
+  hdr.SetNumArcs(pos);
+  if (opts.align && !AlignOutput(strm, kFileAlign)) {
+    LOG(ERROR) << "Could not align file during write after writing states";
+  }
+  for (StateIterator<F> siter(fst); !siter.Done(); siter.Next()) {
+    StateId s = siter.Value();
+    for (ArcIterator<F> aiter(fst, s); !aiter.Done(); aiter.Next()) {
+      const A &arc = aiter.Value();
+      strm.write(reinterpret_cast<const char *>(&arc), sizeof(arc));
+    }
+  }
+  strm.flush();
+  if (!strm) {
+    LOG(ERROR) << "WriteAsVectorFst write failed: " << opts.source;
+    return false;
+  }
+  if (update_header) {
+    return FstImpl<A>::UpdateFstHeader(fst, strm, opts, file_version, type,
+                                       &hdr, start_offset);
+  } else {
+    if (hdr.NumStates() != num_states) {
+      LOG(ERROR) << "Inconsistent number of states observed during write";
+      return false;
+    }
+    if (hdr.NumArcs() != num_arcs) {
+      LOG(ERROR) << "Inconsistent number of arcs observed during write";
+      return false;
+    }
+  }
+  return true;
+}
+
+// Specialization for ConstFst; see generic version in fst.h
+// for sample usage (but use the ConstFst type!). This version
+// should inline.
+template <class A, class U>
+class StateIterator< ConstFst<A, U> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  explicit StateIterator(const ConstFst<A, U> &fst)
+      : nstates_(fst.GetImpl()->NumStates()), s_(0) {}
+
+  bool Done() const { return s_ >= nstates_; }
+
+  StateId Value() const { return s_; }
+
+  void Next() { ++s_; }
+
+  void Reset() { s_ = 0; }
+
+ private:
+  StateId nstates_;
+  StateId s_;
+
+  DISALLOW_COPY_AND_ASSIGN(StateIterator);
+};
+
+
+// Specialization for ConstFst; see generic version in fst.h
+// for sample usage (but use the ConstFst type!). This version
+// should inline.
+template <class A, class U>
+class ArcIterator< ConstFst<A, U> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const ConstFst<A, U> &fst, StateId s)
+      : arcs_(fst.GetImpl()->Arcs(s)),
+        narcs_(fst.GetImpl()->NumArcs(s)), i_(0) {}
+
+  bool Done() const { return i_ >= narcs_; }
+
+  const A& Value() const { return arcs_[i_]; }
+
+  void Next() { ++i_; }
+
+  size_t Position() const { return i_; }
+
+  void Reset() { i_ = 0; }
+
+  void Seek(size_t a) { i_ = a; }
+
+  uint32 Flags() const {
+    return kArcValueFlags;
+  }
+
+  void SetFlags(uint32 f, uint32 m) {}
+
+ private:
+  const A *arcs_;
+  size_t narcs_;
+  size_t i_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+// A useful alias when using StdArc.
+typedef ConstFst<StdArc> StdConstFst;
+
+}  // namespace fst
+
+#endif  // FST_LIB_CONST_FST_H__
diff --git a/src/include/fst/determinize.h b/src/include/fst/determinize.h
new file mode 100644
index 0000000..417142f
--- /dev/null
+++ b/src/include/fst/determinize.h
@@ -0,0 +1,887 @@
+// determinize.h
+
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Functions and classes to determinize an FST.
+
+#ifndef FST_LIB_DETERMINIZE_H__
+#define FST_LIB_DETERMINIZE_H__
+
+#include <algorithm>
+#include <climits>
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <map>
+#include <fst/slist.h>
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+#include <fst/factor-weight.h>
+#include <fst/arc-map.h>
+#include <fst/prune.h>
+#include <fst/test-properties.h>
+
+
+namespace fst {
+
+//
+// COMMON DIVISORS - these are used in determinization to compute
+// the transition weights. In the simplest case, it is just the same
+// as the semiring Plus(). However, other choices permit more efficient
+// determinization when the output contains strings.
+//
+
+// The default common divisor uses the semiring Plus.
+template <class W>
+class DefaultCommonDivisor {
+ public:
+  typedef W Weight;
+
+  W operator()(const W &w1, const W &w2) const { return Plus(w1, w2); }
+};
+
+
+// The label common divisor for a (left) string semiring selects a
+// single letter common prefix or the empty string. This is used in
+// the determinization of output strings so that at most a single
+// letter will appear in the output of a transtion.
+template <typename L, StringType S>
+class LabelCommonDivisor {
+ public:
+  typedef StringWeight<L, S> Weight;
+
+  Weight operator()(const Weight &w1, const Weight &w2) const {
+    StringWeightIterator<L, S> iter1(w1);
+    StringWeightIterator<L, S> iter2(w2);
+
+    if (!(StringWeight<L, S>::Properties() & kLeftSemiring)) {
+      FSTERROR() << "LabelCommonDivisor: Weight needs to be left semiring";
+      return Weight::NoWeight();
+    } else if (w1.Size() == 0 || w2.Size() == 0) {
+      return Weight::One();
+    } else if (w1 == Weight::Zero()) {
+      return Weight(iter2.Value());
+    } else if (w2 == Weight::Zero()) {
+      return Weight(iter1.Value());
+    } else if (iter1.Value() == iter2.Value()) {
+      return Weight(iter1.Value());
+    } else {
+      return Weight::One();
+    }
+  }
+};
+
+
+// The gallic common divisor uses the label common divisor on the
+// string component and the template argument D common divisor on the
+// weight component, which defaults to the default common divisor.
+template <class L, class W, StringType S, class D = DefaultCommonDivisor<W> >
+class GallicCommonDivisor {
+ public:
+  typedef GallicWeight<L, W, S> Weight;
+
+  Weight operator()(const Weight &w1, const Weight &w2) const {
+    return Weight(label_common_divisor_(w1.Value1(), w2.Value1()),
+                  weight_common_divisor_(w1.Value2(), w2.Value2()));
+  }
+
+ private:
+  LabelCommonDivisor<L, S> label_common_divisor_;
+  D weight_common_divisor_;
+};
+
+// Options for finite-state transducer determinization.
+template <class Arc>
+struct DeterminizeFstOptions : CacheOptions {
+  typedef typename Arc::Label Label;
+  float delta;                // Quantization delta for subset weights
+  Label subsequential_label;  // Label used for residual final output
+                              // when producing subsequential transducers.
+
+  explicit DeterminizeFstOptions(const CacheOptions &opts,
+                                 float del = kDelta,
+                                 Label lab = 0)
+      : CacheOptions(opts), delta(del), subsequential_label(lab) {}
+
+  explicit DeterminizeFstOptions(float del = kDelta, Label lab = 0)
+      : delta(del), subsequential_label(lab) {}
+};
+
+
+// Implementation of delayed DeterminizeFst. This base class is
+// common to the variants that implement acceptor and transducer
+// determinization.
+template <class A>
+class DeterminizeFstImplBase : public CacheImpl<A> {
+ public:
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::Properties;
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+
+  using CacheBaseImpl< CacheState<A> >::HasStart;
+  using CacheBaseImpl< CacheState<A> >::HasFinal;
+  using CacheBaseImpl< CacheState<A> >::HasArcs;
+  using CacheBaseImpl< CacheState<A> >::SetFinal;
+  using CacheBaseImpl< CacheState<A> >::SetStart;
+
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef CacheState<A> State;
+
+  DeterminizeFstImplBase(const Fst<A> &fst,
+                         const DeterminizeFstOptions<A> &opts)
+      : CacheImpl<A>(opts), fst_(fst.Copy()) {
+    SetType("determinize");
+    uint64 props = fst.Properties(kFstProperties, false);
+    SetProperties(DeterminizeProperties(props,
+                                        opts.subsequential_label != 0),
+                  kCopyProperties);
+
+    SetInputSymbols(fst.InputSymbols());
+    SetOutputSymbols(fst.OutputSymbols());
+  }
+
+  DeterminizeFstImplBase(const DeterminizeFstImplBase<A> &impl)
+      : CacheImpl<A>(impl),
+        fst_(impl.fst_->Copy(true)) {
+    SetType("determinize");
+    SetProperties(impl.Properties(), kCopyProperties);
+    SetInputSymbols(impl.InputSymbols());
+    SetOutputSymbols(impl.OutputSymbols());
+  }
+
+  virtual ~DeterminizeFstImplBase() { delete fst_; }
+
+  virtual DeterminizeFstImplBase<A> *Copy() = 0;
+
+  StateId Start() {
+    if (!HasStart()) {
+      StateId start = ComputeStart();
+      if (start != kNoStateId) {
+        SetStart(start);
+      }
+    }
+    return CacheImpl<A>::Start();
+  }
+
+  Weight Final(StateId s) {
+    if (!HasFinal(s)) {
+      Weight final = ComputeFinal(s);
+      SetFinal(s, final);
+    }
+    return CacheImpl<A>::Final(s);
+  }
+
+  virtual void Expand(StateId s) = 0;
+
+  size_t NumArcs(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumArcs(s);
+  }
+
+  size_t NumInputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumInputEpsilons(s);
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumOutputEpsilons(s);
+  }
+
+  void InitArcIterator(StateId s, ArcIteratorData<A> *data) {
+    if (!HasArcs(s))
+      Expand(s);
+    CacheImpl<A>::InitArcIterator(s, data);
+  }
+
+  virtual StateId ComputeStart() = 0;
+
+  virtual Weight ComputeFinal(StateId s) = 0;
+
+  const Fst<A> &GetFst() const { return *fst_; }
+
+ private:
+  const Fst<A> *fst_;            // Input Fst
+
+  void operator=(const DeterminizeFstImplBase<A> &);  // disallow
+};
+
+
+// Implementation of delayed determinization for weighted acceptors.
+// It is templated on the arc type A and the common divisor D.
+template <class A, class D>
+class DeterminizeFsaImpl : public DeterminizeFstImplBase<A> {
+ public:
+  using FstImpl<A>::SetProperties;
+  using DeterminizeFstImplBase<A>::GetFst;
+  using DeterminizeFstImplBase<A>::SetArcs;
+
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  struct Element {
+    Element() {}
+
+    Element(StateId s, Weight w) : state_id(s), weight(w) {}
+
+    StateId state_id;  // Input state Id
+    Weight weight;     // Residual weight
+  };
+  typedef slist<Element> Subset;
+  typedef map<Label, Subset*> LabelMap;
+
+  DeterminizeFsaImpl(const Fst<A> &fst, D common_divisor,
+                     const vector<Weight> *in_dist, vector<Weight> *out_dist,
+                     const DeterminizeFstOptions<A> &opts)
+      : DeterminizeFstImplBase<A>(fst, opts),
+        delta_(opts.delta),
+        in_dist_(in_dist),
+        out_dist_(out_dist),
+        common_divisor_(common_divisor),
+        subset_hash_(0, SubsetKey(), SubsetEqual(&elements_)) {
+    if (!fst.Properties(kAcceptor, true)) {
+      FSTERROR()  << "DeterminizeFst: argument not an acceptor";
+      SetProperties(kError, kError);
+    }
+    if (!(Weight::Properties() & kLeftSemiring)) {
+      FSTERROR() << "DeterminizeFst: Weight needs to be left distributive: "
+                 << Weight::Type();
+      SetProperties(kError, kError);
+    }
+    if (out_dist_)
+      out_dist_->clear();
+  }
+
+  DeterminizeFsaImpl(const DeterminizeFsaImpl<A, D> &impl)
+      : DeterminizeFstImplBase<A>(impl),
+        delta_(impl.delta_),
+        in_dist_(0),
+        out_dist_(0),
+        common_divisor_(impl.common_divisor_),
+        subset_hash_(0, SubsetKey(), SubsetEqual(&elements_)) {
+    if (impl.out_dist_) {
+      FSTERROR() << "DeterminizeFsaImpl: cannot copy with out_dist vector";
+      SetProperties(kError, kError);
+    }
+  }
+
+  virtual ~DeterminizeFsaImpl() {
+    for (int i = 0; i < subsets_.size(); ++i)
+      delete subsets_[i];
+  }
+
+  virtual DeterminizeFsaImpl<A, D> *Copy() {
+    return new DeterminizeFsaImpl<A, D>(*this);
+  }
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if ((mask & kError) && (GetFst().Properties(kError, false)))
+      SetProperties(kError, kError);
+    return FstImpl<A>::Properties(mask);
+  }
+
+  virtual StateId ComputeStart() {
+    StateId s = GetFst().Start();
+    if (s == kNoStateId)
+      return kNoStateId;
+    Element element(s, Weight::One());
+    Subset *subset = new Subset;
+    subset->push_front(element);
+    return FindState(subset);
+  }
+
+  virtual Weight ComputeFinal(StateId s) {
+    Subset *subset = subsets_[s];
+    Weight final = Weight::Zero();
+    for (typename Subset::iterator siter = subset->begin();
+         siter != subset->end();
+         ++siter) {
+      Element &element = *siter;
+      final = Plus(final, Times(element.weight,
+                                GetFst().Final(element.state_id)));
+      if (!final.Member())
+        SetProperties(kError, kError);
+    }
+    return final;
+  }
+
+  // Finds the state corresponding to a subset. Only creates a new state
+  // if the subset is not found in the subset hash. FindState takes
+  // ownership of the subset argument (so that it doesn't have to copy it
+  // if it creates a new state).
+  //
+  // The method exploits the following device: all pairs stored in the
+  // associative container subset_hash_ are of the form (subset,
+  // id(subset) + 1), i.e. subset_hash_[subset] > 0 if subset has been
+  // stored previously. For unassigned subsets, the call to
+  // subset_hash_[subset] creates a new pair (subset, 0). As a result,
+  // subset_hash_[subset] == 0 iff subset is new.
+  StateId FindState(Subset *subset) {
+    StateId &assoc_value = subset_hash_[subset];
+    if (assoc_value == 0) {    // subset wasn't present; create new state
+      StateId s = CreateState(subset);
+      assoc_value = s + 1;
+      return  s;
+    } else {
+      delete subset;
+      return assoc_value - 1;  // NB: assoc_value = ID + 1
+    }
+  }
+
+  StateId CreateState(Subset *subset) {
+    StateId s = subsets_.size();
+    subsets_.push_back(subset);
+    if (in_dist_)
+      out_dist_->push_back(ComputeDistance(subset));
+    return s;
+  }
+
+  // Compute distance from a state to the final states in the DFA
+  // given the distances in the NFA.
+  Weight ComputeDistance(const Subset *subset) {
+    Weight outd = Weight::Zero();
+    for (typename Subset::const_iterator siter = subset->begin();
+         siter != subset->end(); ++siter) {
+      const Element &element = *siter;
+      Weight ind = element.state_id < in_dist_->size() ?
+          (*in_dist_)[element.state_id] : Weight::Zero();
+      outd = Plus(outd, Times(element.weight, ind));
+    }
+    return outd;
+  }
+
+  // Computes the outgoing transitions from a state, creating new destination
+  // states as needed.
+  virtual void Expand(StateId s) {
+
+    LabelMap label_map;
+    LabelSubsets(s, &label_map);
+
+    for (typename LabelMap::iterator liter = label_map.begin();
+         liter != label_map.end();
+         ++liter)
+      AddArc(s, liter->first, liter->second);
+    SetArcs(s);
+  }
+
+ private:
+  // Constructs destination subsets per label. At return, subset
+  // element weights include the input automaton label weights and the
+  // subsets may contain duplicate states.
+  void LabelSubsets(StateId s, LabelMap *label_map) {
+    Subset *src_subset = subsets_[s];
+
+    for (typename Subset::iterator siter = src_subset->begin();
+         siter != src_subset->end();
+         ++siter) {
+      Element &src_element = *siter;
+      for (ArcIterator< Fst<A> > aiter(GetFst(), src_element.state_id);
+           !aiter.Done();
+           aiter.Next()) {
+        const A &arc = aiter.Value();
+        Element dest_element(arc.nextstate,
+                             Times(src_element.weight, arc.weight));
+        Subset* &dest_subset = (*label_map)[arc.ilabel];
+        if (dest_subset == 0)
+          dest_subset = new Subset;
+        dest_subset->push_front(dest_element);
+      }
+    }
+  }
+
+  // Adds an arc from state S to the destination state associated
+  // with subset DEST_SUBSET (as created by LabelSubsets).
+  void AddArc(StateId s, Label label, Subset *dest_subset) {
+    A arc;
+    arc.ilabel = label;
+    arc.olabel = label;
+    arc.weight = Weight::Zero();
+
+    typename Subset::iterator oiter;
+    for (typename Subset::iterator diter = dest_subset->begin();
+         diter != dest_subset->end();) {
+      Element &dest_element = *diter;
+      // Computes label weight.
+      arc.weight = common_divisor_(arc.weight, dest_element.weight);
+
+      while (elements_.size() <= dest_element.state_id)
+        elements_.push_back(0);
+      Element *matching_element = elements_[dest_element.state_id];
+      if (matching_element) {
+        // Found duplicate state: sums state weight and deletes dup.
+        matching_element->weight = Plus(matching_element->weight,
+                                        dest_element.weight);
+        if (!matching_element->weight.Member())
+          SetProperties(kError, kError);
+        ++diter;
+        dest_subset->erase_after(oiter);
+      } else {
+        // Saves element so we can check for duplicate for this state.
+        elements_[dest_element.state_id] = &dest_element;
+        oiter = diter;
+        ++diter;
+      }
+    }
+
+    // Divides out label weight from destination subset elements.
+    // Quantizes to ensure comparisons are effective.
+    // Clears element vector.
+    for (typename Subset::iterator diter = dest_subset->begin();
+         diter != dest_subset->end();
+         ++diter) {
+      Element &dest_element = *diter;
+      dest_element.weight = Divide(dest_element.weight, arc.weight,
+                                   DIVIDE_LEFT);
+      dest_element.weight = dest_element.weight.Quantize(delta_);
+      elements_[dest_element.state_id] = 0;
+    }
+
+    arc.nextstate = FindState(dest_subset);
+    CacheImpl<A>::PushArc(s, arc);
+  }
+
+  // Comparison object for hashing Subset(s). Subsets are not sorted in this
+  // implementation, so ordering must not be assumed in the equivalence
+  // test.
+  class SubsetEqual {
+   public:
+    // Constructor takes vector needed to check equality. See immediately
+    // below for constraints on it.
+    explicit SubsetEqual(vector<Element *> *elements)
+        : elements_(elements) {}
+
+    // At each call to operator(), the elements_ vector should contain
+    // only NULLs. When this operator returns, elements_ will still
+    // have this property.
+    bool operator()(Subset* subset1, Subset* subset2) const {
+        if (subset1->size() != subset2->size())
+          return false;
+
+      // Loads first subset elements in element vector.
+      for (typename Subset::iterator iter1 = subset1->begin();
+           iter1 != subset1->end();
+           ++iter1) {
+        Element &element1 = *iter1;
+        while (elements_->size() <= element1.state_id)
+          elements_->push_back(0);
+        (*elements_)[element1.state_id] = &element1;
+      }
+
+      // Checks second subset matches first via element vector.
+      for (typename Subset::iterator iter2 = subset2->begin();
+           iter2 != subset2->end();
+           ++iter2) {
+        Element &element2 = *iter2;
+        while (elements_->size() <= element2.state_id)
+          elements_->push_back(0);
+        Element *element1 = (*elements_)[element2.state_id];
+        if (!element1 || element1->weight != element2.weight) {
+          // Mismatch found. Resets element vector before returning false.
+          for (typename Subset::iterator iter1 = subset1->begin();
+               iter1 != subset1->end();
+               ++iter1)
+            (*elements_)[iter1->state_id] = 0;
+          return false;
+        } else {
+          (*elements_)[element2.state_id] = 0;  // Clears entry
+        }
+      }
+      return true;
+    }
+   private:
+    vector<Element *> *elements_;
+  };
+
+  // Hash function for Subset to Fst states. Subset elements are not
+  // sorted in this implementation, so the hash must be invariant
+  // under subset reordering.
+  class SubsetKey {
+   public:
+    size_t operator()(const Subset* subset) const {
+      size_t hash = 0;
+      for (typename Subset::const_iterator iter = subset->begin();
+           iter != subset->end();
+           ++iter) {
+        const Element &element = *iter;
+        int lshift = element.state_id % (CHAR_BIT * sizeof(size_t) - 1) + 1;
+        int rshift = CHAR_BIT * sizeof(size_t) - lshift;
+        size_t n = element.state_id;
+        hash ^= n << lshift ^ n >> rshift ^ element.weight.Hash();
+      }
+      return hash;
+    }
+  };
+
+  float delta_;                    // Quantization delta for subset weights
+  const vector<Weight> *in_dist_;  // Distance to final NFA states
+  vector<Weight> *out_dist_;       // Distance to final DFA states
+
+  D common_divisor_;
+
+  // Used to test equivalence of subsets.
+  vector<Element *> elements_;
+
+  // Maps from StateId to Subset.
+  vector<Subset *> subsets_;
+
+  // Hashes from Subset to its StateId in the output automaton.
+  typedef unordered_map<Subset *, StateId, SubsetKey, SubsetEqual>
+  SubsetHash;
+
+  // Hashes from Label to Subsets corr. to destination states of current state.
+  SubsetHash subset_hash_;
+
+  void operator=(const DeterminizeFsaImpl<A, D> &);  // disallow
+};
+
+
+// Implementation of delayed determinization for transducers.
+// Transducer determinization is implemented by mapping the input to
+// the Gallic semiring as an acceptor whose weights contain the output
+// strings and using acceptor determinization above to determinize
+// that acceptor.
+template <class A, StringType S>
+class DeterminizeFstImpl : public DeterminizeFstImplBase<A> {
+ public:
+  using FstImpl<A>::SetProperties;
+  using DeterminizeFstImplBase<A>::GetFst;
+  using CacheBaseImpl< CacheState<A> >::GetCacheGc;
+  using CacheBaseImpl< CacheState<A> >::GetCacheLimit;
+
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  typedef ToGallicMapper<A, S> ToMapper;
+  typedef FromGallicMapper<A, S> FromMapper;
+
+  typedef typename ToMapper::ToArc ToArc;
+  typedef ArcMapFst<A, ToArc, ToMapper> ToFst;
+  typedef ArcMapFst<ToArc, A, FromMapper> FromFst;
+
+  typedef GallicCommonDivisor<Label, Weight, S> CommonDivisor;
+  typedef GallicFactor<Label, Weight, S> FactorIterator;
+
+  DeterminizeFstImpl(const Fst<A> &fst, const DeterminizeFstOptions<A> &opts)
+      : DeterminizeFstImplBase<A>(fst, opts),
+        delta_(opts.delta),
+        subsequential_label_(opts.subsequential_label) {
+     Init(GetFst());
+  }
+
+  DeterminizeFstImpl(const DeterminizeFstImpl<A, S> &impl)
+      : DeterminizeFstImplBase<A>(impl),
+        delta_(impl.delta_),
+        subsequential_label_(impl.subsequential_label_) {
+    Init(GetFst());
+  }
+
+  ~DeterminizeFstImpl() { delete from_fst_; }
+
+  virtual DeterminizeFstImpl<A, S> *Copy() {
+    return new DeterminizeFstImpl<A, S>(*this);
+  }
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if ((mask & kError) && (GetFst().Properties(kError, false) ||
+                            from_fst_->Properties(kError, false)))
+      SetProperties(kError, kError);
+    return FstImpl<A>::Properties(mask);
+  }
+
+  virtual StateId ComputeStart() { return from_fst_->Start(); }
+
+  virtual Weight ComputeFinal(StateId s) { return from_fst_->Final(s); }
+
+  virtual void Expand(StateId s) {
+    for (ArcIterator<FromFst> aiter(*from_fst_, s);
+         !aiter.Done();
+         aiter.Next())
+      CacheImpl<A>::PushArc(s, aiter.Value());
+    CacheImpl<A>::SetArcs(s);
+  }
+
+ private:
+  // Initialization of transducer determinization implementation, which
+  // is defined after DeterminizeFst since it calls it.
+  void Init(const Fst<A> &fst);
+
+  float delta_;
+  Label subsequential_label_;
+  FromFst *from_fst_;
+
+  void operator=(const DeterminizeFstImpl<A, S> &);  // disallow
+};
+
+
+// Determinizes a weighted transducer. This version is a delayed
+// Fst. The result will be an equivalent FST that has the property
+// that no state has two transitions with the same input label.
+// For this algorithm, epsilon transitions are treated as regular
+// symbols (cf. RmEpsilon).
+//
+// The transducer must be functional. The weights must be (weakly)
+// left divisible (valid for TropicalWeight and LogWeight for instance)
+// and be zero-sum-free if for all a,b: (Plus(a, b) = 0 => a = b = 0.
+//
+// Complexity:
+// - Determinizable: exponential (polynomial in the size of the output)
+// - Non-determinizable) does not terminate
+//
+// The determinizable automata include all unweighted and all acyclic input.
+//
+// References:
+// - Mehryar Mohri, "Finite-State Transducers in Language and Speech
+//   Processing". Computational Linguistics, 23:2, 1997.
+//
+// This class attaches interface to implementation and handles
+// reference counting, delegating most methods to ImplToFst.
+template <class A>
+class DeterminizeFst : public ImplToFst< DeterminizeFstImplBase<A> >  {
+ public:
+  friend class ArcIterator< DeterminizeFst<A> >;
+  friend class StateIterator< DeterminizeFst<A> >;
+  template <class B, StringType S> friend class DeterminizeFstImpl;
+
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef CacheState<A> State;
+  typedef DeterminizeFstImplBase<A> Impl;
+
+  using ImplToFst<Impl>::SetImpl;
+
+  explicit DeterminizeFst(
+      const Fst<A> &fst,
+      const DeterminizeFstOptions<A> &opts = DeterminizeFstOptions<A>()) {
+    if (fst.Properties(kAcceptor, true)) {
+      // Calls implementation for acceptors.
+      typedef DefaultCommonDivisor<Weight> D;
+      SetImpl(new DeterminizeFsaImpl<A, D>(fst, D(), 0, 0, opts));
+    } else {
+      // Calls implementation for transducers.
+      SetImpl(new DeterminizeFstImpl<A, STRING_LEFT_RESTRICT>(fst, opts));
+    }
+  }
+
+  // This acceptor-only version additionally computes the distance to
+  // final states in the output if provided with those distances for the
+  // input. Useful for e.g. unique N-shortest paths.
+  DeterminizeFst(
+      const Fst<A> &fst,
+      const vector<Weight> &in_dist, vector<Weight> *out_dist,
+      const DeterminizeFstOptions<A> &opts = DeterminizeFstOptions<A>()) {
+    if (!fst.Properties(kAcceptor, true)) {
+      FSTERROR() << "DeterminizeFst:"
+                 << " distance to final states computed for acceptors only";
+      GetImpl()->SetProperties(kError, kError);
+    }
+    typedef DefaultCommonDivisor<Weight> D;
+    SetImpl(new DeterminizeFsaImpl<A, D>(fst, D(), &in_dist, out_dist, opts));
+  }
+
+  // See Fst<>::Copy() for doc.
+  DeterminizeFst(const DeterminizeFst<A> &fst, bool safe = false) {
+    if (safe)
+      SetImpl(fst.GetImpl()->Copy());
+    else
+      SetImpl(fst.GetImpl(), false);
+  }
+
+  // Get a copy of this DeterminizeFst. See Fst<>::Copy() for further doc.
+  virtual DeterminizeFst<A> *Copy(bool safe = false) const {
+    return new DeterminizeFst<A>(*this, safe);
+  }
+
+  virtual inline void InitStateIterator(StateIteratorData<A> *data) const;
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<A> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+ private:
+  // This private version is for passing the common divisor to
+  // FSA determinization.
+  template <class D>
+  DeterminizeFst(const Fst<A> &fst, const D &common_div,
+                 const DeterminizeFstOptions<A> &opts)
+      :  ImplToFst<Impl>(
+          new DeterminizeFsaImpl<A, D>(fst, common_div, 0, 0, opts)) {}
+
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const DeterminizeFst<A> &fst);  // Disallow
+};
+
+
+// Initialization of transducer determinization implementation. which
+// is defined after DeterminizeFst since it calls it.
+template <class A, StringType S>
+void DeterminizeFstImpl<A, S>::Init(const Fst<A> &fst) {
+  // Mapper to an acceptor.
+  ToFst to_fst(fst, ToMapper());
+
+  // Determinize acceptor.
+  // This recursive call terminates since it passes the common divisor
+  // to a private constructor.
+  CacheOptions copts(GetCacheGc(), GetCacheLimit());
+  DeterminizeFstOptions<ToArc> dopts(copts, delta_);
+  DeterminizeFst<ToArc> det_fsa(to_fst, CommonDivisor(), dopts);
+
+  // Mapper back to transducer.
+  FactorWeightOptions<ToArc> fopts(CacheOptions(true, 0), delta_,
+                                   kFactorFinalWeights,
+                                   subsequential_label_,
+                                   subsequential_label_);
+  FactorWeightFst<ToArc, FactorIterator> factored_fst(det_fsa, fopts);
+  from_fst_ = new FromFst(factored_fst, FromMapper(subsequential_label_));
+}
+
+
+// Specialization for DeterminizeFst.
+template <class A>
+class StateIterator< DeterminizeFst<A> >
+    : public CacheStateIterator< DeterminizeFst<A> > {
+ public:
+  explicit StateIterator(const DeterminizeFst<A> &fst)
+      : CacheStateIterator< DeterminizeFst<A> >(fst, fst.GetImpl()) {}
+};
+
+
+// Specialization for DeterminizeFst.
+template <class A>
+class ArcIterator< DeterminizeFst<A> >
+    : public CacheArcIterator< DeterminizeFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const DeterminizeFst<A> &fst, StateId s)
+      : CacheArcIterator< DeterminizeFst<A> >(fst.GetImpl(), s) {
+    if (!fst.GetImpl()->HasArcs(s))
+      fst.GetImpl()->Expand(s);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+
+template <class A> inline
+void DeterminizeFst<A>::InitStateIterator(StateIteratorData<A> *data) const
+{
+  data->base = new StateIterator< DeterminizeFst<A> >(*this);
+}
+
+
+// Useful aliases when using StdArc.
+typedef DeterminizeFst<StdArc> StdDeterminizeFst;
+
+
+template <class Arc>
+struct DeterminizeOptions {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::Label Label;
+
+  float delta;                // Quantization delta for subset weights.
+  Weight weight_threshold;    // Pruning weight threshold.
+  StateId state_threshold;    // Pruning state threshold.
+  Label subsequential_label;  // Label used for residual final output
+  // when producing subsequential transducers.
+
+  explicit DeterminizeOptions(float d = kDelta, Weight w = Weight::Zero(),
+                              StateId n = kNoStateId, Label l = 0)
+      : delta(d), weight_threshold(w), state_threshold(n),
+        subsequential_label(l) {}
+};
+
+
+// Determinizes a weighted transducer.  This version writes the
+// determinized Fst to an output MutableFst.  The result will be an
+// equivalent FSt that has the property that no state has two
+// transitions with the same input label.  For this algorithm, epsilon
+// transitions are treated as regular symbols (cf. RmEpsilon).
+//
+// The transducer must be functional. The weights must be (weakly)
+// left divisible (valid for TropicalWeight and LogWeight).
+//
+// Complexity:
+// - Determinizable: exponential (polynomial in the size of the output)
+// - Non-determinizable: does not terminate
+//
+// The determinizable automata include all unweighted and all acyclic input.
+//
+// References:
+// - Mehryar Mohri, "Finite-State Transducers in Language and Speech
+//   Processing". Computational Linguistics, 23:2, 1997.
+template <class Arc>
+void Determinize(const Fst<Arc> &ifst, MutableFst<Arc> *ofst,
+             const DeterminizeOptions<Arc> &opts
+                 = DeterminizeOptions<Arc>()) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+
+  DeterminizeFstOptions<Arc> nopts;
+  nopts.delta = opts.delta;
+  nopts.subsequential_label = opts.subsequential_label;
+
+  nopts.gc_limit = 0;  // Cache only the last state for fastest copy.
+
+  if (opts.weight_threshold != Weight::Zero() ||
+      opts.state_threshold != kNoStateId) {
+    if (ifst.Properties(kAcceptor, false)) {
+      vector<Weight> idistance, odistance;
+      ShortestDistance(ifst, &idistance, true);
+      DeterminizeFst<Arc> dfst(ifst, idistance, &odistance, nopts);
+      PruneOptions< Arc, AnyArcFilter<Arc> > popts(opts.weight_threshold,
+                                                   opts.state_threshold,
+                                                   AnyArcFilter<Arc>(),
+                                                   &odistance);
+      Prune(dfst, ofst, popts);
+    } else {
+      *ofst = DeterminizeFst<Arc>(ifst, nopts);
+      Prune(ofst, opts.weight_threshold, opts.state_threshold);
+    }
+  } else {
+    *ofst = DeterminizeFst<Arc>(ifst, nopts);
+  }
+}
+
+
+}  // namespace fst
+
+#endif  // FST_LIB_DETERMINIZE_H__
diff --git a/src/include/fst/dfs-visit.h b/src/include/fst/dfs-visit.h
new file mode 100644
index 0000000..b47c78d
--- /dev/null
+++ b/src/include/fst/dfs-visit.h
@@ -0,0 +1,204 @@
+// dfs-visit.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Depth-first search visitation. See visit.h for more general
+// search queue disciplines.
+
+#ifndef FST_LIB_DFS_VISIT_H__
+#define FST_LIB_DFS_VISIT_H__
+
+#include <stack>
+#include <vector>
+using std::vector;
+
+#include <fst/arcfilter.h>
+#include <fst/fst.h>
+
+
+namespace fst {
+
+// Visitor Interface - class determines actions taken during a Dfs.
+// If any of the boolean member functions return false, the DFS is
+// aborted by first calling FinishState() on all currently grey states
+// and then calling FinishVisit().
+//
+// Note this is similar to the more general visitor interface in visit.h
+// except that FinishState returns additional information appropriate only for
+// a DFS and some methods names here are better suited to a DFS.
+//
+// template <class Arc>
+// class Visitor {
+//  public:
+//   typedef typename Arc::StateId StateId;
+//
+//   Visitor(T *return_data);
+//   // Invoked before DFS visit
+//   void InitVisit(const Fst<Arc> &fst);
+//   // Invoked when state discovered (2nd arg is DFS tree root)
+//   bool InitState(StateId s, StateId root);
+//   // Invoked when tree arc examined (to white/undiscovered state)
+//   bool TreeArc(StateId s, const Arc &a);
+//   // Invoked when back arc examined (to grey/unfinished state)
+//   bool BackArc(StateId s, const Arc &a);
+//   // Invoked when forward or cross arc examined (to black/finished state)
+//   bool ForwardOrCrossArc(StateId s, const Arc &a);
+//   // Invoked when state finished (PARENT is kNoStateID and ARC == NULL
+//   // when S is tree root)
+//   void FinishState(StateId s, StateId parent, const Arc *parent_arc);
+//   // Invoked after DFS visit
+//   void FinishVisit();
+// };
+
+// An Fst state's DFS status
+const int kDfsWhite = 0;   // Undiscovered
+const int kDfsGrey =  1;   // Discovered & unfinished
+const int kDfsBlack = 2;   // Finished
+
+// An Fst state's DFS stack state
+template <class Arc>
+struct DfsState {
+  typedef typename Arc::StateId StateId;
+
+  DfsState(const Fst<Arc> &fst, StateId s): state_id(s), arc_iter(fst, s) {}
+
+  StateId state_id;       // Fst state ...
+  ArcIterator< Fst<Arc> > arc_iter;  // and its corresponding arcs
+};
+
+
+// Performs depth-first visitation. Visitor class argument determines
+// actions and contains any return data. ArcFilter determines arcs
+// that are considered.
+//
+// Note this is similar to Visit() in visit.h called with a LIFO
+// queue except this version has a Visitor class specialized and
+// augmented for a DFS.
+template <class Arc, class V, class ArcFilter>
+void DfsVisit(const Fst<Arc> &fst, V *visitor, ArcFilter filter) {
+  typedef typename Arc::StateId StateId;
+
+  visitor->InitVisit(fst);
+
+  StateId start = fst.Start();
+  if (start == kNoStateId) {
+    visitor->FinishVisit();
+    return;
+  }
+
+  vector<char> state_color;                // Fst state DFS status
+  stack<DfsState<Arc> *> state_stack;      // DFS execution stack
+
+  StateId nstates = start + 1;             // # of known states in general case
+  bool expanded = false;
+  if (fst.Properties(kExpanded, false)) {  // tests if expanded case, then
+    nstates = CountStates(fst);            // uses ExpandedFst::NumStates().
+    expanded = true;
+  }
+
+  state_color.resize(nstates, kDfsWhite);
+  StateIterator< Fst<Arc> > siter(fst);
+
+  // Continue DFS while true
+  bool dfs = true;
+
+  // Iterate over trees in DFS forest.
+  for (StateId root = start; dfs && root < nstates;) {
+    state_color[root] = kDfsGrey;
+    state_stack.push(new DfsState<Arc>(fst, root));
+    dfs = visitor->InitState(root, root);
+    while (!state_stack.empty()) {
+      DfsState<Arc> *dfs_state = state_stack.top();
+      StateId s = dfs_state->state_id;
+      if (s >= state_color.size()) {
+        nstates = s + 1;
+        state_color.resize(nstates, kDfsWhite);
+      }
+      ArcIterator< Fst<Arc> > &aiter = dfs_state->arc_iter;
+      if (!dfs || aiter.Done()) {
+        state_color[s] = kDfsBlack;
+        delete dfs_state;
+        state_stack.pop();
+        if (!state_stack.empty()) {
+          DfsState<Arc> *parent_state = state_stack.top();
+          StateId p = parent_state->state_id;
+          ArcIterator< Fst<Arc> > &piter = parent_state->arc_iter;
+          visitor->FinishState(s, p, &piter.Value());
+          piter.Next();
+        } else {
+          visitor->FinishState(s, kNoStateId, 0);
+        }
+        continue;
+      }
+      const Arc &arc = aiter.Value();
+      if (arc.nextstate >= state_color.size()) {
+        nstates = arc.nextstate + 1;
+        state_color.resize(nstates, kDfsWhite);
+      }
+      if (!filter(arc)) {
+        aiter.Next();
+        continue;
+      }
+      int next_color = state_color[arc.nextstate];
+      switch (next_color) {
+        default:
+        case kDfsWhite:
+          dfs = visitor->TreeArc(s, arc);
+          if (!dfs) break;
+          state_color[arc.nextstate] = kDfsGrey;
+          state_stack.push(new DfsState<Arc>(fst, arc.nextstate));
+          dfs = visitor->InitState(arc.nextstate, root);
+          break;
+        case kDfsGrey:
+          dfs = visitor->BackArc(s, arc);
+          aiter.Next();
+          break;
+        case kDfsBlack:
+          dfs = visitor->ForwardOrCrossArc(s, arc);
+          aiter.Next();
+          break;
+      }
+    }
+
+    // Find next tree root
+    for (root = root == start ? 0 : root + 1;
+         root < nstates && state_color[root] != kDfsWhite;
+         ++root);
+
+    // Check for a state beyond the largest known state
+    if (!expanded && root == nstates) {
+      for (; !siter.Done(); siter.Next()) {
+        if (siter.Value() == nstates) {
+          ++nstates;
+          state_color.push_back(kDfsWhite);
+          break;
+        }
+      }
+    }
+  }
+  visitor->FinishVisit();
+}
+
+
+template <class Arc, class V>
+void DfsVisit(const Fst<Arc> &fst, V *visitor) {
+  DfsVisit(fst, visitor, AnyArcFilter<Arc>());
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_DFS_VISIT_H__
diff --git a/src/include/fst/difference.h b/src/include/fst/difference.h
new file mode 100644
index 0000000..8a3306f
--- /dev/null
+++ b/src/include/fst/difference.h
@@ -0,0 +1,189 @@
+// difference.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to compute the difference between two FSAs
+
+#ifndef FST_LIB_DIFFERENCE_H__
+#define FST_LIB_DIFFERENCE_H__
+
+#include <vector>
+using std::vector;
+#include <algorithm>
+
+#include <fst/cache.h>
+#include <fst/compose.h>
+#include <fst/complement.h>
+
+
+namespace fst {
+
+template <class A,
+          class M = Matcher<Fst<A> >,
+          class F = SequenceComposeFilter<M>,
+          class T = GenericComposeStateTable<A, typename F::FilterState> >
+struct DifferenceFstOptions : public ComposeFstOptions<A, M, F, T> {
+  explicit DifferenceFstOptions(const CacheOptions &opts,
+                                M *mat1 = 0, M *mat2 = 0,
+                                F *filt = 0, T *sttable= 0)
+      : ComposeFstOptions<A, M, F, T>(mat1, mat2, filt, sttable) { }
+
+  DifferenceFstOptions() {}
+};
+
+// Computes the difference between two FSAs. This version is a delayed
+// Fst. Only strings that are in the first automaton but not in second
+// are retained in the result.
+//
+// The first argument must be an acceptor; the second argument must be
+// an unweighted, epsilon-free, deterministic acceptor. One of the
+// arguments must be label-sorted.
+//
+// Complexity: same as ComposeFst.
+//
+// Caveats: same as ComposeFst.
+template <class A>
+class DifferenceFst : public ComposeFst<A> {
+ public:
+  using ImplToFst< ComposeFstImplBase<A> >::SetImpl;
+  using ImplToFst< ComposeFstImplBase<A> >::GetImpl;
+
+  using ComposeFst<A>::CreateBase1;
+
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  // A - B = A ^ B'.
+  DifferenceFst(const Fst<A> &fst1, const Fst<A> &fst2,
+                const CacheOptions &opts = CacheOptions()) {
+    typedef RhoMatcher< Matcher<Fst<A> > > R;
+
+    ComplementFst<A> cfst(fst2);
+    ComposeFstOptions<A, R> copts(CacheOptions(),
+                                  new R(fst1, MATCH_NONE),
+                                  new R(cfst, MATCH_INPUT,
+                                        ComplementFst<A>::kRhoLabel));
+    SetImpl(CreateBase1(fst1, cfst, copts));
+
+    if (!fst1.Properties(kAcceptor, true)) {
+      FSTERROR() << "DifferenceFst: 1st argument not an acceptor";
+      GetImpl()->SetProperties(kError, kError);
+    }
+ }
+
+  template <class M, class F, class T>
+  DifferenceFst(const Fst<A> &fst1, const Fst<A> &fst2,
+                const DifferenceFstOptions<A, M, F, T> &opts) {
+    typedef RhoMatcher<M> R;
+
+    ComplementFst<A> cfst(fst2);
+    ComposeFstOptions<A, R> copts(opts);
+    copts.matcher1 = new R(fst1, MATCH_NONE, kNoLabel, MATCHER_REWRITE_ALWAYS,
+                           opts.matcher1);
+    copts.matcher2 = new R(cfst, MATCH_INPUT, ComplementFst<A>::kRhoLabel,
+                           MATCHER_REWRITE_ALWAYS, opts.matcher2);
+
+    SetImpl(CreateBase1(fst1, cfst, copts));
+
+    if (!fst1.Properties(kAcceptor, true)) {
+      FSTERROR() << "DifferenceFst: 1st argument not an acceptor";
+      GetImpl()->SetProperties(kError, kError);
+    }
+  }
+
+  // See Fst<>::Copy() for doc.
+  DifferenceFst(const DifferenceFst<A> &fst, bool safe = false)
+      : ComposeFst<A>(fst, safe) {}
+
+  // Get a copy of this DifferenceFst. See Fst<>::Copy() for further doc.
+  virtual DifferenceFst<A> *Copy(bool safe = false) const {
+    return new DifferenceFst<A>(*this, safe);
+  }
+};
+
+
+// Specialization for DifferenceFst.
+template <class A>
+class StateIterator< DifferenceFst<A> >
+    : public StateIterator< ComposeFst<A> > {
+ public:
+  explicit StateIterator(const DifferenceFst<A> &fst)
+      : StateIterator< ComposeFst<A> >(fst) {}
+};
+
+
+// Specialization for DifferenceFst.
+template <class A>
+class ArcIterator< DifferenceFst<A> >
+    : public ArcIterator< ComposeFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const DifferenceFst<A> &fst, StateId s)
+      : ArcIterator< ComposeFst<A> >(fst, s) {}
+};
+
+// Useful alias when using StdArc.
+typedef DifferenceFst<StdArc> StdDifferenceFst;
+
+
+typedef ComposeOptions DifferenceOptions;
+
+
+// Computes the difference between two FSAs. This version is writes
+// the difference to an output MutableFst. Only strings that are in
+// the first automaton but not in second are retained in the result.
+//
+// The first argument must be an acceptor; the second argument must be
+// an unweighted, epsilon-free, deterministic acceptor.  One of the
+// arguments must be label-sorted.
+//
+// Complexity: same as Compose.
+//
+// Caveats: same as Compose.
+template<class Arc>
+void Difference(const Fst<Arc> &ifst1, const Fst<Arc> &ifst2,
+             MutableFst<Arc> *ofst,
+             const DifferenceOptions &opts = DifferenceOptions()) {
+  typedef Matcher< Fst<Arc> > M;
+
+  if (opts.filter_type == AUTO_FILTER) {
+    CacheOptions nopts;
+    nopts.gc_limit = 0;  // Cache only the last state for fastest copy.
+    *ofst = DifferenceFst<Arc>(ifst1, ifst2, nopts);
+  } else if (opts.filter_type == SEQUENCE_FILTER) {
+    DifferenceFstOptions<Arc> dopts;
+    dopts.gc_limit = 0;  // Cache only the last state for fastest copy.
+    *ofst = DifferenceFst<Arc>(ifst1, ifst2, dopts);
+  } else if (opts.filter_type == ALT_SEQUENCE_FILTER) {
+    DifferenceFstOptions<Arc, M, AltSequenceComposeFilter<M> > dopts;
+    dopts.gc_limit = 0;  // Cache only the last state for fastest copy.
+    *ofst = DifferenceFst<Arc>(ifst1, ifst2, dopts);
+  } else if (opts.filter_type == MATCH_FILTER) {
+    DifferenceFstOptions<Arc, M, MatchComposeFilter<M> > dopts;
+    dopts.gc_limit = 0;  // Cache only the last state for fastest copy.
+    *ofst = DifferenceFst<Arc>(ifst1, ifst2, dopts);
+  }
+
+  if (opts.connect)
+    Connect(ofst);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_DIFFERENCE_H__
diff --git a/src/include/fst/edit-fst.h b/src/include/fst/edit-fst.h
new file mode 100644
index 0000000..303cb24
--- /dev/null
+++ b/src/include/fst/edit-fst.h
@@ -0,0 +1,774 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: dbikel@google.com (Dan Bikel)
+//
+// An \ref Fst implementation that allows non-destructive edit operations on an
+// existing fst.
+
+#ifndef FST_LIB_EDIT_FST_H_
+#define FST_LIB_EDIT_FST_H_
+
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+
+namespace fst {
+
+// The EditFst class enables non-destructive edit operations on a wrapped
+// ExpandedFst. The implementation uses copy-on-write semantics at the node
+// level: if a user has an underlying fst on which he or she wants to perform a
+// relatively small number of edits (read: mutations), then this implementation
+// will copy the edited node to an internal MutableFst and perform any edits in
+// situ on that copied node. This class supports all the methods of MutableFst
+// except for DeleteStates(const vector<StateId> &); thus, new nodes may also be
+// added, and one may add transitions from existing nodes of the wrapped fst to
+// new nodes.
+//
+// N.B.: The documentation for Fst::Copy(true) says that its behavior is
+// undefined if invoked on an fst that has already been accessed.  This class
+// requires that the Fst implementation it wraps provides consistent, reliable
+// behavior when its Copy(true) method is invoked, where consistent means
+// the graph structure, graph properties and state numbering and do not change.
+// VectorFst and CompactFst, for example, are both well-behaved in this regard.
+
+// The EditFstData class is a container for all mutable data for EditFstImpl;
+// also, this class provides most of the actual implementation of what EditFst
+// does (that is, most of EditFstImpl's methods delegate to methods in this, the
+// EditFstData class).  Instances of this class are reference-counted and can be
+// shared between otherwise independent EditFstImpl instances. This scheme
+// allows EditFstImpl to implement the thread-safe, copy-on-write semantics
+// required by Fst::Copy(true).
+//
+// template parameters:
+//   A the type of arc to use
+//   WrappedFstT the type of fst wrapped by the EditFst instance that
+//     this EditFstData instance is backing
+//   MutableFstT the type of mutable fst to use internally for edited states;
+//     crucially, MutableFstT::Copy(false) *must* yield an fst that is
+//     thread-safe for reading (VectorFst, for example, has this property)
+template <typename A,
+          typename WrappedFstT = ExpandedFst<A>,
+          typename MutableFstT = VectorFst<A> >
+class EditFstData {
+ public:
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef typename unordered_map<StateId, StateId>::const_iterator
+      IdMapIterator;
+  typedef typename unordered_map<StateId, Weight>::const_iterator
+      FinalWeightIterator;
+
+
+  EditFstData() : num_new_states_(0) {
+    SetEmptyAndDeleteKeysForInternalMaps();
+  }
+
+  EditFstData(const EditFstData &other) :
+      edits_(other.edits_),
+      external_to_internal_ids_(other.external_to_internal_ids_),
+      edited_final_weights_(other.edited_final_weights_),
+      num_new_states_(other.num_new_states_) {
+  }
+
+  ~EditFstData() {
+  }
+
+  static EditFstData<A, WrappedFstT, MutableFstT> *Read(istream &strm,
+                                                        const FstReadOptions &opts);
+
+  bool Write(ostream &strm, const FstWriteOptions &opts) const {
+    // Serialize all private data members of this class.
+    FstWriteOptions edits_opts(opts);
+    edits_opts.write_header = true;  // Force writing contained header.
+    edits_.Write(strm, edits_opts);
+    WriteType(strm, external_to_internal_ids_);
+    WriteType(strm, edited_final_weights_);
+    WriteType(strm, num_new_states_);
+    if (!strm) {
+      LOG(ERROR) << "EditFstData::Write: write failed: " << opts.source;
+      return false;
+    }
+    return true;
+  }
+
+  int RefCount() const { return ref_count_.count(); }
+  int IncrRefCount() { return ref_count_.Incr(); }
+  int DecrRefCount() { return ref_count_.Decr(); }
+
+  StateId NumNewStates() const {
+    return num_new_states_;
+  }
+
+  // accessor methods for the fst holding edited states
+  StateId EditedStart() const {
+    return edits_.Start();
+  }
+
+  Weight Final(StateId s, const WrappedFstT *wrapped) const {
+    FinalWeightIterator final_weight_it = GetFinalWeightIterator(s);
+    if (final_weight_it == NotInFinalWeightMap()) {
+      IdMapIterator it = GetEditedIdMapIterator(s);
+      return it == NotInEditedMap() ?
+             wrapped->Final(s) : edits_.Final(it->second);
+    }
+    else {
+      return final_weight_it->second;
+    }
+  }
+
+  size_t NumArcs(StateId s, const WrappedFstT *wrapped) const {
+    IdMapIterator it = GetEditedIdMapIterator(s);
+    return it == NotInEditedMap() ?
+           wrapped->NumArcs(s) : edits_.NumArcs(it->second);
+  }
+
+  size_t NumInputEpsilons(StateId s, const WrappedFstT *wrapped) const {
+    IdMapIterator it = GetEditedIdMapIterator(s);
+    return it == NotInEditedMap() ?
+           wrapped->NumInputEpsilons(s) :
+           edits_.NumInputEpsilons(it->second);
+  }
+
+  size_t NumOutputEpsilons(StateId s, const WrappedFstT *wrapped) const {
+    IdMapIterator it = GetEditedIdMapIterator(s);
+    return it == NotInEditedMap() ?
+           wrapped->NumOutputEpsilons(s) :
+           edits_.NumOutputEpsilons(it->second);
+  }
+
+  void SetEditedProperties(uint64 props, uint64 mask) {
+    edits_.SetProperties(props, mask);
+  }
+
+  // non-const MutableFst operations
+
+  // Sets the start state for this fst.
+  void SetStart(StateId s) {
+    edits_.SetStart(s);
+  }
+
+  // Sets the final state for this fst.
+  Weight SetFinal(StateId s, Weight w, const WrappedFstT *wrapped) {
+    Weight old_weight = Final(s, wrapped);
+    IdMapIterator it = GetEditedIdMapIterator(s);
+    // if we haven't already edited state s, don't add it to edited_ (which can
+    // be expensive if s has many transitions); just use the
+    // edited_final_weights_ map
+    if (it == NotInEditedMap()) {
+      edited_final_weights_[s] = w;
+    }
+    else {
+      edits_.SetFinal(GetEditableInternalId(s, wrapped), w);
+    }
+    return old_weight;
+  }
+
+  // Adds a new state to this fst, initially with no arcs.
+  StateId AddState(StateId curr_num_states) {
+    StateId internal_state_id = edits_.AddState();
+    StateId external_state_id = curr_num_states;
+    external_to_internal_ids_[external_state_id] = internal_state_id;
+    num_new_states_++;
+    return external_state_id;
+  }
+
+  // Adds the specified arc to the specified state of this fst.
+  const A *AddArc(StateId s, const Arc &arc, const WrappedFstT *wrapped) {
+    StateId internal_id = GetEditableInternalId(s, wrapped);
+
+    size_t num_arcs = edits_.NumArcs(internal_id);
+    ArcIterator<MutableFstT> arc_it(edits_, internal_id);
+    const A *prev_arc = NULL;
+    if (num_arcs > 0) {
+      // grab the final arc associated with this state in edits_
+      arc_it.Seek(num_arcs - 1);
+      prev_arc = &(arc_it.Value());
+    }
+    edits_.AddArc(internal_id, arc);
+    return prev_arc;
+  }
+
+  void DeleteStates() {
+    edits_.DeleteStates();
+    num_new_states_ = 0;
+    external_to_internal_ids_.clear();
+    edited_final_weights_.clear();
+  }
+
+  // Removes all but the first n outgoing arcs of the specified state.
+  void DeleteArcs(StateId s, size_t n, const WrappedFstT *wrapped) {
+    edits_.DeleteArcs(GetEditableInternalId(s, wrapped), n);
+  }
+
+  // Removes all outgoing arcs from the specified state.
+  void DeleteArcs(StateId s, const WrappedFstT *wrapped) {
+    edits_.DeleteArcs(GetEditableInternalId(s, wrapped));
+  }
+
+  // end methods for non-const MutableFst operations
+
+  // Provides information for the generic arc iterator.
+  void InitArcIterator(StateId s, ArcIteratorData<Arc> *data,
+                       const WrappedFstT *wrapped) const {
+    IdMapIterator id_map_it = GetEditedIdMapIterator(s);
+    if (id_map_it == NotInEditedMap()) {
+      VLOG(3) << "EditFstData::InitArcIterator: iterating on state "
+          << s << " of original fst";
+      wrapped->InitArcIterator(s, data);
+    } else {
+      VLOG(2) << "EditFstData::InitArcIterator: iterating on edited state "
+          << s << " (internal state id: " << id_map_it->second << ")";
+      edits_.InitArcIterator(id_map_it->second, data);
+    }
+  }
+
+    // Provides information for the generic mutable arc iterator.
+  void InitMutableArcIterator(StateId s, MutableArcIteratorData<A> *data,
+                              const WrappedFstT *wrapped) {
+    data->base =
+        new MutableArcIterator<MutableFstT>(&edits_,
+                                            GetEditableInternalId(s, wrapped));
+  }
+
+  // Prints out the map from external to internal state id's (for debugging
+  // purposes).
+  void PrintMap() {
+    for (IdMapIterator map_it = external_to_internal_ids_.begin();
+        map_it != NotInEditedMap(); ++map_it) {
+      LOG(INFO) << "(external,internal)=("
+          << map_it->first << "," << map_it->second << ")";
+    }
+  }
+
+
+ private:
+  void SetEmptyAndDeleteKeysForInternalMaps() {
+  }
+
+  // Returns the iterator of the map from external to internal state id's
+  // of edits_ for the specified external state id.
+  IdMapIterator GetEditedIdMapIterator(StateId s) const {
+    return external_to_internal_ids_.find(s);
+  }
+  IdMapIterator NotInEditedMap() const {
+    return external_to_internal_ids_.end();
+  }
+
+  FinalWeightIterator GetFinalWeightIterator(StateId s) const {
+    return edited_final_weights_.find(s);
+  }
+  FinalWeightIterator NotInFinalWeightMap() const {
+    return edited_final_weights_.end();
+  }
+
+  // Returns the internal state id of the specified external id if the state has
+  // already been made editable, or else copies the state from wrapped_
+  // to edits_ and returns the state id of the newly editable state in edits_.
+  //
+  // \return makes the specified state editable if it isn't already and returns
+  //         its state id in edits_
+  StateId GetEditableInternalId(StateId s, const WrappedFstT *wrapped) {
+    IdMapIterator id_map_it = GetEditedIdMapIterator(s);
+    if (id_map_it == NotInEditedMap()) {
+      StateId new_internal_id = edits_.AddState();
+      VLOG(2) << "EditFstData::GetEditableInternalId: editing state " << s
+          << " of original fst; new internal state id:" << new_internal_id;
+      external_to_internal_ids_[s] = new_internal_id;
+      for (ArcIterator< Fst<A> > arc_iterator(*wrapped, s);
+          !arc_iterator.Done();
+          arc_iterator.Next()) {
+        edits_.AddArc(new_internal_id, arc_iterator.Value());
+      }
+      // copy the final weight
+      FinalWeightIterator final_weight_it = GetFinalWeightIterator(s);
+      if (final_weight_it == NotInFinalWeightMap()) {
+        edits_.SetFinal(new_internal_id, wrapped->Final(s));
+      } else {
+        edits_.SetFinal(new_internal_id, final_weight_it->second);
+        edited_final_weights_.erase(s);
+      }
+      return new_internal_id;
+    } else {
+      return id_map_it->second;
+    }
+  }
+
+  // A mutable fst (by default, a VectorFst) to contain new states, and/or
+  // copies of states from a wrapped ExpandedFst that have been modified in
+  // some way.
+  MutableFstT edits_;
+  // A mapping from external state id's to the internal id's of states that
+  // appear in edits_.
+  unordered_map<StateId, StateId> external_to_internal_ids_;
+  // A mapping from external state id's to final state weights assigned to
+  // those states.  The states in this map are *only* those whose final weight
+  // has been modified; if any other part of the state has been modified,
+  // the entire state is copied to edits_, and all modifications reside there.
+  unordered_map<StateId, Weight> edited_final_weights_;
+  // The number of new states added to this mutable fst impl, which is <= the
+  // number of states in edits_ (since edits_ contains both edited *and* new
+  // states).
+  StateId num_new_states_;
+  RefCounter ref_count_;
+};
+
+// EditFstData method implementations: just the Read method.
+template <typename A, typename WrappedFstT, typename MutableFstT>
+EditFstData<A, WrappedFstT, MutableFstT> *
+EditFstData<A, WrappedFstT, MutableFstT>::Read(istream &strm,
+                                               const FstReadOptions &opts) {
+  EditFstData<A, WrappedFstT, MutableFstT> *data =
+      new EditFstData<A, WrappedFstT, MutableFstT>();
+    // next read in MutabelFstT machine that stores edits
+  FstReadOptions edits_opts(opts);
+  edits_opts.header = 0;  // Contained header was written out, so read it in.
+
+  // Because our internal representation of edited states is a solid object
+  // of type MutableFstT (defaults to VectorFst<A>) and not a pointer,
+  // and because the static Read method allocates a new object on the heap,
+  // we need to call Read, check if there was a failure, use
+  // MutableFstT::operator= to assign the object (not the pointer) to the
+  // edits_ data member (which will increase the ref count by 1 on the impl)
+  // and, finally, delete the heap-allocated object.
+  MutableFstT *edits = MutableFstT::Read(strm, edits_opts);
+  if (!edits) {
+    return 0;
+  }
+  data->edits_ = *edits;
+  delete edits;
+  // finally, read in rest of private data members
+  ReadType(strm, &data->external_to_internal_ids_);
+  ReadType(strm, &data->edited_final_weights_);
+  ReadType(strm, &data->num_new_states_);
+  if (!strm) {
+    LOG(ERROR) << "EditFst::Read: read failed: " << opts.source;
+    return 0;
+  }
+  return data;
+}
+
+// This class enables non-destructive edit operations on a wrapped ExpandedFst.
+// The implementation uses copy-on-write semantics at the node level: if a user
+// has an underlying fst on which he or she wants to perform a relatively small
+// number of edits (read: mutations), then this implementation will copy the
+// edited node to an internal MutableFst and perform any edits in situ on that
+// copied node. This class supports all the methods of MutableFst except for
+// DeleteStates(const vector<StateId> &); thus, new nodes may also be added, and
+// one may add transitions from existing nodes of the wrapped fst to new nodes.
+//
+// template parameters:
+//   A the type of arc to use
+//   WrappedFstT the type of fst wrapped by the EditFst instance that
+//     this EditFstImpl instance is backing
+//   MutableFstT the type of mutable fst to use internally for edited states;
+//     crucially, MutableFstT::Copy(false) *must* yield an fst that is
+//     thread-safe for reading (VectorFst, for example, has this property)
+template <typename A,
+          typename WrappedFstT = ExpandedFst<A>,
+          typename MutableFstT = VectorFst<A> >
+class EditFstImpl : public FstImpl<A> {
+ public:
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+  using FstImpl<A>::WriteHeader;
+
+  typedef A Arc;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  // Constructs an editable fst implementation with no states.  Effectively,
+  // this initially-empty fst will in every way mimic the behavior of
+  // a VectorFst--more precisely, a VectorFstImpl instance--but with slightly
+  // slower performance (by a constant factor), due to the fact that
+  // this class maintains a mapping between external state id's and
+  // their internal equivalents.
+  EditFstImpl() {
+    FstImpl<A>::SetType("edit");
+    wrapped_ = new MutableFstT();
+    InheritPropertiesFromWrapped();
+    data_ = new EditFstData<A, WrappedFstT, MutableFstT>();
+  }
+
+  // Wraps the specified ExpandedFst. This constructor requires that the
+  // specified Fst is an ExpandedFst instance. This requirement is only enforced
+  // at runtime. (See below for the reason.)
+  //
+  // This library uses the pointer-to-implementation or "PIMPL" design pattern.
+  // In particular, to make it convenient to bind an implementation class to its
+  // interface, there are a pair of template "binder" classes, one for immutable
+  // and one for mutable fst's (ImplToFst and ImplToMutableFst, respectively).
+  // As it happens, the API for the ImplToMutableFst<I,F> class requires that
+  // the implementation class--the template parameter "I"--have a constructor
+  // taking a const Fst<A> reference.  Accordingly, the constructor here must
+  // perform a static_cast to the WrappedFstT type required by EditFst and
+  // therefore EditFstImpl.
+  explicit EditFstImpl(const Fst<A> &wrapped)
+      : wrapped_(static_cast<WrappedFstT *>(wrapped.Copy())) {
+    FstImpl<A>::SetType("edit");
+
+    data_ = new EditFstData<A, WrappedFstT, MutableFstT>();
+    // have edits_ inherit all properties from wrapped_
+    data_->SetEditedProperties(wrapped_->Properties(kFstProperties, false),
+                               kFstProperties);
+    InheritPropertiesFromWrapped();
+  }
+
+  // A copy constructor for this implementation class, used to implement
+  // the Copy() method of the Fst interface.
+  EditFstImpl(const EditFstImpl &impl)
+      : wrapped_(static_cast<WrappedFstT *>(impl.wrapped_->Copy(true))),
+        data_(impl.data_) {
+    data_->IncrRefCount();
+    SetProperties(impl.Properties());
+  }
+
+  ~EditFstImpl() {
+    delete wrapped_;
+    if (!data_->DecrRefCount()) {
+      delete data_;
+    }
+  }
+
+  // const Fst/ExpandedFst operations, declared in the Fst and ExpandedFst
+  // interfaces
+  StateId Start() const {
+    StateId edited_start = data_->EditedStart();
+    return edited_start == kNoStateId ? wrapped_->Start() : edited_start;
+  }
+
+  Weight Final(StateId s) const {
+    return data_->Final(s, wrapped_);
+  }
+
+  size_t NumArcs(StateId s) const {
+    return data_->NumArcs(s, wrapped_);
+  }
+
+  size_t NumInputEpsilons(StateId s) const {
+    return data_->NumInputEpsilons(s, wrapped_);
+  }
+
+  size_t NumOutputEpsilons(StateId s) const {
+    return data_->NumOutputEpsilons(s, wrapped_);
+  }
+
+  StateId NumStates() const {
+    return wrapped_->NumStates() + data_->NumNewStates();
+  }
+
+  static EditFstImpl<A, WrappedFstT, MutableFstT> *
+  Read(istream &strm,
+       const FstReadOptions &opts);
+
+  bool Write(ostream &strm, const FstWriteOptions &opts) const {
+    FstHeader hdr;
+    hdr.SetStart(Start());
+    hdr.SetNumStates(NumStates());
+    FstWriteOptions header_opts(opts);
+    header_opts.write_isymbols = false;  // Let contained FST hold any symbols.
+    header_opts.write_osymbols = false;
+    WriteHeader(strm, header_opts, kFileVersion, &hdr);
+
+    // First, serialize wrapped fst to stream.
+    FstWriteOptions wrapped_opts(opts);
+    wrapped_opts.write_header = true;  // Force writing contained header.
+    wrapped_->Write(strm, wrapped_opts);
+
+    data_->Write(strm, opts);
+
+    strm.flush();
+    if (!strm) {
+      LOG(ERROR) << "EditFst::Write: write failed: " << opts.source;
+      return false;
+    }
+    return true;
+  }
+  // end const Fst operations
+
+  // non-const MutableFst operations
+
+  // Sets the start state for this fst.
+  void SetStart(StateId s) {
+    MutateCheck();
+    data_->SetStart(s);
+    SetProperties(SetStartProperties(FstImpl<A>::Properties()));
+  }
+
+  // Sets the final state for this fst.
+  void SetFinal(StateId s, Weight w) {
+    MutateCheck();
+    Weight old_weight = data_->SetFinal(s, w, wrapped_);
+    SetProperties(SetFinalProperties(FstImpl<A>::Properties(), old_weight, w));
+  }
+
+  // Adds a new state to this fst, initially with no arcs.
+  StateId AddState() {
+    MutateCheck();
+    SetProperties(AddStateProperties(FstImpl<A>::Properties()));
+    return data_->AddState(NumStates());
+  }
+
+  // Adds the specified arc to the specified state of this fst.
+  void AddArc(StateId s, const Arc &arc) {
+    MutateCheck();
+    const A *prev_arc = data_->AddArc(s, arc, wrapped_);
+    SetProperties(AddArcProperties(FstImpl<A>::Properties(), s, arc, prev_arc));
+  }
+
+  void DeleteStates(const vector<StateId>& dstates) {
+    FSTERROR() << ": EditFstImpl::DeleteStates(const std::vector<StateId>&): "
+               << " not implemented";
+    SetProperties(kError, kError);
+  }
+
+  // Deletes all states in this fst.
+  void DeleteStates();
+
+  // Removes all but the first n outgoing arcs of the specified state.
+  void DeleteArcs(StateId s, size_t n) {
+    MutateCheck();
+    data_->DeleteArcs(s, n, wrapped_);
+    SetProperties(DeleteArcsProperties(FstImpl<A>::Properties()));
+  }
+
+  // Removes all outgoing arcs from the specified state.
+  void DeleteArcs(StateId s) {
+    MutateCheck();
+    data_->DeleteArcs(s, wrapped_);
+    SetProperties(DeleteArcsProperties(FstImpl<A>::Properties()));
+  }
+
+  void ReserveStates(StateId s) {
+  }
+
+  void ReserveArcs(StateId s, size_t n) {
+  }
+
+  // end non-const MutableFst operations
+
+  // Provides information for the generic state iterator.
+  void InitStateIterator(StateIteratorData<Arc> *data) const {
+    data->base = 0;
+    data->nstates = NumStates();
+  }
+
+  // Provides information for the generic arc iterator.
+  void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) const {
+    data_->InitArcIterator(s, data, wrapped_);
+  }
+
+  // Provides information for the generic mutable arc iterator.
+  void InitMutableArcIterator(StateId s, MutableArcIteratorData<A> *data) {
+    MutateCheck();
+    data_->InitMutableArcIterator(s, data, wrapped_);
+  }
+
+ private:
+  typedef typename unordered_map<StateId, StateId>::const_iterator
+    IdMapIterator;
+  typedef typename unordered_map<StateId, Weight>::const_iterator
+    FinalWeightIterator;
+  // Properties always true of this Fst class
+  static const uint64 kStaticProperties = kExpanded | kMutable;
+  // Current file format version
+  static const int kFileVersion = 2;
+  // Minimum file format version supported
+  static const int kMinFileVersion = 2;
+
+  // Causes this fst to inherit all the properties from its wrapped fst, except
+  // for the two properties that always apply to EditFst instances: kExpanded
+  // and kMutable.
+  void InheritPropertiesFromWrapped() {
+    SetProperties(wrapped_->Properties(kCopyProperties, false) |
+                  kStaticProperties);
+    SetInputSymbols(wrapped_->InputSymbols());
+    SetOutputSymbols(wrapped_->OutputSymbols());
+  }
+
+  // This method ensures that any operations that alter the mutable data
+  // portion of this EditFstImpl cause the data_ member to be copied when its
+  // reference count is greater than 1.  Note that this method is distinct from
+  // MutableFst::Mutate, which gets invoked whenever one of the basic mutation
+  // methods defined in MutableFst is invoked, such as SetInputSymbols.
+  // The MutateCheck here in EditFstImpl is invoked whenever one of the
+  // mutating methods specifically related to the types of edits provided
+  // by EditFst is performed, such as changing an arc of an existing state
+  // of the wrapped fst via a MutableArcIterator, or adding a new state via
+  // AddState().
+  void MutateCheck() {
+    if (data_->RefCount() > 1) {
+      EditFstData<A, WrappedFstT, MutableFstT> *data_copy =
+          new EditFstData<A, WrappedFstT, MutableFstT>(*data_);
+      if (data_ && !data_->DecrRefCount()) {
+        delete data_;
+      }
+      data_ = data_copy;
+    }
+  }
+
+  // The fst that this fst wraps.  The purpose of this class is to enable
+  // non-destructive edits on this wrapped fst.
+  const WrappedFstT *wrapped_;
+  // The mutable data for this EditFst instance, with delegates for all the
+  // methods that can mutate data.
+  EditFstData<A, WrappedFstT, MutableFstT> *data_;
+};
+
+template <typename A, typename WrappedFstT, typename MutableFstT>
+const uint64 EditFstImpl<A, WrappedFstT, MutableFstT>::kStaticProperties;
+
+// EditFstImpl IMPLEMENTATION STARTS HERE
+
+template<typename A, typename WrappedFstT, typename MutableFstT>
+inline void EditFstImpl<A, WrappedFstT, MutableFstT>::DeleteStates() {
+  data_->DeleteStates();
+  delete wrapped_;
+  // we are deleting all states, so just forget about pointer to wrapped_
+  // and do what default constructor does: set wrapped_ to a new VectorFst
+  wrapped_ = new MutableFstT();
+  uint64 newProps = DeleteAllStatesProperties(FstImpl<A>::Properties(),
+                                              kStaticProperties);
+  FstImpl<A>::SetProperties(newProps);
+}
+
+template <typename A, typename WrappedFstT, typename MutableFstT>
+EditFstImpl<A, WrappedFstT, MutableFstT> *
+EditFstImpl<A, WrappedFstT, MutableFstT>::Read(istream &strm,
+                                               const FstReadOptions &opts) {
+  EditFstImpl<A, WrappedFstT, MutableFstT> *impl = new EditFstImpl();
+  FstHeader hdr;
+  if (!impl->ReadHeader(strm, opts, kMinFileVersion, &hdr)) {
+    return 0;
+  }
+  impl->SetStart(hdr.Start());
+
+  // first, read in wrapped fst
+  FstReadOptions wrapped_opts(opts);
+  wrapped_opts.header = 0;  // Contained header was written out, so read it in.
+  Fst<A> *wrapped_fst = Fst<A>::Read(strm, wrapped_opts);
+  if (!wrapped_fst) {
+    return 0;
+  }
+  impl->wrapped_ = static_cast<WrappedFstT *>(wrapped_fst);
+
+  impl->data_ = EditFstData<A, WrappedFstT, MutableFstT>::Read(strm, opts);
+
+  if (!impl->data_) {
+    delete wrapped_fst;
+    return 0;
+  }
+
+  return impl;
+}
+
+// END EditFstImpl IMPLEMENTATION
+
+// Concrete, editable FST.  This class attaches interface to implementation.
+template <typename A,
+          typename WrappedFstT = ExpandedFst<A>,
+          typename MutableFstT = VectorFst<A> >
+class EditFst :
+  public ImplToMutableFst< EditFstImpl<A, WrappedFstT, MutableFstT> > {
+ public:
+  friend class MutableArcIterator< EditFst<A, WrappedFstT, MutableFstT> >;
+
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef EditFstImpl<A, WrappedFstT, MutableFstT> Impl;
+
+  EditFst() : ImplToMutableFst<Impl>(new Impl()) {}
+
+  explicit EditFst(const Fst<A> &fst) :
+      ImplToMutableFst<Impl>(new Impl(fst)) {}
+
+  explicit EditFst(const WrappedFstT &fst) :
+      ImplToMutableFst<Impl>(new Impl(fst)) {}
+
+  // See Fst<>::Copy() for doc.
+  EditFst(const EditFst<A, WrappedFstT, MutableFstT> &fst, bool safe = false) :
+    ImplToMutableFst<Impl>(fst, safe) {}
+
+  virtual ~EditFst() {}
+
+  // Get a copy of this EditFst. See Fst<>::Copy() for further doc.
+  virtual EditFst<A, WrappedFstT, MutableFstT> *Copy(bool safe = false) const {
+    return new EditFst<A, WrappedFstT, MutableFstT>(*this, safe);
+  }
+
+  EditFst<A, WrappedFstT, MutableFstT> &
+  operator=(const EditFst<A, WrappedFstT, MutableFstT> &fst) {
+    SetImpl(fst.GetImpl(), false);
+    return *this;
+  }
+
+  virtual EditFst<A, WrappedFstT, MutableFstT> &operator=(const Fst<A> &fst) {
+    if (this != &fst) {
+      SetImpl(new Impl(fst));
+    }
+    return *this;
+  }
+
+  // Read an EditFst from an input stream; return NULL on error.
+  static EditFst<A, WrappedFstT, MutableFstT> *
+  Read(istream &strm,
+       const FstReadOptions &opts) {
+    Impl* impl = Impl::Read(strm, opts);
+    return impl ? new EditFst<A>(impl) : 0;
+  }
+
+  // Read an EditFst from a file; return NULL on error.
+  // Empty filename reads from standard input.
+  static EditFst<A, WrappedFstT, MutableFstT> *Read(const string &filename) {
+    Impl* impl = ImplToExpandedFst<Impl, MutableFst<A> >::Read(filename);
+    return impl ? new EditFst<A, WrappedFstT, MutableFstT>(impl) : 0;
+  }
+
+  virtual bool Write(ostream &strm, const FstWriteOptions &opts) const {
+    return GetImpl()->Write(strm, opts);
+  }
+
+  virtual bool Write(const string &filename) const {
+    return Fst<A>::WriteFile(filename);
+  }
+
+  virtual void InitStateIterator(StateIteratorData<Arc> *data) const {
+    GetImpl()->InitStateIterator(data);
+  }
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+  virtual
+  void InitMutableArcIterator(StateId s, MutableArcIteratorData<A> *data) {
+    GetImpl()->InitMutableArcIterator(s, data);
+  }
+ private:
+  explicit EditFst(Impl *impl) : ImplToMutableFst<Impl>(impl) {}
+
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst< Impl, MutableFst<A> >::GetImpl(); }
+
+  void SetImpl(Impl *impl, bool own_impl = true) {
+    ImplToFst< Impl, MutableFst<A> >::SetImpl(impl, own_impl);
+  }
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_EDIT_FST_H_
diff --git a/src/include/fst/encode.h b/src/include/fst/encode.h
new file mode 100644
index 0000000..7245b45
--- /dev/null
+++ b/src/include/fst/encode.h
@@ -0,0 +1,599 @@
+// encode.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: johans@google.com (Johan Schalkwyk)
+//
+// \file
+// Class to encode and decoder an fst.
+
+#ifndef FST_LIB_ENCODE_H__
+#define FST_LIB_ENCODE_H__
+
+#include <climits>
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/arc-map.h>
+#include <fst/rmfinalepsilon.h>
+
+
+namespace fst {
+
+static const uint32 kEncodeLabels      = 0x0001;
+static const uint32 kEncodeWeights     = 0x0002;
+static const uint32 kEncodeFlags       = 0x0003;  // All non-internal flags
+
+static const uint32 kEncodeHasISymbols = 0x0004;  // For internal use
+static const uint32 kEncodeHasOSymbols = 0x0008;  // For internal use
+
+enum EncodeType { ENCODE = 1, DECODE = 2 };
+
+// Identifies stream data as an encode table (and its endianity)
+static const int32 kEncodeMagicNumber = 2129983209;
+
+
+// The following class encapsulates implementation details for the
+// encoding and decoding of label/weight tuples used for encoding
+// and decoding of Fsts. The EncodeTable is bidirectional. I.E it
+// stores both the Tuple of encode labels and weights to a unique
+// label, and the reverse.
+template <class A>  class EncodeTable {
+ public:
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+
+  // Encoded data consists of arc input/output labels and arc weight
+  struct Tuple {
+    Tuple() {}
+    Tuple(Label ilabel_, Label olabel_, Weight weight_)
+        : ilabel(ilabel_), olabel(olabel_), weight(weight_) {}
+    Tuple(const Tuple& tuple)
+        : ilabel(tuple.ilabel), olabel(tuple.olabel), weight(tuple.weight) {}
+
+    Label ilabel;
+    Label olabel;
+    Weight weight;
+  };
+
+  // Comparison object for hashing EncodeTable Tuple(s).
+  class TupleEqual {
+   public:
+    bool operator()(const Tuple* x, const Tuple* y) const {
+      return (x->ilabel == y->ilabel &&
+              x->olabel == y->olabel &&
+              x->weight == y->weight);
+    }
+  };
+
+  // Hash function for EncodeTabe Tuples. Based on the encode flags
+  // we either hash the labels, weights or combination of them.
+  class TupleKey {
+   public:
+    TupleKey()
+        : encode_flags_(kEncodeLabels | kEncodeWeights) {}
+
+    TupleKey(const TupleKey& key)
+        : encode_flags_(key.encode_flags_) {}
+
+    explicit TupleKey(uint32 encode_flags)
+        : encode_flags_(encode_flags) {}
+
+    size_t operator()(const Tuple* x) const {
+      size_t hash = x->ilabel;
+      const int lshift = 5;
+      const int rshift = CHAR_BIT * sizeof(size_t) - 5;
+      if (encode_flags_ & kEncodeLabels)
+        hash = hash << lshift ^ hash >> rshift ^ x->olabel;
+      if (encode_flags_ & kEncodeWeights)
+        hash = hash << lshift ^ hash >> rshift ^ x->weight.Hash();
+      return hash;
+    }
+
+   private:
+    int32 encode_flags_;
+  };
+
+  typedef unordered_map<const Tuple*,
+                   Label,
+                   TupleKey,
+                   TupleEqual> EncodeHash;
+
+  explicit EncodeTable(uint32 encode_flags)
+      : flags_(encode_flags),
+        encode_hash_(1024, TupleKey(encode_flags)),
+        isymbols_(0), osymbols_(0) {}
+
+  ~EncodeTable() {
+    for (size_t i = 0; i < encode_tuples_.size(); ++i) {
+      delete encode_tuples_[i];
+    }
+    delete isymbols_;
+    delete osymbols_;
+  }
+
+  // Given an arc encode either input/ouptut labels or input/costs or both
+  Label Encode(const A &arc) {
+    const Tuple tuple(arc.ilabel,
+                      flags_ & kEncodeLabels ? arc.olabel : 0,
+                      flags_ & kEncodeWeights ? arc.weight : Weight::One());
+    typename EncodeHash::const_iterator it = encode_hash_.find(&tuple);
+    if (it == encode_hash_.end()) {
+      encode_tuples_.push_back(new Tuple(tuple));
+      encode_hash_[encode_tuples_.back()] = encode_tuples_.size();
+      return encode_tuples_.size();
+    } else {
+      return it->second;
+    }
+  }
+
+  // Given an arc, look up its encoded label. Returns kNoLabel if not found.
+  Label GetLabel(const A &arc) const {
+    const Tuple tuple(arc.ilabel,
+                      flags_ & kEncodeLabels ? arc.olabel : 0,
+                      flags_ & kEncodeWeights ? arc.weight : Weight::One());
+    typename EncodeHash::const_iterator it = encode_hash_.find(&tuple);
+    if (it == encode_hash_.end()) {
+      return kNoLabel;
+    } else {
+      return it->second;
+    }
+  }
+
+  // Given an encode arc Label decode back to input/output labels and costs
+  const Tuple* Decode(Label key) const {
+    if (key < 1 || key > encode_tuples_.size()) {
+      LOG(ERROR) << "EncodeTable::Decode: unknown decode key: " << key;
+      return 0;
+    }
+    return encode_tuples_[key - 1];
+  }
+
+  size_t Size() const { return encode_tuples_.size(); }
+
+  bool Write(ostream &strm, const string &source) const;
+
+  static EncodeTable<A> *Read(istream &strm, const string &source);
+
+  const uint32 flags() const { return flags_ & kEncodeFlags; }
+
+  int RefCount() const { return ref_count_.count(); }
+  int IncrRefCount() { return ref_count_.Incr(); }
+  int DecrRefCount() { return ref_count_.Decr(); }
+
+
+  SymbolTable *InputSymbols() const { return isymbols_; }
+
+  SymbolTable *OutputSymbols() const { return osymbols_; }
+
+  void SetInputSymbols(const SymbolTable* syms) {
+    if (isymbols_) delete isymbols_;
+    if (syms) {
+      isymbols_ = syms->Copy();
+      flags_ |= kEncodeHasISymbols;
+    } else {
+      isymbols_ = 0;
+      flags_ &= ~kEncodeHasISymbols;
+    }
+  }
+
+  void SetOutputSymbols(const SymbolTable* syms) {
+    if (osymbols_) delete osymbols_;
+    if (syms) {
+      osymbols_ = syms->Copy();
+      flags_ |= kEncodeHasOSymbols;
+    } else {
+      osymbols_ = 0;
+      flags_ &= ~kEncodeHasOSymbols;
+    }
+  }
+
+ private:
+  uint32 flags_;
+  vector<Tuple*> encode_tuples_;
+  EncodeHash encode_hash_;
+  RefCounter ref_count_;
+  SymbolTable *isymbols_;       // Pre-encoded ilabel symbol table
+  SymbolTable *osymbols_;       // Pre-encoded olabel symbol table
+
+  DISALLOW_COPY_AND_ASSIGN(EncodeTable);
+};
+
+template <class A> inline
+bool EncodeTable<A>::Write(ostream &strm, const string &source) const {
+  WriteType(strm, kEncodeMagicNumber);
+  WriteType(strm, flags_);
+  int64 size = encode_tuples_.size();
+  WriteType(strm, size);
+  for (size_t i = 0;  i < size; ++i) {
+    const Tuple* tuple = encode_tuples_[i];
+    WriteType(strm, tuple->ilabel);
+    WriteType(strm, tuple->olabel);
+    tuple->weight.Write(strm);
+  }
+
+  if (flags_ & kEncodeHasISymbols)
+    isymbols_->Write(strm);
+
+  if (flags_ & kEncodeHasOSymbols)
+    osymbols_->Write(strm);
+
+  strm.flush();
+  if (!strm) {
+    LOG(ERROR) << "EncodeTable::Write: write failed: " << source;
+    return false;
+  }
+  return true;
+}
+
+template <class A> inline
+EncodeTable<A> *EncodeTable<A>::Read(istream &strm, const string &source) {
+  int32 magic_number = 0;
+  ReadType(strm, &magic_number);
+  if (magic_number != kEncodeMagicNumber) {
+    LOG(ERROR) << "EncodeTable::Read: Bad encode table header: " << source;
+    return 0;
+  }
+  uint32 flags;
+  ReadType(strm, &flags);
+  EncodeTable<A> *table = new EncodeTable<A>(flags);
+
+  int64 size;
+  ReadType(strm, &size);
+  if (!strm) {
+    LOG(ERROR) << "EncodeTable::Read: read failed: " << source;
+    return 0;
+  }
+
+  for (size_t i = 0; i < size; ++i) {
+    Tuple* tuple = new Tuple();
+    ReadType(strm, &tuple->ilabel);
+    ReadType(strm, &tuple->olabel);
+    tuple->weight.Read(strm);
+    if (!strm) {
+      LOG(ERROR) << "EncodeTable::Read: read failed: " << source;
+      return 0;
+    }
+    table->encode_tuples_.push_back(tuple);
+    table->encode_hash_[table->encode_tuples_.back()] =
+        table->encode_tuples_.size();
+  }
+
+  if (flags & kEncodeHasISymbols)
+    table->isymbols_ = SymbolTable::Read(strm, source);
+
+  if (flags & kEncodeHasOSymbols)
+    table->osymbols_ = SymbolTable::Read(strm, source);
+
+  return table;
+}
+
+
+// A mapper to encode/decode weighted transducers. Encoding of an
+// Fst is useful for performing classical determinization or minimization
+// on a weighted transducer by treating it as an unweighted acceptor over
+// encoded labels.
+//
+// The Encode mapper stores the encoding in a local hash table (EncodeTable)
+// This table is shared (and reference counted) between the encoder and
+// decoder. A decoder has read only access to the EncodeTable.
+//
+// The EncodeMapper allows on the fly encoding of the machine. As the
+// EncodeTable is generated the same table may by used to decode the machine
+// on the fly. For example in the following sequence of operations
+//
+//  Encode -> Determinize -> Decode
+//
+// we will use the encoding table generated during the encode step in the
+// decode, even though the encoding is not complete.
+//
+template <class A> class EncodeMapper {
+  typedef typename A::Weight Weight;
+  typedef typename A::Label  Label;
+ public:
+  EncodeMapper(uint32 flags, EncodeType type)
+    : flags_(flags),
+      type_(type),
+      table_(new EncodeTable<A>(flags)),
+      error_(false) {}
+
+  EncodeMapper(const EncodeMapper& mapper)
+      : flags_(mapper.flags_),
+        type_(mapper.type_),
+        table_(mapper.table_),
+        error_(false) {
+    table_->IncrRefCount();
+  }
+
+  // Copy constructor but setting the type, typically to DECODE
+  EncodeMapper(const EncodeMapper& mapper, EncodeType type)
+      : flags_(mapper.flags_),
+        type_(type),
+        table_(mapper.table_),
+        error_(mapper.error_) {
+    table_->IncrRefCount();
+  }
+
+  ~EncodeMapper() {
+    if (!table_->DecrRefCount()) delete table_;
+  }
+
+  A operator()(const A &arc);
+
+  MapFinalAction FinalAction() const {
+    return (type_ == ENCODE && (flags_ & kEncodeWeights)) ?
+                   MAP_REQUIRE_SUPERFINAL : MAP_NO_SUPERFINAL;
+  }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_CLEAR_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_CLEAR_SYMBOLS;}
+
+  uint64 Properties(uint64 inprops) {
+    uint64 outprops = inprops;
+    if (error_) outprops |= kError;
+
+    uint64 mask = kFstProperties;
+    if (flags_ & kEncodeLabels)
+      mask &= kILabelInvariantProperties & kOLabelInvariantProperties;
+    if (flags_ & kEncodeWeights)
+      mask &= kILabelInvariantProperties & kWeightInvariantProperties &
+          (type_ == ENCODE ? kAddSuperFinalProperties :
+           kRmSuperFinalProperties);
+
+    return outprops & mask;
+  }
+
+  const uint32 flags() const { return flags_; }
+  const EncodeType type() const { return type_; }
+  const EncodeTable<A> &table() const { return *table_; }
+
+  bool Write(ostream &strm, const string& source) {
+    return table_->Write(strm, source);
+  }
+
+  bool Write(const string& filename) {
+    ofstream strm(filename.c_str(), ofstream::out | ofstream::binary);
+    if (!strm) {
+      LOG(ERROR) << "EncodeMap: Can't open file: " << filename;
+      return false;
+    }
+    return Write(strm, filename);
+  }
+
+  static EncodeMapper<A> *Read(istream &strm,
+                               const string& source,
+                               EncodeType type = ENCODE) {
+    EncodeTable<A> *table = EncodeTable<A>::Read(strm, source);
+    return table ? new EncodeMapper(table->flags(), type, table) : 0;
+  }
+
+  static EncodeMapper<A> *Read(const string& filename,
+                               EncodeType type = ENCODE) {
+    ifstream strm(filename.c_str(), ifstream::in | ifstream::binary);
+    if (!strm) {
+      LOG(ERROR) << "EncodeMap: Can't open file: " << filename;
+      return NULL;
+    }
+    return Read(strm, filename, type);
+  }
+
+  SymbolTable *InputSymbols() const { return table_->InputSymbols(); }
+
+  SymbolTable *OutputSymbols() const { return table_->OutputSymbols(); }
+
+  void SetInputSymbols(const SymbolTable* syms) {
+    table_->SetInputSymbols(syms);
+  }
+
+  void SetOutputSymbols(const SymbolTable* syms) {
+    table_->SetOutputSymbols(syms);
+  }
+
+ private:
+  uint32 flags_;
+  EncodeType type_;
+  EncodeTable<A>* table_;
+  bool error_;
+
+  explicit EncodeMapper(uint32 flags, EncodeType type, EncodeTable<A> *table)
+      : flags_(flags), type_(type), table_(table) {}
+  void operator=(const EncodeMapper &);  // Disallow.
+};
+
+template <class A> inline
+A EncodeMapper<A>::operator()(const A &arc) {
+  if (type_ == ENCODE) {  // labels and/or weights to single label
+    if ((arc.nextstate == kNoStateId && !(flags_ & kEncodeWeights)) ||
+        (arc.nextstate == kNoStateId && (flags_ & kEncodeWeights) &&
+         arc.weight == Weight::Zero())) {
+      return arc;
+    } else {
+      Label label = table_->Encode(arc);
+      return A(label,
+               flags_ & kEncodeLabels ? label : arc.olabel,
+               flags_ & kEncodeWeights ? Weight::One() : arc.weight,
+               arc.nextstate);
+    }
+  } else {  // type_ == DECODE
+    if (arc.nextstate == kNoStateId) {
+      return arc;
+    } else {
+      if (arc.ilabel == 0) return arc;
+      if (flags_ & kEncodeLabels && arc.ilabel != arc.olabel) {
+        FSTERROR() << "EncodeMapper: Label-encoded arc has different "
+            "input and output labels";
+        error_ = true;
+      }
+      if (flags_ & kEncodeWeights && arc.weight != Weight::One()) {
+        FSTERROR() <<
+            "EncodeMapper: Weight-encoded arc has non-trivial weight";
+        error_ = true;
+      }
+      const typename EncodeTable<A>::Tuple* tuple = table_->Decode(arc.ilabel);
+      if (!tuple) {
+        FSTERROR() << "EncodeMapper: decode failed";
+        error_ = true;
+        return A(kNoLabel, kNoLabel, Weight::NoWeight(), arc.nextstate);
+      } else {
+        return A(tuple->ilabel,
+                 flags_ & kEncodeLabels ? tuple->olabel : arc.olabel,
+                 flags_ & kEncodeWeights ? tuple->weight : arc.weight,
+                 arc.nextstate);
+      }
+    }
+  }
+}
+
+
+// Complexity: O(nstates + narcs)
+template<class A> inline
+void Encode(MutableFst<A> *fst, EncodeMapper<A>* mapper) {
+  mapper->SetInputSymbols(fst->InputSymbols());
+  mapper->SetOutputSymbols(fst->OutputSymbols());
+  ArcMap(fst, mapper);
+}
+
+template<class A> inline
+void Decode(MutableFst<A>* fst, const EncodeMapper<A>& mapper) {
+  ArcMap(fst, EncodeMapper<A>(mapper, DECODE));
+  RmFinalEpsilon(fst);
+  fst->SetInputSymbols(mapper.InputSymbols());
+  fst->SetOutputSymbols(mapper.OutputSymbols());
+}
+
+
+// On the fly label and/or weight encoding of input Fst
+//
+// Complexity:
+// - Constructor: O(1)
+// - Traversal: O(nstates_visited + narcs_visited), assuming constant
+//   time to visit an input state or arc.
+template <class A>
+class EncodeFst : public ArcMapFst<A, A, EncodeMapper<A> > {
+ public:
+  typedef A Arc;
+  typedef EncodeMapper<A> C;
+  typedef ArcMapFstImpl< A, A, EncodeMapper<A> > Impl;
+  using ImplToFst<Impl>::GetImpl;
+
+  EncodeFst(const Fst<A> &fst, EncodeMapper<A>* encoder)
+      : ArcMapFst<A, A, C>(fst, encoder, ArcMapFstOptions()) {
+    encoder->SetInputSymbols(fst.InputSymbols());
+    encoder->SetOutputSymbols(fst.OutputSymbols());
+  }
+
+  EncodeFst(const Fst<A> &fst, const EncodeMapper<A>& encoder)
+      : ArcMapFst<A, A, C>(fst, encoder, ArcMapFstOptions()) {}
+
+  // See Fst<>::Copy() for doc.
+  EncodeFst(const EncodeFst<A> &fst, bool copy = false)
+      : ArcMapFst<A, A, C>(fst, copy) {}
+
+  // Get a copy of this EncodeFst. See Fst<>::Copy() for further doc.
+  virtual EncodeFst<A> *Copy(bool safe = false) const {
+    if (safe) {
+      FSTERROR() << "EncodeFst::Copy(true): not allowed.";
+      GetImpl()->SetProperties(kError, kError);
+    }
+    return new EncodeFst(*this);
+  }
+};
+
+
+// On the fly label and/or weight encoding of input Fst
+//
+// Complexity:
+// - Constructor: O(1)
+// - Traversal: O(nstates_visited + narcs_visited), assuming constant
+//   time to visit an input state or arc.
+template <class A>
+class DecodeFst : public ArcMapFst<A, A, EncodeMapper<A> > {
+ public:
+  typedef A Arc;
+  typedef EncodeMapper<A> C;
+  typedef ArcMapFstImpl< A, A, EncodeMapper<A> > Impl;
+  using ImplToFst<Impl>::GetImpl;
+
+  DecodeFst(const Fst<A> &fst, const EncodeMapper<A>& encoder)
+      : ArcMapFst<A, A, C>(fst,
+                            EncodeMapper<A>(encoder, DECODE),
+                            ArcMapFstOptions()) {
+    GetImpl()->SetInputSymbols(encoder.InputSymbols());
+    GetImpl()->SetOutputSymbols(encoder.OutputSymbols());
+  }
+
+  // See Fst<>::Copy() for doc.
+  DecodeFst(const DecodeFst<A> &fst, bool safe = false)
+      : ArcMapFst<A, A, C>(fst, safe) {}
+
+  // Get a copy of this DecodeFst. See Fst<>::Copy() for further doc.
+  virtual DecodeFst<A> *Copy(bool safe = false) const {
+    return new DecodeFst(*this, safe);
+  }
+};
+
+
+// Specialization for EncodeFst.
+template <class A>
+class StateIterator< EncodeFst<A> >
+    : public StateIterator< ArcMapFst<A, A, EncodeMapper<A> > > {
+ public:
+  explicit StateIterator(const EncodeFst<A> &fst)
+      : StateIterator< ArcMapFst<A, A, EncodeMapper<A> > >(fst) {}
+};
+
+
+// Specialization for EncodeFst.
+template <class A>
+class ArcIterator< EncodeFst<A> >
+    : public ArcIterator< ArcMapFst<A, A, EncodeMapper<A> > > {
+ public:
+  ArcIterator(const EncodeFst<A> &fst, typename A::StateId s)
+      : ArcIterator< ArcMapFst<A, A, EncodeMapper<A> > >(fst, s) {}
+};
+
+
+// Specialization for DecodeFst.
+template <class A>
+class StateIterator< DecodeFst<A> >
+    : public StateIterator< ArcMapFst<A, A, EncodeMapper<A> > > {
+ public:
+  explicit StateIterator(const DecodeFst<A> &fst)
+      : StateIterator< ArcMapFst<A, A, EncodeMapper<A> > >(fst) {}
+};
+
+
+// Specialization for DecodeFst.
+template <class A>
+class ArcIterator< DecodeFst<A> >
+    : public ArcIterator< ArcMapFst<A, A, EncodeMapper<A> > > {
+ public:
+  ArcIterator(const DecodeFst<A> &fst, typename A::StateId s)
+      : ArcIterator< ArcMapFst<A, A, EncodeMapper<A> > >(fst, s) {}
+};
+
+
+// Useful aliases when using StdArc.
+typedef EncodeFst<StdArc> StdEncodeFst;
+
+typedef DecodeFst<StdArc> StdDecodeFst;
+
+}  // namespace fst
+
+#endif  // FST_LIB_ENCODE_H__
diff --git a/src/include/fst/epsnormalize.h b/src/include/fst/epsnormalize.h
new file mode 100644
index 0000000..696242b
--- /dev/null
+++ b/src/include/fst/epsnormalize.h
@@ -0,0 +1,74 @@
+// epsnormalize.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Function that implements epsilon normalization.
+
+#ifndef FST_LIB_EPSNORMALIZE_H__
+#define FST_LIB_EPSNORMALIZE_H__
+
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <fst/slist.h>
+
+
+#include <fst/factor-weight.h>
+#include <fst/invert.h>
+#include <fst/arc-map.h>
+#include <fst/rmepsilon.h>
+
+
+namespace fst {
+
+enum EpsNormalizeType {EPS_NORM_INPUT, EPS_NORM_OUTPUT};
+
+// Returns an equivalent FST that is epsilon-normalized. An acceptor is
+// epsilon-normalized if it is epsilon-removed. A transducer is input
+// epsilon-normalized if additionally if on each path any epsilon input
+// label follows all non-epsilon input labels. Output epsilon-normalized
+// is defined similarly.
+//
+// The input FST needs to be functional.
+//
+// References:
+// - Mehryar Mohri. "Generic epsilon-removal and input epsilon-normalization
+//   algorithms for weighted transducers", International Journal of Computer
+//   Science, 13(1): 129-143, 2002.
+template <class Arc>
+void EpsNormalize(const Fst<Arc> &ifst, MutableFst<Arc> *ofst,
+                      EpsNormalizeType type = EPS_NORM_INPUT) {
+  VectorFst< GallicArc<Arc, STRING_RIGHT_RESTRICT> > gfst;
+  if (type == EPS_NORM_INPUT)
+    ArcMap(ifst, &gfst, ToGallicMapper<Arc, STRING_RIGHT_RESTRICT>());
+  else // type == EPS_NORM_OUTPUT
+    ArcMap(InvertFst<Arc>(ifst), &gfst,
+           ToGallicMapper<Arc, STRING_RIGHT_RESTRICT>());
+  RmEpsilon(&gfst);
+  FactorWeightFst< GallicArc<Arc, STRING_RIGHT_RESTRICT>,
+    GallicFactor<typename Arc::Label,
+      typename Arc::Weight, STRING_RIGHT_RESTRICT> >
+    fwfst(gfst);
+  ArcMap(fwfst, ofst, FromGallicMapper<Arc, STRING_RIGHT_RESTRICT>());
+  ofst->SetOutputSymbols(ifst.OutputSymbols());
+  if(type == EPS_NORM_OUTPUT)
+    Invert(ofst);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_EPSNORMALIZE_H__
diff --git a/src/include/fst/equal.h b/src/include/fst/equal.h
new file mode 100644
index 0000000..33be198
--- /dev/null
+++ b/src/include/fst/equal.h
@@ -0,0 +1,124 @@
+// test.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Function to test equality of two Fsts.
+
+#ifndef FST_LIB_EQUAL_H__
+#define FST_LIB_EQUAL_H__
+
+#include <fst/fst.h>
+
+
+namespace fst {
+
+// Tests if two Fsts have the same states and arcs in the same order.
+template<class Arc>
+bool Equal(const Fst<Arc> &fst1, const Fst<Arc> &fst2, float delta = kDelta) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+
+  if (fst1.Start() != fst2.Start()) {
+    VLOG(1) << "Equal: mismatched start states";
+    return false;
+  }
+
+  StateIterator< Fst<Arc> > siter1(fst1);
+  StateIterator< Fst<Arc> > siter2(fst2);
+
+  while (!siter1.Done() || !siter2.Done()) {
+    if (siter1.Done() || siter2.Done()) {
+      VLOG(1) << "Equal: mismatched # of states";
+      return false;
+    }
+    StateId s1 = siter1.Value();
+    StateId s2 = siter2.Value();
+    if (s1 != s2) {
+      VLOG(1) << "Equal: mismatched states:"
+              << ", state1 = " << s1
+              << ", state2 = " << s2;
+      return false;
+    }
+    Weight final1 = fst1.Final(s1);
+    Weight final2 = fst2.Final(s2);
+    if (!ApproxEqual(final1, final2, delta)) {
+      VLOG(1) << "Equal: mismatched final weights:"
+              << " state = " << s1
+              << ", final1 = " << final1
+              << ", final2 = " << final2;
+      return false;
+     }
+    ArcIterator< Fst<Arc> > aiter1(fst1, s1);
+    ArcIterator< Fst<Arc> > aiter2(fst2, s2);
+    for (size_t a = 0; !aiter1.Done() || !aiter2.Done(); ++a) {
+      if (aiter1.Done() || aiter2.Done()) {
+        VLOG(1) << "Equal: mismatched # of arcs"
+                << " state = " << s1;
+        return false;
+      }
+      Arc arc1 = aiter1.Value();
+      Arc arc2 = aiter2.Value();
+      if (arc1.ilabel != arc2.ilabel) {
+        VLOG(1) << "Equal: mismatched arc input labels:"
+                << " state = " << s1
+                << ", arc = " << a
+                << ", ilabel1 = " << arc1.ilabel
+                << ", ilabel2 = " << arc2.ilabel;
+        return false;
+      } else  if (arc1.olabel != arc2.olabel) {
+        VLOG(1) << "Equal: mismatched arc output labels:"
+                << " state = " << s1
+                << ", arc = " << a
+                << ", olabel1 = " << arc1.olabel
+                << ", olabel2 = " << arc2.olabel;
+        return false;
+      } else  if (!ApproxEqual(arc1.weight, arc2.weight, delta)) {
+        VLOG(1) << "Equal: mismatched arc weights:"
+                << " state = " << s1
+                << ", arc = " << a
+                << ", weight1 = " << arc1.weight
+                << ", weight2 = " << arc2.weight;
+        return false;
+      } else  if (arc1.nextstate != arc2.nextstate) {
+        VLOG(1) << "Equal: mismatched input label:"
+                << " state = " << s1
+                << ", arc = " << a
+                << ", nextstate1 = " << arc1.nextstate
+                << ", nextstate2 = " << arc2.nextstate;
+        return false;
+      }
+      aiter1.Next();
+      aiter2.Next();
+
+    }
+    // Sanity checks: should never fail
+    if (fst1.NumArcs(s1) != fst2.NumArcs(s2) ||
+        fst1.NumInputEpsilons(s1) != fst2.NumInputEpsilons(s2) ||
+        fst1.NumOutputEpsilons(s1) != fst2.NumOutputEpsilons(s2)) {
+      FSTERROR() << "Equal: inconsistent arc/epsilon counts";
+    }
+
+    siter1.Next();
+    siter2.Next();
+  }
+  return true;
+}
+
+}  // namespace fst
+
+
+#endif  // FST_LIB_EQUAL_H__
diff --git a/src/include/fst/equivalent.h b/src/include/fst/equivalent.h
new file mode 100644
index 0000000..f05ff87
--- /dev/null
+++ b/src/include/fst/equivalent.h
@@ -0,0 +1,274 @@
+// equivalent.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: wojciech@google.com (Wojciech Skut)
+//
+// \file Functions and classes to determine the equivalence of two
+// FSTs.
+
+#ifndef FST_LIB_EQUIVALENT_H__
+#define FST_LIB_EQUIVALENT_H__
+
+#include <algorithm>
+#include <deque>
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+#include <fst/encode.h>
+#include <fst/push.h>
+#include <fst/union-find.h>
+#include <fst/vector-fst.h>
+
+
+namespace fst {
+
+// Traits-like struct holding utility functions/typedefs/constants for
+// the equivalence algorithm.
+//
+// Encoding device: in order to make the statesets of the two acceptors
+// disjoint, we map Arc::StateId on the type MappedId. The states of
+// the first acceptor are mapped on odd numbers (s -> 2s + 1), and
+// those of the second one on even numbers (s -> 2s + 2). The number 0
+// is reserved for an implicit (non-final) 'dead state' (required for
+// the correct treatment of non-coaccessible states; kNoStateId is
+// mapped to kDeadState for both acceptors). The union-find algorithm
+// operates on the mapped IDs.
+template <class Arc>
+struct EquivalenceUtil {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef StateId MappedId;  // ID for an equivalence class.
+
+  // MappedId for an implicit dead state.
+  static const MappedId kDeadState = 0;
+
+  // MappedId for lookup failure.
+  static const MappedId kInvalidId = -1;
+
+  // Maps state ID to the representative of the corresponding
+  // equivalence class. The parameter 'which_fst' takes the values 1
+  // and 2, identifying the input FST.
+  static MappedId MapState(StateId s, int32 which_fst) {
+    return
+      (kNoStateId == s)
+      ?
+      kDeadState
+      :
+      (static_cast<MappedId>(s) << 1) + which_fst;
+  }
+  // Maps set ID to State ID.
+  static StateId UnMapState(MappedId id) {
+    return static_cast<StateId>((--id) >> 1);
+  }
+  // Convenience function: checks if state with MappedId 's' is final
+  // in acceptor 'fa'.
+  static bool IsFinal(const Fst<Arc> &fa, MappedId s) {
+    return
+      (kDeadState == s) ?
+      false : (fa.Final(UnMapState(s)) != Weight::Zero());
+  }
+  // Convenience function: returns the representative of 'id' in 'sets',
+  // creating a new set if needed.
+  static MappedId FindSet(UnionFind<MappedId> *sets, MappedId id) {
+    MappedId repr = sets->FindSet(id);
+    if (repr != kInvalidId) {
+      return repr;
+    } else {
+      sets->MakeSet(id);
+      return id;
+    }
+  }
+};
+
+template <class Arc> const
+typename EquivalenceUtil<Arc>::MappedId EquivalenceUtil<Arc>::kDeadState;
+
+template <class Arc> const
+typename EquivalenceUtil<Arc>::MappedId EquivalenceUtil<Arc>::kInvalidId;
+
+
+// Equivalence checking algorithm: determines if the two FSTs
+// <code>fst1</code> and <code>fst2</code> are equivalent. The input
+// FSTs must be deterministic input-side epsilon-free acceptors,
+// unweighted or with weights over a left semiring. Two acceptors are
+// considered equivalent if they accept exactly the same set of
+// strings (with the same weights).
+//
+// The algorithm (cf. Aho, Hopcroft and Ullman, "The Design and
+// Analysis of Computer Programs") successively constructs sets of
+// states that can be reached by the same prefixes, starting with a
+// set containing the start states of both acceptors. A disjoint tree
+// forest (the union-find algorithm) is used to represent the sets of
+// states. The algorithm returns 'false' if one of the constructed
+// sets contains both final and non-final states. Returns optional error
+// value (when FLAGS_error_fatal = false).
+//
+// Complexity: quasi-linear, i.e. O(n G(n)), where
+//   n = |S1| + |S2| is the number of states in both acceptors
+//   G(n) is a very slowly growing function that can be approximated
+//        by 4 by all practical purposes.
+//
+template <class Arc>
+bool Equivalent(const Fst<Arc> &fst1,
+                const Fst<Arc> &fst2,
+                double delta = kDelta, bool *error = 0) {
+  typedef typename Arc::Weight Weight;
+  if (error) *error = false;
+
+  // Check that the symbol table are compatible
+  if (!CompatSymbols(fst1.InputSymbols(), fst2.InputSymbols()) ||
+      !CompatSymbols(fst1.OutputSymbols(), fst2.OutputSymbols())) {
+    FSTERROR() << "Equivalent: input/output symbol tables of 1st argument "
+               << "do not match input/output symbol tables of 2nd argument";
+    if (error) *error = true;
+    return false;
+  }
+  // Check properties first:
+  uint64 props = kNoEpsilons | kIDeterministic | kAcceptor;
+  if (fst1.Properties(props, true) != props) {
+    FSTERROR() << "Equivalent: first argument not an"
+               << " epsilon-free deterministic acceptor";
+    if (error) *error = true;
+    return false;
+  }
+  if (fst2.Properties(props, true) != props) {
+    FSTERROR() << "Equivalent: second argument not an"
+               << " epsilon-free deterministic acceptor";
+    if (error) *error = true;
+    return false;
+  }
+
+  if ((fst1.Properties(kUnweighted , true) != kUnweighted)
+      || (fst2.Properties(kUnweighted , true) != kUnweighted)) {
+    VectorFst<Arc> efst1(fst1);
+    VectorFst<Arc> efst2(fst2);
+    Push(&efst1, REWEIGHT_TO_INITIAL, delta);
+    Push(&efst2, REWEIGHT_TO_INITIAL, delta);
+    ArcMap(&efst1, QuantizeMapper<Arc>(delta));
+    ArcMap(&efst2, QuantizeMapper<Arc>(delta));
+    EncodeMapper<Arc> mapper(kEncodeWeights|kEncodeLabels, ENCODE);
+    ArcMap(&efst1, &mapper);
+    ArcMap(&efst2, &mapper);
+    return Equivalent(efst1, efst2);
+  }
+
+  // Convenience typedefs:
+  typedef typename Arc::StateId StateId;
+  typedef EquivalenceUtil<Arc> Util;
+  typedef typename Util::MappedId MappedId;
+  enum { FST1 = 1, FST2 = 2 };  // Required by Util::MapState(...)
+
+  MappedId s1 = Util::MapState(fst1.Start(), FST1);
+  MappedId s2 = Util::MapState(fst2.Start(), FST2);
+
+  // The union-find structure.
+  UnionFind<MappedId> eq_classes(1000, Util::kInvalidId);
+
+  // Initialize the union-find structure.
+  eq_classes.MakeSet(s1);
+  eq_classes.MakeSet(s2);
+
+  // Data structure for the (partial) acceptor transition function of
+  // fst1 and fst2: input labels mapped to pairs of MappedId's
+  // representing destination states of the corresponding arcs in fst1
+  // and fst2, respectively.
+  typedef
+    unordered_map<typename Arc::Label, pair<MappedId, MappedId> >
+    Label2StatePairMap;
+
+  Label2StatePairMap arc_pairs;
+
+  // Pairs of MappedId's to be processed, organized in a queue.
+  deque<pair<MappedId, MappedId> > q;
+
+  bool ret = true;
+  // Early return if the start states differ w.r.t. being final.
+  if (Util::IsFinal(fst1, s1) != Util::IsFinal(fst2, s2)) {
+    ret = false;
+  }
+
+  // Main loop: explores the two acceptors in a breadth-first manner,
+  // updating the equivalence relation on the statesets. Loop
+  // invariant: each block of states contains either final states only
+  // or non-final states only.
+  for (q.push_back(make_pair(s1, s2)); ret && !q.empty(); q.pop_front()) {
+    s1 = q.front().first;
+    s2 = q.front().second;
+
+    // Representatives of the equivalence classes of s1/s2.
+    MappedId rep1 = Util::FindSet(&eq_classes, s1);
+    MappedId rep2 = Util::FindSet(&eq_classes, s2);
+
+    if (rep1 != rep2) {
+      eq_classes.Union(rep1, rep2);
+      arc_pairs.clear();
+
+      // Copy outgoing arcs starting at s1 into the hashtable.
+      if (Util::kDeadState != s1) {
+        ArcIterator<Fst<Arc> > arc_iter(fst1, Util::UnMapState(s1));
+        for (; !arc_iter.Done(); arc_iter.Next()) {
+          const Arc &arc = arc_iter.Value();
+          if (arc.weight != Weight::Zero()) {  // Zero-weight arcs
+                                                   // are treated as
+                                                   // non-exisitent.
+            arc_pairs[arc.ilabel].first = Util::MapState(arc.nextstate, FST1);
+          }
+        }
+      }
+      // Copy outgoing arcs starting at s2 into the hashtable.
+      if (Util::kDeadState != s2) {
+        ArcIterator<Fst<Arc> > arc_iter(fst2, Util::UnMapState(s2));
+        for (; !arc_iter.Done(); arc_iter.Next()) {
+          const Arc &arc = arc_iter.Value();
+          if (arc.weight != Weight::Zero()) {  // Zero-weight arcs
+                                                   // are treated as
+                                                   // non-existent.
+            arc_pairs[arc.ilabel].second = Util::MapState(arc.nextstate, FST2);
+          }
+        }
+      }
+      // Iterate through the hashtable and process pairs of target
+      // states.
+      for (typename Label2StatePairMap::const_iterator
+             arc_iter = arc_pairs.begin();
+           arc_iter != arc_pairs.end();
+           ++arc_iter) {
+        const pair<MappedId, MappedId> &p = arc_iter->second;
+        if (Util::IsFinal(fst1, p.first) != Util::IsFinal(fst2, p.second)) {
+          // Detected inconsistency: return false.
+          ret = false;
+          break;
+        }
+        q.push_back(p);
+      }
+    }
+  }
+
+  if (fst1.Properties(kError, false) || fst2.Properties(kError, false)) {
+    if (error) *error = true;
+    return false;
+  }
+
+  return ret;
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_EQUIVALENT_H__
diff --git a/src/include/fst/expanded-fst.h b/src/include/fst/expanded-fst.h
new file mode 100644
index 0000000..b44b81c
--- /dev/null
+++ b/src/include/fst/expanded-fst.h
@@ -0,0 +1,189 @@
+// expanded-fst.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Generic FST augmented with state count - interface class definition.
+//
+
+#ifndef FST_LIB_EXPANDED_FST_H__
+#define FST_LIB_EXPANDED_FST_H__
+
+#include <sys/types.h>
+#include <string>
+
+#include <fst/fst.h>
+
+
+namespace fst {
+
+// A generic FST plus state count.
+template <class A>
+class ExpandedFst : public Fst<A> {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+
+  virtual StateId NumStates() const = 0;  // State count
+
+  // Get a copy of this ExpandedFst. See Fst<>::Copy() for further doc.
+  virtual ExpandedFst<A> *Copy(bool safe = false) const = 0;
+
+  // Read an ExpandedFst from an input stream; return NULL on error.
+  static ExpandedFst<A> *Read(istream &strm, const FstReadOptions &opts) {
+    FstReadOptions ropts(opts);
+    FstHeader hdr;
+    if (ropts.header)
+      hdr = *opts.header;
+    else {
+      if (!hdr.Read(strm, opts.source))
+        return 0;
+      ropts.header = &hdr;
+    }
+    if (!(hdr.Properties() & kExpanded)) {
+      LOG(ERROR) << "ExpandedFst::Read: Not an ExpandedFst: " << ropts.source;
+      return 0;
+    }
+    FstRegister<A> *registr = FstRegister<A>::GetRegister();
+    const typename FstRegister<A>::Reader reader =
+      registr->GetReader(hdr.FstType());
+    if (!reader) {
+      LOG(ERROR) << "ExpandedFst::Read: Unknown FST type \"" << hdr.FstType()
+                 << "\" (arc type = \"" << A::Type()
+                 << "\"): " << ropts.source;
+      return 0;
+    }
+    Fst<A> *fst = reader(strm, ropts);
+    if (!fst) return 0;
+    return static_cast<ExpandedFst<A> *>(fst);
+  }
+
+  // Read an ExpandedFst from a file; return NULL on error.
+  // Empty filename reads from standard input.
+  static ExpandedFst<A> *Read(const string &filename) {
+    if (!filename.empty()) {
+      ifstream strm(filename.c_str(), ifstream::in | ifstream::binary);
+      if (!strm) {
+        LOG(ERROR) << "ExpandedFst::Read: Can't open file: " << filename;
+        return 0;
+      }
+      return Read(strm, FstReadOptions(filename));
+    } else {
+      return Read(std::cin, FstReadOptions("standard input"));
+    }
+  }
+};
+
+
+namespace internal {
+
+//  ExpandedFst<A> case - abstract methods.
+template <class A> inline
+typename A::Weight Final(const ExpandedFst<A> &fst, typename A::StateId s) {
+  return fst.Final(s);
+}
+
+template <class A> inline
+ssize_t NumArcs(const ExpandedFst<A> &fst, typename A::StateId s) {
+  return fst.NumArcs(s);
+}
+
+template <class A> inline
+ssize_t NumInputEpsilons(const ExpandedFst<A> &fst, typename A::StateId s) {
+  return fst.NumInputEpsilons(s);
+}
+
+template <class A> inline
+ssize_t NumOutputEpsilons(const ExpandedFst<A> &fst, typename A::StateId s) {
+  return fst.NumOutputEpsilons(s);
+}
+
+}  // namespace internal
+
+
+// A useful alias when using StdArc.
+typedef ExpandedFst<StdArc> StdExpandedFst;
+
+
+// This is a helper class template useful for attaching an ExpandedFst
+// interface to its implementation, handling reference counting. It
+// delegates to ImplToFst the handling of the Fst interface methods.
+template < class I, class F = ExpandedFst<typename I::Arc> >
+class ImplToExpandedFst : public ImplToFst<I, F> {
+ public:
+  typedef typename I::Arc Arc;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  using ImplToFst<I, F>::GetImpl;
+
+  virtual StateId NumStates() const { return GetImpl()->NumStates(); }
+
+ protected:
+  ImplToExpandedFst() : ImplToFst<I, F>() {}
+
+  ImplToExpandedFst(I *impl) : ImplToFst<I, F>(impl) {}
+
+  ImplToExpandedFst(const ImplToExpandedFst<I, F> &fst)
+      : ImplToFst<I, F>(fst) {}
+
+  ImplToExpandedFst(const ImplToExpandedFst<I, F> &fst, bool safe)
+      : ImplToFst<I, F>(fst, safe) {}
+
+  // Read FST implementation from a file; return NULL on error.
+  // Empty filename reads from standard input.
+  static I *Read(const string &filename) {
+    if (!filename.empty()) {
+      ifstream strm(filename.c_str(), ifstream::in | ifstream::binary);
+      if (!strm) {
+        LOG(ERROR) << "ExpandedFst::Read: Can't open file: " << filename;
+        return 0;
+      }
+      return I::Read(strm, FstReadOptions(filename));
+    } else {
+      return I::Read(std::cin, FstReadOptions("standard input"));
+    }
+  }
+
+ private:
+  // Disallow
+  ImplToExpandedFst<I, F> &operator=(const ImplToExpandedFst<I, F> &fst);
+
+  ImplToExpandedFst<I, F> &operator=(const Fst<Arc> &fst) {
+    FSTERROR() << "ImplToExpandedFst: Assignment operator disallowed";
+    GetImpl()->SetProperties(kError, kError);
+    return *this;
+  }
+};
+
+// Function to return the number of states in an FST, counting them
+// if necessary.
+template <class Arc>
+typename Arc::StateId CountStates(const Fst<Arc> &fst) {
+  if (fst.Properties(kExpanded, false)) {
+    const ExpandedFst<Arc> *efst = static_cast<const ExpandedFst<Arc> *>(&fst);
+    return efst->NumStates();
+  } else {
+    typename Arc::StateId nstates = 0;
+    for (StateIterator< Fst<Arc> > siter(fst); !siter.Done(); siter.Next())
+      ++nstates;
+    return nstates;
+  }
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_EXPANDED_FST_H__
diff --git a/src/include/fst/expectation-weight.h b/src/include/fst/expectation-weight.h
new file mode 100644
index 0000000..5226cad
--- /dev/null
+++ b/src/include/fst/expectation-weight.h
@@ -0,0 +1,142 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: krr@google.com (Kasturi Rangan Raghavan)
+// Inspiration: shumash@google.com (Masha Maria Shugrina)
+// \file
+// Expectation semiring as described by Jason Eisner:
+// See: doi=10.1.1.22.9398
+// Multiplex semiring operations and identities:
+//    One: <One, Zero>
+//    Zero: <Zero, Zero>
+//    Plus: <a1, b1> + <a2, b2> = < (a1 + a2) , (b1 + b2) >
+//    Times: <a1, b1> * <a2, b2> = < (a1 * a2) , [(a1 * b2) + (a2 * b1)] >
+//    Division: Undefined (currently)
+//
+// Usually used to store the pair <probability, random_variable> so that
+// ShortestDistance[Fst<ArcTpl<ExpectationWeight<P, V> > >]
+//    == < PosteriorProbability, Expected_Value[V] >
+
+#ifndef FST_LIB_EXPECTATION_WEIGHT_H_
+#define FST_LIB_EXPECTATION_WEIGHT_H_
+
+#include<string>
+
+#include <fst/pair-weight.h>
+
+
+namespace fst {
+
+// X1 is usually a probability weight like LogWeight
+// X2 is usually a random variable or vector
+//    see SignedLogWeight or SparsePowerWeight
+//
+// If X1 is distinct from X2, it is required that there is an external
+// product between X1 and X2 and if both semriring are commutative, or
+// left or right semirings, then result must have those properties.
+template <class X1, class X2>
+class ExpectationWeight : public PairWeight<X1, X2> {
+ public:
+  using PairWeight<X1, X2>::Value1;
+  using PairWeight<X1, X2>::Value2;
+
+  using PairWeight<X1, X2>::Reverse;
+  using PairWeight<X1, X2>::Quantize;
+  using PairWeight<X1, X2>::Member;
+
+  typedef X1 W1;
+  typedef X2 W2;
+
+  typedef ExpectationWeight<typename X1::ReverseWeight,
+                            typename X2::ReverseWeight> ReverseWeight;
+
+  ExpectationWeight() : PairWeight<X1, X2>(Zero()) { }
+
+  ExpectationWeight(const ExpectationWeight<X1, X2>& w)
+      : PairWeight<X1, X2> (w) { }
+
+  ExpectationWeight(const PairWeight<X1, X2>& w)
+      : PairWeight<X1, X2> (w) { }
+
+  ExpectationWeight(const X1& x1, const X2& x2)
+      : PairWeight<X1, X2>(x1, x2) { }
+
+  static const ExpectationWeight<X1, X2> &Zero() {
+    static const ExpectationWeight<X1, X2> zero(X1::Zero(), X2::Zero());
+    return zero;
+  }
+
+  static const ExpectationWeight<X1, X2> &One() {
+    static const ExpectationWeight<X1, X2> one(X1::One(), X2::Zero());
+    return one;
+  }
+
+  static const ExpectationWeight<X1, X2> &NoWeight() {
+    static const ExpectationWeight<X1, X2> no_weight(X1::NoWeight(),
+                                                     X2::NoWeight());
+    return no_weight;
+  }
+
+  static const string &Type() {
+    static const string type = "expectation_" + X1::Type() + "_" + X2::Type();
+    return type;
+  }
+
+  PairWeight<X1, X2> Quantize(float delta = kDelta) const {
+    return PairWeight<X1, X2>::Quantize();
+  }
+
+  ReverseWeight Reverse() const {
+    return PairWeight<X1, X2>::Reverse();
+  }
+
+  bool Member() const {
+    return PairWeight<X1, X2>::Member();
+  }
+
+  static uint64 Properties() {
+    uint64 props1 = W1::Properties();
+    uint64 props2 = W2::Properties();
+    return props1 & props2 & (kLeftSemiring | kRightSemiring |
+                              kCommutative | kIdempotent);
+  }
+};
+
+template <class X1, class X2>
+inline ExpectationWeight<X1, X2> Plus(const ExpectationWeight<X1, X2> &w,
+                                      const ExpectationWeight<X1, X2> &v) {
+  return ExpectationWeight<X1, X2>(Plus(w.Value1(), v.Value1()),
+                                   Plus(w.Value2(), v.Value2()));
+}
+
+
+template <class X1, class X2>
+inline ExpectationWeight<X1, X2> Times(const ExpectationWeight<X1, X2> &w,
+                                       const ExpectationWeight<X1, X2> &v) {
+  return ExpectationWeight<X1, X2>(Times(w.Value1(), v.Value1()),
+                                   Plus(Times(w.Value1(), v.Value2()),
+                                        Times(w.Value2(), v.Value1())));
+}
+
+template <class X1, class X2>
+inline ExpectationWeight<X1, X2> Divide(const ExpectationWeight<X1, X2> &w,
+                                        const ExpectationWeight<X1, X2> &v,
+                                        DivideType typ = DIVIDE_ANY) {
+  FSTERROR() << "ExpectationWeight::Divide: not implemented";
+  return ExpectationWeight<X1, X2>::NoWeight();
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_EXPECTATION_WEIGHT_H_
diff --git a/src/include/fst/extensions/far/compile-strings.h b/src/include/fst/extensions/far/compile-strings.h
new file mode 100644
index 0000000..d7f4d6b
--- /dev/null
+++ b/src/include/fst/extensions/far/compile-strings.h
@@ -0,0 +1,271 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Authors: allauzen@google.com (Cyril Allauzen)
+//          ttai@google.com (Terry Tai)
+//          jpr@google.com (Jake Ratkiewicz)
+
+
+#ifndef FST_EXTENSIONS_FAR_COMPILE_STRINGS_H_
+#define FST_EXTENSIONS_FAR_COMPILE_STRINGS_H_
+
+#include <libgen.h>
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/extensions/far/far.h>
+#include <fst/string.h>
+
+namespace fst {
+
+// Construct a reader that provides FSTs from a file (stream) either on a
+// line-by-line basis or on a per-stream basis.  Note that the freshly
+// constructed reader is already set to the first input.
+//
+// Sample Usage:
+//   for (StringReader<Arc> reader(...); !reader.Done(); reader.Next()) {
+//     Fst *fst = reader.GetVectorFst();
+//   }
+template <class A>
+class StringReader {
+ public:
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename StringCompiler<A>::TokenType TokenType;
+
+  enum EntryType { LINE = 1, FILE = 2 };
+
+  StringReader(istream &istrm,
+               const string &source,
+               EntryType entry_type,
+               TokenType token_type,
+               bool allow_negative_labels,
+               const SymbolTable *syms = 0,
+               Label unknown_label = kNoStateId)
+      : nline_(0), strm_(istrm), source_(source), entry_type_(entry_type),
+        token_type_(token_type), done_(false),
+        compiler_(token_type, syms, unknown_label, allow_negative_labels) {
+    Next();  // Initialize the reader to the first input.
+  }
+
+  bool Done() {
+    return done_;
+  }
+
+  void Next() {
+    VLOG(1) << "Processing source " << source_ << " at line " << nline_;
+    if (!strm_) {                    // We're done if we have no more input.
+      done_ = true;
+      return;
+    }
+    if (entry_type_ == LINE) {
+      getline(strm_, content_);
+      ++nline_;
+    } else {
+      content_.clear();
+      string line;
+      while (getline(strm_, line)) {
+        ++nline_;
+        content_.append(line);
+        content_.append("\n");
+      }
+    }
+    if (!strm_ && content_.empty())  // We're also done if we read off all the
+      done_ = true;                  // whitespace at the end of a file.
+  }
+
+  VectorFst<A> *GetVectorFst() {
+    VectorFst<A> *fst = new VectorFst<A>;
+    if (compiler_(content_, fst)) {
+      return fst;
+    } else {
+      delete fst;
+      return NULL;
+    }
+  }
+
+  CompactFst<A, StringCompactor<A> > *GetCompactFst() {
+    CompactFst<A, StringCompactor<A> > *fst =
+        new CompactFst<A, StringCompactor<A> >;
+    if (compiler_(content_, fst)) {
+      return fst;
+    } else {
+      delete fst;
+      return NULL;
+    }
+  }
+
+ private:
+  size_t nline_;
+  istream &strm_;
+  string source_;
+  EntryType entry_type_;
+  TokenType token_type_;
+  bool done_;
+  StringCompiler<A> compiler_;
+  string content_;  // The actual content of the input stream's next FST.
+
+  DISALLOW_COPY_AND_ASSIGN(StringReader);
+};
+
+// Compute the minimal length required to encode each line number as a decimal
+// number.
+int KeySize(const char *filename);
+
+template <class Arc>
+void FarCompileStrings(const vector<string> &in_fnames,
+                       const string &out_fname,
+                       const string &fst_type,
+                       const FarType &far_type,
+                       int32 generate_keys,
+                       FarEntryType fet,
+                       FarTokenType tt,
+                       const string &symbols_fname,
+                       const string &unknown_symbol,
+                       bool allow_negative_labels,
+                       bool file_list_input,
+                       const string &key_prefix,
+                       const string &key_suffix) {
+  typename StringReader<Arc>::EntryType entry_type;
+  if (fet == FET_LINE) {
+    entry_type = StringReader<Arc>::LINE;
+  } else if (fet == FET_FILE) {
+    entry_type = StringReader<Arc>::FILE;
+  } else {
+    FSTERROR() << "FarCompileStrings: unknown entry type";
+    return;
+  }
+
+  typename StringCompiler<Arc>::TokenType token_type;
+  if (tt == FTT_SYMBOL) {
+    token_type = StringCompiler<Arc>::SYMBOL;
+  } else if (tt == FTT_BYTE) {
+    token_type = StringCompiler<Arc>::BYTE;
+  } else if (tt == FTT_UTF8) {
+    token_type = StringCompiler<Arc>::UTF8;
+  } else {
+    FSTERROR() << "FarCompileStrings: unknown token type";
+    return;
+  }
+
+  bool compact;
+  if (fst_type.empty() || (fst_type == "vector")) {
+    compact = false;
+  } else if (fst_type == "compact") {
+    compact = true;
+  } else {
+    FSTERROR() << "FarCompileStrings: unknown fst type: "
+               << fst_type;
+    return;
+  }
+
+  const SymbolTable *syms = 0;
+  typename Arc::Label unknown_label = kNoLabel;
+  if (!symbols_fname.empty()) {
+    syms = SymbolTable::ReadText(symbols_fname,
+                                 allow_negative_labels);
+    if (!syms) {
+      FSTERROR() << "FarCompileStrings: error reading symbol table: "
+                 << symbols_fname;
+      return;
+    }
+    if (!unknown_symbol.empty()) {
+      unknown_label = syms->Find(unknown_symbol);
+      if (unknown_label == kNoLabel) {
+        FSTERROR() << "FarCompileStrings: unknown label \"" << unknown_label
+                   << "\" missing from symbol table: " << symbols_fname;
+        return;
+      }
+    }
+  }
+
+  FarWriter<Arc> *far_writer =
+      FarWriter<Arc>::Create(out_fname, far_type);
+  if (!far_writer) return;
+
+  vector<string> inputs;
+  if (file_list_input) {
+    for (int i = 1; i < in_fnames.size(); ++i) {
+      ifstream istrm(in_fnames[i].c_str());
+      string str;
+      while (getline(istrm, str))
+        inputs.push_back(str);
+    }
+  } else {
+    inputs = in_fnames;
+  }
+
+  for (int i = 0, n = 0; i < inputs.size(); ++i) {
+    int key_size = generate_keys ? generate_keys :
+        (entry_type == StringReader<Arc>::FILE ? 1 :
+         KeySize(inputs[i].c_str()));
+    ifstream istrm(inputs[i].c_str());
+
+    for (StringReader<Arc> reader(
+             istrm, inputs[i], entry_type, token_type,
+             allow_negative_labels, syms, unknown_label);
+         !reader.Done();
+         reader.Next()) {
+      ++n;
+      const Fst<Arc> *fst;
+      if (compact)
+        fst = reader.GetCompactFst();
+      else
+        fst = reader.GetVectorFst();
+      if (!fst) {
+        FSTERROR() << "FarCompileStrings: compiling string number " << n
+                   << " in file " << inputs[i] << " failed with token_type = "
+                   << (tt == FTT_BYTE ? "byte" :
+                       (tt == FTT_UTF8 ? "utf8" :
+                        (tt == FTT_SYMBOL ? "symbol" : "unknown")))
+                   << " and entry_type = "
+                   << (fet == FET_LINE ? "line" :
+                       (fet == FET_FILE ? "file" : "unknown"));
+        delete far_writer;
+        delete syms;
+        return;
+      }
+      ostringstream keybuf;
+      keybuf.width(key_size);
+      keybuf.fill('0');
+      keybuf << n;
+      string key;
+      if (generate_keys > 0) {
+        key = keybuf.str();
+      } else {
+        char* filename = new char[inputs[i].size() + 1];
+        strcpy(filename, inputs[i].c_str());
+        key = basename(filename);
+        if (entry_type != StringReader<Arc>::FILE) {
+          key += "-";
+          key += keybuf.str();
+        }
+        delete[] filename;
+      }
+      far_writer->Add(key_prefix + key + key_suffix, *fst);
+      delete fst;
+    }
+    if (generate_keys == 0)
+      n = 0;
+  }
+
+  delete far_writer;
+}
+
+}  // namespace fst
+
+
+#endif  // FST_EXTENSIONS_FAR_COMPILE_STRINGS_H_
diff --git a/src/include/fst/extensions/far/create.h b/src/include/fst/extensions/far/create.h
new file mode 100644
index 0000000..edb31e7
--- /dev/null
+++ b/src/include/fst/extensions/far/create.h
@@ -0,0 +1,87 @@
+// create-main.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+// Modified: jpr@google.com (Jake Ratkiewicz) to use new dispatch
+//
+// \file
+// Creates a finite-state archive from component FSTs.  Includes
+// helper function for farcreate.cc that templates the main on the arc
+// type to support multiple and extensible arc types.
+//
+
+#ifndef FST_EXTENSIONS_FAR_CREATE_H__
+#define FST_EXTENSIONS_FAR_CREATE_H__
+
+#include <libgen.h>
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/extensions/far/far.h>
+
+namespace fst {
+
+template <class Arc>
+void FarCreate(const vector<string> &in_fnames,
+               const string &out_fname,
+               const int32 generate_keys,
+               const bool file_list_input,
+               const FarType &far_type,
+               const string &key_prefix,
+               const string &key_suffix) {
+  FarWriter<Arc> *far_writer =
+      FarWriter<Arc>::Create(out_fname, far_type);
+  if (!far_writer) return;
+
+  vector<string> inputs;
+  if (file_list_input) {
+    for (int i = 1; i < in_fnames.size(); ++i) {
+      ifstream istrm(in_fnames[i].c_str());
+      string str;
+      while (getline(istrm, str))
+        inputs.push_back(str);
+    }
+  } else {
+    inputs = in_fnames;
+  }
+
+  for (int i = 0; i < inputs.size(); ++i) {
+    Fst<Arc> *ifst = Fst<Arc>::Read(inputs[i]);
+    if (!ifst) return;
+    string key;
+    if (generate_keys > 0) {
+      ostringstream keybuf;
+      keybuf.width(generate_keys);
+      keybuf.fill('0');
+      keybuf << i + 1;
+      key = keybuf.str();
+    } else {
+      char* filename = new char[inputs[i].size() + 1];
+      strcpy(filename, inputs[i].c_str());
+      key = basename(filename);
+      delete[] filename;
+    }
+
+    far_writer->Add(key_prefix + key + key_suffix, *ifst);
+    delete ifst;
+  }
+
+  delete far_writer;
+}
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_FAR_CREATE_H__
diff --git a/src/include/fst/extensions/far/extract.h b/src/include/fst/extensions/far/extract.h
new file mode 100644
index 0000000..022ca60
--- /dev/null
+++ b/src/include/fst/extensions/far/extract.h
@@ -0,0 +1,85 @@
+// extract-main.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+// Modified: jpr@google.com (Jake Ratkiewicz) to use the new arc-dispatch
+
+// \file
+// Extracts component FSTs from an finite-state archive.
+//
+
+#ifndef FST_EXTENSIONS_FAR_EXTRACT_H__
+#define FST_EXTENSIONS_FAR_EXTRACT_H__
+
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/extensions/far/far.h>
+
+namespace fst {
+
+template<class Arc>
+void FarExtract(const vector<string> &ifilenames,
+                const int32 &generate_filenames,
+                const string &begin_key,
+                const string &end_key,
+                const string &filename_prefix,
+                const string &filename_suffix) {
+  FarReader<Arc> *far_reader = FarReader<Arc>::Open(ifilenames);
+  if (!far_reader) return;
+
+  if (!begin_key.empty())
+    far_reader->Find(begin_key);
+
+  string okey;
+  int nrep = 0;
+  for (int i = 1; !far_reader->Done(); far_reader->Next(), ++i) {
+    string key = far_reader->GetKey();
+    if (!end_key.empty() && end_key < key)
+      break;
+    const Fst<Arc> &fst = far_reader->GetFst();
+
+    if (key == okey)
+      ++nrep;
+    else
+      nrep = 0;
+
+    okey = key;
+
+    string ofilename;
+    if (generate_filenames) {
+      ostringstream tmp;
+      tmp.width(generate_filenames);
+      tmp.fill('0');
+      tmp << i;
+      ofilename = tmp.str();
+    } else {
+      if (nrep > 0) {
+        ostringstream tmp;
+        tmp << '.' << nrep;
+        key += tmp.str();
+      }
+      ofilename = key;
+    }
+    fst.Write(filename_prefix + ofilename + filename_suffix);
+  }
+
+  return;
+}
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_FAR_EXTRACT_H__
diff --git a/src/include/fst/extensions/far/far.h b/src/include/fst/extensions/far/far.h
new file mode 100644
index 0000000..82b9e5c
--- /dev/null
+++ b/src/include/fst/extensions/far/far.h
@@ -0,0 +1,360 @@
+// far.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Finite-State Transducer (FST) archive classes.
+//
+
+#ifndef FST_EXTENSIONS_FAR_FAR_H__
+#define FST_EXTENSIONS_FAR_FAR_H__
+
+#include <fst/extensions/far/stlist.h>
+#include <fst/extensions/far/sttable.h>
+#include <fst/fst.h>
+#include <fst/vector-fst.h>
+
+namespace fst {
+
+enum FarEntryType { FET_LINE, FET_FILE };
+enum FarTokenType { FTT_SYMBOL, FTT_BYTE, FTT_UTF8 };
+
+// FST archive header class
+class FarHeader {
+ public:
+  const string &FarType() const { return fartype_; }
+  const string &ArcType() const { return arctype_; }
+
+  bool Read(const string &filename) {
+    FstHeader fsthdr;
+    if (filename.empty()) {  // Header reading unsupported on stdin.
+      return false;
+    } else if (IsSTTable(filename)) {  // Check if STTable
+      ReadSTTableHeader(filename, &fsthdr);
+      fartype_ = "sttable";
+      arctype_ = fsthdr.ArcType().empty() ? "unknown" : fsthdr.ArcType();
+      return true;
+    } else if (IsSTList(filename)) {  // Check if STList
+      ReadSTListHeader(filename, &fsthdr);
+      fartype_ = "sttable";
+      arctype_ = fsthdr.ArcType().empty() ? "unknown" : fsthdr.ArcType();
+      return true;
+    }
+    return false;
+  }
+
+ private:
+  string fartype_;
+  string arctype_;
+};
+
+enum FarType { FAR_DEFAULT = 0, FAR_STTABLE = 1, FAR_STLIST = 2,
+               FAR_SSTABLE = 3 };
+
+// This class creates an archive of FSTs.
+template <class A>
+class FarWriter {
+ public:
+  typedef A Arc;
+
+  // Creates a new (empty) FST archive; returns NULL on error.
+  static FarWriter *Create(const string &filename, FarType type = FAR_DEFAULT);
+
+  // Adds an FST to the end of an archive. Keys must be non-empty and
+  // in lexicographic order. FSTs must have a suitable write method.
+  virtual void Add(const string &key, const Fst<A> &fst) = 0;
+
+  virtual FarType Type() const = 0;
+
+  virtual bool Error() const = 0;
+
+  virtual ~FarWriter() {}
+
+ protected:
+  FarWriter() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(FarWriter);
+};
+
+
+// This class iterates through an existing archive of FSTs.
+template <class A>
+class FarReader {
+ public:
+ typedef A Arc;
+
+  // Opens an existing FST archive in a single file; returns NULL on error.
+  // Sets current position to the beginning of the achive.
+  static FarReader *Open(const string &filename);
+
+  // Opens an existing FST archive in multiple files; returns NULL on error.
+  // Sets current position to the beginning of the achive.
+  static FarReader *Open(const vector<string> &filenames);
+
+  // Resets current posision to beginning of archive.
+  virtual void Reset() = 0;
+
+  // Sets current position to first entry >= key.  Returns true if a match.
+  virtual bool Find(const string &key) = 0;
+
+  // Current position at end of archive?
+  virtual bool Done() const = 0;
+
+  // Move current position to next FST.
+  virtual void Next() = 0;
+
+  // Returns key at the current position. This reference is invalidated if
+  // the current position in the archive is changed.
+  virtual const string &GetKey() const = 0;
+
+  // Returns FST at the current position. This reference is invalidated if
+  // the current position in the archive is changed.
+  virtual const Fst<A> &GetFst() const = 0;
+
+  virtual FarType Type() const = 0;
+
+  virtual bool Error() const = 0;
+
+  virtual ~FarReader() {}
+
+ protected:
+  FarReader() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(FarReader);
+};
+
+
+template <class A>
+class FstWriter {
+ public:
+  void operator()(ostream &strm, const Fst<A> &fst) const {
+    fst.Write(strm, FstWriteOptions());
+  }
+};
+
+
+template <class A>
+class STTableFarWriter : public FarWriter<A> {
+ public:
+  typedef A Arc;
+
+  static STTableFarWriter *Create(const string filename) {
+    STTableWriter<Fst<A>, FstWriter<A> > *writer =
+        STTableWriter<Fst<A>, FstWriter<A> >::Create(filename);
+    return new STTableFarWriter(writer);
+  }
+
+  void Add(const string &key, const Fst<A> &fst) { writer_->Add(key, fst); }
+
+  FarType Type() const { return FAR_STTABLE; }
+
+  bool Error() const { return writer_->Error(); }
+
+  ~STTableFarWriter() { delete writer_; }
+
+ private:
+  explicit STTableFarWriter(STTableWriter<Fst<A>, FstWriter<A> > *writer)
+      : writer_(writer) {}
+
+ private:
+  STTableWriter<Fst<A>, FstWriter<A> > *writer_;
+
+  DISALLOW_COPY_AND_ASSIGN(STTableFarWriter);
+};
+
+
+template <class A>
+class STListFarWriter : public FarWriter<A> {
+ public:
+  typedef A Arc;
+
+  static STListFarWriter *Create(const string filename) {
+    STListWriter<Fst<A>, FstWriter<A> > *writer =
+        STListWriter<Fst<A>, FstWriter<A> >::Create(filename);
+    return new STListFarWriter(writer);
+  }
+
+  void Add(const string &key, const Fst<A> &fst) { writer_->Add(key, fst); }
+
+  FarType Type() const { return FAR_STLIST; }
+
+  bool Error() const { return writer_->Error(); }
+
+  ~STListFarWriter() { delete writer_; }
+
+ private:
+  explicit STListFarWriter(STListWriter<Fst<A>, FstWriter<A> > *writer)
+      : writer_(writer) {}
+
+ private:
+  STListWriter<Fst<A>, FstWriter<A> > *writer_;
+
+  DISALLOW_COPY_AND_ASSIGN(STListFarWriter);
+};
+
+
+template <class A>
+FarWriter<A> *FarWriter<A>::Create(const string &filename, FarType type) {
+  switch(type) {
+    case FAR_DEFAULT:
+      if (filename.empty())
+        return STListFarWriter<A>::Create(filename);
+    case FAR_STTABLE:
+      return STTableFarWriter<A>::Create(filename);
+      break;
+    case FAR_STLIST:
+      return STListFarWriter<A>::Create(filename);
+      break;
+    default:
+      LOG(ERROR) << "FarWriter::Create: unknown far type";
+      return 0;
+  }
+}
+
+
+template <class A>
+class FstReader {
+ public:
+  Fst<A> *operator()(istream &strm) const {
+    return Fst<A>::Read(strm, FstReadOptions());
+  }
+};
+
+
+template <class A>
+class STTableFarReader : public FarReader<A> {
+ public:
+  typedef A Arc;
+
+  static STTableFarReader *Open(const string &filename) {
+    STTableReader<Fst<A>, FstReader<A> > *reader =
+        STTableReader<Fst<A>, FstReader<A> >::Open(filename);
+    // TODO: error check
+    return new STTableFarReader(reader);
+  }
+
+  static STTableFarReader *Open(const vector<string> &filenames) {
+    STTableReader<Fst<A>, FstReader<A> > *reader =
+        STTableReader<Fst<A>, FstReader<A> >::Open(filenames);
+    // TODO: error check
+    return new STTableFarReader(reader);
+  }
+
+  void Reset() { reader_->Reset(); }
+
+  bool Find(const string &key) { return reader_->Find(key); }
+
+  bool Done() const { return reader_->Done(); }
+
+  void Next() { return reader_->Next(); }
+
+  const string &GetKey() const { return reader_->GetKey(); }
+
+  const Fst<A> &GetFst() const { return reader_->GetEntry(); }
+
+  FarType Type() const { return FAR_STTABLE; }
+
+  bool Error() const { return reader_->Error(); }
+
+  ~STTableFarReader() { delete reader_; }
+
+ private:
+  explicit STTableFarReader(STTableReader<Fst<A>, FstReader<A> > *reader)
+      : reader_(reader) {}
+
+ private:
+  STTableReader<Fst<A>, FstReader<A> > *reader_;
+
+  DISALLOW_COPY_AND_ASSIGN(STTableFarReader);
+};
+
+
+template <class A>
+class STListFarReader : public FarReader<A> {
+ public:
+  typedef A Arc;
+
+  static STListFarReader *Open(const string &filename) {
+    STListReader<Fst<A>, FstReader<A> > *reader =
+        STListReader<Fst<A>, FstReader<A> >::Open(filename);
+    // TODO: error check
+    return new STListFarReader(reader);
+  }
+
+  static STListFarReader *Open(const vector<string> &filenames) {
+    STListReader<Fst<A>, FstReader<A> > *reader =
+        STListReader<Fst<A>, FstReader<A> >::Open(filenames);
+    // TODO: error check
+    return new STListFarReader(reader);
+  }
+
+  void Reset() { reader_->Reset(); }
+
+  bool Find(const string &key) { return reader_->Find(key); }
+
+  bool Done() const { return reader_->Done(); }
+
+  void Next() { return reader_->Next(); }
+
+  const string &GetKey() const { return reader_->GetKey(); }
+
+  const Fst<A> &GetFst() const { return reader_->GetEntry(); }
+
+  FarType Type() const { return FAR_STLIST; }
+
+  bool Error() const { return reader_->Error(); }
+
+  ~STListFarReader() { delete reader_; }
+
+ private:
+  explicit STListFarReader(STListReader<Fst<A>, FstReader<A> > *reader)
+      : reader_(reader) {}
+
+ private:
+  STListReader<Fst<A>, FstReader<A> > *reader_;
+
+  DISALLOW_COPY_AND_ASSIGN(STListFarReader);
+};
+
+
+template <class A>
+FarReader<A> *FarReader<A>::Open(const string &filename) {
+  if (filename.empty())
+    return STListFarReader<A>::Open(filename);
+  else if (IsSTTable(filename))
+    return STTableFarReader<A>::Open(filename);
+  else if (IsSTList(filename))
+    return STListFarReader<A>::Open(filename);
+  return 0;
+}
+
+
+template <class A>
+FarReader<A> *FarReader<A>::Open(const vector<string> &filenames) {
+  if (!filenames.empty() && filenames[0].empty())
+    return STListFarReader<A>::Open(filenames);
+  else if (!filenames.empty() && IsSTTable(filenames[0]))
+    return STTableFarReader<A>::Open(filenames);
+  else if (!filenames.empty() && IsSTList(filenames[0]))
+    return STListFarReader<A>::Open(filenames);
+  return 0;
+}
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_FAR_FAR_H__
diff --git a/src/include/fst/extensions/far/farlib.h b/src/include/fst/extensions/far/farlib.h
new file mode 100644
index 0000000..91ba224
--- /dev/null
+++ b/src/include/fst/extensions/far/farlib.h
@@ -0,0 +1,31 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+// A finite-state archive (FAR) is used to store an indexable collection of
+// FSTs in a single file. Utilities are provided to create FARs from FSTs,
+// to iterate over FARs, and to extract specific FSTs from FARs.
+
+#ifndef FST_EXTENSIONS_FAR_FARLIB_H_
+#define FST_EXTENSIONS_FAR_FARLIB_H_
+
+#include <fst/extensions/far/far.h>
+#include <fst/extensions/far/compile-strings.h>
+#include <fst/extensions/far/create.h>
+#include <fst/extensions/far/extract.h>
+#include <fst/extensions/far/info.h>
+#include <fst/extensions/far/print-strings.h>
+
+#endif  // FST_EXTENSIONS_FAR_FARLIB_H_
diff --git a/src/include/fst/extensions/far/farscript.h b/src/include/fst/extensions/far/farscript.h
new file mode 100644
index 0000000..9c3b1ca
--- /dev/null
+++ b/src/include/fst/extensions/far/farscript.h
@@ -0,0 +1,234 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+// Convenience file for including all of the FAR operations,
+// or registering them for new arc types.
+
+#ifndef FST_EXTENSIONS_FAR_FARSCRIPT_H_
+#define FST_EXTENSIONS_FAR_FARSCRIPT_H_
+
+#include <vector>
+using std::vector;
+#include <string>
+
+#include <fst/script/arg-packs.h>
+#include <fst/extensions/far/compile-strings.h>
+#include <fst/extensions/far/create.h>
+#include <fst/extensions/far/extract.h>
+#include <fst/extensions/far/info.h>
+#include <fst/extensions/far/print-strings.h>
+#include <fst/extensions/far/far.h>
+
+#include <fst/types.h>
+
+namespace fst {
+namespace script {
+
+// Note: it is safe to pass these strings as references because
+// this struct is only used to pass them deeper in the call graph.
+// Be sure you understand why this is so before using this struct
+// for anything else!
+struct FarCompileStringsArgs {
+  const vector<string> &in_fnames;
+  const string &out_fname;
+  const string &fst_type;
+  const FarType &far_type;
+  const int32 generate_keys;
+  const FarEntryType fet;
+  const FarTokenType tt;
+  const string &symbols_fname;
+  const string &unknown_symbol;
+  const bool allow_negative_labels;
+  const bool file_list_input;
+  const string &key_prefix;
+  const string &key_suffix;
+
+  FarCompileStringsArgs(const vector<string> &in_fnames,
+                        const string &out_fname,
+                        const string &fst_type,
+                        const FarType &far_type,
+                        int32 generate_keys,
+                        FarEntryType fet,
+                        FarTokenType tt,
+                        const string &symbols_fname,
+                        const string &unknown_symbol,
+                        bool allow_negative_labels,
+                        bool file_list_input,
+                        const string &key_prefix,
+                        const string &key_suffix) :
+      in_fnames(in_fnames), out_fname(out_fname), fst_type(fst_type),
+      far_type(far_type), generate_keys(generate_keys), fet(fet),
+      tt(tt), symbols_fname(symbols_fname), unknown_symbol(unknown_symbol),
+      allow_negative_labels(allow_negative_labels),
+      file_list_input(file_list_input), key_prefix(key_prefix),
+      key_suffix(key_suffix) { }
+};
+
+template <class Arc>
+void FarCompileStrings(FarCompileStringsArgs *args) {
+  fst::FarCompileStrings<Arc>(
+      args->in_fnames, args->out_fname, args->fst_type, args->far_type,
+      args->generate_keys, args->fet, args->tt, args->symbols_fname,
+      args->unknown_symbol, args->allow_negative_labels, args->file_list_input,
+      args->key_prefix, args->key_suffix);
+}
+
+void FarCompileStrings(
+    const vector<string> &in_fnames,
+    const string &out_fname,
+    const string &arc_type,
+    const string &fst_type,
+    const FarType &far_type,
+    int32 generate_keys,
+    FarEntryType fet,
+    FarTokenType tt,
+    const string &symbols_fname,
+    const string &unknown_symbol,
+    bool allow_negative_labels,
+    bool file_list_input,
+    const string &key_prefix,
+    const string &key_suffix);
+
+
+// Note: it is safe to pass these strings as references because
+// this struct is only used to pass them deeper in the call graph.
+// Be sure you understand why this is so before using this struct
+// for anything else!
+struct FarCreateArgs {
+  const vector<string> &in_fnames;
+  const string &out_fname;
+  const int32 generate_keys;
+  const bool file_list_input;
+  const FarType &far_type;
+  const string &key_prefix;
+  const string &key_suffix;
+
+  FarCreateArgs(
+      const vector<string> &in_fnames, const string &out_fname,
+      const int32 generate_keys, const bool file_list_input,
+      const FarType &far_type, const string &key_prefix,
+      const string &key_suffix)
+      : in_fnames(in_fnames), out_fname(out_fname),
+        generate_keys(generate_keys), file_list_input(file_list_input),
+        far_type(far_type), key_prefix(key_prefix), key_suffix(key_suffix) { }
+};
+
+template<class Arc>
+void FarCreate(FarCreateArgs *args) {
+  fst::FarCreate<Arc>(args->in_fnames, args->out_fname, args->generate_keys,
+                          args->file_list_input, args->far_type,
+                          args->key_prefix, args->key_suffix);
+}
+
+void FarCreate(const vector<string> &in_fnames,
+               const string &out_fname,
+               const string &arc_type,
+               const int32 generate_keys,
+               const bool file_list_input,
+               const FarType &far_type,
+               const string &key_prefix,
+               const string &key_suffix);
+
+
+typedef args::Package<const vector<string> &, int32,
+                      const string&, const string&, const string&,
+                      const string&> FarExtractArgs;
+
+template<class Arc>
+void FarExtract(FarExtractArgs *args) {
+  fst::FarExtract<Arc>(
+      args->arg1, args->arg2, args->arg3, args->arg4, args->arg5, args->arg6);
+}
+
+void FarExtract(const vector<string> &ifilenames,
+                const string &arc_type,
+                int32 generate_filenames, const string &begin_key,
+                const string &end_key, const string &filename_prefix,
+                const string &filename_suffix);
+
+typedef args::Package<const vector<string> &, const string &,
+                      const string &, const bool> FarInfoArgs;
+
+template <class Arc>
+void FarInfo(FarInfoArgs *args) {
+  fst::FarInfo<Arc>(args->arg1, args->arg2, args->arg3, args->arg4);
+}
+
+void FarInfo(const vector<string> &filenames,
+             const string &arc_type,
+             const string &begin_key,
+             const string &end_key,
+             const bool list_fsts);
+
+struct FarPrintStringsArgs {
+  const vector<string> &ifilenames;
+  const FarEntryType entry_type;
+  const FarTokenType token_type;
+  const string &begin_key;
+  const string &end_key;
+  const bool print_key;
+  const string &symbols_fname;
+  const int32 generate_filenames;
+  const string &filename_prefix;
+  const string &filename_suffix;
+
+  FarPrintStringsArgs(
+      const vector<string> &ifilenames, const FarEntryType entry_type,
+      const FarTokenType token_type, const string &begin_key,
+      const string &end_key,  const bool print_key,
+      const string &symbols_fname, const int32 generate_filenames,
+      const string &filename_prefix, const string &filename_suffix) :
+      ifilenames(ifilenames), entry_type(entry_type), token_type(token_type),
+      begin_key(begin_key), end_key(end_key), print_key(print_key),
+      symbols_fname(symbols_fname),
+      generate_filenames(generate_filenames), filename_prefix(filename_prefix),
+      filename_suffix(filename_suffix) { }
+};
+
+template <class Arc>
+void FarPrintStrings(FarPrintStringsArgs *args) {
+  fst::FarPrintStrings<Arc>(
+      args->ifilenames, args->entry_type, args->token_type,
+      args->begin_key, args->end_key, args->print_key,
+      args->symbols_fname, args->generate_filenames, args->filename_prefix,
+      args->filename_suffix);
+}
+
+
+void FarPrintStrings(const vector<string> &ifilenames,
+                     const string &arc_type,
+                     const FarEntryType entry_type,
+                     const FarTokenType token_type,
+                     const string &begin_key,
+                     const string &end_key,
+                     const bool print_key,
+                     const string &symbols_fname,
+                     const int32 generate_filenames,
+                     const string &filename_prefix,
+                     const string &filename_suffix);
+
+}  // namespace script
+}  // namespace fst
+
+
+#define REGISTER_FST_FAR_OPERATIONS(ArcType)                            \
+  REGISTER_FST_OPERATION(FarCompileStrings, ArcType, FarCompileStringsArgs); \
+  REGISTER_FST_OPERATION(FarCreate, ArcType, FarCreateArgs);            \
+  REGISTER_FST_OPERATION(FarExtract, ArcType, FarExtractArgs);          \
+  REGISTER_FST_OPERATION(FarInfo, ArcType, FarInfoArgs);                \
+  REGISTER_FST_OPERATION(FarPrintStrings, ArcType, FarPrintStringsArgs)
+
+#endif  // FST_EXTENSIONS_FAR_FARSCRIPT_H_
diff --git a/src/include/fst/extensions/far/info.h b/src/include/fst/extensions/far/info.h
new file mode 100644
index 0000000..f010546
--- /dev/null
+++ b/src/include/fst/extensions/far/info.h
@@ -0,0 +1,128 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+// Modified: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_EXTENSIONS_FAR_INFO_H_
+#define FST_EXTENSIONS_FAR_INFO_H_
+
+#include <iomanip>
+#include <set>
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/extensions/far/far.h>
+#include <fst/extensions/far/main.h>  // For FarTypeToString
+
+namespace fst {
+
+template <class Arc>
+void CountStatesAndArcs(const Fst<Arc> &fst, size_t *nstate, size_t *narc) {
+  StateIterator<Fst<Arc> > siter(fst);
+  for (; !siter.Done(); siter.Next(), ++(*nstate)) {
+    ArcIterator<Fst<Arc> > aiter(fst, siter.Value());
+    for (; !aiter.Done(); aiter.Next(), ++(*narc));
+  }
+}
+
+struct KeyInfo {
+  string key;
+  string type;
+  size_t nstate;
+  size_t narc;
+
+  KeyInfo(string k, string t, int64 ns = 0, int64 na = 0)
+  : key(k), type(t), nstate(ns), narc(na) {}
+};
+
+template <class Arc>
+void FarInfo(const vector<string> &filenames, const string &begin_key,
+             const string &end_key, const bool list_fsts) {
+  FarReader<Arc> *far_reader = FarReader<Arc>::Open(filenames);
+  if (!far_reader) return;
+
+  if (!begin_key.empty())
+    far_reader->Find(begin_key);
+
+  vector<KeyInfo> *infos = list_fsts ? new vector<KeyInfo>() : 0;
+  size_t nfst = 0, nstate = 0, narc = 0;
+  set<string> fst_types;
+  for (; !far_reader->Done(); far_reader->Next()) {
+    string key = far_reader->GetKey();
+    if (!end_key.empty() && end_key < key)
+      break;
+    ++nfst;
+    const Fst<Arc> &fst = far_reader->GetFst();
+    fst_types.insert(fst.Type());
+    if (infos) {
+      KeyInfo info(key, fst.Type());
+      CountStatesAndArcs(fst, &info.nstate, &info.narc);
+      nstate += info.nstate;
+      nstate += info.narc;
+      infos->push_back(info);
+    } else {
+      CountStatesAndArcs(fst, &nstate, &narc);
+    }
+  }
+
+  if (!infos) {
+    cout << std::left << setw(50) << "far type"
+         << FarTypeToString(far_reader->Type()) << endl;
+    cout << std::left << setw(50) << "arc type" << Arc::Type() << endl;
+    cout << std::left << setw(50) << "fst type";
+    for (set<string>::const_iterator iter = fst_types.begin();
+         iter != fst_types.end();
+         ++iter) {
+      if (iter != fst_types.begin())
+        cout << ",";
+      cout << *iter;
+    }
+    cout << endl;
+    cout << std::left << setw(50) << "# of FSTs" << nfst << endl;
+    cout << std::left << setw(50) << "total # of states" << nstate << endl;
+    cout << std::left << setw(50) << "total # of arcs" << narc << endl;
+
+  } else  {
+    int wkey = 10, wtype = 10, wnstate = 16, wnarc = 16;
+    for (size_t i = 0; i < infos->size(); ++i) {
+      const KeyInfo &info = (*infos)[i];
+      if (info.key.size() + 2 > wkey)
+        wkey = info.key.size() + 2;
+      if (info.type.size() + 2 > wtype)
+        wtype = info.type.size() + 2;
+      if (ceil(log10(info.nstate)) + 2 > wnstate)
+        wnstate = ceil(log10(info.nstate)) + 2;
+      if (ceil(log10(info.narc)) + 2 > wnarc)
+        wnarc = ceil(log10(info.narc)) + 2;
+    }
+
+    cout << std::left << setw(wkey) << "key" << setw(wtype) << "type"
+         << std::right << setw(wnstate) << "# of states"
+         << setw(wnarc) << "# of arcs" << endl;
+
+    for (size_t i = 0; i < infos->size(); ++i) {
+      const KeyInfo &info = (*infos)[i];
+      cout << std::left << setw(wkey) << info.key << setw(wtype) << info.type
+           << std::right << setw(wnstate) << info.nstate
+           << setw(wnarc) << info.narc << endl;
+    }
+  }
+}
+
+}  // namespace fst
+
+
+#endif  // FST_EXTENSIONS_FAR_INFO_H_
diff --git a/src/include/fst/extensions/far/main.h b/src/include/fst/extensions/far/main.h
new file mode 100644
index 0000000..00ccfef
--- /dev/null
+++ b/src/include/fst/extensions/far/main.h
@@ -0,0 +1,43 @@
+// main.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Classes and functions for registering and invoking Far main
+// functions that support multiple and extensible arc types.
+
+#ifndef FST_EXTENSIONS_FAR_MAIN_H__
+#define FST_EXTENSIONS_FAR_MAIN_H__
+
+#include <fst/extensions/far/far.h>
+
+namespace fst {
+
+FarEntryType StringToFarEntryType(const string &s);
+FarTokenType StringToFarTokenType(const string &s);
+
+// Return the 'FarType' value corresponding to a far type name.
+FarType FarTypeFromString(const string &str);
+
+// Return the textual name  corresponding to a 'FarType;.
+string FarTypeToString(FarType type);
+
+string LoadArcTypeFromFar(const string& far_fname);
+string LoadArcTypeFromFst(const string& far_fname);
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_FAR_MAIN_H__
diff --git a/src/include/fst/extensions/far/print-strings.h b/src/include/fst/extensions/far/print-strings.h
new file mode 100644
index 0000000..aff1e51
--- /dev/null
+++ b/src/include/fst/extensions/far/print-strings.h
@@ -0,0 +1,126 @@
+// printstrings-main.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+// Modified by: jpr@google.com (Jake Ratkiewicz)
+//
+// \file
+// Output as strings the string FSTs in a finite-state archive.
+
+#ifndef FST_EXTENSIONS_FAR_PRINT_STRINGS_H__
+#define FST_EXTENSIONS_FAR_PRINT_STRINGS_H__
+
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/extensions/far/far.h>
+#include <fst/string.h>
+
+namespace fst {
+
+template <class Arc>
+void FarPrintStrings(
+    const vector<string> &ifilenames, const FarEntryType entry_type,
+    const FarTokenType far_token_type, const string &begin_key,
+    const string &end_key, const bool print_key, const string &symbols_fname,
+    const int32 generate_filenames, const string &filename_prefix,
+    const string &filename_suffix) {
+
+  typename StringPrinter<Arc>::TokenType token_type;
+  if (far_token_type == FTT_SYMBOL) {
+    token_type = StringPrinter<Arc>::SYMBOL;
+  } else if (far_token_type == FTT_BYTE) {
+    token_type = StringPrinter<Arc>::BYTE;
+  } else if (far_token_type == FTT_UTF8) {
+    token_type = StringPrinter<Arc>::UTF8;
+  } else {
+    FSTERROR() << "FarPrintStrings: unknown token type";
+    return;
+  }
+
+  const SymbolTable *syms = 0;
+  if (!symbols_fname.empty()) {
+    // allow negative flag?
+    syms = SymbolTable::ReadText(symbols_fname, true);
+    if (!syms) {
+      FSTERROR() << "FarPrintStrings: error reading symbol table: "
+                 << symbols_fname;
+      return;
+    }
+  }
+
+  StringPrinter<Arc> string_printer(token_type, syms);
+
+  FarReader<Arc> *far_reader = FarReader<Arc>::Open(ifilenames);
+  if (!far_reader) return;
+
+  if (!begin_key.empty())
+    far_reader->Find(begin_key);
+
+  string okey;
+  int nrep = 0;
+  for (int i = 1; !far_reader->Done(); far_reader->Next(), ++i) {
+    string key = far_reader->GetKey();
+    if (!end_key.empty() && end_key < key)
+      break;
+    if (okey == key)
+      ++nrep;
+    else
+      nrep = 0;
+    okey = key;
+
+    const Fst<Arc> &fst = far_reader->GetFst();
+    string str;
+    VLOG(2) << "Handling key: " << key;
+    string_printer(fst, &str);
+
+    if (entry_type == FET_LINE) {
+      if (print_key)
+        cout << key << "\t";
+      cout << str << endl;
+    } else if (entry_type == FET_FILE) {
+      stringstream sstrm;
+      if (generate_filenames) {
+        sstrm.fill('0');
+        sstrm << std::right << setw(generate_filenames) << i;
+      } else {
+        sstrm << key;
+        if (nrep > 0)
+          sstrm << "." << nrep;
+      }
+
+      string filename;
+      filename = filename_prefix +  sstrm.str() + filename_suffix;
+
+      ofstream ostrm(filename.c_str());
+      if (!ostrm) {
+        FSTERROR() << "FarPrintStrings: Can't open file:" << filename;
+        delete syms;
+        delete far_reader;
+        return;
+      }
+      ostrm << str;
+      if (token_type == StringPrinter<Arc>::SYMBOL)
+        ostrm << "\n";
+    }
+  }
+}
+
+
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_FAR_PRINT_STRINGS_H__
diff --git a/src/include/fst/extensions/far/stlist.h b/src/include/fst/extensions/far/stlist.h
new file mode 100644
index 0000000..4738181
--- /dev/null
+++ b/src/include/fst/extensions/far/stlist.h
@@ -0,0 +1,304 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// A generic (string,type) list file format.
+//
+// This is a stripped-down version of STTable that does
+// not support the Find() operation but that does support
+// reading/writting from standard in/out.
+
+#ifndef FST_EXTENSIONS_FAR_STLIST_H_
+#define FST_EXTENSIONS_FAR_STLIST_H_
+
+#include <iostream>
+#include <fstream>
+#include <fst/util.h>
+
+#include <algorithm>
+#include <functional>
+#include <queue>
+#include <string>
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+namespace fst {
+
+static const int32 kSTListMagicNumber = 5656924;
+static const int32 kSTListFileVersion = 1;
+
+// String-type list writing class for object of type 'T' using functor 'W'
+// to write an object of type 'T' from a stream. 'W' must conform to the
+// following interface:
+//
+//   struct Writer {
+//     void operator()(ostream &, const T &) const;
+//   };
+//
+template <class T, class W>
+class STListWriter {
+ public:
+  typedef T EntryType;
+  typedef W EntryWriter;
+
+  explicit STListWriter(const string filename)
+      : stream_(
+          filename.empty() ? &std::cout :
+          new ofstream(filename.c_str(), ofstream::out | ofstream::binary)),
+        error_(false) {
+    WriteType(*stream_, kSTListMagicNumber);
+    WriteType(*stream_, kSTListFileVersion);
+    if (!stream_) {
+      FSTERROR() << "STListWriter::STListWriter: error writing to file: "
+                 << filename;
+      error_ = true;
+    }
+  }
+
+  static STListWriter<T, W> *Create(const string &filename) {
+    return new STListWriter<T, W>(filename);
+  }
+
+  void Add(const string &key, const T &t) {
+    if (key == "") {
+      FSTERROR() << "STListWriter::Add: key empty: " << key;
+      error_ = true;
+    } else if (key < last_key_) {
+      FSTERROR() << "STListWriter::Add: key disorder: " << key;
+      error_ = true;
+    }
+    if (error_) return;
+    last_key_ = key;
+    WriteType(*stream_, key);
+    entry_writer_(*stream_, t);
+  }
+
+  bool Error() const { return error_; }
+
+  ~STListWriter() {
+    WriteType(*stream_, string());
+    if (stream_ != &std::cout)
+      delete stream_;
+  }
+
+ private:
+  EntryWriter entry_writer_;  // Write functor for 'EntryType'
+  ostream *stream_;           // Output stream
+  string last_key_;           // Last key
+  bool error_;
+
+  DISALLOW_COPY_AND_ASSIGN(STListWriter);
+};
+
+
+// String-type list reading class for object of type 'T' using functor 'R'
+// to read an object of type 'T' form a stream. 'R' must conform to the
+// following interface:
+//
+//   struct Reader {
+//     T *operator()(istream &) const;
+//   };
+//
+template <class T, class R>
+class STListReader {
+ public:
+  typedef T EntryType;
+  typedef R EntryReader;
+
+  explicit STListReader(const vector<string> &filenames)
+      : sources_(filenames), entry_(0), error_(false) {
+    streams_.resize(filenames.size(), 0);
+    bool has_stdin = false;
+    for (size_t i = 0; i < filenames.size(); ++i) {
+      if (filenames[i].empty()) {
+        if (!has_stdin) {
+          streams_[i] = &std::cin;
+          sources_[i] = "stdin";
+          has_stdin = true;
+        } else {
+          FSTERROR() << "STListReader::STListReader: stdin should only "
+                     << "appear once in the input file list.";
+          error_ = true;
+          return;
+        }
+      } else {
+        streams_[i] = new ifstream(
+            filenames[i].c_str(), ifstream::in | ifstream::binary);
+      }
+      int32 magic_number = 0, file_version = 0;
+      ReadType(*streams_[i], &magic_number);
+      ReadType(*streams_[i], &file_version);
+      if (magic_number != kSTListMagicNumber) {
+        FSTERROR() << "STListReader::STTableReader: wrong file type: "
+                   << filenames[i];
+        error_ = true;
+        return;
+      }
+      if (file_version != kSTListFileVersion) {
+        FSTERROR() << "STListReader::STTableReader: wrong file version: "
+                   << filenames[i];
+        error_ = true;
+        return;
+      }
+      string key;
+      ReadType(*streams_[i], &key);
+      if (!key.empty())
+        heap_.push(make_pair(key, i));
+      if (!*streams_[i]) {
+        FSTERROR() << "STTableReader: error reading file: " << sources_[i];
+        error_ = true;
+        return;
+      }
+    }
+    if (heap_.empty()) return;
+    size_t current = heap_.top().second;
+    entry_ = entry_reader_(*streams_[current]);
+    if (!entry_ || !*streams_[current]) {
+      FSTERROR() << "STTableReader: error reading entry for key: "
+                 << heap_.top().first << ", file: " << sources_[current];
+      error_ = true;
+    }
+  }
+
+  ~STListReader() {
+    for (size_t i = 0; i < streams_.size(); ++i) {
+      if (streams_[i] != &std::cin)
+        delete streams_[i];
+    }
+    if (entry_)
+      delete entry_;
+  }
+
+  static STListReader<T, R> *Open(const string &filename) {
+    vector<string> filenames;
+    filenames.push_back(filename);
+    return new STListReader<T, R>(filenames);
+  }
+
+  static STListReader<T, R> *Open(const vector<string> &filenames) {
+    return new STListReader<T, R>(filenames);
+  }
+
+  void Reset() {
+    FSTERROR()
+        << "STListReader::Reset: stlist does not support reset operation";
+    error_ = true;
+  }
+
+  bool Find(const string &key) {
+    FSTERROR()
+        << "STListReader::Find: stlist does not support find operation";
+    error_ = true;
+    return false;
+  }
+
+  bool Done() const {
+    return error_ || heap_.empty();
+  }
+
+  void Next() {
+    if (error_) return;
+    size_t current = heap_.top().second;
+    string key;
+    heap_.pop();
+    ReadType(*(streams_[current]), &key);
+    if (!*streams_[current]) {
+      FSTERROR() << "STTableReader: error reading file: "
+                 << sources_[current];
+      error_ = true;
+      return;
+    }
+    if (!key.empty())
+      heap_.push(make_pair(key, current));
+
+    if(!heap_.empty()) {
+      current = heap_.top().second;
+      if (entry_)
+        delete entry_;
+      entry_ = entry_reader_(*streams_[current]);
+      if (!entry_ || !*streams_[current]) {
+        FSTERROR() << "STTableReader: error reading entry for key: "
+                   << heap_.top().first << ", file: " << sources_[current];
+        error_ = true;
+      }
+    }
+  }
+
+  const string &GetKey() const {
+    return heap_.top().first;
+  }
+
+  const EntryType &GetEntry() const {
+    return *entry_;
+  }
+
+  bool Error() const { return error_; }
+
+ private:
+  EntryReader entry_reader_;   // Read functor for 'EntryType'
+  vector<istream*> streams_;   // Input streams
+  vector<string> sources_;     // and corresponding file names
+  priority_queue<
+    pair<string, size_t>, vector<pair<string, size_t> >,
+    greater<pair<string, size_t> > > heap_;  // (Key, stream id) heap
+  mutable EntryType *entry_;   // Pointer to the currently read entry
+  bool error_;
+
+  DISALLOW_COPY_AND_ASSIGN(STListReader);
+};
+
+
+// String-type list header reading function template on the entry header
+// type 'H' having a member function:
+//   Read(istream &strm, const string &filename);
+// Checks that 'filename' is an STTable and call the H::Read() on the last
+// entry in the STTable.
+// Does not support reading from stdin.
+template <class H>
+bool ReadSTListHeader(const string &filename, H *header) {
+  if (filename.empty()) {
+    LOG(ERROR) << "ReadSTListHeader: reading header not supported on stdin";
+    return false;
+  }
+  ifstream strm(filename.c_str(), ifstream::in | ifstream::binary);
+  int32 magic_number = 0, file_version = 0;
+  ReadType(strm, &magic_number);
+  ReadType(strm, &file_version);
+  if (magic_number != kSTListMagicNumber) {
+    LOG(ERROR) << "ReadSTTableHeader: wrong file type: " << filename;
+    return false;
+  }
+  if (file_version != kSTListFileVersion) {
+    LOG(ERROR) << "ReadSTTableHeader: wrong file version: " << filename;
+    return false;
+  }
+  string key;
+  ReadType(strm, &key);
+  header->Read(strm, filename + ":" + key);
+  if (!strm) {
+    LOG(ERROR) << "ReadSTTableHeader: error reading file: " << filename;
+    return false;
+  }
+  return true;
+}
+
+bool IsSTList(const string &filename);
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_FAR_STLIST_H_
diff --git a/src/include/fst/extensions/far/sttable.h b/src/include/fst/extensions/far/sttable.h
new file mode 100644
index 0000000..3a03133
--- /dev/null
+++ b/src/include/fst/extensions/far/sttable.h
@@ -0,0 +1,370 @@
+// sttable.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// A generic string-to-type table file format
+//
+// This is not meant as a generalization of SSTable. This is more of
+// a simple replacement for SSTable in order to provide an open-source
+// implementation of the FAR format for the external version of the
+// FST Library.
+
+#ifndef FST_EXTENSIONS_FAR_STTABLE_H_
+#define FST_EXTENSIONS_FAR_STTABLE_H_
+
+#include <algorithm>
+#include <iostream>
+#include <fstream>
+#include <fst/util.h>
+
+namespace fst {
+
+static const int32 kSTTableMagicNumber = 2125656924;
+static const int32 kSTTableFileVersion = 1;
+
+// String-to-type table writing class for object of type 'T' using functor 'W'
+// to write an object of type 'T' from a stream. 'W' must conform to the
+// following interface:
+//
+//   struct Writer {
+//     void operator()(ostream &, const T &) const;
+//   };
+//
+template <class T, class W>
+class STTableWriter {
+ public:
+  typedef T EntryType;
+  typedef W EntryWriter;
+
+  explicit STTableWriter(const string &filename)
+      : stream_(filename.c_str(), ofstream::out | ofstream::binary),
+        error_(false) {
+    WriteType(stream_, kSTTableMagicNumber);
+    WriteType(stream_, kSTTableFileVersion);
+    if (!stream_) {
+      FSTERROR() << "STTableWriter::STTableWriter: error writing to file: "
+                 << filename;
+      error_=true;
+    }
+  }
+
+  static STTableWriter<T, W> *Create(const string &filename) {
+    if (filename.empty()) {
+      LOG(ERROR) << "STTableWriter: writing to standard out unsupported.";
+      return 0;
+    }
+    return new STTableWriter<T, W>(filename);
+  }
+
+  void Add(const string &key, const T &t) {
+    if (key == "") {
+      FSTERROR() << "STTableWriter::Add: key empty: " << key;
+      error_ = true;
+    } else if (key < last_key_) {
+      FSTERROR() << "STTableWriter::Add: key disorder: " << key;
+      error_ = true;
+    }
+    if (error_) return;
+    last_key_ = key;
+    positions_.push_back(stream_.tellp());
+    WriteType(stream_, key);
+    entry_writer_(stream_, t);
+  }
+
+  bool Error() const { return error_; }
+
+  ~STTableWriter() {
+    WriteType(stream_, positions_);
+    WriteType(stream_, static_cast<int64>(positions_.size()));
+  }
+
+ private:
+  EntryWriter entry_writer_;  // Write functor for 'EntryType'
+  ofstream stream_;           // Output stream
+  vector<int64> positions_;   // Position in file of each key-entry pair
+  string last_key_;           // Last key
+  bool error_;
+
+  DISALLOW_COPY_AND_ASSIGN(STTableWriter);
+};
+
+
+// String-to-type table reading class for object of type 'T' using functor 'R'
+// to read an object of type 'T' form a stream. 'R' must conform to the
+// following interface:
+//
+//   struct Reader {
+//     T *operator()(istream &) const;
+//   };
+//
+template <class T, class R>
+class STTableReader {
+ public:
+  typedef T EntryType;
+  typedef R EntryReader;
+
+  explicit STTableReader(const vector<string> &filenames)
+      : sources_(filenames), entry_(0), error_(false) {
+    compare_ = new Compare(&keys_);
+    keys_.resize(filenames.size());
+    streams_.resize(filenames.size(), 0);
+    positions_.resize(filenames.size());
+    for (size_t i = 0; i < filenames.size(); ++i) {
+      streams_[i] = new ifstream(
+          filenames[i].c_str(), ifstream::in | ifstream::binary);
+      int32 magic_number = 0, file_version = 0;
+      ReadType(*streams_[i], &magic_number);
+      ReadType(*streams_[i], &file_version);
+      if (magic_number != kSTTableMagicNumber) {
+        FSTERROR() << "STTableReader::STTableReader: wrong file type: "
+                   << filenames[i];
+        error_ = true;
+        return;
+      }
+      if (file_version != kSTTableFileVersion) {
+        FSTERROR() << "STTableReader::STTableReader: wrong file version: "
+                   << filenames[i];
+        error_ = true;
+        return;
+      }
+      int64 num_entries;
+      streams_[i]->seekg(-static_cast<int>(sizeof(int64)), ios_base::end);
+      ReadType(*streams_[i], &num_entries);
+      streams_[i]->seekg(-static_cast<int>(sizeof(int64)) *
+                         (num_entries + 1), ios_base::end);
+      positions_[i].resize(num_entries);
+      for (size_t j = 0; (j < num_entries) && (*streams_[i]); ++j)
+        ReadType(*streams_[i], &(positions_[i][j]));
+      streams_[i]->seekg(positions_[i][0]);
+      if (!*streams_[i]) {
+        FSTERROR() << "STTableReader::STTableReader: error reading file: "
+                   << filenames[i];
+        error_ = true;
+        return;
+      }
+
+    }
+    MakeHeap();
+  }
+
+  ~STTableReader() {
+    for (size_t i = 0; i < streams_.size(); ++i)
+      delete streams_[i];
+    delete compare_;
+    if (entry_)
+      delete entry_;
+  }
+
+  static STTableReader<T, R> *Open(const string &filename) {
+    if (filename.empty()) {
+      LOG(ERROR) << "STTableReader: reading from standard in not supported";
+      return 0;
+    }
+    vector<string> filenames;
+    filenames.push_back(filename);
+    return new STTableReader<T, R>(filenames);
+  }
+
+  static STTableReader<T, R> *Open(const vector<string> &filenames) {
+    return new STTableReader<T, R>(filenames);
+  }
+
+  void Reset() {
+    if (error_) return;
+    for (size_t i = 0; i < streams_.size(); ++i)
+      streams_[i]->seekg(positions_[i].front());
+    MakeHeap();
+  }
+
+  bool Find(const string &key) {
+    if (error_) return false;
+    for (size_t i = 0; i < streams_.size(); ++i)
+      LowerBound(i, key);
+    MakeHeap();
+    return keys_[current_] == key;
+  }
+
+  bool Done() const { return error_ || heap_.empty(); }
+
+  void Next() {
+    if (error_) return;
+    if (streams_[current_]->tellg() <= positions_[current_].back()) {
+      ReadType(*(streams_[current_]), &(keys_[current_]));
+      if (!*streams_[current_]) {
+        FSTERROR() << "STTableReader: error reading file: "
+                   << sources_[current_];
+        error_ = true;
+        return;
+      }
+      push_heap(heap_.begin(), heap_.end(), *compare_);
+    } else {
+      heap_.pop_back();
+    }
+    if (!heap_.empty())
+      PopHeap();
+  }
+
+  const string &GetKey() const {
+    return keys_[current_];
+  }
+
+  const EntryType &GetEntry() const {
+    return *entry_;
+  }
+
+  bool Error() const { return error_; }
+
+ private:
+  // Comparison functor used to compare stream IDs in the heap
+  struct Compare {
+    Compare(const vector<string> *keys) : keys_(keys) {}
+
+    bool operator()(size_t i, size_t j) const {
+      return (*keys_)[i] > (*keys_)[j];
+    };
+
+   private:
+    const vector<string> *keys_;
+  };
+
+  // Position the stream with ID 'id' at the position corresponding
+  // to the lower bound for key 'find_key'
+  void LowerBound(size_t id, const string &find_key) {
+    ifstream *strm = streams_[id];
+    const vector<int64> &positions = positions_[id];
+    size_t low = 0, high = positions.size() - 1;
+
+    while (low < high) {
+      size_t mid = (low + high)/2;
+      strm->seekg(positions[mid]);
+      string key;
+      ReadType(*strm, &key);
+      if (key > find_key) {
+        high = mid;
+      } else if (key < find_key) {
+        low = mid + 1;
+      } else {
+        for (size_t i = mid; i > low; --i) {
+          strm->seekg(positions[i - 1]);
+          ReadType(*strm, &key);
+          if (key != find_key) {
+            strm->seekg(positions[i]);
+            return;
+          }
+        }
+        strm->seekg(positions[low]);
+        return;
+      }
+    }
+    strm->seekg(positions[low]);
+  }
+
+  // Add all streams to the heap
+  void MakeHeap() {
+    heap_.clear();
+    for (size_t i = 0; i < streams_.size(); ++i) {
+      ReadType(*streams_[i], &(keys_[i]));
+      if (!*streams_[i]) {
+        FSTERROR() << "STTableReader: error reading file: " << sources_[i];
+        error_ = true;
+        return;
+      }
+      heap_.push_back(i);
+    }
+    make_heap(heap_.begin(), heap_.end(), *compare_);
+    PopHeap();
+  }
+
+  // Position the stream with the lowest key at the top
+  // of the heap, set 'current_' to the ID of that stream
+  // and read the current entry from that stream
+  void PopHeap() {
+    pop_heap(heap_.begin(), heap_.end(), *compare_);
+    current_ = heap_.back();
+    if (entry_)
+      delete entry_;
+    entry_ = entry_reader_(*streams_[current_]);
+    if (!entry_)
+      error_ = true;
+    if (!*streams_[current_]) {
+      FSTERROR() << "STTableReader: error reading entry for key: "
+                 << keys_[current_] << ", file: " << sources_[current_];
+      error_ = true;
+    }
+  }
+
+
+  EntryReader entry_reader_;   // Read functor for 'EntryType'
+  vector<ifstream*> streams_;  // Input streams
+  vector<string> sources_;     // and corresponding file names
+  vector<vector<int64> > positions_;  // Index of positions for each stream
+  vector<string> keys_;  // Lowest unread key for each stream
+  vector<int64> heap_;   // Heap containing ID of streams with unread keys
+  int64 current_;        // Id of current stream to be read
+  Compare *compare_;     // Functor comparing stream IDs for the heap
+  mutable EntryType *entry_;  // Pointer to the currently read entry
+  bool error_;
+
+  DISALLOW_COPY_AND_ASSIGN(STTableReader);
+};
+
+
+// String-to-type table header reading function template on the entry header
+// type 'H' having a member function:
+//   Read(istream &strm, const string &filename);
+// Checks that 'filename' is an STTable and call the H::Read() on the last
+// entry in the STTable.
+template <class H>
+bool ReadSTTableHeader(const string &filename, H *header) {
+  ifstream strm(filename.c_str(), ifstream::in | ifstream::binary);
+  int32 magic_number = 0, file_version = 0;
+  ReadType(strm, &magic_number);
+  ReadType(strm, &file_version);
+  if (magic_number != kSTTableMagicNumber) {
+    LOG(ERROR) << "ReadSTTableHeader: wrong file type: " << filename;
+    return false;
+  }
+  if (file_version != kSTTableFileVersion) {
+    LOG(ERROR) << "ReadSTTableHeader: wrong file version: " << filename;
+    return false;
+  }
+  int64 i = -1;
+  strm.seekg(-static_cast<int>(sizeof(int64)), ios_base::end);
+  ReadType(strm, &i);  // Read number of entries
+  if (!strm) {
+    LOG(ERROR) << "ReadSTTableHeader: error reading file: " << filename;
+    return false;
+  }
+  if (i == 0) return true;  // No entry header to read
+  strm.seekg(-2 * static_cast<int>(sizeof(int64)), ios_base::end);
+  ReadType(strm, &i);  // Read position for last entry in file
+  strm.seekg(i);
+  string key;
+  ReadType(strm, &key);
+  header->Read(strm, filename + ":" + key);
+  if (!strm) {
+    LOG(ERROR) << "ReadSTTableHeader: error reading file: " << filename;
+    return false;
+  }
+  return true;
+}
+
+bool IsSTTable(const string &filename);
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_FAR_STTABLE_H_
diff --git a/src/include/fst/extensions/pdt/collection.h b/src/include/fst/extensions/pdt/collection.h
new file mode 100644
index 0000000..26be504
--- /dev/null
+++ b/src/include/fst/extensions/pdt/collection.h
@@ -0,0 +1,122 @@
+// collection.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to store a collection of sets with elements of type T.
+
+#ifndef FST_EXTENSIONS_PDT_COLLECTION_H__
+#define FST_EXTENSIONS_PDT_COLLECTION_H__
+
+#include <algorithm>
+#include <vector>
+using std::vector;
+
+#include <fst/bi-table.h>
+
+namespace fst {
+
+// Stores a collection of non-empty sets with elements of type T. A
+// default constructor, equality ==, a total order <, and an STL-style
+// hash class must be defined on the elements. Provides signed
+// integer ID (of type I) of each unique set. The IDs are allocated
+// starting from 0 in order.
+template <class I, class T>
+class Collection {
+ public:
+  struct Node {  // Trie node
+    I node_id;   // Root is kNoNodeId;
+    T element;
+
+    Node() : node_id(kNoNodeId), element(T()) {}
+    Node(I i, const T &t) : node_id(i), element(t) {}
+
+    bool operator==(const Node& n) const {
+      return n.node_id == node_id && n.element == element;
+    }
+  };
+
+  struct NodeHash {
+    size_t operator()(const Node &n) const {
+      return n.node_id + hash_(n.element) * kPrime;
+    }
+  };
+
+  typedef CompactHashBiTable<I, Node, NodeHash> NodeTable;
+
+  class SetIterator {
+   public:
+    SetIterator(I id, Node node, NodeTable *node_table)
+        :id_(id), node_(node), node_table_(node_table) {}
+
+    bool Done() const { return id_ == kNoNodeId; }
+
+    const T &Element() const { return node_.element; }
+
+    void Next() {
+      id_ = node_.node_id;
+      if (id_ != kNoNodeId)
+        node_ = node_table_->FindEntry(id_);
+    }
+
+   private:
+    I id_;                     // Iterator set node id
+    Node node_;                // Iterator set node
+    NodeTable *node_table_;
+  };
+
+  Collection() {}
+
+  // Lookups integer ID from set. If it doesn't exist, then adds it.
+  // Set elements should be in strict order (and therefore unique).
+  I FindId(const vector<T> &set) {
+    I node_id = kNoNodeId;
+    for (ssize_t i = set.size() - 1; i >= 0; --i) {
+      Node node(node_id, set[i]);
+      node_id = node_table_.FindId(node);
+    }
+    return node_id;
+  }
+
+  // Finds set given integer ID. Returns true if ID corresponds
+  // to set. Use iterators below to traverse result.
+  SetIterator FindSet(I id) {
+    if (id < 0 && id >= node_table_.Size()) {
+      return SetIterator(kNoNodeId, Node(kNoNodeId, T()), &node_table_);
+    } else {
+      return SetIterator(id, node_table_.FindEntry(id), &node_table_);
+    }
+  }
+
+ private:
+  static const I kNoNodeId;
+  static const size_t kPrime;
+  static std::tr1::hash<T> hash_;
+
+  NodeTable node_table_;
+
+  DISALLOW_COPY_AND_ASSIGN(Collection);
+};
+
+template<class I, class T> const I Collection<I, T>::kNoNodeId = -1;
+
+template <class I, class T> const size_t Collection<I, T>::kPrime = 7853;
+
+template <class I, class T> std::tr1::hash<T> Collection<I, T>::hash_;
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_PDT_COLLECTION_H__
diff --git a/src/include/fst/extensions/pdt/compose.h b/src/include/fst/extensions/pdt/compose.h
new file mode 100644
index 0000000..364d76f
--- /dev/null
+++ b/src/include/fst/extensions/pdt/compose.h
@@ -0,0 +1,146 @@
+// compose.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Compose a PDT and an FST.
+
+#ifndef FST_EXTENSIONS_PDT_COMPOSE_H__
+#define FST_EXTENSIONS_PDT_COMPOSE_H__
+
+#include <fst/compose.h>
+
+namespace fst {
+
+// Class to setup composition options for PDT composition.
+// Default is for the PDT as the first composition argument.
+template <class Arc, bool left_pdt = true>
+class PdtComposeOptions : public
+ComposeFstOptions<Arc,
+                  MultiEpsMatcher< Matcher<Fst<Arc> > >,
+                  MultiEpsFilter<AltSequenceComposeFilter<
+                                   MultiEpsMatcher<
+                                     Matcher<Fst<Arc> > > > > > {
+ public:
+  typedef typename Arc::Label Label;
+  typedef MultiEpsMatcher< Matcher<Fst<Arc> > > PdtMatcher;
+  typedef MultiEpsFilter<AltSequenceComposeFilter<PdtMatcher> > PdtFilter;
+  typedef ComposeFstOptions<Arc, PdtMatcher, PdtFilter> COptions;
+  using COptions::matcher1;
+  using COptions::matcher2;
+  using COptions::filter;
+
+  PdtComposeOptions(const Fst<Arc> &ifst1,
+                    const vector<pair<Label, Label> > &parens,
+                    const Fst<Arc> &ifst2) {
+    matcher1 = new PdtMatcher(ifst1, MATCH_OUTPUT, kMultiEpsList);
+    matcher2 = new PdtMatcher(ifst2, MATCH_INPUT, kMultiEpsLoop);
+
+    // Treat parens as multi-epsilons when composing.
+    for (size_t i = 0; i < parens.size(); ++i) {
+      matcher1->AddMultiEpsLabel(parens[i].first);
+      matcher1->AddMultiEpsLabel(parens[i].second);
+      matcher2->AddMultiEpsLabel(parens[i].first);
+      matcher2->AddMultiEpsLabel(parens[i].second);
+    }
+
+    filter = new PdtFilter(ifst1, ifst2, matcher1, matcher2, true);
+  }
+};
+
+// Class to setup composition options for PDT with FST composition.
+// Specialization is for the FST as the first composition argument.
+template <class Arc>
+class PdtComposeOptions<Arc, false> : public
+ComposeFstOptions<Arc,
+                  MultiEpsMatcher< Matcher<Fst<Arc> > >,
+                  MultiEpsFilter<SequenceComposeFilter<
+                                   MultiEpsMatcher<
+                                     Matcher<Fst<Arc> > > > > > {
+ public:
+  typedef typename Arc::Label Label;
+  typedef MultiEpsMatcher< Matcher<Fst<Arc> > > PdtMatcher;
+  typedef MultiEpsFilter<SequenceComposeFilter<PdtMatcher> > PdtFilter;
+  typedef ComposeFstOptions<Arc, PdtMatcher, PdtFilter> COptions;
+  using COptions::matcher1;
+  using COptions::matcher2;
+  using COptions::filter;
+
+  PdtComposeOptions(const Fst<Arc> &ifst1,
+                    const Fst<Arc> &ifst2,
+                    const vector<pair<Label, Label> > &parens) {
+    matcher1 = new PdtMatcher(ifst1, MATCH_OUTPUT, kMultiEpsLoop);
+    matcher2 = new PdtMatcher(ifst2, MATCH_INPUT, kMultiEpsList);
+
+    // Treat parens as multi-epsilons when composing.
+    for (size_t i = 0; i < parens.size(); ++i) {
+      matcher1->AddMultiEpsLabel(parens[i].first);
+      matcher1->AddMultiEpsLabel(parens[i].second);
+      matcher2->AddMultiEpsLabel(parens[i].first);
+      matcher2->AddMultiEpsLabel(parens[i].second);
+    }
+
+    filter = new PdtFilter(ifst1, ifst2, matcher1, matcher2, true);
+  }
+};
+
+
+// Composes pushdown transducer (PDT) encoded as an FST (1st arg) and
+// an FST (2nd arg) with the result also a PDT encoded as an Fst. (3rd arg).
+// In the PDTs, some transitions are labeled with open or close
+// parentheses. To be interpreted as a PDT, the parens must balance on
+// a path (see PdtExpand()). The open-close parenthesis label pairs
+// are passed in 'parens'.
+template <class Arc>
+void Compose(const Fst<Arc> &ifst1,
+             const vector<pair<typename Arc::Label,
+                               typename Arc::Label> > &parens,
+             const Fst<Arc> &ifst2,
+             MutableFst<Arc> *ofst,
+             const ComposeOptions &opts = ComposeOptions()) {
+
+  PdtComposeOptions<Arc, true> copts(ifst1, parens, ifst2);
+  copts.gc_limit = 0;
+  *ofst = ComposeFst<Arc>(ifst1, ifst2, copts);
+  if (opts.connect)
+    Connect(ofst);
+}
+
+
+// Composes an FST (1st arg) and pushdown transducer (PDT) encoded as
+// an FST (2nd arg) with the result also a PDT encoded as an Fst (3rd arg).
+// In the PDTs, some transitions are labeled with open or close
+// parentheses. To be interpreted as a PDT, the parens must balance on
+// a path (see ExpandFst()). The open-close parenthesis label pairs
+// are passed in 'parens'.
+template <class Arc>
+void Compose(const Fst<Arc> &ifst1,
+             const Fst<Arc> &ifst2,
+             const vector<pair<typename Arc::Label,
+                               typename Arc::Label> > &parens,
+             MutableFst<Arc> *ofst,
+             const ComposeOptions &opts = ComposeOptions()) {
+
+  PdtComposeOptions<Arc, false> copts(ifst1, ifst2, parens);
+  copts.gc_limit = 0;
+  *ofst = ComposeFst<Arc>(ifst1, ifst2, copts);
+  if (opts.connect)
+    Connect(ofst);
+}
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_PDT_COMPOSE_H__
diff --git a/src/include/fst/extensions/pdt/expand.h b/src/include/fst/extensions/pdt/expand.h
new file mode 100644
index 0000000..f464403
--- /dev/null
+++ b/src/include/fst/extensions/pdt/expand.h
@@ -0,0 +1,975 @@
+// expand.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Expand a PDT to an FST.
+
+#ifndef FST_EXTENSIONS_PDT_EXPAND_H__
+#define FST_EXTENSIONS_PDT_EXPAND_H__
+
+#include <vector>
+using std::vector;
+
+#include <fst/extensions/pdt/pdt.h>
+#include <fst/extensions/pdt/paren.h>
+#include <fst/extensions/pdt/shortest-path.h>
+#include <fst/extensions/pdt/reverse.h>
+#include <fst/cache.h>
+#include <fst/mutable-fst.h>
+#include <fst/queue.h>
+#include <fst/state-table.h>
+#include <fst/test-properties.h>
+
+namespace fst {
+
+template <class Arc>
+struct ExpandFstOptions : public CacheOptions {
+  bool keep_parentheses;
+  PdtStack<typename Arc::StateId, typename Arc::Label> *stack;
+  PdtStateTable<typename Arc::StateId, typename Arc::StateId> *state_table;
+
+  ExpandFstOptions(
+      const CacheOptions &opts = CacheOptions(),
+      bool kp = false,
+      PdtStack<typename Arc::StateId, typename Arc::Label> *s = 0,
+      PdtStateTable<typename Arc::StateId, typename Arc::StateId> *st = 0)
+      : CacheOptions(opts), keep_parentheses(kp), stack(s), state_table(st) {}
+};
+
+// Properties for an expanded PDT.
+inline uint64 ExpandProperties(uint64 inprops) {
+  return inprops & (kAcceptor | kAcyclic | kInitialAcyclic | kUnweighted);
+}
+
+
+// Implementation class for ExpandFst
+template <class A>
+class ExpandFstImpl
+    : public CacheImpl<A> {
+ public:
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::Properties;
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+
+  using CacheBaseImpl< CacheState<A> >::PushArc;
+  using CacheBaseImpl< CacheState<A> >::HasArcs;
+  using CacheBaseImpl< CacheState<A> >::HasFinal;
+  using CacheBaseImpl< CacheState<A> >::HasStart;
+  using CacheBaseImpl< CacheState<A> >::SetArcs;
+  using CacheBaseImpl< CacheState<A> >::SetFinal;
+  using CacheBaseImpl< CacheState<A> >::SetStart;
+
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef StateId StackId;
+  typedef PdtStateTuple<StateId, StackId> StateTuple;
+
+  ExpandFstImpl(const Fst<A> &fst,
+                const vector<pair<typename Arc::Label,
+                                  typename Arc::Label> > &parens,
+                const ExpandFstOptions<A> &opts)
+      : CacheImpl<A>(opts), fst_(fst.Copy()),
+        stack_(opts.stack ? opts.stack: new PdtStack<StateId, Label>(parens)),
+        state_table_(opts.state_table ? opts.state_table :
+                     new PdtStateTable<StateId, StackId>()),
+        own_stack_(opts.stack == 0), own_state_table_(opts.state_table == 0),
+        keep_parentheses_(opts.keep_parentheses) {
+    SetType("expand");
+
+    uint64 props = fst.Properties(kFstProperties, false);
+    SetProperties(ExpandProperties(props), kCopyProperties);
+
+    SetInputSymbols(fst.InputSymbols());
+    SetOutputSymbols(fst.OutputSymbols());
+  }
+
+  ExpandFstImpl(const ExpandFstImpl &impl)
+      : CacheImpl<A>(impl),
+        fst_(impl.fst_->Copy(true)),
+        stack_(new PdtStack<StateId, Label>(*impl.stack_)),
+        state_table_(new PdtStateTable<StateId, StackId>()),
+        own_stack_(true), own_state_table_(true),
+        keep_parentheses_(impl.keep_parentheses_) {
+    SetType("expand");
+    SetProperties(impl.Properties(), kCopyProperties);
+    SetInputSymbols(impl.InputSymbols());
+    SetOutputSymbols(impl.OutputSymbols());
+  }
+
+  ~ExpandFstImpl() {
+    delete fst_;
+    if (own_stack_)
+      delete stack_;
+    if (own_state_table_)
+      delete state_table_;
+  }
+
+  StateId Start() {
+    if (!HasStart()) {
+      StateId s = fst_->Start();
+      if (s == kNoStateId)
+        return kNoStateId;
+      StateTuple tuple(s, 0);
+      StateId start = state_table_->FindState(tuple);
+      SetStart(start);
+    }
+    return CacheImpl<A>::Start();
+  }
+
+  Weight Final(StateId s) {
+    if (!HasFinal(s)) {
+      const StateTuple &tuple = state_table_->Tuple(s);
+      Weight w = fst_->Final(tuple.state_id);
+      if (w != Weight::Zero() && tuple.stack_id == 0)
+        SetFinal(s, w);
+      else
+        SetFinal(s, Weight::Zero());
+    }
+    return CacheImpl<A>::Final(s);
+  }
+
+  size_t NumArcs(StateId s) {
+    if (!HasArcs(s)) {
+      ExpandState(s);
+    }
+    return CacheImpl<A>::NumArcs(s);
+  }
+
+  size_t NumInputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      ExpandState(s);
+    return CacheImpl<A>::NumInputEpsilons(s);
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      ExpandState(s);
+    return CacheImpl<A>::NumOutputEpsilons(s);
+  }
+
+  void InitArcIterator(StateId s, ArcIteratorData<A> *data) {
+    if (!HasArcs(s))
+      ExpandState(s);
+    CacheImpl<A>::InitArcIterator(s, data);
+  }
+
+  // Computes the outgoing transitions from a state, creating new destination
+  // states as needed.
+  void ExpandState(StateId s) {
+    StateTuple tuple = state_table_->Tuple(s);
+    for (ArcIterator< Fst<A> > aiter(*fst_, tuple.state_id);
+         !aiter.Done(); aiter.Next()) {
+      Arc arc = aiter.Value();
+      StackId stack_id = stack_->Find(tuple.stack_id, arc.ilabel);
+      if (stack_id == -1) {
+        // Non-matching close parenthesis
+        continue;
+      } else if ((stack_id != tuple.stack_id) && !keep_parentheses_) {
+        // Stack push/pop
+        arc.ilabel = arc.olabel = 0;
+      }
+
+      StateTuple ntuple(arc.nextstate, stack_id);
+      arc.nextstate = state_table_->FindState(ntuple);
+      PushArc(s, arc);
+    }
+    SetArcs(s);
+  }
+
+  const PdtStack<StackId, Label> &GetStack() const { return *stack_; }
+
+  const PdtStateTable<StateId, StackId> &GetStateTable() const {
+    return *state_table_;
+  }
+
+ private:
+  const Fst<A> *fst_;
+
+  PdtStack<StackId, Label> *stack_;
+  PdtStateTable<StateId, StackId> *state_table_;
+  bool own_stack_;
+  bool own_state_table_;
+  bool keep_parentheses_;
+
+  void operator=(const ExpandFstImpl<A> &);  // disallow
+};
+
+// Expands a pushdown transducer (PDT) encoded as an FST into an FST.
+// This version is a delayed Fst.  In the PDT, some transitions are
+// labeled with open or close parentheses. To be interpreted as a PDT,
+// the parens must balance on a path. The open-close parenthesis label
+// pairs are passed in 'parens'. The expansion enforces the
+// parenthesis constraints. The PDT must be expandable as an FST.
+//
+// This class attaches interface to implementation and handles
+// reference counting, delegating most methods to ImplToFst.
+template <class A>
+class ExpandFst : public ImplToFst< ExpandFstImpl<A> > {
+ public:
+  friend class ArcIterator< ExpandFst<A> >;
+  friend class StateIterator< ExpandFst<A> >;
+
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef StateId StackId;
+  typedef CacheState<A> State;
+  typedef ExpandFstImpl<A> Impl;
+
+  ExpandFst(const Fst<A> &fst,
+            const vector<pair<typename Arc::Label,
+                              typename Arc::Label> > &parens)
+      : ImplToFst<Impl>(new Impl(fst, parens, ExpandFstOptions<A>())) {}
+
+  ExpandFst(const Fst<A> &fst,
+            const vector<pair<typename Arc::Label,
+                              typename Arc::Label> > &parens,
+            const ExpandFstOptions<A> &opts)
+      : ImplToFst<Impl>(new Impl(fst, parens, opts)) {}
+
+  // See Fst<>::Copy() for doc.
+  ExpandFst(const ExpandFst<A> &fst, bool safe = false)
+      : ImplToFst<Impl>(fst, safe) {}
+
+  // Get a copy of this ExpandFst. See Fst<>::Copy() for further doc.
+  virtual ExpandFst<A> *Copy(bool safe = false) const {
+    return new ExpandFst<A>(*this, safe);
+  }
+
+  virtual inline void InitStateIterator(StateIteratorData<A> *data) const;
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<A> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+  const PdtStack<StackId, Label> &GetStack() const {
+    return GetImpl()->GetStack();
+  }
+
+  const PdtStateTable<StateId, StackId> &GetStateTable() const {
+    return GetImpl()->GetStateTable();
+  }
+
+ private:
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const ExpandFst<A> &fst);  // Disallow
+};
+
+
+// Specialization for ExpandFst.
+template<class A>
+class StateIterator< ExpandFst<A> >
+    : public CacheStateIterator< ExpandFst<A> > {
+ public:
+  explicit StateIterator(const ExpandFst<A> &fst)
+      : CacheStateIterator< ExpandFst<A> >(fst, fst.GetImpl()) {}
+};
+
+
+// Specialization for ExpandFst.
+template <class A>
+class ArcIterator< ExpandFst<A> >
+    : public CacheArcIterator< ExpandFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const ExpandFst<A> &fst, StateId s)
+      : CacheArcIterator< ExpandFst<A> >(fst.GetImpl(), s) {
+    if (!fst.GetImpl()->HasArcs(s))
+      fst.GetImpl()->ExpandState(s);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+
+template <class A> inline
+void ExpandFst<A>::InitStateIterator(StateIteratorData<A> *data) const
+{
+  data->base = new StateIterator< ExpandFst<A> >(*this);
+}
+
+//
+// PrunedExpand Class
+//
+
+// Prunes the delayed expansion of a pushdown transducer (PDT) encoded
+// as an FST into an FST.  In the PDT, some transitions are labeled
+// with open or close parentheses. To be interpreted as a PDT, the
+// parens must balance on a path. The open-close parenthesis label
+// pairs are passed in 'parens'. The expansion enforces the
+// parenthesis constraints.
+//
+// The algorithm works by visiting the delayed ExpandFst using a
+// shortest-stack first queue discipline and relies on the
+// shortest-distance information computed using a reverse
+// shortest-path call to perform the pruning.
+//
+// The algorithm maintains the same state ordering between the ExpandFst
+// being visited 'efst_' and the result of pruning written into the
+// MutableFst 'ofst_' to improve readability of the code.
+//
+template <class A>
+class PrunedExpand {
+ public:
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+  typedef StateId StackId;
+  typedef PdtStack<StackId, Label> Stack;
+  typedef PdtStateTable<StateId, StackId> StateTable;
+  typedef typename PdtBalanceData<Arc>::SetIterator SetIterator;
+
+  // Constructor taking as input a PDT specified by 'ifst' and 'parens'.
+  // 'keep_parentheses' specifies whether parentheses are replaced by
+  // epsilons or not during the expansion. 'opts' is the cache options
+  // used to instantiate the underlying ExpandFst.
+  PrunedExpand(const Fst<A> &ifst,
+               const vector<pair<Label, Label> > &parens,
+               bool keep_parentheses = false,
+               const CacheOptions &opts = CacheOptions())
+      : ifst_(ifst.Copy()),
+        keep_parentheses_(keep_parentheses),
+        stack_(parens),
+        efst_(ifst, parens,
+              ExpandFstOptions<Arc>(opts, true, &stack_, &state_table_)),
+        queue_(state_table_, stack_, stack_length_, distance_, fdistance_) {
+    Reverse(*ifst_, parens, &rfst_);
+    VectorFst<Arc> path;
+    reverse_shortest_path_ = new SP(
+        rfst_, parens,
+        PdtShortestPathOptions<A, FifoQueue<StateId> >(true, false));
+    reverse_shortest_path_->ShortestPath(&path);
+    balance_data_ = reverse_shortest_path_->GetBalanceData()->Reverse(
+        rfst_.NumStates(), 10, -1);
+
+    InitCloseParenMultimap(parens);
+  }
+
+  ~PrunedExpand() {
+    delete ifst_;
+    delete reverse_shortest_path_;
+    delete balance_data_;
+  }
+
+  // Expands and prunes with weight threshold 'threshold' the input PDT.
+  // Writes the result in 'ofst'.
+  void Expand(MutableFst<A> *ofst, const Weight &threshold);
+
+ private:
+  static const uint8 kEnqueued;
+  static const uint8 kExpanded;
+  static const uint8 kSourceState;
+
+  // Comparison functor used by the queue:
+  // 1. states corresponding to shortest stack first,
+  // 2. among stacks of the same length, reverse lexicographic order is used,
+  // 3. among states with the same stack, shortest-first order is used.
+  class StackCompare {
+   public:
+    StackCompare(const StateTable &st,
+                 const Stack &s, const vector<StackId> &sl,
+                 const vector<Weight> &d, const vector<Weight> &fd)
+        : state_table_(st), stack_(s), stack_length_(sl),
+          distance_(d), fdistance_(fd) {}
+
+    bool operator()(StateId s1, StateId s2) const {
+      StackId si1 = state_table_.Tuple(s1).stack_id;
+      StackId si2 = state_table_.Tuple(s2).stack_id;
+      if (stack_length_[si1] < stack_length_[si2])
+        return true;
+      if  (stack_length_[si1] > stack_length_[si2])
+        return false;
+      // If stack id equal, use A*
+      if (si1 == si2) {
+        Weight w1 = (s1 < distance_.size()) && (s1 < fdistance_.size()) ?
+            Times(distance_[s1], fdistance_[s1]) : Weight::Zero();
+        Weight w2 = (s2 < distance_.size()) && (s2 < fdistance_.size()) ?
+            Times(distance_[s2], fdistance_[s2]) : Weight::Zero();
+        return less_(w1, w2);
+      }
+      // If lenghts are equal, use reverse lexico.
+      for (; si1 != si2; si1 = stack_.Pop(si1), si2 = stack_.Pop(si2)) {
+        if (stack_.Top(si1) < stack_.Top(si2)) return true;
+        if (stack_.Top(si1) > stack_.Top(si2)) return false;
+      }
+      return false;
+    }
+
+   private:
+    const StateTable &state_table_;
+    const Stack &stack_;
+    const vector<StackId> &stack_length_;
+    const vector<Weight> &distance_;
+    const vector<Weight> &fdistance_;
+    NaturalLess<Weight> less_;
+  };
+
+  class ShortestStackFirstQueue
+      : public ShortestFirstQueue<StateId, StackCompare> {
+   public:
+    ShortestStackFirstQueue(
+        const PdtStateTable<StateId, StackId> &st,
+        const Stack &s,
+        const vector<StackId> &sl,
+        const vector<Weight> &d, const vector<Weight> &fd)
+        : ShortestFirstQueue<StateId, StackCompare>(
+            StackCompare(st, s, sl, d, fd)) {}
+  };
+
+
+  void InitCloseParenMultimap(const vector<pair<Label, Label> > &parens);
+  Weight DistanceToDest(StateId state, StateId source) const;
+  uint8 Flags(StateId s) const;
+  void SetFlags(StateId s, uint8 flags, uint8 mask);
+  Weight Distance(StateId s) const;
+  void SetDistance(StateId s, Weight w);
+  Weight FinalDistance(StateId s) const;
+  void SetFinalDistance(StateId s, Weight w);
+  StateId SourceState(StateId s) const;
+  void SetSourceState(StateId s, StateId p);
+  void AddStateAndEnqueue(StateId s);
+  void Relax(StateId s, const A &arc, Weight w);
+  bool PruneArc(StateId s, const A &arc);
+  void ProcStart();
+  void ProcFinal(StateId s);
+  bool ProcNonParen(StateId s, const A &arc, bool add_arc);
+  bool ProcOpenParen(StateId s, const A &arc, StackId si, StackId nsi);
+  bool ProcCloseParen(StateId s, const A &arc);
+  void ProcDestStates(StateId s, StackId si);
+
+  Fst<A> *ifst_;                   // Input PDT
+  VectorFst<Arc> rfst_;            // Reversed PDT
+  bool keep_parentheses_;          // Keep parentheses in ofst?
+  StateTable state_table_;         // State table for efst_
+  Stack stack_;                    // Stack trie
+  ExpandFst<Arc> efst_;            // Expanded PDT
+  vector<StackId> stack_length_;   // Length of stack for given stack id
+  vector<Weight> distance_;        // Distance from initial state in efst_/ofst
+  vector<Weight> fdistance_;       // Distance to final states in efst_/ofst
+  ShortestStackFirstQueue queue_;  // Queue used to visit efst_
+  vector<uint8> flags_;            // Status flags for states in efst_/ofst
+  vector<StateId> sources_;        // PDT source state for each expanded state
+
+  typedef PdtShortestPath<Arc, FifoQueue<StateId> > SP;
+  typedef typename SP::CloseParenMultimap ParenMultimap;
+  SP *reverse_shortest_path_;  // Shortest path for rfst_
+  PdtBalanceData<Arc> *balance_data_;   // Not owned by shortest_path_
+  ParenMultimap close_paren_multimap_;  // Maps open paren arcs to
+  // balancing close paren arcs.
+
+  MutableFst<Arc> *ofst_;  // Output fst
+  Weight limit_;           // Weight limit
+
+  typedef unordered_map<StateId, Weight> DestMap;
+  DestMap dest_map_;
+  StackId current_stack_id_;
+  // 'current_stack_id_' is the stack id of the states currently at the top
+  // of queue, i.e., the states currently being popped and processed.
+  // 'dest_map_' maps a state 's' in 'ifst_' that is the source
+  // of a close parentheses matching the top of 'current_stack_id_; to
+  // the shortest-distance from '(s, current_stack_id_)' to the final
+  // states in 'efst_'.
+  ssize_t current_paren_id_;  // Paren id at top of current stack
+  ssize_t cached_stack_id_;
+  StateId cached_source_;
+  slist<pair<StateId, Weight> > cached_dest_list_;
+  // 'cached_dest_list_' contains the set of pair of destination
+  // states and weight to final states for source state
+  // 'cached_source_' and paren id 'cached_paren_id': the set of
+  // source state of a close parenthesis with paren id
+  // 'cached_paren_id' balancing an incoming open parenthesis with
+  // paren id 'cached_paren_id' in state 'cached_source_'.
+
+  NaturalLess<Weight> less_;
+};
+
+template <class A> const uint8 PrunedExpand<A>::kEnqueued = 0x01;
+template <class A> const uint8 PrunedExpand<A>::kExpanded = 0x02;
+template <class A> const uint8 PrunedExpand<A>::kSourceState = 0x04;
+
+
+// Initializes close paren multimap, mapping pairs (s,paren_id) to
+// all the arcs out of s labeled with close parenthese for paren_id.
+template <class A>
+void PrunedExpand<A>::InitCloseParenMultimap(
+    const vector<pair<Label, Label> > &parens) {
+  unordered_map<Label, Label> paren_id_map;
+  for (Label i = 0; i < parens.size(); ++i) {
+    const pair<Label, Label>  &p = parens[i];
+    paren_id_map[p.first] = i;
+    paren_id_map[p.second] = i;
+  }
+
+  for (StateIterator<Fst<Arc> > siter(*ifst_); !siter.Done(); siter.Next()) {
+    StateId s = siter.Value();
+    for (ArcIterator<Fst<Arc> > aiter(*ifst_, s);
+         !aiter.Done(); aiter.Next()) {
+      const Arc &arc = aiter.Value();
+      typename unordered_map<Label, Label>::const_iterator pit
+          = paren_id_map.find(arc.ilabel);
+      if (pit == paren_id_map.end()) continue;
+      if (arc.ilabel == parens[pit->second].second) {  // Close paren
+        ParenState<Arc> paren_state(pit->second, s);
+        close_paren_multimap_.insert(make_pair(paren_state, arc));
+      }
+    }
+  }
+}
+
+
+// Returns the weight of the shortest balanced path from 'source' to 'dest'
+// in 'ifst_', 'dest' must be the source state of a close paren arc.
+template <class A>
+typename A::Weight PrunedExpand<A>::DistanceToDest(StateId source,
+                                                   StateId dest) const {
+  typename SP::SearchState s(source + 1, dest + 1);
+  VLOG(2) << "D(" << source << ", " << dest << ") ="
+            << reverse_shortest_path_->GetShortestPathData().Distance(s);
+  return reverse_shortest_path_->GetShortestPathData().Distance(s);
+}
+
+// Returns the flags for state 's' in 'ofst_'.
+template <class A>
+uint8 PrunedExpand<A>::Flags(StateId s) const {
+  return s < flags_.size() ? flags_[s] : 0;
+}
+
+// Modifies the flags for state 's' in 'ofst_'.
+template <class A>
+void PrunedExpand<A>::SetFlags(StateId s, uint8 flags, uint8 mask) {
+  while (flags_.size() <= s) flags_.push_back(0);
+  flags_[s] &= ~mask;
+  flags_[s] |= flags & mask;
+}
+
+
+// Returns the shortest distance from the initial state to 's' in 'ofst_'.
+template <class A>
+typename A::Weight PrunedExpand<A>::Distance(StateId s) const {
+  return s < distance_.size() ? distance_[s] : Weight::Zero();
+}
+
+// Sets the shortest distance from the initial state to 's' in 'ofst_' to 'w'.
+template <class A>
+void PrunedExpand<A>::SetDistance(StateId s, Weight w) {
+  while (distance_.size() <= s ) distance_.push_back(Weight::Zero());
+  distance_[s] = w;
+}
+
+
+// Returns the shortest distance from 's' to the final states in 'ofst_'.
+template <class A>
+typename A::Weight PrunedExpand<A>::FinalDistance(StateId s) const {
+  return s < fdistance_.size() ? fdistance_[s] : Weight::Zero();
+}
+
+// Sets the shortest distance from 's' to the final states in 'ofst_' to 'w'.
+template <class A>
+void PrunedExpand<A>::SetFinalDistance(StateId s, Weight w) {
+  while (fdistance_.size() <= s) fdistance_.push_back(Weight::Zero());
+  fdistance_[s] = w;
+}
+
+// Returns the PDT "source" state of state 's' in 'ofst_'.
+template <class A>
+typename A::StateId PrunedExpand<A>::SourceState(StateId s) const {
+  return s < sources_.size() ? sources_[s] : kNoStateId;
+}
+
+// Sets the PDT "source" state of state 's' in 'ofst_' to state 'p' in 'ifst_'.
+template <class A>
+void PrunedExpand<A>::SetSourceState(StateId s, StateId p) {
+  while (sources_.size() <= s) sources_.push_back(kNoStateId);
+  sources_[s] = p;
+}
+
+// Adds state 's' of 'efst_' to 'ofst_' and inserts it in the queue,
+// modifying the flags for 's' accordingly.
+template <class A>
+void PrunedExpand<A>::AddStateAndEnqueue(StateId s) {
+  if (!(Flags(s) & (kEnqueued | kExpanded))) {
+    while (ofst_->NumStates() <= s) ofst_->AddState();
+    queue_.Enqueue(s);
+    SetFlags(s, kEnqueued, kEnqueued);
+  } else if (Flags(s) & kEnqueued) {
+    queue_.Update(s);
+  }
+  // TODO(allauzen): Check everything is fine when kExpanded?
+}
+
+// Relaxes arc 'arc' out of state 's' in 'ofst_':
+// * if the distance to 's' times the weight of 'arc' is smaller than
+//   the currently stored distance for 'arc.nextstate',
+//   updates 'Distance(arc.nextstate)' with new estimate;
+// * if 'fd' is less than the currently stored distance from 'arc.nextstate'
+//   to the final state, updates with new estimate.
+template <class A>
+void PrunedExpand<A>::Relax(StateId s, const A &arc, Weight fd) {
+  Weight nd = Times(Distance(s), arc.weight);
+  if (less_(nd, Distance(arc.nextstate))) {
+    SetDistance(arc.nextstate, nd);
+    SetSourceState(arc.nextstate, SourceState(s));
+  }
+  if (less_(fd, FinalDistance(arc.nextstate)))
+    SetFinalDistance(arc.nextstate, fd);
+  VLOG(2) << "Relax: " << s << ", d[s] = " << Distance(s) << ", to "
+            << arc.nextstate << ", d[ns] = " << Distance(arc.nextstate)
+            << ", nd = " << nd;
+}
+
+// Returns 'true' if the arc 'arc' out of state 's' in 'efst_' needs to
+// be pruned.
+template <class A>
+bool PrunedExpand<A>::PruneArc(StateId s, const A &arc) {
+  VLOG(2) << "Prune ?";
+  Weight fd = Weight::Zero();
+
+  if ((cached_source_ != SourceState(s)) ||
+      (cached_stack_id_ != current_stack_id_)) {
+    cached_source_ = SourceState(s);
+    cached_stack_id_ = current_stack_id_;
+    cached_dest_list_.clear();
+    if (cached_source_ != ifst_->Start()) {
+      for (SetIterator set_iter =
+               balance_data_->Find(current_paren_id_, cached_source_);
+           !set_iter.Done(); set_iter.Next()) {
+        StateId dest = set_iter.Element();
+        typename DestMap::const_iterator iter = dest_map_.find(dest);
+        cached_dest_list_.push_front(*iter);
+      }
+    } else {
+      // TODO(allauzen): queue discipline should prevent this never
+      // from happening; replace by a check.
+      cached_dest_list_.push_front(
+          make_pair(rfst_.Start() -1, Weight::One()));
+    }
+  }
+
+  for (typename slist<pair<StateId, Weight> >::const_iterator iter =
+           cached_dest_list_.begin();
+       iter != cached_dest_list_.end();
+       ++iter) {
+    fd = Plus(fd,
+              Times(DistanceToDest(state_table_.Tuple(arc.nextstate).state_id,
+                                   iter->first),
+                    iter->second));
+  }
+  Relax(s, arc, fd);
+  Weight w = Times(Distance(s), Times(arc.weight, fd));
+  return less_(limit_, w);
+}
+
+// Adds start state of 'efst_' to 'ofst_', enqueues it and initializes
+// the distance data structures.
+template <class A>
+void PrunedExpand<A>::ProcStart() {
+  StateId s = efst_.Start();
+  AddStateAndEnqueue(s);
+  ofst_->SetStart(s);
+  SetSourceState(s, ifst_->Start());
+
+  current_stack_id_ = 0;
+  current_paren_id_ = -1;
+  stack_length_.push_back(0);
+  dest_map_[rfst_.Start() - 1] = Weight::One(); // not needed
+
+  cached_source_ = ifst_->Start();
+  cached_stack_id_ = 0;
+  cached_dest_list_.push_front(
+          make_pair(rfst_.Start() -1, Weight::One()));
+
+  PdtStateTuple<StateId, StackId> tuple(rfst_.Start() - 1, 0);
+  SetFinalDistance(state_table_.FindState(tuple), Weight::One());
+  SetDistance(s, Weight::One());
+  SetFinalDistance(s, DistanceToDest(ifst_->Start(), rfst_.Start() - 1));
+  VLOG(2) << DistanceToDest(ifst_->Start(), rfst_.Start() - 1);
+}
+
+// Makes 's' final in 'ofst_' if shortest accepting path ending in 's'
+// is below threshold.
+template <class A>
+void PrunedExpand<A>::ProcFinal(StateId s) {
+  Weight final = efst_.Final(s);
+  if ((final == Weight::Zero()) || less_(limit_, Times(Distance(s), final)))
+    return;
+  ofst_->SetFinal(s, final);
+}
+
+// Returns true when arc (or meta-arc) 'arc' out of 's' in 'efst_' is
+// below the threshold.  When 'add_arc' is true, 'arc' is added to 'ofst_'.
+template <class A>
+bool PrunedExpand<A>::ProcNonParen(StateId s, const A &arc, bool add_arc) {
+  VLOG(2) << "ProcNonParen: " << s << " to " << arc.nextstate
+          << ", " << arc.ilabel << ":" << arc.olabel << " / " << arc.weight
+          << ", add_arc = " << (add_arc ? "true" : "false");
+  if (PruneArc(s, arc)) return false;
+  if(add_arc) ofst_->AddArc(s, arc);
+  AddStateAndEnqueue(arc.nextstate);
+  return true;
+}
+
+// Processes an open paren arc 'arc' out of state 's' in 'ofst_'.
+// When 'arc' is labeled with an open paren,
+// 1. considers each (shortest) balanced path starting in 's' by
+//    taking 'arc' and ending by a close paren balancing the open
+//    paren of 'arc' as a meta-arc, processes and prunes each meta-arc
+//    as a non-paren arc, inserting its destination to the queue;
+// 2. if at least one of these meta-arcs has not been pruned,
+//    adds the destination of 'arc' to 'ofst_' as a new source state
+//    for the stack id 'nsi' and inserts it in the queue.
+template <class A>
+bool PrunedExpand<A>::ProcOpenParen(StateId s, const A &arc, StackId si,
+                                    StackId nsi) {
+  // Update the stack lenght when needed: |nsi| = |si| + 1.
+  while (stack_length_.size() <= nsi) stack_length_.push_back(-1);
+  if (stack_length_[nsi] == -1)
+    stack_length_[nsi] = stack_length_[si] + 1;
+
+  StateId ns = arc.nextstate;
+  VLOG(2) << "Open paren: " << s << "(" << state_table_.Tuple(s).state_id
+            << ") to " << ns << "(" << state_table_.Tuple(ns).state_id << ")";
+  bool proc_arc = false;
+  Weight fd = Weight::Zero();
+  ssize_t paren_id = stack_.ParenId(arc.ilabel);
+  slist<StateId> sources;
+  for (SetIterator set_iter =
+           balance_data_->Find(paren_id, state_table_.Tuple(ns).state_id);
+       !set_iter.Done(); set_iter.Next()) {
+    sources.push_front(set_iter.Element());
+  }
+  for (typename slist<StateId>::const_iterator sources_iter = sources.begin();
+       sources_iter != sources.end();
+       ++ sources_iter) {
+    StateId source = *sources_iter;
+    VLOG(2) << "Close paren source: " << source;
+    ParenState<Arc> paren_state(paren_id, source);
+    for (typename ParenMultimap::const_iterator iter =
+             close_paren_multimap_.find(paren_state);
+         iter != close_paren_multimap_.end() && paren_state == iter->first;
+         ++iter) {
+      Arc meta_arc = iter->second;
+      PdtStateTuple<StateId, StackId> tuple(meta_arc.nextstate, si);
+      meta_arc.nextstate =  state_table_.FindState(tuple);
+      VLOG(2) << state_table_.Tuple(ns).state_id << ", " << source;
+      VLOG(2) << "Meta arc weight = " << arc.weight << " Times "
+                << DistanceToDest(state_table_.Tuple(ns).state_id, source)
+                << " Times " << meta_arc.weight;
+      meta_arc.weight = Times(
+          arc.weight,
+          Times(DistanceToDest(state_table_.Tuple(ns).state_id, source),
+                meta_arc.weight));
+      proc_arc |= ProcNonParen(s, meta_arc, false);
+      fd = Plus(fd, Times(
+          Times(
+              DistanceToDest(state_table_.Tuple(ns).state_id, source),
+              iter->second.weight),
+          FinalDistance(meta_arc.nextstate)));
+    }
+  }
+  if (proc_arc) {
+    VLOG(2) << "Proc open paren " << s << " to " << arc.nextstate;
+    ofst_->AddArc(
+      s, keep_parentheses_ ? arc : Arc(0, 0, arc.weight, arc.nextstate));
+    AddStateAndEnqueue(arc.nextstate);
+    Weight nd = Times(Distance(s), arc.weight);
+    if(less_(nd, Distance(arc.nextstate)))
+      SetDistance(arc.nextstate, nd);
+    // FinalDistance not necessary for source state since pruning
+    // decided using the meta-arcs above.  But this is a problem with
+    // A*, hence:
+    if (less_(fd, FinalDistance(arc.nextstate)))
+      SetFinalDistance(arc.nextstate, fd);
+    SetFlags(arc.nextstate, kSourceState, kSourceState);
+  }
+  return proc_arc;
+}
+
+// Checks that shortest path through close paren arc in 'efst_' is
+// below threshold, if so adds it to 'ofst_'.
+template <class A>
+bool PrunedExpand<A>::ProcCloseParen(StateId s, const A &arc) {
+  Weight w = Times(Distance(s),
+                   Times(arc.weight, FinalDistance(arc.nextstate)));
+  if (less_(limit_, w))
+    return false;
+  ofst_->AddArc(
+      s, keep_parentheses_ ? arc : Arc(0, 0, arc.weight, arc.nextstate));
+  return true;
+}
+
+// When 's' in 'ofst_' is a source state for stack id 'si', identifies
+// all the corresponding possible destination states, that is, all the
+// states in 'ifst_' that have an outgoing close paren arc balancing
+// the incoming open paren taken to get to 's', and for each such
+// state 't', computes the shortest distance from (t, si) to the final
+// states in 'ofst_'. Stores this information in 'dest_map_'.
+template <class A>
+void PrunedExpand<A>::ProcDestStates(StateId s, StackId si) {
+  if (!(Flags(s) & kSourceState)) return;
+  if (si != current_stack_id_) {
+    dest_map_.clear();
+    current_stack_id_ = si;
+    current_paren_id_ = stack_.Top(current_stack_id_);
+    VLOG(2) << "StackID " << si << " dequeued for first time";
+  }
+  // TODO(allauzen): clean up source state business; rename current function to
+  // ProcSourceState.
+  SetSourceState(s, state_table_.Tuple(s).state_id);
+
+  ssize_t paren_id = stack_.Top(si);
+  for (SetIterator set_iter =
+           balance_data_->Find(paren_id, state_table_.Tuple(s).state_id);
+       !set_iter.Done(); set_iter.Next()) {
+    StateId dest_state = set_iter.Element();
+    if (dest_map_.find(dest_state) != dest_map_.end())
+      continue;
+    Weight dest_weight = Weight::Zero();
+    ParenState<Arc> paren_state(paren_id, dest_state);
+    for (typename ParenMultimap::const_iterator iter =
+             close_paren_multimap_.find(paren_state);
+         iter != close_paren_multimap_.end() && paren_state == iter->first;
+         ++iter) {
+      const Arc &arc = iter->second;
+      PdtStateTuple<StateId, StackId> tuple(arc.nextstate, stack_.Pop(si));
+      dest_weight = Plus(dest_weight,
+                         Times(arc.weight,
+                               FinalDistance(state_table_.FindState(tuple))));
+    }
+    dest_map_[dest_state] = dest_weight;
+    VLOG(2) << "State " << dest_state << " is a dest state for stack id "
+              << si << " with weight " << dest_weight;
+  }
+}
+
+// Expands and prunes with weight threshold 'threshold' the input PDT.
+// Writes the result in 'ofst'.
+template <class A>
+void PrunedExpand<A>::Expand(
+    MutableFst<A> *ofst, const typename A::Weight &threshold) {
+  ofst_ = ofst;
+  ofst_->DeleteStates();
+  ofst_->SetInputSymbols(ifst_->InputSymbols());
+  ofst_->SetOutputSymbols(ifst_->OutputSymbols());
+
+  limit_ = Times(DistanceToDest(ifst_->Start(), rfst_.Start() - 1), threshold);
+  flags_.clear();
+
+  ProcStart();
+
+  while (!queue_.Empty()) {
+    StateId s = queue_.Head();
+    queue_.Dequeue();
+    SetFlags(s, kExpanded, kExpanded | kEnqueued);
+    VLOG(2) << s << " dequeued!";
+
+    ProcFinal(s);
+    StackId stack_id = state_table_.Tuple(s).stack_id;
+    ProcDestStates(s, stack_id);
+
+    for (ArcIterator<ExpandFst<Arc> > aiter(efst_, s);
+         !aiter.Done();
+         aiter.Next()) {
+      Arc arc = aiter.Value();
+      StackId nextstack_id = state_table_.Tuple(arc.nextstate).stack_id;
+      if (stack_id == nextstack_id)
+        ProcNonParen(s, arc, true);
+      else if (stack_id == stack_.Pop(nextstack_id))
+        ProcOpenParen(s, arc, stack_id, nextstack_id);
+      else
+        ProcCloseParen(s, arc);
+    }
+    VLOG(2) << "d[" << s << "] = " << Distance(s)
+            << ", fd[" << s << "] = " << FinalDistance(s);
+  }
+}
+
+//
+// Expand() Functions
+//
+
+template <class Arc>
+struct ExpandOptions {
+  bool connect;
+  bool keep_parentheses;
+  typename Arc::Weight weight_threshold;
+
+  ExpandOptions(bool c  = true, bool k = false,
+                typename Arc::Weight w = Arc::Weight::Zero())
+      : connect(c), keep_parentheses(k), weight_threshold(w) {}
+};
+
+// Expands a pushdown transducer (PDT) encoded as an FST into an FST.
+// This version writes the expanded PDT result to a MutableFst.
+// In the PDT, some transitions are labeled with open or close
+// parentheses. To be interpreted as a PDT, the parens must balance on
+// a path. The open-close parenthesis label pairs are passed in
+// 'parens'. The expansion enforces the parenthesis constraints. The
+// PDT must be expandable as an FST.
+template <class Arc>
+void Expand(
+    const Fst<Arc> &ifst,
+    const vector<pair<typename Arc::Label, typename Arc::Label> > &parens,
+    MutableFst<Arc> *ofst,
+    const ExpandOptions<Arc> &opts) {
+  typedef typename Arc::Label Label;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef typename ExpandFst<Arc>::StackId StackId;
+
+  ExpandFstOptions<Arc> eopts;
+  eopts.gc_limit = 0;
+  if (opts.weight_threshold == Weight::Zero()) {
+    eopts.keep_parentheses = opts.keep_parentheses;
+    *ofst = ExpandFst<Arc>(ifst, parens, eopts);
+  } else {
+    PrunedExpand<Arc> pruned_expand(ifst, parens, opts.keep_parentheses);
+    pruned_expand.Expand(ofst, opts.weight_threshold);
+  }
+
+  if (opts.connect)
+    Connect(ofst);
+}
+
+// Expands a pushdown transducer (PDT) encoded as an FST into an FST.
+// This version writes the expanded PDT result to a MutableFst.
+// In the PDT, some transitions are labeled with open or close
+// parentheses. To be interpreted as a PDT, the parens must balance on
+// a path. The open-close parenthesis label pairs are passed in
+// 'parens'. The expansion enforces the parenthesis constraints. The
+// PDT must be expandable as an FST.
+template<class Arc>
+void Expand(
+    const Fst<Arc> &ifst,
+    const vector<pair<typename Arc::Label, typename Arc::Label> > &parens,
+    MutableFst<Arc> *ofst,
+    bool connect = true, bool keep_parentheses = false) {
+  Expand(ifst, parens, ofst, ExpandOptions<Arc>(connect, keep_parentheses));
+}
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_PDT_EXPAND_H__
diff --git a/src/include/fst/extensions/pdt/info.h b/src/include/fst/extensions/pdt/info.h
new file mode 100644
index 0000000..ef9a860
--- /dev/null
+++ b/src/include/fst/extensions/pdt/info.h
@@ -0,0 +1,175 @@
+// info.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Prints information about a PDT.
+
+#ifndef FST_EXTENSIONS_PDT_INFO_H__
+#define FST_EXTENSIONS_PDT_INFO_H__
+
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <tr1/unordered_set>
+using std::tr1::unordered_set;
+using std::tr1::unordered_multiset;
+#include <vector>
+using std::vector;
+
+#include <fst/fst.h>
+#include <fst/extensions/pdt/pdt.h>
+
+namespace fst {
+
+// Compute various information about PDTs, helper class for pdtinfo.cc.
+template <class A> class PdtInfo {
+public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+
+  PdtInfo(const Fst<A> &fst,
+          const vector<pair<typename A::Label,
+          typename A::Label> > &parens);
+
+  const string& FstType() const { return fst_type_; }
+  const string& ArcType() const { return A::Type(); }
+
+  int64 NumStates() const { return nstates_; }
+  int64 NumArcs() const { return narcs_; }
+  int64 NumOpenParens() const { return nopen_parens_; }
+  int64 NumCloseParens() const { return nclose_parens_; }
+  int64 NumUniqueOpenParens() const { return nuniq_open_parens_; }
+  int64 NumUniqueCloseParens() const { return nuniq_close_parens_; }
+  int64 NumOpenParenStates() const { return nopen_paren_states_; }
+  int64 NumCloseParenStates() const { return nclose_paren_states_; }
+
+ private:
+  string fst_type_;
+  int64 nstates_;
+  int64 narcs_;
+  int64 nopen_parens_;
+  int64 nclose_parens_;
+  int64 nuniq_open_parens_;
+  int64 nuniq_close_parens_;
+  int64 nopen_paren_states_;
+  int64 nclose_paren_states_;
+
+  DISALLOW_COPY_AND_ASSIGN(PdtInfo);
+};
+
+template <class A>
+PdtInfo<A>::PdtInfo(const Fst<A> &fst,
+                 const vector<pair<typename A::Label,
+                                   typename A::Label> > &parens)
+  : fst_type_(fst.Type()),
+    nstates_(0),
+    narcs_(0),
+    nopen_parens_(0),
+    nclose_parens_(0),
+    nuniq_open_parens_(0),
+    nuniq_close_parens_(0),
+    nopen_paren_states_(0),
+    nclose_paren_states_(0) {
+  unordered_map<Label, size_t> paren_map;
+  unordered_set<Label> paren_set;
+  unordered_set<StateId> open_paren_state_set;
+  unordered_set<StateId> close_paren_state_set;
+
+  for (size_t i = 0; i < parens.size(); ++i) {
+    const pair<Label, Label>  &p = parens[i];
+    paren_map[p.first] = i;
+    paren_map[p.second] = i;
+  }
+
+  for (StateIterator< Fst<A> > siter(fst);
+       !siter.Done();
+       siter.Next()) {
+    ++nstates_;
+    StateId s = siter.Value();
+    for (ArcIterator< Fst<A> > aiter(fst, s);
+         !aiter.Done();
+         aiter.Next()) {
+      const A &arc = aiter.Value();
+      ++narcs_;
+      typename unordered_map<Label, size_t>::const_iterator pit
+        = paren_map.find(arc.ilabel);
+      if (pit != paren_map.end()) {
+        Label open_paren =  parens[pit->second].first;
+        Label close_paren =  parens[pit->second].second;
+        if (arc.ilabel == open_paren) {
+          ++nopen_parens_;
+          if (!paren_set.count(open_paren)) {
+            ++nuniq_open_parens_;
+            paren_set.insert(open_paren);
+          }
+          if (!open_paren_state_set.count(arc.nextstate)) {
+            ++nopen_paren_states_;
+            open_paren_state_set.insert(arc.nextstate);
+          }
+        } else {
+          ++nclose_parens_;
+          if (!paren_set.count(close_paren)) {
+            ++nuniq_close_parens_;
+            paren_set.insert(close_paren);
+          }
+          if (!close_paren_state_set.count(s)) {
+            ++nclose_paren_states_;
+            close_paren_state_set.insert(s);
+          }
+
+        }
+      }
+    }
+  }
+}
+
+
+template <class A>
+void PrintPdtInfo(const PdtInfo<A> &pdtinfo) {
+  ios_base::fmtflags old = cout.setf(ios::left);
+  cout.width(50);
+  cout << "fst type" << pdtinfo.FstType().c_str() << endl;
+  cout.width(50);
+  cout << "arc type" << pdtinfo.ArcType().c_str() << endl;
+  cout.width(50);
+  cout << "# of states" << pdtinfo.NumStates() << endl;
+  cout.width(50);
+  cout << "# of arcs" << pdtinfo.NumArcs() << endl;
+  cout.width(50);
+  cout << "# of open parentheses" << pdtinfo.NumOpenParens() << endl;
+  cout.width(50);
+  cout << "# of close parentheses" << pdtinfo.NumCloseParens() << endl;
+  cout.width(50);
+  cout << "# of unique open parentheses"
+       << pdtinfo.NumUniqueOpenParens() << endl;
+  cout.width(50);
+  cout << "# of unique close parentheses"
+       << pdtinfo.NumUniqueCloseParens() << endl;
+  cout.width(50);
+  cout << "# of open parenthesis dest. states"
+       << pdtinfo.NumOpenParenStates() << endl;
+  cout.width(50);
+  cout << "# of close parenthesis source states"
+       << pdtinfo.NumCloseParenStates() << endl;
+  cout.setf(old);
+}
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_PDT_INFO_H__
diff --git a/src/include/fst/extensions/pdt/paren.h b/src/include/fst/extensions/pdt/paren.h
new file mode 100644
index 0000000..7b9887f
--- /dev/null
+++ b/src/include/fst/extensions/pdt/paren.h
@@ -0,0 +1,496 @@
+// paren.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// Common classes for PDT parentheses
+
+// \file
+
+#ifndef FST_EXTENSIONS_PDT_PAREN_H_
+#define FST_EXTENSIONS_PDT_PAREN_H_
+
+#include <algorithm>
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <tr1/unordered_set>
+using std::tr1::unordered_set;
+using std::tr1::unordered_multiset;
+#include <set>
+
+#include <fst/extensions/pdt/pdt.h>
+#include <fst/extensions/pdt/collection.h>
+#include <fst/fst.h>
+#include <fst/dfs-visit.h>
+
+
+namespace fst {
+
+//
+// ParenState: Pair of an open (close) parenthesis and
+// its destination (source) state.
+//
+
+template <class A>
+class ParenState {
+ public:
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+
+  struct Hash {
+    size_t operator()(const ParenState<A> &p) const {
+      return p.paren_id + p.state_id * kPrime;
+    }
+  };
+
+  Label paren_id;     // ID of open (close) paren
+  StateId state_id;   // destination (source) state of open (close) paren
+
+  ParenState() : paren_id(kNoLabel), state_id(kNoStateId) {}
+
+  ParenState(Label p, StateId s) : paren_id(p), state_id(s) {}
+
+  bool operator==(const ParenState<A> &p) const {
+    if (&p == this)
+      return true;
+    return p.paren_id == this->paren_id && p.state_id == this->state_id;
+  }
+
+  bool operator!=(const ParenState<A> &p) const { return !(p == *this); }
+
+  bool operator<(const ParenState<A> &p) const {
+    return paren_id < this->paren.id ||
+        (p.paren_id == this->paren.id && p.state_id < this->state_id);
+  }
+
+ private:
+  static const size_t kPrime;
+};
+
+template <class A>
+const size_t ParenState<A>::kPrime = 7853;
+
+
+// Creates an FST-style iterator from STL map and iterator.
+template <class M>
+class MapIterator {
+ public:
+  typedef typename M::const_iterator StlIterator;
+  typedef typename M::value_type PairType;
+  typedef typename PairType::second_type ValueType;
+
+  MapIterator(const M &m, StlIterator iter)
+      : map_(m), begin_(iter), iter_(iter) {}
+
+  bool Done() const {
+    return iter_ == map_.end() || iter_->first != begin_->first;
+  }
+
+  ValueType Value() const { return iter_->second; }
+  void Next() { ++iter_; }
+  void Reset() { iter_ = begin_; }
+
+ private:
+  const M &map_;
+  StlIterator begin_;
+  StlIterator iter_;
+};
+
+//
+// PdtParenReachable: Provides various parenthesis reachability information
+// on a PDT.
+//
+
+template <class A>
+class PdtParenReachable {
+ public:
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+ public:
+  // Maps from state ID to reachable paren IDs from (to) that state.
+  typedef unordered_multimap<StateId, Label> ParenMultiMap;
+
+  // Maps from paren ID and state ID to reachable state set ID
+  typedef unordered_map<ParenState<A>, ssize_t,
+                   typename ParenState<A>::Hash> StateSetMap;
+
+  // Maps from paren ID and state ID to arcs exiting that state with that
+  // Label.
+  typedef unordered_multimap<ParenState<A>, A,
+                        typename ParenState<A>::Hash> ParenArcMultiMap;
+
+  typedef MapIterator<ParenMultiMap> ParenIterator;
+
+  typedef MapIterator<ParenArcMultiMap> ParenArcIterator;
+
+  typedef typename Collection<ssize_t, StateId>::SetIterator SetIterator;
+
+  // Computes close (open) parenthesis reachabilty information for
+  // a PDT with bounded stack.
+  PdtParenReachable(const Fst<A> &fst,
+                    const vector<pair<Label, Label> > &parens, bool close)
+      : fst_(fst),
+        parens_(parens),
+        close_(close) {
+    for (Label i = 0; i < parens.size(); ++i) {
+      const pair<Label, Label>  &p = parens[i];
+      paren_id_map_[p.first] = i;
+      paren_id_map_[p.second] = i;
+    }
+
+    if (close_) {
+      StateId start = fst.Start();
+      if (start == kNoStateId)
+        return;
+      DFSearch(start, start);
+    } else {
+      FSTERROR() << "PdtParenReachable: open paren info not implemented";
+    }
+  }
+
+  // Given a state ID, returns an iterator over paren IDs
+  // for close (open) parens reachable from that state along balanced
+  // paths.
+  ParenIterator FindParens(StateId s) const {
+    return ParenIterator(paren_multimap_, paren_multimap_.find(s));
+  }
+
+  // Given a paren ID and a state ID s, returns an iterator over
+  // states that can be reached along balanced paths from (to) s that
+  // have have close (open) parentheses matching the paren ID exiting
+  // (entering) those states.
+  SetIterator FindStates(Label paren_id, StateId s) const {
+    ParenState<A> paren_state(paren_id, s);
+    typename StateSetMap::const_iterator id_it = set_map_.find(paren_state);
+    if (id_it == set_map_.end()) {
+      return state_sets_.FindSet(-1);
+    } else {
+      return state_sets_.FindSet(id_it->second);
+    }
+  }
+
+  // Given a paren Id and a state ID s, return an iterator over
+  // arcs that exit (enter) s and are labeled with a close (open)
+  // parenthesis matching the paren ID.
+  ParenArcIterator FindParenArcs(Label paren_id, StateId s) const {
+    ParenState<A> paren_state(paren_id, s);
+    return ParenArcIterator(paren_arc_multimap_,
+                            paren_arc_multimap_.find(paren_state));
+  }
+
+ private:
+  // DFS that gathers paren and state set information.
+  // Bool returns false when cycle detected.
+  bool DFSearch(StateId s, StateId start);
+
+  // Unions state sets together gathered by the DFS.
+  void ComputeStateSet(StateId s);
+
+  // Gather state set(s) from state 'nexts'.
+  void UpdateStateSet(StateId nexts, set<Label> *paren_set,
+                      vector< set<StateId> > *state_sets) const;
+
+  const Fst<A> &fst_;
+  const vector<pair<Label, Label> > &parens_;         // Paren ID -> Labels
+  bool close_;                                        // Close/open paren info?
+  unordered_map<Label, Label> paren_id_map_;               // Paren labels -> ID
+  ParenMultiMap paren_multimap_;                      // Paren reachability
+  ParenArcMultiMap paren_arc_multimap_;               // Paren Arcs
+  vector<char> state_color_;                          // DFS state
+  mutable Collection<ssize_t, StateId> state_sets_;   // Reachable states -> ID
+  StateSetMap set_map_;                               // ID -> Reachable states
+  DISALLOW_COPY_AND_ASSIGN(PdtParenReachable);
+};
+
+// DFS that gathers paren and state set information.
+template <class A>
+bool PdtParenReachable<A>::DFSearch(StateId s, StateId start) {
+  if (s >= state_color_.size())
+    state_color_.resize(s + 1, kDfsWhite);
+
+  if (state_color_[s] == kDfsBlack)
+    return true;
+
+  if (state_color_[s] == kDfsGrey)
+    return false;
+
+  state_color_[s] = kDfsGrey;
+
+  for (ArcIterator<Fst<A> > aiter(fst_, s);
+       !aiter.Done();
+       aiter.Next()) {
+    const A &arc = aiter.Value();
+
+    typename unordered_map<Label, Label>::const_iterator pit
+        = paren_id_map_.find(arc.ilabel);
+    if (pit != paren_id_map_.end()) {               // paren?
+      Label paren_id = pit->second;
+      if (arc.ilabel == parens_[paren_id].first) {  // open paren
+        DFSearch(arc.nextstate, arc.nextstate);
+        for (SetIterator set_iter = FindStates(paren_id, arc.nextstate);
+             !set_iter.Done(); set_iter.Next()) {
+          for (ParenArcIterator paren_arc_iter =
+                   FindParenArcs(paren_id, set_iter.Element());
+               !paren_arc_iter.Done();
+               paren_arc_iter.Next()) {
+            const A &cparc = paren_arc_iter.Value();
+            DFSearch(cparc.nextstate, start);
+          }
+        }
+      }
+    } else {                                       // non-paren
+      if(!DFSearch(arc.nextstate, start)) {
+        FSTERROR() << "PdtReachable: Underlying cyclicity not supported";
+        return true;
+      }
+    }
+  }
+  ComputeStateSet(s);
+  state_color_[s] = kDfsBlack;
+  return true;
+}
+
+// Unions state sets together gathered by the DFS.
+template <class A>
+void PdtParenReachable<A>::ComputeStateSet(StateId s) {
+  set<Label> paren_set;
+  vector< set<StateId> > state_sets(parens_.size());
+  for (ArcIterator< Fst<A> > aiter(fst_, s);
+       !aiter.Done();
+       aiter.Next()) {
+    const A &arc = aiter.Value();
+
+    typename unordered_map<Label, Label>::const_iterator pit
+        = paren_id_map_.find(arc.ilabel);
+    if (pit != paren_id_map_.end()) {               // paren?
+      Label paren_id = pit->second;
+      if (arc.ilabel == parens_[paren_id].first) {  // open paren
+        for (SetIterator set_iter =
+                 FindStates(paren_id, arc.nextstate);
+             !set_iter.Done(); set_iter.Next()) {
+          for (ParenArcIterator paren_arc_iter =
+                   FindParenArcs(paren_id, set_iter.Element());
+               !paren_arc_iter.Done();
+               paren_arc_iter.Next()) {
+            const A &cparc = paren_arc_iter.Value();
+            UpdateStateSet(cparc.nextstate, &paren_set, &state_sets);
+          }
+        }
+      } else {                                      // close paren
+        paren_set.insert(paren_id);
+        state_sets[paren_id].insert(s);
+        ParenState<A> paren_state(paren_id, s);
+        paren_arc_multimap_.insert(make_pair(paren_state, arc));
+      }
+    } else {                                        // non-paren
+      UpdateStateSet(arc.nextstate, &paren_set, &state_sets);
+    }
+  }
+
+  vector<StateId> state_set;
+  for (typename set<Label>::iterator paren_iter = paren_set.begin();
+       paren_iter != paren_set.end(); ++paren_iter) {
+    state_set.clear();
+    Label paren_id = *paren_iter;
+    paren_multimap_.insert(make_pair(s, paren_id));
+    for (typename set<StateId>::iterator state_iter
+             = state_sets[paren_id].begin();
+         state_iter != state_sets[paren_id].end();
+         ++state_iter) {
+      state_set.push_back(*state_iter);
+    }
+    ParenState<A> paren_state(paren_id, s);
+    set_map_[paren_state] = state_sets_.FindId(state_set);
+  }
+}
+
+// Gather state set(s) from state 'nexts'.
+template <class A>
+void PdtParenReachable<A>::UpdateStateSet(
+    StateId nexts, set<Label> *paren_set,
+    vector< set<StateId> > *state_sets) const {
+  for(ParenIterator paren_iter = FindParens(nexts);
+      !paren_iter.Done(); paren_iter.Next()) {
+    Label paren_id = paren_iter.Value();
+    paren_set->insert(paren_id);
+    for (SetIterator set_iter = FindStates(paren_id, nexts);
+         !set_iter.Done(); set_iter.Next()) {
+      (*state_sets)[paren_id].insert(set_iter.Element());
+    }
+  }
+}
+
+
+// Store balancing parenthesis data for a PDT. Allows on-the-fly
+// construction (e.g. in PdtShortestPath) unlike PdtParenReachable above.
+template <class A>
+class PdtBalanceData {
+ public:
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+
+  // Hash set for open parens
+  typedef unordered_set<ParenState<A>, typename ParenState<A>::Hash> OpenParenSet;
+
+  // Maps from open paren destination state to parenthesis ID.
+  typedef unordered_multimap<StateId, Label> OpenParenMap;
+
+  // Maps from open paren state to source states of matching close parens
+  typedef unordered_multimap<ParenState<A>, StateId,
+                        typename ParenState<A>::Hash> CloseParenMap;
+
+  // Maps from open paren state to close source set ID
+  typedef unordered_map<ParenState<A>, ssize_t,
+                   typename ParenState<A>::Hash> CloseSourceMap;
+
+  typedef typename Collection<ssize_t, StateId>::SetIterator SetIterator;
+
+  PdtBalanceData() {}
+
+  void Clear() {
+    open_paren_map_.clear();
+    close_paren_map_.clear();
+  }
+
+  // Adds an open parenthesis with destination state 'open_dest'.
+  void OpenInsert(Label paren_id, StateId open_dest) {
+    ParenState<A> key(paren_id, open_dest);
+    if (!open_paren_set_.count(key)) {
+      open_paren_set_.insert(key);
+      open_paren_map_.insert(make_pair(open_dest, paren_id));
+    }
+  }
+
+  // Adds a matching closing parenthesis with source state
+  // 'close_source' that balances an open_parenthesis with destination
+  // state 'open_dest' if OpenInsert() previously called
+  // (o.w. CloseInsert() does nothing).
+  void CloseInsert(Label paren_id, StateId open_dest, StateId close_source) {
+    ParenState<A> key(paren_id, open_dest);
+    if (open_paren_set_.count(key))
+      close_paren_map_.insert(make_pair(key, close_source));
+  }
+
+  // Find close paren source states matching an open parenthesis.
+  // Methods that follow, iterate through those matching states.
+  // Should be called only after FinishInsert(open_dest).
+  SetIterator Find(Label paren_id, StateId open_dest) {
+    ParenState<A> close_key(paren_id, open_dest);
+    typename CloseSourceMap::const_iterator id_it =
+        close_source_map_.find(close_key);
+    if (id_it == close_source_map_.end()) {
+      return close_source_sets_.FindSet(-1);
+    } else {
+      return close_source_sets_.FindSet(id_it->second);
+    }
+  }
+
+  // Call when all open and close parenthesis insertions wrt open
+  // parentheses entering 'open_dest' are finished. Must be called
+  // before Find(open_dest). Stores close paren source state sets
+  // efficiently.
+  void FinishInsert(StateId open_dest) {
+    vector<StateId> close_sources;
+    for (typename OpenParenMap::iterator oit = open_paren_map_.find(open_dest);
+         oit != open_paren_map_.end() && oit->first == open_dest;) {
+      Label paren_id = oit->second;
+      close_sources.clear();
+      ParenState<A> okey(paren_id, open_dest);
+      open_paren_set_.erase(open_paren_set_.find(okey));
+      for (typename CloseParenMap::iterator cit = close_paren_map_.find(okey);
+           cit != close_paren_map_.end() && cit->first == okey;) {
+        close_sources.push_back(cit->second);
+        close_paren_map_.erase(cit++);
+      }
+      sort(close_sources.begin(), close_sources.end());
+      typename vector<StateId>::iterator unique_end =
+          unique(close_sources.begin(), close_sources.end());
+      close_sources.resize(unique_end - close_sources.begin());
+
+      if (!close_sources.empty())
+        close_source_map_[okey] = close_source_sets_.FindId(close_sources);
+      open_paren_map_.erase(oit++);
+    }
+  }
+
+  // Return a new balance data object representing the reversed balance
+  // information.
+  PdtBalanceData<A> *Reverse(StateId num_states,
+                               StateId num_split,
+                               StateId state_id_shift) const;
+
+ private:
+  OpenParenSet open_paren_set_;                      // open par. at dest?
+
+  OpenParenMap open_paren_map_;                      // open parens per state
+  ParenState<A> open_dest_;                          // cur open dest. state
+  typename OpenParenMap::const_iterator open_iter_;  // cur open parens/state
+
+  CloseParenMap close_paren_map_;                    // close states/open
+                                                     //  paren and state
+
+  CloseSourceMap close_source_map_;                  // paren, state to set ID
+  mutable Collection<ssize_t, StateId> close_source_sets_;
+};
+
+// Return a new balance data object representing the reversed balance
+// information.
+template <class A>
+PdtBalanceData<A> *PdtBalanceData<A>::Reverse(
+    StateId num_states,
+    StateId num_split,
+    StateId state_id_shift) const {
+  PdtBalanceData<A> *bd = new PdtBalanceData<A>;
+  unordered_set<StateId> close_sources;
+  StateId split_size = num_states / num_split;
+
+  for (StateId i = 0; i < num_states; i+= split_size) {
+    close_sources.clear();
+
+    for (typename CloseSourceMap::const_iterator
+             sit = close_source_map_.begin();
+         sit != close_source_map_.end();
+         ++sit) {
+      ParenState<A> okey = sit->first;
+      StateId open_dest = okey.state_id;
+      Label paren_id = okey.paren_id;
+      for (SetIterator set_iter = close_source_sets_.FindSet(sit->second);
+           !set_iter.Done(); set_iter.Next()) {
+        StateId close_source = set_iter.Element();
+        if ((close_source < i) || (close_source >= i + split_size))
+          continue;
+        close_sources.insert(close_source + state_id_shift);
+        bd->OpenInsert(paren_id, close_source + state_id_shift);
+        bd->CloseInsert(paren_id, close_source + state_id_shift,
+                        open_dest + state_id_shift);
+      }
+    }
+
+    for (typename unordered_set<StateId>::const_iterator it
+             = close_sources.begin();
+         it != close_sources.end();
+         ++it) {
+      bd->FinishInsert(*it);
+    }
+
+  }
+  return bd;
+}
+
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_PDT_PAREN_H_
diff --git a/src/include/fst/extensions/pdt/pdt.h b/src/include/fst/extensions/pdt/pdt.h
new file mode 100644
index 0000000..171541f
--- /dev/null
+++ b/src/include/fst/extensions/pdt/pdt.h
@@ -0,0 +1,212 @@
+// pdt.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Common classes for PDT expansion/traversal.
+
+#ifndef FST_EXTENSIONS_PDT_PDT_H__
+#define FST_EXTENSIONS_PDT_PDT_H__
+
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <map>
+#include <set>
+
+#include <fst/state-table.h>
+#include <fst/fst.h>
+
+namespace fst {
+
+// Provides bijection between parenthesis stacks and signed integral
+// stack IDs. Each stack ID is unique to each distinct stack.  The
+// open-close parenthesis label pairs are passed in 'parens'.
+template <typename K, typename L>
+class PdtStack {
+ public:
+  typedef K StackId;
+  typedef L Label;
+
+  // The stacks are stored in a tree. The nodes are stored in vector
+  // 'nodes_'. Each node represents the top of some stack and is
+  // ID'ed by its position in the vector. Its parent node represents
+  // the stack with the top 'popped' and its children are stored in
+  // 'child_map_' accessed by stack_id and label. The paren_id is
+  // the position in 'parens' of the parenthesis for that node.
+  struct StackNode {
+    StackId parent_id;
+    size_t paren_id;
+
+    StackNode(StackId p, size_t i) : parent_id(p), paren_id(i) {}
+  };
+
+  PdtStack(const vector<pair<Label, Label> > &parens)
+      : parens_(parens), min_paren_(kNoLabel), max_paren_(kNoLabel) {
+    for (size_t i = 0; i < parens.size(); ++i) {
+      const pair<Label, Label>  &p = parens[i];
+      paren_map_[p.first] = i;
+      paren_map_[p.second] = i;
+
+      if (min_paren_ == kNoLabel || p.first < min_paren_)
+        min_paren_ = p.first;
+      if (p.second < min_paren_)
+        min_paren_ = p.second;
+
+      if (max_paren_ == kNoLabel || p.first > max_paren_)
+        max_paren_ = p.first;
+      if (p.second > max_paren_)
+        max_paren_ = p.second;
+    }
+    nodes_.push_back(StackNode(-1, -1));  // Tree root.
+  }
+
+  // Returns stack ID given the current stack ID (0 if empty) and
+  // label read. 'Pushes' onto a stack if the label is an open
+  // parenthesis, returning the new stack ID. 'Pops' the stack if the
+  // label is a close parenthesis that matches the top of the stack,
+  // returning the parent stack ID. Returns -1 if label is an
+  // unmatched close parenthesis. Otherwise, returns the current stack
+  // ID.
+  StackId Find(StackId stack_id, Label label) {
+    if (min_paren_ == kNoLabel || label < min_paren_ || label > max_paren_)
+      return stack_id;                       // Non-paren.
+
+    typename unordered_map<Label, size_t>::const_iterator pit
+        = paren_map_.find(label);
+    if (pit == paren_map_.end())             // Non-paren.
+      return stack_id;
+    ssize_t paren_id = pit->second;
+
+    if (label == parens_[paren_id].first) {  // Open paren.
+      StackId &child_id = child_map_[make_pair(stack_id, label)];
+      if (child_id == 0) {                   // Child not found, push label.
+        child_id = nodes_.size();
+        nodes_.push_back(StackNode(stack_id, paren_id));
+      }
+      return child_id;
+    }
+
+    const StackNode &node = nodes_[stack_id];
+    if (paren_id == node.paren_id)           // Matching close paren.
+      return node.parent_id;
+
+    return -1;                               // Non-matching close paren.
+  }
+
+  // Returns the stack ID obtained by "popping" the label at the top
+  // of the current stack ID.
+  StackId Pop(StackId stack_id) const {
+    return nodes_[stack_id].parent_id;
+  }
+
+  // Returns the paren ID at the top of the stack for 'stack_id'
+  ssize_t Top(StackId stack_id) const {
+    return nodes_[stack_id].paren_id;
+  }
+
+  ssize_t ParenId(Label label) const {
+    typename unordered_map<Label, size_t>::const_iterator pit
+        = paren_map_.find(label);
+    if (pit == paren_map_.end())  // Non-paren.
+      return -1;
+    return pit->second;
+  }
+
+ private:
+  struct ChildHash {
+    size_t operator()(const pair<StackId, Label> &p) const {
+      return p.first + p.second * kPrime;
+    }
+  };
+
+  static const size_t kPrime;
+
+  vector<pair<Label, Label> > parens_;
+  vector<StackNode> nodes_;
+  unordered_map<Label, size_t> paren_map_;
+  unordered_map<pair<StackId, Label>,
+           StackId, ChildHash> child_map_;   // Child of stack node wrt label
+  Label min_paren_;                          // For faster paren. check
+  Label max_paren_;                          // For faster paren. check
+};
+
+template <typename T, typename L>
+const size_t PdtStack<T, L>::kPrime = 7853;
+
+
+// State tuple for PDT expansion
+template <typename S, typename K>
+struct PdtStateTuple {
+  typedef S StateId;
+  typedef K StackId;
+
+  StateId state_id;
+  StackId stack_id;
+
+  PdtStateTuple()
+      : state_id(kNoStateId), stack_id(-1) {}
+
+  PdtStateTuple(StateId fs, StackId ss)
+      : state_id(fs), stack_id(ss) {}
+};
+
+// Equality of PDT state tuples.
+template <typename S, typename K>
+inline bool operator==(const PdtStateTuple<S, K>& x,
+                       const PdtStateTuple<S, K>& y) {
+  if (&x == &y)
+    return true;
+  return x.state_id == y.state_id && x.stack_id == y.stack_id;
+}
+
+
+// Hash function object for PDT state tuples
+template <class T>
+class PdtStateHash {
+ public:
+  size_t operator()(const T &tuple) const {
+    return tuple.state_id + tuple.stack_id * kPrime;
+  }
+
+ private:
+  static const size_t kPrime;
+};
+
+template <typename T>
+const size_t PdtStateHash<T>::kPrime = 7853;
+
+
+// Tuple to PDT state bijection.
+template <class S, class K>
+class PdtStateTable
+    : public CompactHashStateTable<PdtStateTuple<S, K>,
+                                   PdtStateHash<PdtStateTuple<S, K> > > {
+ public:
+  typedef S StateId;
+  typedef K StackId;
+
+  PdtStateTable() {}
+
+  PdtStateTable(const PdtStateTable<S, K> &table) {}
+
+ private:
+  void operator=(const PdtStateTable<S, K> &table);  // disallow
+};
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_PDT_PDT_H__
diff --git a/src/include/fst/extensions/pdt/pdtlib.h b/src/include/fst/extensions/pdt/pdtlib.h
new file mode 100644
index 0000000..71c8123
--- /dev/null
+++ b/src/include/fst/extensions/pdt/pdtlib.h
@@ -0,0 +1,30 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+// This is an experimental push-down transducer(PDT) library. A PDT is
+// encoded as an FST, where some transitions are labeled with open or close
+// parentheses. To be interpreted as a PDT, the parentheses must balance on a
+// path.
+
+#ifndef FST_EXTENSIONS_PDT_PDTLIB_H_
+#define FST_EXTENSIONS_PDT_PDTLIB_H_
+
+#include <fst/extensions/pdt/pdt.h>
+#include <fst/extensions/pdt/compose.h>
+#include <fst/extensions/pdt/expand.h>
+#include <fst/extensions/pdt/replace.h>
+
+#endif  // FST_EXTENSIONS_PDT_PDTLIB_H_
diff --git a/src/include/fst/extensions/pdt/pdtscript.h b/src/include/fst/extensions/pdt/pdtscript.h
new file mode 100644
index 0000000..c2a1cf4
--- /dev/null
+++ b/src/include/fst/extensions/pdt/pdtscript.h
@@ -0,0 +1,284 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+// Convenience file for including all PDT operations at once, and/or
+// registering them for new arc types.
+
+#ifndef FST_EXTENSIONS_PDT_PDTSCRIPT_H_
+#define FST_EXTENSIONS_PDT_PDTSCRIPT_H_
+
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+#include <fst/compose.h>  // for ComposeOptions
+#include <fst/util.h>
+
+#include <fst/script/fst-class.h>
+#include <fst/script/arg-packs.h>
+#include <fst/script/shortest-path.h>
+
+#include <fst/extensions/pdt/compose.h>
+#include <fst/extensions/pdt/expand.h>
+#include <fst/extensions/pdt/info.h>
+#include <fst/extensions/pdt/replace.h>
+#include <fst/extensions/pdt/reverse.h>
+#include <fst/extensions/pdt/shortest-path.h>
+
+
+namespace fst {
+namespace script {
+
+// PDT COMPOSE
+
+typedef args::Package<const FstClass &,
+                      const FstClass &,
+                      const vector<pair<int64, int64> >&,
+                      MutableFstClass *,
+                      const ComposeOptions &,
+                      bool> PdtComposeArgs;
+
+template<class Arc>
+void PdtCompose(PdtComposeArgs *args) {
+  const Fst<Arc> &ifst1 = *(args->arg1.GetFst<Arc>());
+  const Fst<Arc> &ifst2 = *(args->arg2.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg4->GetMutableFst<Arc>();
+
+  vector<pair<typename Arc::Label, typename Arc::Label> > parens(
+      args->arg3.size());
+
+  for (size_t i = 0; i < parens.size(); ++i) {
+    parens[i].first = args->arg3[i].first;
+    parens[i].second = args->arg3[i].second;
+  }
+
+  if (args->arg6) {
+    Compose(ifst1, parens, ifst2, ofst, args->arg5);
+  } else {
+    Compose(ifst1, ifst2, parens, ofst, args->arg5);
+  }
+}
+
+void PdtCompose(const FstClass & ifst1,
+                const FstClass & ifst2,
+                const vector<pair<int64, int64> > &parens,
+                MutableFstClass *ofst,
+                const ComposeOptions &copts,
+                bool left_pdt);
+
+// PDT EXPAND
+
+struct PdtExpandOptions {
+  bool connect;
+  bool keep_parentheses;
+  WeightClass weight_threshold;
+
+  PdtExpandOptions(bool c = true, bool k = false,
+                   WeightClass w = WeightClass::Zero())
+      : connect(c), keep_parentheses(k), weight_threshold(w) {}
+};
+
+typedef args::Package<const FstClass &,
+                      const vector<pair<int64, int64> >&,
+                      MutableFstClass *, PdtExpandOptions> PdtExpandArgs;
+
+template<class Arc>
+void PdtExpand(PdtExpandArgs *args) {
+  const Fst<Arc> &fst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg3->GetMutableFst<Arc>();
+
+  vector<pair<typename Arc::Label, typename Arc::Label> > parens(
+      args->arg2.size());
+  for (size_t i = 0; i < parens.size(); ++i) {
+    parens[i].first = args->arg2[i].first;
+    parens[i].second = args->arg2[i].second;
+  }
+  Expand(fst, parens, ofst,
+         ExpandOptions<Arc>(
+             args->arg4.connect, args->arg4.keep_parentheses,
+             *(args->arg4.weight_threshold.GetWeight<typename Arc::Weight>())));
+}
+
+void PdtExpand(const FstClass &ifst,
+               const vector<pair<int64, int64> > &parens,
+               MutableFstClass *ofst, const PdtExpandOptions &opts);
+
+void PdtExpand(const FstClass &ifst,
+               const vector<pair<int64, int64> > &parens,
+               MutableFstClass *ofst, bool connect);
+
+// PDT REPLACE
+
+typedef args::Package<const vector<pair<int64, const FstClass*> > &,
+                      MutableFstClass *,
+                      vector<pair<int64, int64> > *,
+                      const int64 &> PdtReplaceArgs;
+template<class Arc>
+void PdtReplace(PdtReplaceArgs *args) {
+  vector<pair<typename Arc::Label, const Fst<Arc> *> > tuples(
+      args->arg1.size());
+  for (size_t i = 0; i < tuples.size(); ++i) {
+    tuples[i].first = args->arg1[i].first;
+    tuples[i].second = (args->arg1[i].second)->GetFst<Arc>();
+  }
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+  vector<pair<typename Arc::Label, typename Arc::Label> > parens(
+      args->arg3->size());
+
+  for (size_t i = 0; i < parens.size(); ++i) {
+    parens[i].first = args->arg3->at(i).first;
+    parens[i].second = args->arg3->at(i).second;
+  }
+  Replace(tuples, ofst, &parens, args->arg4);
+
+  // now copy parens back
+  args->arg3->resize(parens.size());
+  for (size_t i = 0; i < parens.size(); ++i) {
+    (*args->arg3)[i].first = parens[i].first;
+    (*args->arg3)[i].second = parens[i].second;
+  }
+}
+
+void PdtReplace(const vector<pair<int64, const FstClass*> > &fst_tuples,
+                MutableFstClass *ofst,
+                vector<pair<int64, int64> > *parens,
+                const int64 &root);
+
+// PDT REVERSE
+
+typedef args::Package<const FstClass &,
+                      const vector<pair<int64, int64> >&,
+                      MutableFstClass *> PdtReverseArgs;
+
+template<class Arc>
+void PdtReverse(PdtReverseArgs *args) {
+  const Fst<Arc> &fst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg3->GetMutableFst<Arc>();
+
+  vector<pair<typename Arc::Label, typename Arc::Label> > parens(
+      args->arg2.size());
+  for (size_t i = 0; i < parens.size(); ++i) {
+    parens[i].first = args->arg2[i].first;
+    parens[i].second = args->arg2[i].second;
+  }
+  Reverse(fst, parens, ofst);
+}
+
+void PdtReverse(const FstClass &ifst,
+                const vector<pair<int64, int64> > &parens,
+                MutableFstClass *ofst);
+
+
+// PDT SHORTESTPATH
+
+struct PdtShortestPathOptions {
+  QueueType queue_type;
+  bool keep_parentheses;
+  bool path_gc;
+
+  PdtShortestPathOptions(QueueType qt = FIFO_QUEUE,
+                         bool kp = false, bool gc = true)
+      : queue_type(qt), keep_parentheses(kp), path_gc(gc) {}
+};
+
+typedef args::Package<const FstClass &,
+                      const vector<pair<int64, int64> >&,
+                      MutableFstClass *,
+                      const PdtShortestPathOptions &> PdtShortestPathArgs;
+
+template<class Arc>
+void PdtShortestPath(PdtShortestPathArgs *args) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  const Fst<Arc> &fst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg3->GetMutableFst<Arc>();
+  const PdtShortestPathOptions &opts = args->arg4;
+
+
+  vector<pair<Label, Label> > parens(args->arg2.size());
+  for (size_t i = 0; i < parens.size(); ++i) {
+    parens[i].first = args->arg2[i].first;
+    parens[i].second = args->arg2[i].second;
+  }
+
+  switch (opts.queue_type) {
+    default:
+      FSTERROR() << "Unknown queue type: " << opts.queue_type;
+    case FIFO_QUEUE: {
+      typedef FifoQueue<StateId> Queue;
+      fst::PdtShortestPathOptions<Arc, Queue> spopts(opts.keep_parentheses,
+                                                         opts.path_gc);
+      ShortestPath(fst, parens, ofst, spopts);
+      return;
+    }
+    case LIFO_QUEUE: {
+      typedef LifoQueue<StateId> Queue;
+      fst::PdtShortestPathOptions<Arc, Queue> spopts(opts.keep_parentheses,
+                                                         opts.path_gc);
+      ShortestPath(fst, parens, ofst, spopts);
+      return;
+    }
+    case STATE_ORDER_QUEUE: {
+      typedef StateOrderQueue<StateId> Queue;
+      fst::PdtShortestPathOptions<Arc, Queue> spopts(opts.keep_parentheses,
+                                                         opts.path_gc);
+      ShortestPath(fst, parens, ofst, spopts);
+      return;
+    }
+  }
+}
+
+void PdtShortestPath(const FstClass &ifst,
+                     const vector<pair<int64, int64> > &parens,
+                     MutableFstClass *ofst,
+                     const PdtShortestPathOptions &opts =
+                     PdtShortestPathOptions());
+
+// PRINT INFO
+
+typedef args::Package<const FstClass &,
+                      const vector<pair<int64, int64> > &> PrintPdtInfoArgs;
+
+template<class Arc>
+void PrintPdtInfo(PrintPdtInfoArgs *args) {
+  const Fst<Arc> &fst = *(args->arg1.GetFst<Arc>());
+  vector<pair<typename Arc::Label, typename Arc::Label> > parens(
+      args->arg2.size());
+  for (size_t i = 0; i < parens.size(); ++i) {
+    parens[i].first = args->arg2[i].first;
+    parens[i].second = args->arg2[i].second;
+  }
+  PdtInfo<Arc> pdtinfo(fst, parens);
+  PrintPdtInfo(pdtinfo);
+}
+
+void PrintPdtInfo(const FstClass &ifst,
+                  const vector<pair<int64, int64> > &parens);
+
+}  // namespace script
+}  // namespace fst
+
+
+#define REGISTER_FST_PDT_OPERATIONS(ArcType)                                \
+  REGISTER_FST_OPERATION(PdtCompose, ArcType, PdtComposeArgs);              \
+  REGISTER_FST_OPERATION(PdtExpand, ArcType, PdtExpandArgs);                \
+  REGISTER_FST_OPERATION(PdtReplace, ArcType, PdtReplaceArgs);              \
+  REGISTER_FST_OPERATION(PdtReverse, ArcType, PdtReverseArgs);              \
+  REGISTER_FST_OPERATION(PdtShortestPath, ArcType, PdtShortestPathArgs);    \
+  REGISTER_FST_OPERATION(PrintPdtInfo, ArcType, PrintPdtInfoArgs)
+#endif  // FST_EXTENSIONS_PDT_PDTSCRIPT_H_
diff --git a/src/include/fst/extensions/pdt/replace.h b/src/include/fst/extensions/pdt/replace.h
new file mode 100644
index 0000000..a85d0fe
--- /dev/null
+++ b/src/include/fst/extensions/pdt/replace.h
@@ -0,0 +1,192 @@
+// replace.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Recursively replace Fst arcs with other Fst(s) returning a PDT.
+
+#ifndef FST_EXTENSIONS_PDT_REPLACE_H__
+#define FST_EXTENSIONS_PDT_REPLACE_H__
+
+#include <fst/replace.h>
+
+namespace fst {
+
+// Hash to paren IDs
+template <typename S>
+struct ReplaceParenHash {
+  size_t operator()(const pair<size_t, S> &p) const {
+    return p.first + p.second * kPrime;
+  }
+ private:
+  static const size_t kPrime = 7853;
+};
+
+template <typename S> const size_t ReplaceParenHash<S>::kPrime;
+
+// Builds a pushdown transducer (PDT) from an RTN specification
+// identical to that in fst/lib/replace.h. The result is a PDT
+// encoded as the FST 'ofst' where some transitions are labeled with
+// open or close parentheses. To be interpreted as a PDT, the parens
+// must balance on a path (see PdtExpand()). The open/close
+// parenthesis label pairs are returned in 'parens'.
+template <class Arc>
+void Replace(const vector<pair<typename Arc::Label,
+             const Fst<Arc>* > >& ifst_array,
+             MutableFst<Arc> *ofst,
+             vector<pair<typename Arc::Label,
+             typename Arc::Label> > *parens,
+             typename Arc::Label root) {
+  typedef typename Arc::Label Label;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+
+  ofst->DeleteStates();
+  parens->clear();
+
+  unordered_map<Label, size_t> label2id;
+  for (size_t i = 0; i < ifst_array.size(); ++i)
+    label2id[ifst_array[i].first] = i;
+
+  Label max_label = kNoLabel;
+
+  deque<size_t> non_term_queue;  // Queue of non-terminals to replace
+  unordered_set<Label> non_term_set;  // Set of non-terminals to replace
+  non_term_queue.push_back(root);
+  non_term_set.insert(root);
+
+  // PDT state corr. to ith replace FST start state.
+  vector<StateId> fst_start(ifst_array.size(), kNoLabel);
+  // PDT state, weight pairs corr. to ith replace FST final state & weights.
+  vector< vector<pair<StateId, Weight> > > fst_final(ifst_array.size());
+
+  // Builds single Fst combining all referenced input Fsts. Leaves in the
+  // non-termnals for now.  Tabulate the PDT states that correspond to
+  // the start and final states of the input Fsts.
+  for (StateId soff = 0; !non_term_queue.empty(); soff = ofst->NumStates()) {
+    Label label = non_term_queue.front();
+    non_term_queue.pop_front();
+    size_t fst_id = label2id[label];
+
+    const Fst<Arc> *ifst = ifst_array[fst_id].second;
+    for (StateIterator< Fst<Arc> > siter(*ifst);
+         !siter.Done(); siter.Next()) {
+      StateId is = siter.Value();
+      StateId os = ofst->AddState();
+      if (is == ifst->Start()) {
+        fst_start[fst_id] = os;
+        if (label == root)
+          ofst->SetStart(os);
+      }
+      if (ifst->Final(is) != Weight::Zero()) {
+        if (label == root)
+          ofst->SetFinal(os, ifst->Final(is));
+        fst_final[fst_id].push_back(make_pair(os, ifst->Final(is)));
+      }
+      for (ArcIterator< Fst<Arc> > aiter(*ifst, is);
+           !aiter.Done(); aiter.Next()) {
+        Arc arc = aiter.Value();
+        if (max_label == kNoLabel || arc.olabel > max_label)
+          max_label = arc.olabel;
+        typename unordered_map<Label, size_t>::const_iterator it =
+            label2id.find(arc.olabel);
+        if (it != label2id.end()) {
+          size_t nfst_id = it->second;
+          if (ifst_array[nfst_id].second->Start() == -1)
+            continue;
+          if (non_term_set.count(arc.olabel) == 0) {
+            non_term_queue.push_back(arc.olabel);
+            non_term_set.insert(arc.olabel);
+          }
+        }
+        arc.nextstate += soff;
+        ofst->AddArc(os, arc);
+      }
+    }
+  }
+
+  // Changes each non-terminal transition to an open parenthesis
+  // transition redirected to the PDT state that corresponds to the
+  // start state of the input FST for the non-terminal. Adds close parenthesis
+  // transitions from the PDT states corr. to the final states of the
+  // input FST for the non-terminal to the former destination state of the
+  // non-terminal transition.
+
+  typedef MutableArcIterator< MutableFst<Arc> > MIter;
+  typedef unordered_map<pair<size_t, StateId >, size_t,
+                   ReplaceParenHash<StateId> > ParenMap;
+
+  // Parenthesis pair ID per fst, state pair.
+  ParenMap paren_map;
+  // # of parenthesis pairs per fst.
+  vector<size_t> nparens(ifst_array.size(), 0);
+  // Initial open parenthesis label
+  Label first_paren = max_label + 1;
+
+  for (StateIterator< Fst<Arc> > siter(*ofst);
+       !siter.Done(); siter.Next()) {
+    StateId os = siter.Value();
+    MIter *aiter = new MIter(ofst, os);
+    for (size_t n = 0; !aiter->Done(); aiter->Next(), ++n) {
+      Arc arc = aiter->Value();
+      typename unordered_map<Label, size_t>::const_iterator lit =
+          label2id.find(arc.olabel);
+      if (lit != label2id.end()) {
+        size_t nfst_id = lit->second;
+
+        // Get parentheses. Ensures distinct parenthesis pair per
+        // non-terminal and destination state but otherwise reuses them.
+        Label open_paren = kNoLabel, close_paren = kNoLabel;
+        pair<size_t, StateId> paren_key(nfst_id, arc.nextstate);
+        typename ParenMap::const_iterator pit = paren_map.find(paren_key);
+        if (pit != paren_map.end()) {
+          size_t paren_id = pit->second;
+          open_paren = (*parens)[paren_id].first;
+          close_paren = (*parens)[paren_id].second;
+        } else {
+          size_t paren_id = nparens[nfst_id]++;
+          open_paren = first_paren + 2 * paren_id;
+          close_paren = open_paren + 1;
+          paren_map[paren_key] = paren_id;
+          if (paren_id >= parens->size())
+            parens->push_back(make_pair(open_paren, close_paren));
+        }
+
+        // Sets open parenthesis.
+        Arc sarc(open_paren, open_paren, arc.weight, fst_start[nfst_id]);
+        aiter->SetValue(sarc);
+
+        // Adds close parentheses.
+        for (size_t i = 0; i < fst_final[nfst_id].size(); ++i) {
+          pair<StateId, Weight> &p = fst_final[nfst_id][i];
+          Arc farc(close_paren, close_paren, p.second, arc.nextstate);
+
+          ofst->AddArc(p.first, farc);
+          if (os == p.first) {  // Invalidated iterator
+            delete aiter;
+            aiter = new MIter(ofst, os);
+            aiter->Seek(n);
+          }
+        }
+      }
+    }
+    delete aiter;
+  }
+}
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_PDT_REPLACE_H__
diff --git a/src/include/fst/extensions/pdt/reverse.h b/src/include/fst/extensions/pdt/reverse.h
new file mode 100644
index 0000000..b20e1c5
--- /dev/null
+++ b/src/include/fst/extensions/pdt/reverse.h
@@ -0,0 +1,58 @@
+// reverse.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Expand a PDT to an FST.
+
+#ifndef FST_EXTENSIONS_PDT_REVERSE_H__
+#define FST_EXTENSIONS_PDT_REVERSE_H__
+
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <vector>
+using std::vector;
+
+#include <fst/mutable-fst.h>
+#include <fst/relabel.h>
+#include <fst/reverse.h>
+
+namespace fst {
+
+// Reverses a pushdown transducer (PDT) encoded as an FST.
+template<class Arc, class RevArc>
+void Reverse(const Fst<Arc> &ifst,
+             const vector<pair<typename Arc::Label,
+             typename Arc::Label> > &parens,
+             MutableFst<RevArc> *ofst) {
+  typedef typename Arc::Label Label;
+
+  // Reverses FST
+  Reverse(ifst, ofst);
+
+  // Exchanges open and close parenthesis pairs
+  vector<pair<Label, Label> > relabel_pairs;
+  for (size_t i = 0; i < parens.size(); ++i) {
+    relabel_pairs.push_back(make_pair(parens[i].first, parens[i].second));
+    relabel_pairs.push_back(make_pair(parens[i].second, parens[i].first));
+  }
+  Relabel(ofst, relabel_pairs, relabel_pairs);
+}
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_PDT_REVERSE_H__
diff --git a/src/include/fst/extensions/pdt/shortest-path.h b/src/include/fst/extensions/pdt/shortest-path.h
new file mode 100644
index 0000000..e90471b
--- /dev/null
+++ b/src/include/fst/extensions/pdt/shortest-path.h
@@ -0,0 +1,790 @@
+// shortest-path.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Functions to find shortest paths in a PDT.
+
+#ifndef FST_EXTENSIONS_PDT_SHORTEST_PATH_H__
+#define FST_EXTENSIONS_PDT_SHORTEST_PATH_H__
+
+#include <fst/shortest-path.h>
+#include <fst/extensions/pdt/paren.h>
+#include <fst/extensions/pdt/pdt.h>
+
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <tr1/unordered_set>
+using std::tr1::unordered_set;
+using std::tr1::unordered_multiset;
+#include <stack>
+#include <vector>
+using std::vector;
+
+namespace fst {
+
+template <class Arc, class Queue>
+struct PdtShortestPathOptions {
+  bool keep_parentheses;
+  bool path_gc;
+
+  PdtShortestPathOptions(bool kp = false, bool gc = true)
+      : keep_parentheses(kp), path_gc(gc) {}
+};
+
+
+// Class to store PDT shortest path results. Stores shortest path
+// tree info 'Distance()', Parent(), and ArcParent() information keyed
+// on two types:
+// (1) By SearchState: This is a usual node in a shortest path tree but:
+//    (a) is w.r.t a PDT search state - a pair of a PDT state and
+//        a 'start' state, which is either the PDT start state or
+//        the destination state of an open parenthesis.
+//    (b) the Distance() is from this 'start' state to the search state.
+//    (c) Parent().state is kNoLabel for the 'start' state.
+//
+// (2) By ParenSpec: This connects shortest path trees depending on the
+// the parenthesis taken. Given the parenthesis spec:
+//    (a) the Distance() is from the Parent() 'start' state to the
+//     parenthesis destination state.
+//    (b) the ArcParent() is the parenthesis arc.
+template <class Arc>
+class PdtShortestPathData {
+ public:
+  static const uint8 kFinal;
+
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::Label Label;
+
+  struct SearchState {
+    SearchState() : state(kNoStateId), start(kNoStateId) {}
+
+    SearchState(StateId s, StateId t) : state(s), start(t) {}
+
+    bool operator==(const SearchState &s) const {
+      if (&s == this)
+        return true;
+      return s.state == this->state && s.start == this->start;
+    }
+
+    StateId state;  // PDT state
+    StateId start;  // PDT paren 'source' state
+  };
+
+
+  // Specifies paren id, source and dest 'start' states of a paren.
+  // These are the 'start' states of the respective sub-graphs.
+  struct ParenSpec {
+    ParenSpec()
+        : paren_id(kNoLabel), src_start(kNoStateId), dest_start(kNoStateId) {}
+
+    ParenSpec(Label id, StateId s, StateId d)
+        : paren_id(id), src_start(s), dest_start(d) {}
+
+    Label paren_id;        // Id of parenthesis
+    StateId src_start;     // sub-graph 'start' state for paren source.
+    StateId dest_start;    // sub-graph 'start' state for paren dest.
+
+    bool operator==(const ParenSpec &x) const {
+      if (&x == this)
+        return true;
+      return x.paren_id == this->paren_id &&
+          x.src_start == this->src_start &&
+          x.dest_start == this->dest_start;
+    }
+  };
+
+  struct SearchData {
+    SearchData() : distance(Weight::Zero()),
+                   parent(kNoStateId, kNoStateId),
+                   paren_id(kNoLabel),
+                   flags(0) {}
+
+    Weight distance;     // Distance to this state from PDT 'start' state
+    SearchState parent;  // Parent state in shortest path tree
+    int16 paren_id;      // If parent arc has paren, paren ID, o.w. kNoLabel
+    uint8 flags;         // First byte reserved for PdtShortestPathData use
+  };
+
+  PdtShortestPathData(bool gc)
+      : state_(kNoStateId, kNoStateId),
+        paren_(kNoLabel, kNoStateId, kNoStateId),
+        gc_(gc),
+        nstates_(0),
+        ngc_(0),
+        finished_(false) {}
+
+  ~PdtShortestPathData() {
+    VLOG(1) << "opm size: " << paren_map_.size();
+    VLOG(1) << "# of search states: " << nstates_;
+    if (gc_)
+      VLOG(1) << "# of GC'd search states: " << ngc_;
+  }
+
+  void Clear() {
+    search_map_.clear();
+    search_multimap_.clear();
+    paren_map_.clear();
+    state_ = SearchState(kNoStateId, kNoStateId);
+    nstates_ = 0;
+    ngc_ = 0;
+  }
+
+  Weight Distance(SearchState s) const {
+    SearchData *data = GetSearchData(s);
+    return data->distance;
+  }
+
+  Weight Distance(const ParenSpec &paren) const {
+    SearchData *data = GetSearchData(paren);
+    return data->distance;
+  }
+
+  SearchState Parent(SearchState s) const {
+    SearchData *data = GetSearchData(s);
+    return data->parent;
+  }
+
+  SearchState Parent(const ParenSpec &paren) const {
+    SearchData *data = GetSearchData(paren);
+    return data->parent;
+  }
+
+  Label ParenId(SearchState s) const {
+    SearchData *data = GetSearchData(s);
+    return data->paren_id;
+  }
+
+  uint8 Flags(SearchState s) const {
+    SearchData *data = GetSearchData(s);
+    return data->flags;
+  }
+
+  void SetDistance(SearchState s, Weight w) {
+    SearchData *data = GetSearchData(s);
+    data->distance = w;
+  }
+
+  void SetDistance(const ParenSpec &paren, Weight w) {
+    SearchData *data = GetSearchData(paren);
+    data->distance = w;
+  }
+
+  void SetParent(SearchState s, SearchState p) {
+    SearchData *data = GetSearchData(s);
+    data->parent = p;
+  }
+
+  void SetParent(const ParenSpec &paren, SearchState p) {
+    SearchData *data = GetSearchData(paren);
+    data->parent = p;
+  }
+
+  void SetParenId(SearchState s, Label p) {
+    if (p >= 32768)
+      FSTERROR() << "PdtShortestPathData: Paren ID does not fits in an int16";
+    SearchData *data = GetSearchData(s);
+    data->paren_id = p;
+  }
+
+  void SetFlags(SearchState s, uint8 f, uint8 mask) {
+    SearchData *data = GetSearchData(s);
+    data->flags &= ~mask;
+    data->flags |= f & mask;
+  }
+
+  void GC(StateId s);
+
+  void Finish() { finished_ = true; }
+
+ private:
+  static const Arc kNoArc;
+  static const size_t kPrime0;
+  static const size_t kPrime1;
+  static const uint8 kInited;
+  static const uint8 kMarked;
+
+  // Hash for search state
+  struct SearchStateHash {
+    size_t operator()(const SearchState &s) const {
+      return s.state + s.start * kPrime0;
+    }
+  };
+
+  // Hash for paren map
+  struct ParenHash {
+    size_t operator()(const ParenSpec &paren) const {
+      return paren.paren_id + paren.src_start * kPrime0 +
+          paren.dest_start * kPrime1;
+    }
+  };
+
+  typedef unordered_map<SearchState, SearchData, SearchStateHash> SearchMap;
+
+  typedef unordered_multimap<StateId, StateId> SearchMultimap;
+
+  // Hash map from paren spec to open paren data
+  typedef unordered_map<ParenSpec, SearchData, ParenHash> ParenMap;
+
+  SearchData *GetSearchData(SearchState s) const {
+    if (s == state_)
+      return state_data_;
+    if (finished_) {
+      typename SearchMap::iterator it = search_map_.find(s);
+      if (it == search_map_.end())
+        return &null_search_data_;
+      state_ = s;
+      return state_data_ = &(it->second);
+    } else {
+      state_ = s;
+      state_data_ = &search_map_[s];
+      if (!(state_data_->flags & kInited)) {
+        ++nstates_;
+        if (gc_)
+          search_multimap_.insert(make_pair(s.start, s.state));
+        state_data_->flags = kInited;
+      }
+      return state_data_;
+    }
+  }
+
+  SearchData *GetSearchData(ParenSpec paren) const {
+    if (paren == paren_)
+      return paren_data_;
+    if (finished_) {
+      typename ParenMap::iterator it = paren_map_.find(paren);
+      if (it == paren_map_.end())
+        return &null_search_data_;
+      paren_ = paren;
+      return state_data_ = &(it->second);
+    } else {
+      paren_ = paren;
+      return paren_data_ = &paren_map_[paren];
+    }
+  }
+
+  mutable SearchMap search_map_;            // Maps from search state to data
+  mutable SearchMultimap search_multimap_;  // Maps from 'start' to subgraph
+  mutable ParenMap paren_map_;              // Maps paren spec to search data
+  mutable SearchState state_;               // Last state accessed
+  mutable SearchData *state_data_;          // Last state data accessed
+  mutable ParenSpec paren_;                 // Last paren spec accessed
+  mutable SearchData *paren_data_;          // Last paren data accessed
+  bool gc_;                                 // Allow GC?
+  mutable size_t nstates_;                  // Total number of search states
+  size_t ngc_;                              // Number of GC'd search states
+  mutable SearchData null_search_data_;     // Null search data
+  bool finished_;                           // Read-only access when true
+
+  DISALLOW_COPY_AND_ASSIGN(PdtShortestPathData);
+};
+
+// Deletes inaccessible search data from a given 'start' (open paren dest)
+// state. Assumes 'final' (close paren source or PDT final) states have
+// been flagged 'kFinal'.
+template<class Arc>
+void  PdtShortestPathData<Arc>::GC(StateId start) {
+  if (!gc_)
+    return;
+  vector<StateId> final;
+  for (typename SearchMultimap::iterator mmit = search_multimap_.find(start);
+       mmit != search_multimap_.end() && mmit->first == start;
+       ++mmit) {
+    SearchState s(mmit->second, start);
+    const SearchData &data = search_map_[s];
+    if (data.flags & kFinal)
+      final.push_back(s.state);
+  }
+
+  // Mark phase
+  for (size_t i = 0; i < final.size(); ++i) {
+    SearchState s(final[i], start);
+    while (s.state != kNoLabel) {
+      SearchData *sdata = &search_map_[s];
+      if (sdata->flags & kMarked)
+        break;
+      sdata->flags |= kMarked;
+      SearchState p = sdata->parent;
+      if (p.start != start && p.start != kNoLabel) {  // entering sub-subgraph
+        ParenSpec paren(sdata->paren_id, s.start, p.start);
+        SearchData *pdata = &paren_map_[paren];
+        s = pdata->parent;
+      } else {
+        s = p;
+      }
+    }
+  }
+
+  // Sweep phase
+  typename SearchMultimap::iterator mmit = search_multimap_.find(start);
+  while (mmit != search_multimap_.end() && mmit->first == start) {
+    SearchState s(mmit->second, start);
+    typename SearchMap::iterator mit = search_map_.find(s);
+    const SearchData &data = mit->second;
+    if (!(data.flags & kMarked)) {
+      search_map_.erase(mit);
+      ++ngc_;
+    }
+    search_multimap_.erase(mmit++);
+  }
+}
+
+template<class Arc> const Arc PdtShortestPathData<Arc>::kNoArc
+    = Arc(kNoLabel, kNoLabel, Weight::Zero(), kNoStateId);
+
+template<class Arc> const size_t PdtShortestPathData<Arc>::kPrime0 = 7853;
+
+template<class Arc> const size_t PdtShortestPathData<Arc>::kPrime1 = 7867;
+
+template<class Arc> const uint8 PdtShortestPathData<Arc>::kInited = 0x01;
+
+template<class Arc> const uint8 PdtShortestPathData<Arc>::kFinal =  0x02;
+
+template<class Arc> const uint8 PdtShortestPathData<Arc>::kMarked = 0x04;
+
+
+// This computes the single source shortest (balanced) path (SSSP)
+// through a weighted PDT that has a bounded stack (i.e. is expandable
+// as an FST). It is a generalization of the classic SSSP graph
+// algorithm that removes a state s from a queue (defined by a
+// user-provided queue type) and relaxes the destination states of
+// transitions leaving s. In this PDT version, states that have
+// entering open parentheses are treated as source states for a
+// sub-graph SSSP problem with the shortest path up to the open
+// parenthesis being first saved. When a close parenthesis is then
+// encountered any balancing open parenthesis is examined for this
+// saved information and multiplied back. In this way, each sub-graph
+// is entered only once rather than repeatedly.  If every state in the
+// input PDT has the property that there is a unique 'start' state for
+// it with entering open parentheses, then this algorithm is quite
+// straight-forward. In general, this will not be the case, so the
+// algorithm (implicitly) creates a new graph where each state is a
+// pair of an original state and a possible parenthesis 'start' state
+// for that state.
+template<class Arc, class Queue>
+class PdtShortestPath {
+ public:
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::Label Label;
+
+  typedef PdtShortestPathData<Arc> SpData;
+  typedef typename SpData::SearchState SearchState;
+  typedef typename SpData::ParenSpec ParenSpec;
+
+  typedef typename PdtParenReachable<Arc>::SetIterator StateSetIterator;
+  typedef typename PdtBalanceData<Arc>::SetIterator CloseSourceIterator;
+
+  PdtShortestPath(const Fst<Arc> &ifst,
+                  const vector<pair<Label, Label> > &parens,
+                  const PdtShortestPathOptions<Arc, Queue> &opts)
+      : kFinal(SpData::kFinal),
+        ifst_(ifst.Copy()),
+        parens_(parens),
+        keep_parens_(opts.keep_parentheses),
+        start_(ifst.Start()),
+        sp_data_(opts.path_gc),
+        error_(false) {
+
+    if ((Weight::Properties() & (kPath | kRightSemiring))
+        != (kPath | kRightSemiring)) {
+      FSTERROR() << "SingleShortestPath: Weight needs to have the path"
+                 << " property and be right distributive: " << Weight::Type();
+      error_ = true;
+    }
+
+    for (Label i = 0; i < parens.size(); ++i) {
+      const pair<Label, Label>  &p = parens[i];
+      paren_id_map_[p.first] = i;
+      paren_id_map_[p.second] = i;
+    }
+  };
+
+  ~PdtShortestPath() {
+    VLOG(1) << "# of input states: " << CountStates(*ifst_);
+    VLOG(1) << "# of enqueued: " << nenqueued_;
+    VLOG(1) << "cpmm size: " << close_paren_multimap_.size();
+    delete ifst_;
+  }
+
+  void ShortestPath(MutableFst<Arc> *ofst) {
+    Init(ofst);
+    GetDistance(start_);
+    GetPath();
+    sp_data_.Finish();
+    if (error_) ofst->SetProperties(kError, kError);
+  }
+
+  const PdtShortestPathData<Arc> &GetShortestPathData() const {
+    return sp_data_;
+  }
+
+  PdtBalanceData<Arc> *GetBalanceData() { return &balance_data_; }
+
+ private:
+  static const Arc kNoArc;
+  static const uint8 kEnqueued;
+  static const uint8 kExpanded;
+  const uint8 kFinal;
+
+ public:
+  // Hash multimap from close paren label to an paren arc.
+  typedef unordered_multimap<ParenState<Arc>, Arc,
+                        typename ParenState<Arc>::Hash> CloseParenMultimap;
+
+  const CloseParenMultimap &GetCloseParenMultimap() const {
+    return close_paren_multimap_;
+  }
+
+ private:
+  void Init(MutableFst<Arc> *ofst);
+  void GetDistance(StateId start);
+  void ProcFinal(SearchState s);
+  void ProcArcs(SearchState s);
+  void ProcOpenParen(Label paren_id, SearchState s, Arc arc, Weight w);
+  void ProcCloseParen(Label paren_id, SearchState s, const Arc &arc, Weight w);
+  void ProcNonParen(SearchState s, const Arc &arc, Weight w);
+  void Relax(SearchState s, SearchState t, Arc arc, Weight w, Label paren_id);
+  void Enqueue(SearchState d);
+  void GetPath();
+  Arc GetPathArc(SearchState s, SearchState p, Label paren_id, bool open);
+
+  Fst<Arc> *ifst_;
+  MutableFst<Arc> *ofst_;
+  const vector<pair<Label, Label> > &parens_;
+  bool keep_parens_;
+  Queue *state_queue_;                   // current state queue
+  StateId start_;
+  Weight f_distance_;
+  SearchState f_parent_;
+  SpData sp_data_;
+  unordered_map<Label, Label> paren_id_map_;
+  CloseParenMultimap close_paren_multimap_;
+  PdtBalanceData<Arc> balance_data_;
+  ssize_t nenqueued_;
+  bool error_;
+
+  DISALLOW_COPY_AND_ASSIGN(PdtShortestPath);
+};
+
+template<class Arc, class Queue>
+void PdtShortestPath<Arc, Queue>::Init(MutableFst<Arc> *ofst) {
+  ofst_ = ofst;
+  ofst->DeleteStates();
+  ofst->SetInputSymbols(ifst_->InputSymbols());
+  ofst->SetOutputSymbols(ifst_->OutputSymbols());
+
+  if (ifst_->Start() == kNoStateId)
+    return;
+
+  f_distance_ = Weight::Zero();
+  f_parent_ = SearchState(kNoStateId, kNoStateId);
+
+  sp_data_.Clear();
+  close_paren_multimap_.clear();
+  balance_data_.Clear();
+  nenqueued_ = 0;
+
+  // Find open parens per destination state and close parens per source state.
+  for (StateIterator<Fst<Arc> > siter(*ifst_); !siter.Done(); siter.Next()) {
+    StateId s = siter.Value();
+    for (ArcIterator<Fst<Arc> > aiter(*ifst_, s);
+         !aiter.Done(); aiter.Next()) {
+      const Arc &arc = aiter.Value();
+      typename unordered_map<Label, Label>::const_iterator pit
+          = paren_id_map_.find(arc.ilabel);
+      if (pit != paren_id_map_.end()) {               // Is a paren?
+        Label paren_id = pit->second;
+        if (arc.ilabel == parens_[paren_id].first) {  // Open paren
+          balance_data_.OpenInsert(paren_id, arc.nextstate);
+        } else {                                      // Close paren
+          ParenState<Arc> paren_state(paren_id, s);
+          close_paren_multimap_.insert(make_pair(paren_state, arc));
+        }
+      }
+    }
+  }
+}
+
+// Computes the shortest distance stored in a recursive way. Each
+// sub-graph (i.e. different paren 'start' state) begins with weight One().
+template<class Arc, class Queue>
+void PdtShortestPath<Arc, Queue>::GetDistance(StateId start) {
+  if (start == kNoStateId)
+    return;
+
+  Queue state_queue;
+  state_queue_ = &state_queue;
+  SearchState q(start, start);
+  Enqueue(q);
+  sp_data_.SetDistance(q, Weight::One());
+
+  while (!state_queue_->Empty()) {
+    StateId state = state_queue_->Head();
+    state_queue_->Dequeue();
+    SearchState s(state, start);
+    sp_data_.SetFlags(s, 0, kEnqueued);
+    ProcFinal(s);
+    ProcArcs(s);
+    sp_data_.SetFlags(s, kExpanded, kExpanded);
+  }
+  balance_data_.FinishInsert(start);
+  sp_data_.GC(start);
+}
+
+// Updates best complete path.
+template<class Arc, class Queue>
+void PdtShortestPath<Arc, Queue>::ProcFinal(SearchState s) {
+  if (ifst_->Final(s.state) != Weight::Zero() && s.start == start_) {
+    Weight w = Times(sp_data_.Distance(s),
+                     ifst_->Final(s.state));
+    if (f_distance_ != Plus(f_distance_, w)) {
+      if (f_parent_.state != kNoStateId)
+        sp_data_.SetFlags(f_parent_, 0, kFinal);
+      sp_data_.SetFlags(s, kFinal, kFinal);
+
+      f_distance_ = Plus(f_distance_, w);
+      f_parent_ = s;
+    }
+  }
+}
+
+// Processes all arcs leaving the state s.
+template<class Arc, class Queue>
+void PdtShortestPath<Arc, Queue>::ProcArcs(SearchState s) {
+  for (ArcIterator< Fst<Arc> > aiter(*ifst_, s.state);
+       !aiter.Done();
+       aiter.Next()) {
+    Arc arc = aiter.Value();
+    Weight w = Times(sp_data_.Distance(s), arc.weight);
+
+    typename unordered_map<Label, Label>::const_iterator pit
+        = paren_id_map_.find(arc.ilabel);
+    if (pit != paren_id_map_.end()) {  // Is a paren?
+      Label paren_id = pit->second;
+      if (arc.ilabel == parens_[paren_id].first)
+        ProcOpenParen(paren_id, s, arc, w);
+      else
+        ProcCloseParen(paren_id, s, arc, w);
+    } else {
+      ProcNonParen(s, arc, w);
+    }
+  }
+}
+
+// Saves the shortest path info for reaching this parenthesis
+// and starts a new SSSP in the sub-graph pointed to by the parenthesis
+// if previously unvisited. Otherwise it finds any previously encountered
+// closing parentheses and relaxes them using the recursively stored
+// shortest distance to them.
+template<class Arc, class Queue> inline
+void PdtShortestPath<Arc, Queue>::ProcOpenParen(
+    Label paren_id, SearchState s, Arc arc, Weight w) {
+
+  SearchState d(arc.nextstate, arc.nextstate);
+  ParenSpec paren(paren_id, s.start, d.start);
+  Weight pdist = sp_data_.Distance(paren);
+  if (pdist != Plus(pdist, w)) {
+    sp_data_.SetDistance(paren, w);
+    sp_data_.SetParent(paren, s);
+    Weight dist = sp_data_.Distance(d);
+    if (dist == Weight::Zero()) {
+      Queue *state_queue = state_queue_;
+      GetDistance(d.start);
+      state_queue_ = state_queue;
+    }
+    for (CloseSourceIterator set_iter =
+             balance_data_.Find(paren_id, arc.nextstate);
+         !set_iter.Done(); set_iter.Next()) {
+      SearchState cpstate(set_iter.Element(), d.start);
+      ParenState<Arc> paren_state(paren_id, cpstate.state);
+      for (typename CloseParenMultimap::const_iterator cpit =
+               close_paren_multimap_.find(paren_state);
+           cpit != close_paren_multimap_.end() && paren_state == cpit->first;
+           ++cpit) {
+        const Arc &cparc = cpit->second;
+        Weight cpw = Times(w, Times(sp_data_.Distance(cpstate),
+                                    cparc.weight));
+        Relax(cpstate, s, cparc, cpw, paren_id);
+      }
+    }
+  }
+}
+
+// Saves the correspondence between each closing parenthesis and its
+// balancing open parenthesis info. Relaxes any close parenthesis
+// destination state that has a balancing previously encountered open
+// parenthesis.
+template<class Arc, class Queue> inline
+void PdtShortestPath<Arc, Queue>::ProcCloseParen(
+    Label paren_id, SearchState s, const Arc &arc, Weight w) {
+  ParenState<Arc> paren_state(paren_id, s.start);
+  if (!(sp_data_.Flags(s) & kExpanded)) {
+    balance_data_.CloseInsert(paren_id, s.start, s.state);
+    sp_data_.SetFlags(s, kFinal, kFinal);
+  }
+}
+
+// For non-parentheses, classical relaxation.
+template<class Arc, class Queue> inline
+void PdtShortestPath<Arc, Queue>::ProcNonParen(
+    SearchState s, const Arc &arc, Weight w) {
+  Relax(s, s, arc, w, kNoLabel);
+}
+
+// Classical relaxation on the search graph for 'arc' from state 's'.
+// State 't' is in the same sub-graph as the nextstate should be (i.e.
+// has the same paren 'start'.
+template<class Arc, class Queue> inline
+void PdtShortestPath<Arc, Queue>::Relax(
+    SearchState s, SearchState t, Arc arc, Weight w, Label paren_id) {
+  SearchState d(arc.nextstate, t.start);
+  Weight dist = sp_data_.Distance(d);
+  if (dist != Plus(dist, w)) {
+    sp_data_.SetParent(d, s);
+    sp_data_.SetParenId(d, paren_id);
+    sp_data_.SetDistance(d, Plus(dist, w));
+    Enqueue(d);
+  }
+}
+
+template<class Arc, class Queue> inline
+void PdtShortestPath<Arc, Queue>::Enqueue(SearchState s) {
+  if (!(sp_data_.Flags(s) & kEnqueued)) {
+    state_queue_->Enqueue(s.state);
+    sp_data_.SetFlags(s, kEnqueued, kEnqueued);
+    ++nenqueued_;
+  } else {
+    state_queue_->Update(s.state);
+  }
+}
+
+// Follows parent pointers to find the shortest path. Uses a stack
+// since the shortest distance is stored recursively.
+template<class Arc, class Queue>
+void PdtShortestPath<Arc, Queue>::GetPath() {
+  SearchState s = f_parent_, d = SearchState(kNoStateId, kNoStateId);
+  StateId s_p = kNoStateId, d_p = kNoStateId;
+  Arc arc(kNoArc);
+  Label paren_id = kNoLabel;
+  stack<ParenSpec> paren_stack;
+  while (s.state != kNoStateId) {
+    d_p = s_p;
+    s_p = ofst_->AddState();
+    if (d.state == kNoStateId) {
+      ofst_->SetFinal(s_p, ifst_->Final(f_parent_.state));
+    } else {
+      if (paren_id != kNoLabel) {                     // paren?
+        if (arc.ilabel == parens_[paren_id].first) {  // open paren
+          paren_stack.pop();
+        } else {                                      // close paren
+          ParenSpec paren(paren_id, d.start, s.start);
+          paren_stack.push(paren);
+        }
+        if (!keep_parens_)
+          arc.ilabel = arc.olabel = 0;
+      }
+      arc.nextstate = d_p;
+      ofst_->AddArc(s_p, arc);
+    }
+    d = s;
+    s = sp_data_.Parent(d);
+    paren_id = sp_data_.ParenId(d);
+    if (s.state != kNoStateId) {
+      arc = GetPathArc(s, d, paren_id, false);
+    } else if (!paren_stack.empty()) {
+      ParenSpec paren = paren_stack.top();
+      s = sp_data_.Parent(paren);
+      paren_id = paren.paren_id;
+      arc = GetPathArc(s, d, paren_id, true);
+    }
+  }
+  ofst_->SetStart(s_p);
+  ofst_->SetProperties(
+      ShortestPathProperties(ofst_->Properties(kFstProperties, false)),
+      kFstProperties);
+}
+
+
+// Finds transition with least weight between two states with label matching
+// paren_id and open/close paren type or a non-paren if kNoLabel.
+template<class Arc, class Queue>
+Arc PdtShortestPath<Arc, Queue>::GetPathArc(
+    SearchState s, SearchState d, Label paren_id, bool open_paren) {
+  Arc path_arc = kNoArc;
+  for (ArcIterator< Fst<Arc> > aiter(*ifst_, s.state);
+       !aiter.Done();
+       aiter.Next()) {
+    const Arc &arc = aiter.Value();
+    if (arc.nextstate != d.state)
+      continue;
+    Label arc_paren_id = kNoLabel;
+    typename unordered_map<Label, Label>::const_iterator pit
+        = paren_id_map_.find(arc.ilabel);
+    if (pit != paren_id_map_.end()) {
+      arc_paren_id = pit->second;
+      bool arc_open_paren = arc.ilabel == parens_[arc_paren_id].first;
+      if (arc_open_paren != open_paren)
+        continue;
+    }
+    if (arc_paren_id != paren_id)
+      continue;
+    if (arc.weight == Plus(arc.weight, path_arc.weight))
+      path_arc = arc;
+  }
+  if (path_arc.nextstate == kNoStateId) {
+    FSTERROR() << "PdtShortestPath::GetPathArc failed to find arc";
+    error_ = true;
+  }
+  return path_arc;
+}
+
+template<class Arc, class Queue>
+const Arc PdtShortestPath<Arc, Queue>::kNoArc
+    = Arc(kNoLabel, kNoLabel, Weight::Zero(), kNoStateId);
+
+template<class Arc, class Queue>
+const uint8 PdtShortestPath<Arc, Queue>::kEnqueued = 0x10;
+
+template<class Arc, class Queue>
+const uint8 PdtShortestPath<Arc, Queue>::kExpanded = 0x20;
+
+template<class Arc, class Queue>
+void ShortestPath(const Fst<Arc> &ifst,
+                  const vector<pair<typename Arc::Label,
+                                    typename Arc::Label> > &parens,
+                  MutableFst<Arc> *ofst,
+                  const PdtShortestPathOptions<Arc, Queue> &opts) {
+  PdtShortestPath<Arc, Queue> psp(ifst, parens, opts);
+  psp.ShortestPath(ofst);
+}
+
+template<class Arc>
+void ShortestPath(const Fst<Arc> &ifst,
+                  const vector<pair<typename Arc::Label,
+                                    typename Arc::Label> > &parens,
+                  MutableFst<Arc> *ofst) {
+  typedef FifoQueue<typename Arc::StateId> Queue;
+  PdtShortestPathOptions<Arc, Queue> opts;
+  PdtShortestPath<Arc, Queue> psp(ifst, parens, opts);
+  psp.ShortestPath(ofst);
+}
+
+}  // namespace fst
+
+#endif  // FST_EXTENSIONS_PDT_SHORTEST_PATH_H__
diff --git a/src/include/fst/factor-weight.h b/src/include/fst/factor-weight.h
new file mode 100644
index 0000000..ce0d58d
--- /dev/null
+++ b/src/include/fst/factor-weight.h
@@ -0,0 +1,476 @@
+// factor-weight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Classes to factor weights in an FST.
+
+#ifndef FST_LIB_FACTOR_WEIGHT_H__
+#define FST_LIB_FACTOR_WEIGHT_H__
+
+#include <algorithm>
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <fst/slist.h>
+#include <string>
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+#include <fst/test-properties.h>
+
+
+namespace fst {
+
+const uint32 kFactorFinalWeights = 0x00000001;
+const uint32 kFactorArcWeights   = 0x00000002;
+
+template <class Arc>
+struct FactorWeightOptions : CacheOptions {
+  typedef typename Arc::Label Label;
+  float delta;
+  uint32 mode;         // factor arc weights and/or final weights
+  Label final_ilabel;  // input label of arc created when factoring final w's
+  Label final_olabel;  // output label of arc created when factoring final w's
+
+  FactorWeightOptions(const CacheOptions &opts, float d,
+                      uint32 m = kFactorArcWeights | kFactorFinalWeights,
+                      Label il = 0, Label ol = 0)
+      : CacheOptions(opts), delta(d), mode(m), final_ilabel(il),
+        final_olabel(ol) {}
+
+  explicit FactorWeightOptions(
+      float d, uint32 m = kFactorArcWeights | kFactorFinalWeights,
+      Label il = 0, Label ol = 0)
+      : delta(d), mode(m), final_ilabel(il), final_olabel(ol) {}
+
+  FactorWeightOptions(uint32 m = kFactorArcWeights | kFactorFinalWeights,
+                      Label il = 0, Label ol = 0)
+      : delta(kDelta), mode(m), final_ilabel(il), final_olabel(ol) {}
+};
+
+
+// A factor iterator takes as argument a weight w and returns a
+// sequence of pairs of weights (xi,yi) such that the sum of the
+// products xi times yi is equal to w. If w is fully factored,
+// the iterator should return nothing.
+//
+// template <class W>
+// class FactorIterator {
+//  public:
+//   FactorIterator(W w);
+//   bool Done() const;
+//   void Next();
+//   pair<W, W> Value() const;
+//   void Reset();
+// }
+
+
+// Factor trivially.
+template <class W>
+class IdentityFactor {
+ public:
+  IdentityFactor(const W &w) {}
+  bool Done() const { return true; }
+  void Next() {}
+  pair<W, W> Value() const { return make_pair(W::One(), W::One()); } // unused
+  void Reset() {}
+};
+
+
+// Factor a StringWeight w as 'ab' where 'a' is a label.
+template <typename L, StringType S = STRING_LEFT>
+class StringFactor {
+ public:
+  StringFactor(const StringWeight<L, S> &w)
+      : weight_(w), done_(w.Size() <= 1) {}
+
+  bool Done() const { return done_; }
+
+  void Next() { done_ = true; }
+
+  pair< StringWeight<L, S>, StringWeight<L, S> > Value() const {
+    StringWeightIterator<L, S> iter(weight_);
+    StringWeight<L, S> w1(iter.Value());
+    StringWeight<L, S> w2;
+    for (iter.Next(); !iter.Done(); iter.Next())
+      w2.PushBack(iter.Value());
+    return make_pair(w1, w2);
+  }
+
+  void Reset() { done_ = weight_.Size() <= 1; }
+
+ private:
+  StringWeight<L, S> weight_;
+  bool done_;
+};
+
+
+// Factor a GallicWeight using StringFactor.
+template <class L, class W, StringType S = STRING_LEFT>
+class GallicFactor {
+ public:
+  GallicFactor(const GallicWeight<L, W, S> &w)
+      : weight_(w), done_(w.Value1().Size() <= 1) {}
+
+  bool Done() const { return done_; }
+
+  void Next() { done_ = true; }
+
+  pair< GallicWeight<L, W, S>, GallicWeight<L, W, S> > Value() const {
+    StringFactor<L, S> iter(weight_.Value1());
+    GallicWeight<L, W, S> w1(iter.Value().first, weight_.Value2());
+    GallicWeight<L, W, S> w2(iter.Value().second, W::One());
+    return make_pair(w1, w2);
+  }
+
+  void Reset() { done_ = weight_.Value1().Size() <= 1; }
+
+ private:
+  GallicWeight<L, W, S> weight_;
+  bool done_;
+};
+
+
+// Implementation class for FactorWeight
+template <class A, class F>
+class FactorWeightFstImpl
+    : public CacheImpl<A> {
+ public:
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+
+  using CacheBaseImpl< CacheState<A> >::PushArc;
+  using CacheBaseImpl< CacheState<A> >::HasStart;
+  using CacheBaseImpl< CacheState<A> >::HasFinal;
+  using CacheBaseImpl< CacheState<A> >::HasArcs;
+  using CacheBaseImpl< CacheState<A> >::SetArcs;
+  using CacheBaseImpl< CacheState<A> >::SetFinal;
+  using CacheBaseImpl< CacheState<A> >::SetStart;
+
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef F FactorIterator;
+
+  struct Element {
+    Element() {}
+
+    Element(StateId s, Weight w) : state(s), weight(w) {}
+
+    StateId state;     // Input state Id
+    Weight weight;     // Residual weight
+  };
+
+  FactorWeightFstImpl(const Fst<A> &fst, const FactorWeightOptions<A> &opts)
+      : CacheImpl<A>(opts),
+        fst_(fst.Copy()),
+        delta_(opts.delta),
+        mode_(opts.mode),
+        final_ilabel_(opts.final_ilabel),
+        final_olabel_(opts.final_olabel) {
+    SetType("factor_weight");
+    uint64 props = fst.Properties(kFstProperties, false);
+    SetProperties(FactorWeightProperties(props), kCopyProperties);
+
+    SetInputSymbols(fst.InputSymbols());
+    SetOutputSymbols(fst.OutputSymbols());
+
+    if (mode_ == 0)
+      LOG(WARNING) << "FactorWeightFst: factor mode is set to 0: "
+                   << "factoring neither arc weights nor final weights.";
+  }
+
+  FactorWeightFstImpl(const FactorWeightFstImpl<A, F> &impl)
+      : CacheImpl<A>(impl),
+        fst_(impl.fst_->Copy(true)),
+        delta_(impl.delta_),
+        mode_(impl.mode_),
+        final_ilabel_(impl.final_ilabel_),
+        final_olabel_(impl.final_olabel_) {
+    SetType("factor_weight");
+    SetProperties(impl.Properties(), kCopyProperties);
+    SetInputSymbols(impl.InputSymbols());
+    SetOutputSymbols(impl.OutputSymbols());
+  }
+
+  ~FactorWeightFstImpl() {
+    delete fst_;
+  }
+
+  StateId Start() {
+    if (!HasStart()) {
+      StateId s = fst_->Start();
+      if (s == kNoStateId)
+        return kNoStateId;
+      StateId start = FindState(Element(fst_->Start(), Weight::One()));
+      SetStart(start);
+    }
+    return CacheImpl<A>::Start();
+  }
+
+  Weight Final(StateId s) {
+    if (!HasFinal(s)) {
+      const Element &e = elements_[s];
+      // TODO: fix so cast is unnecessary
+      Weight w = e.state == kNoStateId
+                 ? e.weight
+                 : (Weight) Times(e.weight, fst_->Final(e.state));
+      FactorIterator f(w);
+      if (!(mode_ & kFactorFinalWeights) || f.Done())
+        SetFinal(s, w);
+      else
+        SetFinal(s, Weight::Zero());
+    }
+    return CacheImpl<A>::Final(s);
+  }
+
+  size_t NumArcs(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumArcs(s);
+  }
+
+  size_t NumInputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumInputEpsilons(s);
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumOutputEpsilons(s);
+  }
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if ((mask & kError) && fst_->Properties(kError, false))
+      SetProperties(kError, kError);
+    return FstImpl<Arc>::Properties(mask);
+  }
+
+  void InitArcIterator(StateId s, ArcIteratorData<A> *data) {
+    if (!HasArcs(s))
+      Expand(s);
+    CacheImpl<A>::InitArcIterator(s, data);
+  }
+
+
+  // Find state corresponding to an element. Create new state
+  // if element not found.
+  StateId FindState(const Element &e) {
+    if (!(mode_ & kFactorArcWeights) && e.weight == Weight::One()) {
+      while (unfactored_.size() <= e.state)
+        unfactored_.push_back(kNoStateId);
+      if (unfactored_[e.state] == kNoStateId) {
+        unfactored_[e.state] = elements_.size();
+        elements_.push_back(e);
+      }
+      return unfactored_[e.state];
+    } else {
+      typename ElementMap::iterator eit = element_map_.find(e);
+      if (eit != element_map_.end()) {
+        return (*eit).second;
+      } else {
+        StateId s = elements_.size();
+        elements_.push_back(e);
+        element_map_.insert(pair<const Element, StateId>(e, s));
+        return s;
+      }
+    }
+  }
+
+  // Computes the outgoing transitions from a state, creating new destination
+  // states as needed.
+  void Expand(StateId s) {
+    Element e = elements_[s];
+    if (e.state != kNoStateId) {
+      for (ArcIterator< Fst<A> > ait(*fst_, e.state);
+           !ait.Done();
+           ait.Next()) {
+        const A &arc = ait.Value();
+        Weight w = Times(e.weight, arc.weight);
+        FactorIterator fit(w);
+        if (!(mode_ & kFactorArcWeights) || fit.Done()) {
+          StateId d = FindState(Element(arc.nextstate, Weight::One()));
+          PushArc(s, Arc(arc.ilabel, arc.olabel, w, d));
+        } else {
+          for (; !fit.Done(); fit.Next()) {
+            const pair<Weight, Weight> &p = fit.Value();
+            StateId d = FindState(Element(arc.nextstate,
+                                          p.second.Quantize(delta_)));
+            PushArc(s, Arc(arc.ilabel, arc.olabel, p.first, d));
+          }
+        }
+      }
+    }
+
+    if ((mode_ & kFactorFinalWeights) &&
+        ((e.state == kNoStateId) ||
+         (fst_->Final(e.state) != Weight::Zero()))) {
+      Weight w = e.state == kNoStateId
+                 ? e.weight
+                 : Times(e.weight, fst_->Final(e.state));
+      for (FactorIterator fit(w);
+           !fit.Done();
+           fit.Next()) {
+        const pair<Weight, Weight> &p = fit.Value();
+        StateId d = FindState(Element(kNoStateId,
+                                      p.second.Quantize(delta_)));
+        PushArc(s, Arc(final_ilabel_, final_olabel_, p.first, d));
+      }
+    }
+    SetArcs(s);
+  }
+
+ private:
+  static const size_t kPrime = 7853;
+
+  // Equality function for Elements, assume weights have been quantized.
+  class ElementEqual {
+   public:
+    bool operator()(const Element &x, const Element &y) const {
+      return x.state == y.state && x.weight == y.weight;
+    }
+  };
+
+  // Hash function for Elements to Fst states.
+  class ElementKey {
+   public:
+    size_t operator()(const Element &x) const {
+      return static_cast<size_t>(x.state * kPrime + x.weight.Hash());
+    }
+   private:
+  };
+
+  typedef unordered_map<Element, StateId, ElementKey, ElementEqual> ElementMap;
+
+  const Fst<A> *fst_;
+  float delta_;
+  uint32 mode_;               // factoring arc and/or final weights
+  Label final_ilabel_;        // ilabel of arc created when factoring final w's
+  Label final_olabel_;        // olabel of arc created when factoring final w's
+  vector<Element> elements_;  // mapping Fst state to Elements
+  ElementMap element_map_;    // mapping Elements to Fst state
+  // mapping between old/new 'StateId' for states that do not need to
+  // be factored when 'mode_' is '0' or 'kFactorFinalWeights'
+  vector<StateId> unfactored_;
+
+  void operator=(const FactorWeightFstImpl<A, F> &);  // disallow
+};
+
+template <class A, class F> const size_t FactorWeightFstImpl<A, F>::kPrime;
+
+
+// FactorWeightFst takes as template parameter a FactorIterator as
+// defined above. The result of weight factoring is a transducer
+// equivalent to the input whose path weights have been factored
+// according to the FactorIterator. States and transitions will be
+// added as necessary. The algorithm is a generalization to arbitrary
+// weights of the second step of the input epsilon-normalization
+// algorithm due to Mohri, "Generic epsilon-removal and input
+// epsilon-normalization algorithms for weighted transducers",
+// International Journal of Computer Science 13(1): 129-143 (2002).
+//
+// This class attaches interface to implementation and handles
+// reference counting, delegating most methods to ImplToFst.
+template <class A, class F>
+class FactorWeightFst : public ImplToFst< FactorWeightFstImpl<A, F> > {
+ public:
+  friend class ArcIterator< FactorWeightFst<A, F> >;
+  friend class StateIterator< FactorWeightFst<A, F> >;
+
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef CacheState<A> State;
+  typedef FactorWeightFstImpl<A, F> Impl;
+
+  FactorWeightFst(const Fst<A> &fst)
+      : ImplToFst<Impl>(new Impl(fst, FactorWeightOptions<A>())) {}
+
+  FactorWeightFst(const Fst<A> &fst,  const FactorWeightOptions<A> &opts)
+      : ImplToFst<Impl>(new Impl(fst, opts)) {}
+
+  // See Fst<>::Copy() for doc.
+  FactorWeightFst(const FactorWeightFst<A, F> &fst, bool copy)
+      : ImplToFst<Impl>(fst, copy) {}
+
+  // Get a copy of this FactorWeightFst. See Fst<>::Copy() for further doc.
+  virtual FactorWeightFst<A, F> *Copy(bool copy = false) const {
+    return new FactorWeightFst<A, F>(*this, copy);
+  }
+
+  virtual inline void InitStateIterator(StateIteratorData<A> *data) const;
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<A> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+ private:
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const FactorWeightFst<A, F> &fst);  // Disallow
+};
+
+
+// Specialization for FactorWeightFst.
+template<class A, class F>
+class StateIterator< FactorWeightFst<A, F> >
+    : public CacheStateIterator< FactorWeightFst<A, F> > {
+ public:
+  explicit StateIterator(const FactorWeightFst<A, F> &fst)
+      : CacheStateIterator< FactorWeightFst<A, F> >(fst, fst.GetImpl()) {}
+};
+
+
+// Specialization for FactorWeightFst.
+template <class A, class F>
+class ArcIterator< FactorWeightFst<A, F> >
+    : public CacheArcIterator< FactorWeightFst<A, F> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const FactorWeightFst<A, F> &fst, StateId s)
+      : CacheArcIterator< FactorWeightFst<A, F> >(fst.GetImpl(), s) {
+    if (!fst.GetImpl()->HasArcs(s))
+      fst.GetImpl()->Expand(s);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+template <class A, class F> inline
+void FactorWeightFst<A, F>::InitStateIterator(StateIteratorData<A> *data) const
+{
+  data->base = new StateIterator< FactorWeightFst<A, F> >(*this);
+}
+
+
+}  // namespace fst
+
+#endif // FST_LIB_FACTOR_WEIGHT_H__
diff --git a/src/include/fst/flags.h b/src/include/fst/flags.h
new file mode 100644
index 0000000..ec3d301
--- /dev/null
+++ b/src/include/fst/flags.h
@@ -0,0 +1,224 @@
+// flags.h
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Google-style flag handling declarations and inline definitions.
+
+#ifndef FST_LIB_FLAGS_H__
+#define FST_LIB_FLAGS_H__
+
+#include <iostream>
+#include <map>
+#include <string>
+
+#include <fst/types.h>
+#include <fst/lock.h>
+
+using std::string;
+
+//
+// FLAGS USAGE:
+//
+// Definition example:
+//
+//    DEFINE_int32(length, 0, "length");
+//
+// This defines variable FLAGS_length, initialized to 0.
+//
+// Declaration example:
+//
+//    DECLARE_int32(length);
+//
+// SetFlags() can be used to set flags from the command line
+// using, for example, '--length=2'.
+//
+// ShowUsage() can be used to print out command and flag usage.
+//
+
+#define DECLARE_bool(name) extern bool FLAGS_ ## name
+#define DECLARE_string(name) extern string FLAGS_ ## name
+#define DECLARE_int32(name) extern int32 FLAGS_ ## name
+#define DECLARE_int64(name) extern int64 FLAGS_ ## name
+#define DECLARE_double(name) extern double FLAGS_ ## name
+
+template <typename T>
+struct FlagDescription {
+  FlagDescription(T *addr, const char *doc, const char *type, const T val)
+      : address(addr), doc_string(doc), type_name(type), default_value(val) {}
+
+  T *address;
+  const char *doc_string;
+  const char *type_name;
+  const T default_value;
+};
+
+template <typename T>
+class FlagRegister {
+ public:
+  static FlagRegister<T> *GetRegister() {
+    fst::FstOnceInit(&register_init_, &FlagRegister<T>::Init);
+    return register_;
+  }
+
+  const FlagDescription<T> &GetFlagDescription(const string &name) const {
+    fst::MutexLock l(register_lock_);
+    typename std::map< string, FlagDescription<T> >::const_iterator it =
+      flag_table_.find(name);
+    return it != flag_table_.end() ? it->second : 0;
+  }
+  void SetDescription(const string &name,
+                      const FlagDescription<T> &desc) {
+    fst::MutexLock l(register_lock_);
+    flag_table_.insert(make_pair(name, desc));
+  }
+
+  bool SetFlag(const string &val, bool *address) const {
+    if (val == "true" || val == "1" || val.empty()) {
+      *address = true;
+      return true;
+    } else if (val == "false" || val == "0") {
+      *address = false;
+      return true;
+    }
+    else {
+      return false;
+    }
+  }
+  bool SetFlag(const string &val, string *address) const {
+    *address = val;
+    return true;
+  }
+  bool SetFlag(const string &val, int32 *address) const {
+    char *p = 0;
+    *address = strtol(val.c_str(), &p, 0);
+    return !val.empty() && *p == '\0';
+  }
+  bool SetFlag(const string &val, int64 *address) const {
+    char *p = 0;
+    *address = strtoll(val.c_str(), &p, 0);
+    return !val.empty() && *p == '\0';
+  }
+  bool SetFlag(const string &val, double *address) const {
+    char *p = 0;
+    *address = strtod(val.c_str(), &p);
+    return !val.empty() && *p == '\0';
+  }
+
+  bool SetFlag(const string &arg, const string &val) const {
+    for (typename std::map< string,
+             FlagDescription<T> >::const_iterator it =
+           flag_table_.begin();
+         it != flag_table_.end();
+         ++it) {
+      const string &name = it->first;
+      const FlagDescription<T> &desc = it->second;
+      if (arg == name)
+        return SetFlag(val, desc.address);
+    }
+    return false;
+  }
+
+  void ShowDefault(bool default_value) const {
+    std::cout << ", default = ";
+    std::cout << (default_value ? "true" : "false");
+  }
+  void ShowDefault(const string &default_value) const {
+    std::cout << ", default = ";
+    std::cout << "\"" << default_value << "\"";
+  }
+  template<typename V> void ShowDefault(const V& default_value) const {
+    std::cout << ", default = ";
+    std::cout << default_value;
+  }
+  void ShowUsage() const {
+    for (typename std::map< string,
+             FlagDescription<T> >::const_iterator it =
+           flag_table_.begin();
+         it != flag_table_.end();
+         ++it) {
+      const string &name = it->first;
+      const FlagDescription<T> &desc = it->second;
+      std::cout << "    --" << name
+           << ": type = " << desc.type_name;
+      ShowDefault(desc.default_value);
+      std::cout << "\n      " << desc.doc_string  << "\n";
+    }
+  }
+
+ private:
+  static void Init() {
+    register_lock_ = new fst::Mutex;
+    register_ = new FlagRegister<T>;
+  }
+  static fst::FstOnceType register_init_;   // ensures only called once
+  static fst::Mutex* register_lock_;        // multithreading lock
+  static FlagRegister<T> *register_;
+
+  std::map< string, FlagDescription<T> > flag_table_;
+};
+
+template <class T>
+fst::FstOnceType FlagRegister<T>::register_init_ = fst::FST_ONCE_INIT;
+
+template <class T>
+fst::Mutex *FlagRegister<T>::register_lock_ = 0;
+
+template <class T>
+FlagRegister<T> *FlagRegister<T>::register_ = 0;
+
+
+template <typename T>
+class FlagRegisterer {
+ public:
+  FlagRegisterer(const string &name, const FlagDescription<T> &desc) {
+    FlagRegister<T> *registr = FlagRegister<T>::GetRegister();
+    registr->SetDescription(name, desc);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(FlagRegisterer);
+};
+
+
+#define DEFINE_VAR(type, name, value, doc)                                \
+  type FLAGS_ ## name = value;                                            \
+  static FlagRegisterer<type>                                             \
+  name ## _flags_registerer(#name, FlagDescription<type>(&FLAGS_ ## name, \
+                                                         doc,             \
+                                                         #type,           \
+                                                         value))
+
+#define DEFINE_bool(name, value, doc) DEFINE_VAR(bool, name, value, doc)
+#define DEFINE_string(name, value, doc) \
+  DEFINE_VAR(string, name, value, doc)
+#define DEFINE_int32(name, value, doc) DEFINE_VAR(int32, name, value, doc)
+#define DEFINE_int64(name, value, doc) DEFINE_VAR(int64, name, value, doc)
+#define DEFINE_double(name, value, doc) DEFINE_VAR(double, name, value, doc)
+
+
+// Temporary directory
+DECLARE_string(tmpdir);
+
+void SetFlags(const char *usage, int *argc, char ***argv, bool remove_flags);
+
+// Deprecated - for backward compatibility
+inline void InitFst(const char *usage, int *argc, char ***argv, bool rmflags) {
+  return SetFlags(usage, argc, argv, rmflags);
+}
+
+void ShowUsage();
+
+#endif  // FST_LIB_FLAGS_H__
diff --git a/src/include/fst/float-weight.h b/src/include/fst/float-weight.h
new file mode 100644
index 0000000..530cbdd
--- /dev/null
+++ b/src/include/fst/float-weight.h
@@ -0,0 +1,598 @@
+// float-weight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Float weight set and associated semiring operation definitions.
+//
+
+#ifndef FST_LIB_FLOAT_WEIGHT_H__
+#define FST_LIB_FLOAT_WEIGHT_H__
+
+#include <limits>
+#include <climits>
+#include <sstream>
+#include <string>
+
+#include <fst/util.h>
+#include <fst/weight.h>
+
+
+namespace fst {
+
+// numeric limits class
+template <class T>
+class FloatLimits {
+ public:
+  static const T kPosInfinity;
+  static const T kNegInfinity;
+  static const T kNumberBad;
+};
+
+template <class T>
+const T FloatLimits<T>::kPosInfinity = numeric_limits<T>::infinity();
+
+template <class T>
+const T FloatLimits<T>::kNegInfinity = -FloatLimits<T>::kPosInfinity;
+
+template <class T>
+const T FloatLimits<T>::kNumberBad = numeric_limits<T>::quiet_NaN();
+
+// weight class to be templated on floating-points types
+template <class T = float>
+class FloatWeightTpl {
+ public:
+  FloatWeightTpl() {}
+
+  FloatWeightTpl(T f) : value_(f) {}
+
+  FloatWeightTpl(const FloatWeightTpl<T> &w) : value_(w.value_) {}
+
+  FloatWeightTpl<T> &operator=(const FloatWeightTpl<T> &w) {
+    value_ = w.value_;
+    return *this;
+  }
+
+  istream &Read(istream &strm) {
+    return ReadType(strm, &value_);
+  }
+
+  ostream &Write(ostream &strm) const {
+    return WriteType(strm, value_);
+  }
+
+  size_t Hash() const {
+    union {
+      T f;
+      size_t s;
+    } u;
+    u.s = 0;
+    u.f = value_;
+    return u.s;
+  }
+
+  const T &Value() const { return value_; }
+
+ protected:
+  void SetValue(const T &f) { value_ = f; }
+
+  inline static string GetPrecisionString() {
+    int64 size = sizeof(T);
+    if (size == sizeof(float)) return "";
+    size *= CHAR_BIT;
+
+    string result;
+    Int64ToStr(size, &result);
+    return result;
+  }
+
+ private:
+  T value_;
+};
+
+// Single-precision float weight
+typedef FloatWeightTpl<float> FloatWeight;
+
+template <class T>
+inline bool operator==(const FloatWeightTpl<T> &w1,
+                       const FloatWeightTpl<T> &w2) {
+  // Volatile qualifier thwarts over-aggressive compiler optimizations
+  // that lead to problems esp. with NaturalLess().
+  volatile T v1 = w1.Value();
+  volatile T v2 = w2.Value();
+  return v1 == v2;
+}
+
+inline bool operator==(const FloatWeightTpl<double> &w1,
+                       const FloatWeightTpl<double> &w2) {
+  return operator==<double>(w1, w2);
+}
+
+inline bool operator==(const FloatWeightTpl<float> &w1,
+                       const FloatWeightTpl<float> &w2) {
+  return operator==<float>(w1, w2);
+}
+
+template <class T>
+inline bool operator!=(const FloatWeightTpl<T> &w1,
+                       const FloatWeightTpl<T> &w2) {
+  return !(w1 == w2);
+}
+
+inline bool operator!=(const FloatWeightTpl<double> &w1,
+                       const FloatWeightTpl<double> &w2) {
+  return operator!=<double>(w1, w2);
+}
+
+inline bool operator!=(const FloatWeightTpl<float> &w1,
+                       const FloatWeightTpl<float> &w2) {
+  return operator!=<float>(w1, w2);
+}
+
+template <class T>
+inline bool ApproxEqual(const FloatWeightTpl<T> &w1,
+                        const FloatWeightTpl<T> &w2,
+                        float delta = kDelta) {
+  return w1.Value() <= w2.Value() + delta && w2.Value() <= w1.Value() + delta;
+}
+
+template <class T>
+inline ostream &operator<<(ostream &strm, const FloatWeightTpl<T> &w) {
+  if (w.Value() == FloatLimits<T>::kPosInfinity)
+    return strm << "Infinity";
+  else if (w.Value() == FloatLimits<T>::kNegInfinity)
+    return strm << "-Infinity";
+  else if (w.Value() != w.Value())   // Fails for NaN
+    return strm << "BadNumber";
+  else
+    return strm << w.Value();
+}
+
+template <class T>
+inline istream &operator>>(istream &strm, FloatWeightTpl<T> &w) {
+  string s;
+  strm >> s;
+  if (s == "Infinity") {
+    w = FloatWeightTpl<T>(FloatLimits<T>::kPosInfinity);
+  } else if (s == "-Infinity") {
+    w = FloatWeightTpl<T>(FloatLimits<T>::kNegInfinity);
+  } else {
+    char *p;
+    T f = strtod(s.c_str(), &p);
+    if (p < s.c_str() + s.size())
+      strm.clear(std::ios::badbit);
+    else
+      w = FloatWeightTpl<T>(f);
+  }
+  return strm;
+}
+
+
+// Tropical semiring: (min, +, inf, 0)
+template <class T>
+class TropicalWeightTpl : public FloatWeightTpl<T> {
+ public:
+  using FloatWeightTpl<T>::Value;
+
+  typedef TropicalWeightTpl<T> ReverseWeight;
+
+  TropicalWeightTpl() : FloatWeightTpl<T>() {}
+
+  TropicalWeightTpl(T f) : FloatWeightTpl<T>(f) {}
+
+  TropicalWeightTpl(const TropicalWeightTpl<T> &w) : FloatWeightTpl<T>(w) {}
+
+  static const TropicalWeightTpl<T> Zero() {
+    return TropicalWeightTpl<T>(FloatLimits<T>::kPosInfinity); }
+
+  static const TropicalWeightTpl<T> One() {
+    return TropicalWeightTpl<T>(0.0F); }
+
+  static const TropicalWeightTpl<T> NoWeight() {
+    return TropicalWeightTpl<T>(FloatLimits<T>::kNumberBad); }
+
+  static const string &Type() {
+    static const string type = "tropical" +
+        FloatWeightTpl<T>::GetPrecisionString();
+    return type;
+  }
+
+  bool Member() const {
+    // First part fails for IEEE NaN
+    return Value() == Value() && Value() != FloatLimits<T>::kNegInfinity;
+  }
+
+  TropicalWeightTpl<T> Quantize(float delta = kDelta) const {
+    if (Value() == FloatLimits<T>::kNegInfinity ||
+        Value() == FloatLimits<T>::kPosInfinity ||
+        Value() != Value())
+      return *this;
+    else
+      return TropicalWeightTpl<T>(floor(Value()/delta + 0.5F) * delta);
+  }
+
+  TropicalWeightTpl<T> Reverse() const { return *this; }
+
+  static uint64 Properties() {
+    return kLeftSemiring | kRightSemiring | kCommutative |
+        kPath | kIdempotent;
+  }
+};
+
+// Single precision tropical weight
+typedef TropicalWeightTpl<float> TropicalWeight;
+
+template <class T>
+inline TropicalWeightTpl<T> Plus(const TropicalWeightTpl<T> &w1,
+                                 const TropicalWeightTpl<T> &w2) {
+  if (!w1.Member() || !w2.Member())
+    return TropicalWeightTpl<T>::NoWeight();
+  return w1.Value() < w2.Value() ? w1 : w2;
+}
+
+inline TropicalWeightTpl<float> Plus(const TropicalWeightTpl<float> &w1,
+                                     const TropicalWeightTpl<float> &w2) {
+  return Plus<float>(w1, w2);
+}
+
+inline TropicalWeightTpl<double> Plus(const TropicalWeightTpl<double> &w1,
+                                      const TropicalWeightTpl<double> &w2) {
+  return Plus<double>(w1, w2);
+}
+
+template <class T>
+inline TropicalWeightTpl<T> Times(const TropicalWeightTpl<T> &w1,
+                                  const TropicalWeightTpl<T> &w2) {
+  if (!w1.Member() || !w2.Member())
+    return TropicalWeightTpl<T>::NoWeight();
+  T f1 = w1.Value(), f2 = w2.Value();
+  if (f1 == FloatLimits<T>::kPosInfinity)
+    return w1;
+  else if (f2 == FloatLimits<T>::kPosInfinity)
+    return w2;
+  else
+    return TropicalWeightTpl<T>(f1 + f2);
+}
+
+inline TropicalWeightTpl<float> Times(const TropicalWeightTpl<float> &w1,
+                                      const TropicalWeightTpl<float> &w2) {
+  return Times<float>(w1, w2);
+}
+
+inline TropicalWeightTpl<double> Times(const TropicalWeightTpl<double> &w1,
+                                       const TropicalWeightTpl<double> &w2) {
+  return Times<double>(w1, w2);
+}
+
+template <class T>
+inline TropicalWeightTpl<T> Divide(const TropicalWeightTpl<T> &w1,
+                                   const TropicalWeightTpl<T> &w2,
+                                   DivideType typ = DIVIDE_ANY) {
+  if (!w1.Member() || !w2.Member())
+    return TropicalWeightTpl<T>::NoWeight();
+  T f1 = w1.Value(), f2 = w2.Value();
+  if (f2 == FloatLimits<T>::kPosInfinity)
+    return FloatLimits<T>::kNumberBad;
+  else if (f1 == FloatLimits<T>::kPosInfinity)
+    return FloatLimits<T>::kPosInfinity;
+  else
+    return TropicalWeightTpl<T>(f1 - f2);
+}
+
+inline TropicalWeightTpl<float> Divide(const TropicalWeightTpl<float> &w1,
+                                       const TropicalWeightTpl<float> &w2,
+                                       DivideType typ = DIVIDE_ANY) {
+  return Divide<float>(w1, w2, typ);
+}
+
+inline TropicalWeightTpl<double> Divide(const TropicalWeightTpl<double> &w1,
+                                        const TropicalWeightTpl<double> &w2,
+                                        DivideType typ = DIVIDE_ANY) {
+  return Divide<double>(w1, w2, typ);
+}
+
+
+// Log semiring: (log(e^-x + e^y), +, inf, 0)
+template <class T>
+class LogWeightTpl : public FloatWeightTpl<T> {
+ public:
+  using FloatWeightTpl<T>::Value;
+
+  typedef LogWeightTpl ReverseWeight;
+
+  LogWeightTpl() : FloatWeightTpl<T>() {}
+
+  LogWeightTpl(T f) : FloatWeightTpl<T>(f) {}
+
+  LogWeightTpl(const LogWeightTpl<T> &w) : FloatWeightTpl<T>(w) {}
+
+  static const LogWeightTpl<T> Zero() {
+    return LogWeightTpl<T>(FloatLimits<T>::kPosInfinity);
+  }
+
+  static const LogWeightTpl<T> One() {
+    return LogWeightTpl<T>(0.0F);
+  }
+
+  static const LogWeightTpl<T> NoWeight() {
+    return LogWeightTpl<T>(FloatLimits<T>::kNumberBad); }
+
+  static const string &Type() {
+    static const string type = "log" + FloatWeightTpl<T>::GetPrecisionString();
+    return type;
+  }
+
+  bool Member() const {
+    // First part fails for IEEE NaN
+    return Value() == Value() && Value() != FloatLimits<T>::kNegInfinity;
+  }
+
+  LogWeightTpl<T> Quantize(float delta = kDelta) const {
+    if (Value() == FloatLimits<T>::kNegInfinity ||
+        Value() == FloatLimits<T>::kPosInfinity ||
+        Value() != Value())
+      return *this;
+    else
+      return LogWeightTpl<T>(floor(Value()/delta + 0.5F) * delta);
+  }
+
+  LogWeightTpl<T> Reverse() const { return *this; }
+
+  static uint64 Properties() {
+    return kLeftSemiring | kRightSemiring | kCommutative;
+  }
+};
+
+// Single-precision log weight
+typedef LogWeightTpl<float> LogWeight;
+// Double-precision log weight
+typedef LogWeightTpl<double> Log64Weight;
+
+template <class T>
+inline T LogExp(T x) { return log(1.0F + exp(-x)); }
+
+template <class T>
+inline LogWeightTpl<T> Plus(const LogWeightTpl<T> &w1,
+                            const LogWeightTpl<T> &w2) {
+  T f1 = w1.Value(), f2 = w2.Value();
+  if (f1 == FloatLimits<T>::kPosInfinity)
+    return w2;
+  else if (f2 == FloatLimits<T>::kPosInfinity)
+    return w1;
+  else if (f1 > f2)
+    return LogWeightTpl<T>(f2 - LogExp(f1 - f2));
+  else
+    return LogWeightTpl<T>(f1 - LogExp(f2 - f1));
+}
+
+inline LogWeightTpl<float> Plus(const LogWeightTpl<float> &w1,
+                                const LogWeightTpl<float> &w2) {
+  return Plus<float>(w1, w2);
+}
+
+inline LogWeightTpl<double> Plus(const LogWeightTpl<double> &w1,
+                                 const LogWeightTpl<double> &w2) {
+  return Plus<double>(w1, w2);
+}
+
+template <class T>
+inline LogWeightTpl<T> Times(const LogWeightTpl<T> &w1,
+                             const LogWeightTpl<T> &w2) {
+  if (!w1.Member() || !w2.Member())
+    return LogWeightTpl<T>::NoWeight();
+  T f1 = w1.Value(), f2 = w2.Value();
+  if (f1 == FloatLimits<T>::kPosInfinity)
+    return w1;
+  else if (f2 == FloatLimits<T>::kPosInfinity)
+    return w2;
+  else
+    return LogWeightTpl<T>(f1 + f2);
+}
+
+inline LogWeightTpl<float> Times(const LogWeightTpl<float> &w1,
+                                 const LogWeightTpl<float> &w2) {
+  return Times<float>(w1, w2);
+}
+
+inline LogWeightTpl<double> Times(const LogWeightTpl<double> &w1,
+                                  const LogWeightTpl<double> &w2) {
+  return Times<double>(w1, w2);
+}
+
+template <class T>
+inline LogWeightTpl<T> Divide(const LogWeightTpl<T> &w1,
+                              const LogWeightTpl<T> &w2,
+                              DivideType typ = DIVIDE_ANY) {
+  if (!w1.Member() || !w2.Member())
+    return LogWeightTpl<T>::NoWeight();
+  T f1 = w1.Value(), f2 = w2.Value();
+  if (f2 == FloatLimits<T>::kPosInfinity)
+    return FloatLimits<T>::kNumberBad;
+  else if (f1 == FloatLimits<T>::kPosInfinity)
+    return FloatLimits<T>::kPosInfinity;
+  else
+    return LogWeightTpl<T>(f1 - f2);
+}
+
+inline LogWeightTpl<float> Divide(const LogWeightTpl<float> &w1,
+                                  const LogWeightTpl<float> &w2,
+                                  DivideType typ = DIVIDE_ANY) {
+  return Divide<float>(w1, w2, typ);
+}
+
+inline LogWeightTpl<double> Divide(const LogWeightTpl<double> &w1,
+                                   const LogWeightTpl<double> &w2,
+                                   DivideType typ = DIVIDE_ANY) {
+  return Divide<double>(w1, w2, typ);
+}
+
+// MinMax semiring: (min, max, inf, -inf)
+template <class T>
+class MinMaxWeightTpl : public FloatWeightTpl<T> {
+ public:
+  using FloatWeightTpl<T>::Value;
+
+  typedef MinMaxWeightTpl<T> ReverseWeight;
+
+  MinMaxWeightTpl() : FloatWeightTpl<T>() {}
+
+  MinMaxWeightTpl(T f) : FloatWeightTpl<T>(f) {}
+
+  MinMaxWeightTpl(const MinMaxWeightTpl<T> &w) : FloatWeightTpl<T>(w) {}
+
+  static const MinMaxWeightTpl<T> Zero() {
+    return MinMaxWeightTpl<T>(FloatLimits<T>::kPosInfinity);
+  }
+
+  static const MinMaxWeightTpl<T> One() {
+    return MinMaxWeightTpl<T>(FloatLimits<T>::kNegInfinity);
+  }
+
+  static const MinMaxWeightTpl<T> NoWeight() {
+    return MinMaxWeightTpl<T>(FloatLimits<T>::kNumberBad); }
+
+  static const string &Type() {
+    static const string type = "minmax" +
+        FloatWeightTpl<T>::GetPrecisionString();
+    return type;
+  }
+
+  bool Member() const {
+    // Fails for IEEE NaN
+    return Value() == Value();
+  }
+
+  MinMaxWeightTpl<T> Quantize(float delta = kDelta) const {
+    // If one of infinities, or a NaN
+    if (Value() == FloatLimits<T>::kNegInfinity ||
+        Value() == FloatLimits<T>::kPosInfinity ||
+        Value() != Value())
+      return *this;
+    else
+      return MinMaxWeightTpl<T>(floor(Value()/delta + 0.5F) * delta);
+  }
+
+  MinMaxWeightTpl<T> Reverse() const { return *this; }
+
+  static uint64 Properties() {
+    return kLeftSemiring | kRightSemiring | kCommutative | kIdempotent | kPath;
+  }
+};
+
+// Single-precision min-max weight
+typedef MinMaxWeightTpl<float> MinMaxWeight;
+
+// Min
+template <class T>
+inline MinMaxWeightTpl<T> Plus(
+    const MinMaxWeightTpl<T> &w1, const MinMaxWeightTpl<T> &w2) {
+  if (!w1.Member() || !w2.Member())
+    return MinMaxWeightTpl<T>::NoWeight();
+  return w1.Value() < w2.Value() ? w1 : w2;
+}
+
+inline MinMaxWeightTpl<float> Plus(
+    const MinMaxWeightTpl<float> &w1, const MinMaxWeightTpl<float> &w2) {
+  return Plus<float>(w1, w2);
+}
+
+inline MinMaxWeightTpl<double> Plus(
+    const MinMaxWeightTpl<double> &w1, const MinMaxWeightTpl<double> &w2) {
+  return Plus<double>(w1, w2);
+}
+
+// Max
+template <class T>
+inline MinMaxWeightTpl<T> Times(
+    const MinMaxWeightTpl<T> &w1, const MinMaxWeightTpl<T> &w2) {
+  if (!w1.Member() || !w2.Member())
+    return MinMaxWeightTpl<T>::NoWeight();
+  return w1.Value() >= w2.Value() ? w1 : w2;
+}
+
+inline MinMaxWeightTpl<float> Times(
+    const MinMaxWeightTpl<float> &w1, const MinMaxWeightTpl<float> &w2) {
+  return Times<float>(w1, w2);
+}
+
+inline MinMaxWeightTpl<double> Times(
+    const MinMaxWeightTpl<double> &w1, const MinMaxWeightTpl<double> &w2) {
+  return Times<double>(w1, w2);
+}
+
+// Defined only for special cases
+template <class T>
+inline MinMaxWeightTpl<T> Divide(const MinMaxWeightTpl<T> &w1,
+                                 const MinMaxWeightTpl<T> &w2,
+                                 DivideType typ = DIVIDE_ANY) {
+  if (!w1.Member() || !w2.Member())
+    return MinMaxWeightTpl<T>::NoWeight();
+  // min(w1, x) = w2, w1 >= w2 => min(w1, x) = w2, x = w2
+  return w1.Value() >= w2.Value() ? w1 : FloatLimits<T>::kNumberBad;
+}
+
+inline MinMaxWeightTpl<float> Divide(const MinMaxWeightTpl<float> &w1,
+                                     const MinMaxWeightTpl<float> &w2,
+                                     DivideType typ = DIVIDE_ANY) {
+  return Divide<float>(w1, w2, typ);
+}
+
+inline MinMaxWeightTpl<double> Divide(const MinMaxWeightTpl<double> &w1,
+                                      const MinMaxWeightTpl<double> &w2,
+                                      DivideType typ = DIVIDE_ANY) {
+  return Divide<double>(w1, w2, typ);
+}
+
+//
+// WEIGHT CONVERTER SPECIALIZATIONS.
+//
+
+// Convert to tropical
+template <>
+struct WeightConvert<LogWeight, TropicalWeight> {
+  TropicalWeight operator()(LogWeight w) const { return w.Value(); }
+};
+
+template <>
+struct WeightConvert<Log64Weight, TropicalWeight> {
+  TropicalWeight operator()(Log64Weight w) const { return w.Value(); }
+};
+
+// Convert to log
+template <>
+struct WeightConvert<TropicalWeight, LogWeight> {
+  LogWeight operator()(TropicalWeight w) const { return w.Value(); }
+};
+
+template <>
+struct WeightConvert<Log64Weight, LogWeight> {
+  LogWeight operator()(Log64Weight w) const { return w.Value(); }
+};
+
+// Convert to log64
+template <>
+struct WeightConvert<TropicalWeight, Log64Weight> {
+  Log64Weight operator()(TropicalWeight w) const { return w.Value(); }
+};
+
+template <>
+struct WeightConvert<LogWeight, Log64Weight> {
+  Log64Weight operator()(LogWeight w) const { return w.Value(); }
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_FLOAT_WEIGHT_H__
diff --git a/src/include/fst/fst-decl.h b/src/include/fst/fst-decl.h
new file mode 100644
index 0000000..0e2cdf1
--- /dev/null
+++ b/src/include/fst/fst-decl.h
@@ -0,0 +1,125 @@
+// fst-decl.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// This file contains declarations of classes in the Fst template library.
+//
+
+#ifndef FST_LIB_FST_DECL_H__
+#define FST_LIB_FST_DECL_H__
+
+#include <fst/types.h>
+
+namespace fst {
+
+class SymbolTable;
+class SymbolTableIterator;
+
+template <class W> class FloatWeightTpl;
+template <class W> class TropicalWeightTpl;
+template <class W> class LogWeightTpl;
+template <class W> class MinMaxWeightTpl;
+
+typedef FloatWeightTpl<float> FloatWeight;
+typedef TropicalWeightTpl<float> TropicalWeight;
+typedef LogWeightTpl<float> LogWeight;
+typedef MinMaxWeightTpl<float> MinMaxWeight;
+
+template <class W> class ArcTpl;
+typedef ArcTpl<TropicalWeight> StdArc;
+typedef ArcTpl<LogWeight> LogArc;
+
+template <class A, class C, class U = uint32> class CompactFst;
+template <class A, class U = uint32> class ConstFst;
+template <class A, class W, class M> class EditFst;
+template <class A> class ExpandedFst;
+template <class A> class Fst;
+template <class A> class MutableFst;
+template <class A> class VectorFst;
+
+template <class A, class C> class ArcSortFst;
+template <class A> class ClosureFst;
+template <class A> class ComposeFst;
+template <class A> class ConcatFst;
+template <class A> class DeterminizeFst;
+template <class A> class DeterminizeFst;
+template <class A> class DifferenceFst;
+template <class A> class IntersectFst;
+template <class A> class InvertFst;
+template <class A, class B, class C> class ArcMapFst;
+template <class A> class ProjectFst;
+template <class A, class B, class S> class RandGenFst;
+template <class A> class RelabelFst;
+template <class A, class T> class ReplaceFst;
+template <class A> class RmEpsilonFst;
+template <class A> class UnionFst;
+
+template <class T, class Compare, bool max> class Heap;
+
+template <class A> class AcceptorCompactor;
+template <class A> class StringCompactor;
+template <class A> class UnweightedAcceptorCompactor;
+template <class A> class UnweightedCompactor;
+template <class A> class WeightedStringCompactor;
+
+template <class A, class P> class DefaultReplaceStateTable;
+
+typedef CompactFst<StdArc, AcceptorCompactor<StdArc> >
+StdCompactAcceptorFst;
+typedef CompactFst< StdArc, StringCompactor<StdArc> >
+StdCompactStringFst;
+typedef CompactFst<StdArc, UnweightedAcceptorCompactor<StdArc> >
+StdCompactUnweightedAcceptorFst;
+typedef CompactFst<StdArc, UnweightedCompactor<StdArc> >
+StdCompactUnweightedFst;
+typedef CompactFst< StdArc, WeightedStringCompactor<StdArc> >
+StdCompactWeightedStringFst;
+typedef ConstFst<StdArc> StdConstFst;
+typedef ExpandedFst<StdArc> StdExpandedFst;
+typedef Fst<StdArc> StdFst;
+typedef MutableFst<StdArc> StdMutableFst;
+typedef VectorFst<StdArc> StdVectorFst;
+
+
+template <class C> class StdArcSortFst;
+typedef ClosureFst<StdArc> StdClosureFst;
+typedef ComposeFst<StdArc> StdComposeFst;
+typedef ConcatFst<StdArc> StdConcatFst;
+typedef DeterminizeFst<StdArc> StdDeterminizeFst;
+typedef DifferenceFst<StdArc> StdDifferenceFst;
+typedef IntersectFst<StdArc> StdIntersectFst;
+typedef InvertFst<StdArc> StdInvertFst;
+typedef ProjectFst<StdArc> StdProjectFst;
+typedef RelabelFst<StdArc> StdRelabelFst;
+typedef ReplaceFst<StdArc, DefaultReplaceStateTable<StdArc, ssize_t> >
+StdReplaceFst;
+typedef RmEpsilonFst<StdArc> StdRmEpsilonFst;
+typedef UnionFst<StdArc> StdUnionFst;
+
+template <typename T> class IntegerFilterState;
+typedef IntegerFilterState<signed char> CharFilterState;
+typedef IntegerFilterState<short> ShortFilterState;
+typedef IntegerFilterState<int> IntFilterState;
+
+template <class F> class Matcher;
+template <class M1, class M2 = M1> class SequenceComposeFilter;
+template <class M1, class M2 = M1> class AltSequenceComposeFilter;
+template <class M1, class M2 = M1> class MatchComposeFilter;
+
+}  // namespace fst
+
+#endif  // FST_LIB_FST_DECL_H__
diff --git a/src/include/fst/fst.h b/src/include/fst/fst.h
new file mode 100644
index 0000000..9c4d0db
--- /dev/null
+++ b/src/include/fst/fst.h
@@ -0,0 +1,942 @@
+// fst.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Finite-State Transducer (FST) - abstract base class definition,
+// state and arc iterator interface, and suggested base implementation.
+//
+
+#ifndef FST_LIB_FST_H__
+#define FST_LIB_FST_H__
+
+#include <stddef.h>
+#include <sys/types.h>
+#include <cmath>
+#include <string>
+
+#include <fst/compat.h>
+#include <fst/types.h>
+
+#include <fst/arc.h>
+#include <fst/properties.h>
+#include <fst/register.h>
+#include <iostream>
+#include <fstream>
+#include <fst/symbol-table.h>
+#include <fst/util.h>
+
+
+DECLARE_bool(fst_align);
+
+namespace fst {
+
+bool IsFstHeader(istream &, const string &);
+
+class FstHeader;
+template <class A> class StateIteratorData;
+template <class A> class ArcIteratorData;
+template <class A> class MatcherBase;
+
+struct FstReadOptions {
+  string source;                // Where you're reading from
+  const FstHeader *header;      // Pointer to Fst header. If non-zero, use
+                                // this info (don't read a stream header)
+  const SymbolTable* isymbols;  // Pointer to input symbols. If non-zero, use
+                                // this info (read and skip stream isymbols)
+  const SymbolTable* osymbols;  // Pointer to output symbols. If non-zero, use
+                                // this info (read and skip stream osymbols)
+
+  explicit FstReadOptions(const string& src = "<unspecfied>",
+                          const FstHeader *hdr = 0,
+                          const SymbolTable* isym = 0,
+                          const SymbolTable* osym = 0)
+      : source(src), header(hdr), isymbols(isym), osymbols(osym) {}
+
+  explicit FstReadOptions(const string& src,
+                          const SymbolTable* isym,
+                          const SymbolTable* osym = 0)
+      : source(src), header(0), isymbols(isym), osymbols(osym) {}
+};
+
+
+struct FstWriteOptions {
+  string source;                 // Where you're writing to
+  bool write_header;             // Write the header?
+  bool write_isymbols;           // Write input symbols?
+  bool write_osymbols;           // Write output symbols?
+  bool align;                    // Write data aligned where appropriate;
+                                 // this may fail on pipes
+
+  explicit FstWriteOptions(const string& src = "<unspecifed>",
+                           bool hdr = true, bool isym = true,
+                           bool osym = true, bool alig = FLAGS_fst_align)
+      : source(src), write_header(hdr),
+        write_isymbols(isym), write_osymbols(osym), align(alig) {}
+};
+
+//
+// Fst HEADER CLASS
+//
+// This is the recommended Fst file header representation.
+//
+class FstHeader {
+ public:
+  enum {
+    HAS_ISYMBOLS = 0x1,          // Has input symbol table
+    HAS_OSYMBOLS = 0x2,          // Has output symbol table
+    IS_ALIGNED   = 0x4,          // Memory-aligned (where appropriate)
+  } Flags;
+
+  FstHeader() : version_(0), flags_(0), properties_(0), start_(-1),
+                numstates_(0), numarcs_(0) {}
+  const string &FstType() const { return fsttype_; }
+  const string &ArcType() const { return arctype_; }
+  int32 Version() const { return version_; }
+  int32 GetFlags() const { return flags_; }
+  uint64 Properties() const { return properties_; }
+  int64 Start() const { return start_; }
+  int64 NumStates() const { return numstates_; }
+  int64 NumArcs() const { return numarcs_; }
+
+  void SetFstType(const string& type) { fsttype_ = type; }
+  void SetArcType(const string& type) { arctype_ = type; }
+  void SetVersion(int32 version) { version_ = version; }
+  void SetFlags(int32 flags) { flags_ = flags; }
+  void SetProperties(uint64 properties) { properties_ = properties; }
+  void SetStart(int64 start) { start_ = start; }
+  void SetNumStates(int64 numstates) { numstates_ = numstates; }
+  void SetNumArcs(int64 numarcs) { numarcs_ = numarcs; }
+
+  bool Read(istream &strm, const string &source, bool rewind = false);
+  bool Write(ostream &strm, const string &source) const;
+
+ private:
+
+  string fsttype_;                   // E.g. "vector"
+  string arctype_;                   // E.g. "standard"
+  int32 version_;                    // Type version #
+  int32 flags_;                      // File format bits
+  uint64 properties_;                // FST property bits
+  int64 start_;                      // Start state
+  int64 numstates_;                  // # of states
+  int64 numarcs_;                    // # of arcs
+};
+
+
+// Specifies matcher action.
+enum MatchType { MATCH_INPUT,      // Match input label.
+                 MATCH_OUTPUT,     // Match output label.
+                 MATCH_BOTH,       // Match input or output label.
+                 MATCH_NONE,       // Match nothing.
+                 MATCH_UNKNOWN };  // Match type unknown.
+
+//
+// Fst INTERFACE CLASS DEFINITION
+//
+
+// A generic FST, templated on the arc definition, with
+// common-demoninator methods (use StateIterator and ArcIterator to
+// iterate over its states and arcs).
+template <class A>
+class Fst {
+ public:
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  virtual ~Fst() {}
+
+  virtual StateId Start() const = 0;          // Initial state
+
+  virtual Weight Final(StateId) const = 0;    // State's final weight
+
+  virtual size_t NumArcs(StateId) const = 0;  // State's arc count
+
+  virtual size_t NumInputEpsilons(StateId)
+      const = 0;                              // State's input epsilon count
+
+  virtual size_t NumOutputEpsilons(StateId)
+      const = 0;                              // State's output epsilon count
+
+  // If test=false, return stored properties bits for mask (some poss. unknown)
+  // If test=true, return property bits for mask (computing o.w. unknown)
+  virtual uint64 Properties(uint64 mask, bool test)
+      const = 0;  // Property bits
+
+  virtual const string& Type() const = 0;    // Fst type name
+
+  // Get a copy of this Fst. The copying behaves as follows:
+  //
+  // (1) The copying is constant time if safe = false or if safe = true
+  // and is on an otherwise unaccessed Fst.
+  //
+  // (2) If safe = true, the copy is thread-safe in that the original
+  // and copy can be safely accessed (but not necessarily mutated) by
+  // separate threads. For some Fst types, 'Copy(true)' should only be
+  // called on an Fst that has not otherwise been accessed. Its behavior
+  // is undefined otherwise.
+  //
+  // (3) If a MutableFst is copied and then mutated, then the original is
+  // unmodified and vice versa (often by a copy-on-write on the initial
+  // mutation, which may not be constant time).
+  virtual Fst<A> *Copy(bool safe = false) const = 0;
+
+  // Read an Fst from an input stream; returns NULL on error
+  static Fst<A> *Read(istream &strm, const FstReadOptions &opts) {
+    FstReadOptions ropts(opts);
+    FstHeader hdr;
+    if (ropts.header)
+      hdr = *opts.header;
+    else {
+      if (!hdr.Read(strm, opts.source))
+        return 0;
+      ropts.header = &hdr;
+    }
+    FstRegister<A> *registr = FstRegister<A>::GetRegister();
+    const typename FstRegister<A>::Reader reader =
+      registr->GetReader(hdr.FstType());
+    if (!reader) {
+      LOG(ERROR) << "Fst::Read: Unknown FST type \"" << hdr.FstType()
+                 << "\" (arc type = \"" << A::Type()
+                 << "\"): " << ropts.source;
+      return 0;
+    }
+    return reader(strm, ropts);
+  };
+
+  // Read an Fst from a file; return NULL on error
+  // Empty filename reads from standard input
+  static Fst<A> *Read(const string &filename) {
+    if (!filename.empty()) {
+      ifstream strm(filename.c_str(), ifstream::in | ifstream::binary);
+      if (!strm) {
+        LOG(ERROR) << "Fst::Read: Can't open file: " << filename;
+        return 0;
+      }
+      return Read(strm, FstReadOptions(filename));
+    } else {
+      return Read(std::cin, FstReadOptions("standard input"));
+    }
+  }
+
+  // Write an Fst to an output stream; return false on error
+  virtual bool Write(ostream &strm, const FstWriteOptions &opts) const {
+    LOG(ERROR) << "Fst::Write: No write stream method for " << Type()
+               << " Fst type";
+    return false;
+  }
+
+  // Write an Fst to a file; return false on error
+  // Empty filename writes to standard output
+  virtual bool Write(const string &filename) const {
+    LOG(ERROR) << "Fst::Write: No write filename method for " << Type()
+               << " Fst type";
+    return false;
+  }
+
+  // Return input label symbol table; return NULL if not specified
+  virtual const SymbolTable* InputSymbols() const = 0;
+
+  // Return output label symbol table; return NULL if not specified
+  virtual const SymbolTable* OutputSymbols() const = 0;
+
+  // For generic state iterator construction; not normally called
+  // directly by users.
+  virtual void InitStateIterator(StateIteratorData<A> *) const = 0;
+
+  // For generic arc iterator construction; not normally called
+  // directly by users.
+  virtual void InitArcIterator(StateId s, ArcIteratorData<A> *) const = 0;
+
+  // For generic matcher construction; not normally called
+  // directly by users.
+  virtual MatcherBase<A> *InitMatcher(MatchType match_type) const;
+
+ protected:
+
+  bool WriteFile(const string &filename) const {
+    if (!filename.empty()) {
+      ofstream strm(filename.c_str(), ofstream::out | ofstream::binary);
+      if (!strm) {
+        LOG(ERROR) << "Fst::Write: Can't open file: " << filename;
+        return false;
+      }
+      return Write(strm, FstWriteOptions(filename));
+    } else {
+      return Write(std::cout, FstWriteOptions("standard output"));
+    }
+  }
+};
+
+
+//
+// STATE and ARC ITERATOR DEFINITIONS
+//
+
+// State iterator interface templated on the Arc definition; used
+// for StateIterator specializations returned by the InitStateIterator
+// Fst method.
+template <class A>
+class StateIteratorBase {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+
+  virtual ~StateIteratorBase() {}
+
+  bool Done() const { return Done_(); }       // End of iterator?
+  StateId Value() const { return Value_(); }  // Current state (when !Done)
+  void Next() { Next_(); }      // Advance to next state (when !Done)
+  void Reset() { Reset_(); }    // Return to initial condition
+
+ private:
+  // This allows base class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual bool Done_() const = 0;
+  virtual StateId Value_() const = 0;
+  virtual void Next_() = 0;
+  virtual void Reset_() = 0;
+};
+
+
+// StateIterator initialization data
+
+template <class A> struct StateIteratorData {
+  StateIteratorBase<A> *base;   // Specialized iterator if non-zero
+  typename A::StateId nstates;  // O.w. total # of states
+};
+
+
+// Generic state iterator, templated on the FST definition
+// - a wrapper around pointer to specific one.
+// Here is a typical use: \code
+//   for (StateIterator<StdFst> siter(fst);
+//        !siter.Done();
+//        siter.Next()) {
+//     StateId s = siter.Value();
+//     ...
+//   } \endcode
+template <class F>
+class StateIterator {
+ public:
+  typedef F FST;
+  typedef typename F::Arc Arc;
+  typedef typename Arc::StateId StateId;
+
+  explicit StateIterator(const F &fst) : s_(0) {
+    fst.InitStateIterator(&data_);
+  }
+
+  ~StateIterator() { if (data_.base) delete data_.base; }
+
+  bool Done() const {
+    return data_.base ? data_.base->Done() : s_ >= data_.nstates;
+  }
+
+  StateId Value() const { return data_.base ? data_.base->Value() : s_; }
+
+  void Next() {
+    if (data_.base)
+      data_.base->Next();
+    else
+      ++s_;
+  }
+
+  void Reset() {
+    if (data_.base)
+      data_.base->Reset();
+    else
+      s_ = 0;
+  }
+
+ private:
+  StateIteratorData<Arc> data_;
+  StateId s_;
+
+  DISALLOW_COPY_AND_ASSIGN(StateIterator);
+};
+
+
+// Flags to control the behavior on an arc iterator:
+static const uint32 kArcILabelValue    = 0x0001;  // Value() gives valid ilabel
+static const uint32 kArcOLabelValue    = 0x0002;  //  "       "     "    olabel
+static const uint32 kArcWeightValue    = 0x0004;  //  "       "     "    weight
+static const uint32 kArcNextStateValue = 0x0008;  //  "       "     " nextstate
+static const uint32 kArcNoCache   = 0x0010;       // No need to cache arcs
+
+static const uint32 kArcValueFlags =
+                  kArcILabelValue | kArcOLabelValue |
+                  kArcWeightValue | kArcNextStateValue;
+
+static const uint32 kArcFlags = kArcValueFlags | kArcNoCache;
+
+
+// Arc iterator interface, templated on the Arc definition; used
+// for Arc iterator specializations that are returned by the InitArcIterator
+// Fst method.
+template <class A>
+class ArcIteratorBase {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+
+  virtual ~ArcIteratorBase() {}
+
+  bool Done() const { return Done_(); }            // End of iterator?
+  const A& Value() const { return Value_(); }      // Current arc (when !Done)
+  void Next() { Next_(); }           // Advance to next arc (when !Done)
+  size_t Position() const { return Position_(); }  // Return current position
+  void Reset() { Reset_(); }         // Return to initial condition
+  void Seek(size_t a) { Seek_(a); }  // Random arc access by position
+  uint32 Flags() const { return Flags_(); }  // Return current behavorial flags
+  void SetFlags(uint32 flags, uint32 mask) {  // Set behavorial flags
+    SetFlags_(flags, mask);
+  }
+
+ private:
+  // This allows base class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual bool Done_() const = 0;
+  virtual const A& Value_() const = 0;
+  virtual void Next_() = 0;
+  virtual size_t Position_() const = 0;
+  virtual void Reset_() = 0;
+  virtual void Seek_(size_t a) = 0;
+  virtual uint32 Flags_() const = 0;
+  virtual void SetFlags_(uint32 flags, uint32 mask) = 0;
+};
+
+
+// ArcIterator initialization data
+template <class A> struct ArcIteratorData {
+  ArcIteratorBase<A> *base;  // Specialized iterator if non-zero
+  const A *arcs;             // O.w. arcs pointer
+  size_t narcs;              // ... and arc count
+  int *ref_count;            // ... and reference count if non-zero
+};
+
+
+// Generic arc iterator, templated on the FST definition
+// - a wrapper around pointer to specific one.
+// Here is a typical use: \code
+//   for (ArcIterator<StdFst> aiter(fst, s));
+//        !aiter.Done();
+//         aiter.Next()) {
+//     StdArc &arc = aiter.Value();
+//     ...
+//   } \endcode
+template <class F>
+class ArcIterator {
+   public:
+  typedef F FST;
+  typedef typename F::Arc Arc;
+  typedef typename Arc::StateId StateId;
+
+  ArcIterator(const F &fst, StateId s) : i_(0) {
+    fst.InitArcIterator(s, &data_);
+  }
+
+  explicit ArcIterator(const ArcIteratorData<Arc> &data) : data_(data), i_(0) {
+    if (data_.ref_count)
+      ++(*data_.ref_count);
+  }
+
+  ~ArcIterator() {
+    if (data_.base)
+      delete data_.base;
+    else if (data_.ref_count)
+      --(*data_.ref_count);
+  }
+
+  bool Done() const {
+    return data_.base ?  data_.base->Done() : i_ >= data_.narcs;
+  }
+
+  const Arc& Value() const {
+    return data_.base ? data_.base->Value() : data_.arcs[i_];
+  }
+
+  void Next() {
+    if (data_.base)
+      data_.base->Next();
+    else
+      ++i_;
+  }
+
+  void Reset() {
+    if (data_.base)
+      data_.base->Reset();
+    else
+      i_ = 0;
+  }
+
+  void Seek(size_t a) {
+    if (data_.base)
+      data_.base->Seek(a);
+    else
+      i_ = a;
+  }
+
+  size_t Position() const {
+    return data_.base ? data_.base->Position() : i_;
+  }
+
+  uint32 Flags() const {
+    if (data_.base)
+      return data_.base->Flags();
+    else
+      return kArcValueFlags;
+  }
+
+  void SetFlags(uint32 flags, uint32 mask) {
+    if (data_.base)
+      data_.base->SetFlags(flags, mask);
+  }
+
+ private:
+  ArcIteratorData<Arc> data_;
+  size_t i_;
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+//
+// MATCHER DEFINITIONS
+//
+
+template <class A>
+MatcherBase<A> *Fst<A>::InitMatcher(MatchType match_type) const {
+  return 0;  // Use the default matcher
+}
+
+
+//
+// FST ACCESSORS - Useful functions in high-performance cases.
+//
+
+namespace internal {
+
+// General case - requires non-abstract, 'final' methods. Use for inlining.
+template <class F> inline
+typename F::Arc::Weight Final(const F &fst, typename F::Arc::StateId s) {
+  return fst.F::Final(s);
+}
+
+template <class F> inline
+ssize_t NumArcs(const F &fst, typename F::Arc::StateId s) {
+  return fst.F::NumArcs(s);
+}
+
+template <class F> inline
+ssize_t NumInputEpsilons(const F &fst, typename F::Arc::StateId s) {
+  return fst.F::NumInputEpsilons(s);
+}
+
+template <class F> inline
+ssize_t NumOutputEpsilons(const F &fst, typename F::Arc::StateId s) {
+  return fst.F::NumOutputEpsilons(s);
+}
+
+
+//  Fst<A> case - abstract methods.
+template <class A> inline
+typename A::Weight Final(const Fst<A> &fst, typename A::StateId s) {
+  return fst.Final(s);
+}
+
+template <class A> inline
+ssize_t NumArcs(const Fst<A> &fst, typename A::StateId s) {
+  return fst.NumArcs(s);
+}
+
+template <class A> inline
+ssize_t NumInputEpsilons(const Fst<A> &fst, typename A::StateId s) {
+  return fst.NumInputEpsilons(s);
+}
+
+template <class A> inline
+ssize_t NumOutputEpsilons(const Fst<A> &fst, typename A::StateId s) {
+  return fst.NumOutputEpsilons(s);
+}
+
+}  // namespace internal
+
+// A useful alias when using StdArc.
+typedef Fst<StdArc> StdFst;
+
+
+//
+//  CONSTANT DEFINITIONS
+//
+
+const int kNoStateId   =  -1;  // Not a valid state ID
+const int kNoLabel     =  -1;  // Not a valid label
+
+//
+// Fst IMPLEMENTATION BASE
+//
+// This is the recommended Fst implementation base class. It will
+// handle reference counts, property bits, type information and symbols.
+//
+
+template <class A> class FstImpl {
+ public:
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  FstImpl()
+      : properties_(0), type_("null"), isymbols_(0), osymbols_(0) {}
+
+  FstImpl(const FstImpl<A> &impl)
+      : properties_(impl.properties_), type_(impl.type_),
+        isymbols_(impl.isymbols_ ? impl.isymbols_->Copy() : 0),
+        osymbols_(impl.osymbols_ ? impl.osymbols_->Copy() : 0) {}
+
+  virtual ~FstImpl() {
+    delete isymbols_;
+    delete osymbols_;
+  }
+
+  const string& Type() const { return type_; }
+
+  void SetType(const string &type) { type_ = type; }
+
+  virtual uint64 Properties() const { return properties_; }
+
+  virtual uint64 Properties(uint64 mask) const { return properties_ & mask; }
+
+  void SetProperties(uint64 props) {
+    properties_ &= kError;          // kError can't be cleared
+    properties_ |= props;
+  }
+
+  void SetProperties(uint64 props, uint64 mask) {
+    properties_ &= ~mask | kError;  // kError can't be cleared
+    properties_ |= props & mask;
+  }
+
+  // Allows (only) setting error bit on const FST impls
+  void SetProperties(uint64 props, uint64 mask) const {
+    if (mask != kError)
+      FSTERROR() << "FstImpl::SetProperties() const: can only set kError";
+    properties_ |= kError;
+  }
+
+  const SymbolTable* InputSymbols() const { return isymbols_; }
+
+  const SymbolTable* OutputSymbols() const { return osymbols_; }
+
+  SymbolTable* InputSymbols() { return isymbols_; }
+
+  SymbolTable* OutputSymbols() { return osymbols_; }
+
+  void SetInputSymbols(const SymbolTable* isyms) {
+    if (isymbols_) delete isymbols_;
+    isymbols_ = isyms ? isyms->Copy() : 0;
+  }
+
+  void SetOutputSymbols(const SymbolTable* osyms) {
+    if (osymbols_) delete osymbols_;
+    osymbols_ = osyms ? osyms->Copy() : 0;
+  }
+
+  int RefCount() const {
+    return ref_count_.count();
+  }
+
+  int IncrRefCount() {
+    return ref_count_.Incr();
+  }
+
+  int DecrRefCount() {
+    return ref_count_.Decr();
+  }
+
+  // Read-in header and symbols from input stream, initialize Fst, and
+  // return the header.  If opts.header is non-null, skip read-in and
+  // use the option value.  If opts.[io]symbols is non-null, read-in
+  // (if present), but use the option value.
+  bool ReadHeader(istream &strm, const FstReadOptions& opts,
+                  int min_version, FstHeader *hdr);
+
+  // Write-out header and symbols from output stream.
+  // If a opts.header is false, skip writing header.
+  // If opts.[io]symbols is false, skip writing those symbols.
+  // This method is needed for Impl's that implement Write methods.
+  void WriteHeader(ostream &strm, const FstWriteOptions& opts,
+                   int version, FstHeader *hdr) const {
+    if (opts.write_header) {
+      hdr->SetFstType(type_);
+      hdr->SetArcType(A::Type());
+      hdr->SetVersion(version);
+      hdr->SetProperties(properties_);
+      int32 file_flags = 0;
+      if (isymbols_ && opts.write_isymbols)
+        file_flags |= FstHeader::HAS_ISYMBOLS;
+      if (osymbols_ && opts.write_osymbols)
+        file_flags |= FstHeader::HAS_OSYMBOLS;
+      if (opts.align)
+        file_flags |= FstHeader::IS_ALIGNED;
+      hdr->SetFlags(file_flags);
+      hdr->Write(strm, opts.source);
+    }
+    if (isymbols_ && opts.write_isymbols) isymbols_->Write(strm);
+    if (osymbols_ && opts.write_osymbols) osymbols_->Write(strm);
+  }
+
+  // Write-out header and symbols to output stream.
+  // If a opts.header is false, skip writing header.
+  // If opts.[io]symbols is false, skip writing those symbols.
+  // type is the Fst type being written.
+  // This method is used in the cross-type serialization methods Fst::WriteFst.
+  static void WriteFstHeader(const Fst<A> &fst, ostream &strm,
+                             const FstWriteOptions& opts, int version,
+                             const string &type, FstHeader *hdr) {
+    if (opts.write_header) {
+      hdr->SetFstType(type);
+      hdr->SetArcType(A::Type());
+      hdr->SetVersion(version);
+      hdr->SetProperties(fst.Properties(kFstProperties, false));
+      int32 file_flags = 0;
+      if (fst.InputSymbols() && opts.write_isymbols)
+        file_flags |= FstHeader::HAS_ISYMBOLS;
+      if (fst.OutputSymbols() && opts.write_osymbols)
+        file_flags |= FstHeader::HAS_OSYMBOLS;
+      if (opts.align)
+        file_flags |= FstHeader::IS_ALIGNED;
+      hdr->SetFlags(file_flags);
+      hdr->Write(strm, opts.source);
+    }
+    if (fst.InputSymbols() && opts.write_isymbols) {
+      fst.InputSymbols()->Write(strm);
+    }
+    if (fst.OutputSymbols() && opts.write_osymbols) {
+      fst.OutputSymbols()->Write(strm);
+    }
+  }
+
+  // In serialization routines where the header cannot be written until after
+  // the machine has been serialized, this routine can be called to seek to
+  // the beginning of the file an rewrite the header with updated fields.
+  // It repositions the file pointer back at the end of the file.
+  // returns true on success, false on failure.
+  static bool UpdateFstHeader(const Fst<A> &fst, ostream &strm,
+                              const FstWriteOptions& opts, int version,
+                              const string &type, FstHeader *hdr,
+                              size_t header_offset) {
+    strm.seekp(header_offset);
+    if (!strm) {
+      LOG(ERROR) << "Fst::UpdateFstHeader: write failed: " << opts.source;
+      return false;
+    }
+    WriteFstHeader(fst, strm, opts, version, type, hdr);
+    if (!strm) {
+      LOG(ERROR) << "Fst::UpdateFstHeader: write failed: " << opts.source;
+      return false;
+    }
+    strm.seekp(0, ios_base::end);
+    if (!strm) {
+      LOG(ERROR) << "Fst::UpdateFstHeader: write failed: " << opts.source;
+      return false;
+    }
+    return true;
+  }
+
+ protected:
+  mutable uint64 properties_;           // Property bits
+
+ private:
+  string type_;                 // Unique name of Fst class
+  SymbolTable *isymbols_;       // Ilabel symbol table
+  SymbolTable *osymbols_;       // Olabel symbol table
+  RefCounter ref_count_;        // Reference count
+
+  void operator=(const FstImpl<A> &impl);  // disallow
+};
+
+template <class A> inline
+bool FstImpl<A>::ReadHeader(istream &strm, const FstReadOptions& opts,
+                            int min_version, FstHeader *hdr) {
+  if (opts.header)
+    *hdr = *opts.header;
+  else if (!hdr->Read(strm, opts.source))
+    return false;
+
+  if (FLAGS_v >= 2) {
+    LOG(INFO) << "FstImpl::ReadHeader: source: " << opts.source
+              << ", fst_type: " << hdr->FstType()
+              << ", arc_type: " << A::Type()
+              << ", version: " << hdr->Version()
+              << ", flags: " << hdr->GetFlags();
+  }
+
+  if (hdr->FstType() != type_) {
+    LOG(ERROR) << "FstImpl::ReadHeader: Fst not of type \"" << type_
+               << "\": " << opts.source;
+    return false;
+  }
+  if (hdr->ArcType() != A::Type()) {
+    LOG(ERROR) << "FstImpl::ReadHeader: Arc not of type \"" << A::Type()
+               << "\": " << opts.source;
+    return false;
+  }
+  if (hdr->Version() < min_version) {
+    LOG(ERROR) << "FstImpl::ReadHeader: Obsolete " << type_
+               << " Fst version: " << opts.source;
+    return false;
+  }
+  properties_ = hdr->Properties();
+  if (hdr->GetFlags() & FstHeader::HAS_ISYMBOLS)
+    isymbols_ = SymbolTable::Read(strm, opts.source);
+  if (hdr->GetFlags() & FstHeader::HAS_OSYMBOLS)
+    osymbols_ =SymbolTable::Read(strm, opts.source);
+
+  if (opts.isymbols) {
+    delete isymbols_;
+    isymbols_ = opts.isymbols->Copy();
+  }
+  if (opts.osymbols) {
+    delete osymbols_;
+    osymbols_ = opts.osymbols->Copy();
+  }
+  return true;
+}
+
+
+template<class Arc>
+uint64 TestProperties(const Fst<Arc> &fst, uint64 mask, uint64 *known);
+
+
+// This is a helper class template useful for attaching an Fst interface to
+// its implementation, handling reference counting.
+template < class I, class F = Fst<typename I::Arc> >
+class ImplToFst : public F {
+ public:
+  typedef typename I::Arc Arc;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  virtual ~ImplToFst() { if (!impl_->DecrRefCount()) delete impl_;  }
+
+  virtual StateId Start() const { return impl_->Start(); }
+
+  virtual Weight Final(StateId s) const { return impl_->Final(s); }
+
+  virtual size_t NumArcs(StateId s) const { return impl_->NumArcs(s); }
+
+  virtual size_t NumInputEpsilons(StateId s) const {
+    return impl_->NumInputEpsilons(s);
+  }
+
+  virtual size_t NumOutputEpsilons(StateId s) const {
+    return impl_->NumOutputEpsilons(s);
+  }
+
+  virtual uint64 Properties(uint64 mask, bool test) const {
+    if (test) {
+      uint64 knownprops, testprops = TestProperties(*this, mask, &knownprops);
+      impl_->SetProperties(testprops, knownprops);
+      return testprops & mask;
+    } else {
+      return impl_->Properties(mask);
+    }
+  }
+
+  virtual const string& Type() const { return impl_->Type(); }
+
+  virtual const SymbolTable* InputSymbols() const {
+    return impl_->InputSymbols();
+  }
+
+  virtual const SymbolTable* OutputSymbols() const {
+    return impl_->OutputSymbols();
+  }
+
+ protected:
+  ImplToFst() : impl_(0) {}
+
+  ImplToFst(I *impl) : impl_(impl) {}
+
+  ImplToFst(const ImplToFst<I, F> &fst) {
+    impl_ = fst.impl_;
+    impl_->IncrRefCount();
+  }
+
+  // This constructor presumes there is a copy constructor for the
+  // implementation.
+  ImplToFst(const ImplToFst<I, F> &fst, bool safe) {
+    if (safe) {
+      impl_ = new I(*(fst.impl_));
+    } else {
+      impl_ = fst.impl_;
+      impl_->IncrRefCount();
+    }
+  }
+
+  I *GetImpl() const { return impl_; }
+
+  // Change Fst implementation pointer. If 'own_impl' is true,
+  // ownership of the input implementation is given to this
+  // object; otherwise, the input implementation's reference count
+  // should be incremented.
+  void SetImpl(I *impl, bool own_impl = true) {
+    if (!own_impl)
+      impl->IncrRefCount();
+    if (impl_ && !impl_->DecrRefCount()) delete impl_;
+    impl_ = impl;
+  }
+
+ private:
+  // Disallow
+  ImplToFst<I, F> &operator=(const ImplToFst<I, F> &fst);
+
+  ImplToFst<I, F> &operator=(const Fst<Arc> &fst) {
+    FSTERROR() << "ImplToFst: Assignment operator disallowed";
+    GetImpl()->SetProperties(kError, kError);
+    return *this;
+  }
+
+  I *impl_;
+};
+
+
+// Converts FSTs by casting their implementations, where this makes
+// sense (which excludes implementations with weight-dependent virtual
+// methods). Must be a friend of the Fst classes involved (currently
+// the concrete Fsts: VectorFst, ConstFst, CompactFst).
+template<class F, class G> void Cast(const F &ifst, G *ofst) {
+  ofst->SetImpl(reinterpret_cast<typename G::Impl *>(ifst.GetImpl()), false);
+}
+
+// Fst Serialization
+template <class A>
+void FstToString(const Fst<A> &fst, string *result) {
+  ostringstream ostrm;
+  fst.Write(ostrm, FstWriteOptions("FstToString"));
+  *result = ostrm.str();
+}
+
+template <class A>
+Fst<A> *StringToFst(const string &s) {
+  istringstream istrm(s);
+  return Fst<A>::Read(istrm, FstReadOptions("StringToFst"));
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_FST_H__
diff --git a/src/include/fst/fstlib.h b/src/include/fst/fstlib.h
new file mode 100644
index 0000000..c05c775
--- /dev/null
+++ b/src/include/fst/fstlib.h
@@ -0,0 +1,151 @@
+// fstlib.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \page FstLib FST - Weighted Finite State Transducers
+// This is a library for constructing, combining, optimizing, and
+// searching "weighted finite-state transducers" (FSTs). Weighted
+// finite-state transducers are automata where each transition has an
+// input label, an output label, and a weight. The more familiar
+// finite-state acceptor is represented as a transducer with each
+// transition's input and output the same.  Finite-state acceptors
+// are used to represent sets of strings (specifically, "regular" or
+// "rational sets"); finite-state transducers are used to represent
+// binary relations between pairs of strings (specifically, "rational
+// transductions"). The weights can be used to represent the cost of
+// taking a particular transition.
+//
+// In this library, the transducers are templated on the Arc
+// (transition) definition, which allows changing the label, weight,
+// and state ID sets. Labels and state IDs are restricted to signed
+// integral types but the weight can be an arbitrary type whose
+// members satisfy certain algebraic ("semiring") properties.
+//
+// For more information, see the FST Library Wiki page:
+// http://wiki.corp.google.com/twiki/bin/view/Main/FstLibrary
+
+// \file
+// This convenience file includes all other FST inl.h files.
+//
+
+#ifndef FST_LIB_FSTLIB_H__
+#define FST_LIB_FSTLIB_H__
+
+
+// Abstract FST classes
+#include <fst/fst.h>
+#include <fst/expanded-fst.h>
+#include <fst/mutable-fst.h>
+
+// Concrete FST classes
+#include <fst/compact-fst.h>
+#include <fst/const-fst.h>
+#include <fst/edit-fst.h>
+#include <fst/vector-fst.h>
+
+// FST algorithms and delayed FST classes
+#include <fst/arcsort.h>
+#include <fst/arc-map.h>
+#include <fst/closure.h>
+#include <fst/compose.h>
+#include <fst/concat.h>
+#include <fst/connect.h>
+#include <fst/determinize.h>
+#include <fst/difference.h>
+#include <fst/encode.h>
+#include <fst/epsnormalize.h>
+#include <fst/equal.h>
+#include <fst/equivalent.h>
+#include <fst/factor-weight.h>
+#include <fst/intersect.h>
+#include <fst/invert.h>
+#include <fst/map.h>
+#include <fst/minimize.h>
+#include <fst/project.h>
+#include <fst/prune.h>
+#include <fst/push.h>
+#include <fst/randequivalent.h>
+#include <fst/randgen.h>
+#include <fst/rational.h>
+#include <fst/relabel.h>
+#include <fst/replace.h>
+#include <fst/replace-util.h>
+#include <fst/reverse.h>
+#include <fst/reweight.h>
+#include <fst/rmepsilon.h>
+#include <fst/rmfinalepsilon.h>
+#include <fst/shortest-distance.h>
+#include <fst/shortest-path.h>
+#include <fst/statesort.h>
+#include <fst/state-map.h>
+#include <fst/synchronize.h>
+#include <fst/topsort.h>
+#include <fst/union.h>
+#include <fst/verify.h>
+#include <fst/visit.h>
+
+// Weights
+#include <fst/weight.h>
+#include <fst/expectation-weight.h>
+#include <fst/float-weight.h>
+#include <fst/lexicographic-weight.h>
+#include <fst/pair-weight.h>
+#include <fst/power-weight.h>
+#include <fst/product-weight.h>
+#include <fst/random-weight.h>
+#include <fst/signed-log-weight.h>
+#include <fst/sparse-power-weight.h>
+#include <fst/sparse-tuple-weight.h>
+#include <fst/string-weight.h>
+#include <fst/tuple-weight.h>
+
+// Auxiliary classes for composition
+#include <fst/compose-filter.h>
+#include <fst/lookahead-filter.h>
+#include <fst/lookahead-matcher.h>
+#include <fst/matcher-fst.h>
+#include <fst/matcher.h>
+#include <fst/state-table.h>
+
+// Data structures
+#include <fst/heap.h>
+#include <fst/interval-set.h>
+#include <fst/queue.h>
+#include <fst/union-find.h>
+
+// Miscellaneous
+#include <fst/accumulator.h>
+#include <fst/add-on.h>
+#include <fst/arc.h>
+#include <fst/arcfilter.h>
+#include <fst/cache.h>
+#include <fst/complement.h>
+#include <fst/dfs-visit.h>
+#include <fst/generic-register.h>
+#include <fst/label-reachable.h>
+#include <fst/partition.h>
+#include <fst/properties.h>
+#include <fst/register.h>
+#include <fst/state-reachable.h>
+#include <iostream>
+#include <fstream>
+#include <fst/symbol-table.h>
+#include <fst/symbol-table-ops.h>
+#include <fst/test-properties.h>
+#include <fst/util.h>
+
+
+#endif  // FST_LIB_FSTLIB_H__
diff --git a/src/include/fst/generic-register.h b/src/include/fst/generic-register.h
new file mode 100644
index 0000000..4f8b512
--- /dev/null
+++ b/src/include/fst/generic-register.h
@@ -0,0 +1,159 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_LIB_GENERIC_REGISTER_H_
+#define FST_LIB_GENERIC_REGISTER_H_
+
+#include <map>
+#include <string>
+
+#include <fst/compat.h>
+#include <fst/types.h>
+
+// Generic class representing a globally-stored correspondence between
+// objects of KeyType and EntryType.
+// KeyType must:
+//  a) be such as can be stored as a key in a map<>
+//  b) be concatenable with a const char* with the + operator
+//     (or you must subclass and redefine LoadEntryFromSharedObject)
+// EntryType must be default constructible.
+//
+// The third template parameter should be the type of a subclass of this class
+// (think CRTP). This is to allow GetRegister() to instantiate and return
+// an object of the appropriate type.
+
+namespace fst {
+
+template<class KeyType, class EntryType, class RegisterType>
+class GenericRegister {
+ public:
+  typedef KeyType Key;
+  typedef EntryType Entry;
+
+  static RegisterType *GetRegister() {
+    FstOnceInit(&register_init_,
+                   &RegisterType::Init);
+
+    return register_;
+  }
+
+  void SetEntry(const KeyType &key,
+                const EntryType &entry) {
+    MutexLock l(register_lock_);
+
+    register_table_.insert(make_pair(key, entry));
+  }
+
+  EntryType GetEntry(const KeyType &key) const {
+    const EntryType *entry = LookupEntry(key);
+    if (entry) {
+      return *entry;
+    } else {
+      return LoadEntryFromSharedObject(key);
+    }
+  }
+
+  virtual ~GenericRegister() { }
+
+ protected:
+  // Override this if you want to be able to load missing definitions from
+  // shared object files.
+  virtual EntryType LoadEntryFromSharedObject(const KeyType &key) const {
+    string so_filename = ConvertKeyToSoFilename(key);
+
+    void *handle = dlopen(so_filename.c_str(), RTLD_LAZY);
+    if (handle == 0) {
+      LOG(ERROR) << "GenericRegister::GetEntry : " << dlerror();
+      return EntryType();
+    }
+
+    // We assume that the DSO constructs a static object in its global
+    // scope that does the registration. Thus we need only load it, not
+    // call any methods.
+    const EntryType *entry = this->LookupEntry(key);
+    if (entry == 0) {
+      LOG(ERROR) << "GenericRegister::GetEntry : "
+                 << "lookup failed in shared object: " << so_filename;
+      return EntryType();
+    }
+    return *entry;
+  }
+
+  // Override this to define how to turn a key into an SO filename.
+  virtual string ConvertKeyToSoFilename(const KeyType& key) const = 0;
+
+  virtual const EntryType *LookupEntry(
+      const KeyType &key) const {
+    MutexLock l(register_lock_);
+
+    typename RegisterMapType::const_iterator it = register_table_.find(key);
+
+    if (it != register_table_.end()) {
+      return &it->second;
+    } else {
+      return 0;
+    }
+  }
+
+ private:
+  typedef map<KeyType, EntryType> RegisterMapType;
+
+  static void Init() {
+    register_lock_ = new Mutex;
+    register_ = new RegisterType;
+  }
+
+  static FstOnceType register_init_;
+  static Mutex *register_lock_;
+  static RegisterType *register_;
+
+  RegisterMapType register_table_;
+};
+
+template<class KeyType, class EntryType, class RegisterType>
+FstOnceType GenericRegister<KeyType, EntryType,
+                               RegisterType>::register_init_ = FST_ONCE_INIT;
+
+template<class KeyType, class EntryType, class RegisterType>
+Mutex *GenericRegister<KeyType, EntryType, RegisterType>::register_lock_ = 0;
+
+template<class KeyType, class EntryType, class RegisterType>
+RegisterType *GenericRegister<KeyType, EntryType, RegisterType>::register_ = 0;
+
+//
+// GENERIC REGISTRATION
+//
+
+// Generic register-er class capable of creating new register entries in the
+// given RegisterType template parameter. This type must define types Key
+// and Entry, and have appropriate static GetRegister() and instance
+// SetEntry() functions. An easy way to accomplish this is to have RegisterType
+// be the type of a subclass of GenericRegister.
+template<class RegisterType>
+class GenericRegisterer {
+ public:
+  typedef typename RegisterType::Key Key;
+  typedef typename RegisterType::Entry Entry;
+
+  GenericRegisterer(Key key, Entry entry) {
+    RegisterType *reg = RegisterType::GetRegister();
+    reg->SetEntry(key, entry);
+  }
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_GENERIC_REGISTER_H_
diff --git a/src/include/fst/heap.h b/src/include/fst/heap.h
new file mode 100644
index 0000000..a7affbd
--- /dev/null
+++ b/src/include/fst/heap.h
@@ -0,0 +1,206 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// All Rights Reserved.
+// Author: Johan Schalkwyk (johans@google.com)
+//
+// \file
+// Implementation of a heap as in STL, but allows tracking positions
+// in heap using a key. The key can be used to do an in-place update of
+// values in the heap.
+
+#ifndef FST_LIB_HEAP_H__
+#define FST_LIB_HEAP_H__
+
+#include <vector>
+using std::vector;
+#include <functional>
+
+#include <fst/compat.h>
+namespace fst {
+
+//
+// \class Heap
+// \brief A templated heap implementation that support in-place update
+//        of values.
+//
+// The templated heap implementation is a little different from the
+// STL priority_queue and the *_heap operations in STL. This heap
+// supports indexing of values in the heap via an associated key.
+//
+// Each value is internally associated with a key which is returned
+// to the calling functions on heap insert. This key can be used
+// to later update the specific value in the heap.
+//
+// \param T the element type of the hash, can be POD, Data or Ptr to Data
+// \param Compare Comparison class for determiningg min-heapness.
+// \param  whether heap top should be max or min element w.r.t. Compare
+//
+
+static const int kNoKey = -1;
+template <class T, class Compare, bool max>
+class Heap {
+ public:
+
+  // Initialize with a specific comparator
+  Heap(Compare comp) : comp_(comp), size_(0) { }
+
+  // Create a heap with initial size of internal arrays of 0
+  Heap() : size_(0) { }
+
+  ~Heap() { }
+
+  // Insert a value into the heap
+  int Insert(const T& val) {
+    if (size_ < A_.size()) {
+      A_[size_] = val;
+      pos_[key_[size_]] = size_;
+    } else {
+      A_.push_back(val);
+      pos_.push_back(size_);
+      key_.push_back(size_);
+    }
+
+    ++size_;
+    return Insert(val, size_ - 1);
+  }
+
+  // Update a value at position given by the key. The pos array is first
+  // indexed by the key. The position gives the position in the heap array.
+  // Once we have the position we can then use the standard heap operations
+  // to calculate the parent and child positions.
+  void Update(int key, const T& val) {
+    int i = pos_[key];
+    if (Better(val, A_[Parent(i)])) {
+      Insert(val, i);
+    } else {
+      A_[i] = val;
+      Heapify(i);
+    }
+  }
+
+  // Return the greatest (max=true) / least (max=false) value w.r.t.
+  // from the heap.
+  T Pop() {
+    T top = A_[0];
+
+    Swap(0, size_-1);
+    size_--;
+    Heapify(0);
+    return top;
+  }
+
+  // Return the greatest (max=true) / least (max=false) value w.r.t.
+  // comp object from the heap.
+  T Top() const {
+    return A_[0];
+  }
+
+  // Check if the heap is empty
+  bool Empty() const {
+    return size_ == 0;
+  }
+
+  void Clear() {
+    size_ = 0;
+  }
+
+
+  //
+  // The following protected routines are used in a supportive role
+  // for managing the heap and keeping the heap properties.
+  //
+ private:
+  // Compute left child of parent
+  int Left(int i) {
+    return 2*(i+1)-1;   // 0 -> 1, 1 -> 3
+  }
+
+  // Compute right child of parent
+  int Right(int i) {
+    return 2*(i+1);     // 0 -> 2, 1 -> 4
+  }
+
+  // Given a child compute parent
+  int Parent(int i) {
+    return (i-1)/2;     // 1 -> 0, 2 -> 0,  3 -> 1,  4-> 1
+  }
+
+  // Swap a child, parent. Use to move element up/down tree.
+  // Note a little tricky here. When we swap we need to swap:
+  //   the value
+  //   the associated keys
+  //   the position of the value in the heap
+  void Swap(int j, int k) {
+    int tkey = key_[j];
+    pos_[key_[j] = key_[k]] = j;
+    pos_[key_[k] = tkey]    = k;
+
+    T val  = A_[j];
+    A_[j]  = A_[k];
+    A_[k]  = val;
+  }
+
+  // Returns the greater (max=true) / least (max=false) of two
+  // elements.
+  bool Better(const T& x, const T& y) {
+    return max ? comp_(y, x) : comp_(x, y);
+  }
+
+  // Heapify subtree rooted at index i.
+  void Heapify(int i) {
+    int l = Left(i);
+    int r = Right(i);
+    int largest;
+
+    if (l < size_ && Better(A_[l], A_[i]) )
+      largest = l;
+    else
+      largest = i;
+
+    if (r < size_ && Better(A_[r], A_[largest]) )
+      largest = r;
+
+    if (largest != i) {
+      Swap(i, largest);
+      Heapify(largest);
+    }
+  }
+
+
+  // Insert (update) element at subtree rooted at index i
+  int Insert(const T& val, int i) {
+    int p;
+    while (i > 0 && !Better(A_[p = Parent(i)], val)) {
+      Swap(i, p);
+      i = p;
+    }
+
+    return key_[i];
+  }
+
+ private:
+  Compare comp_;
+
+  vector<int> pos_;
+  vector<int> key_;
+  vector<T>   A_;
+  int  size_;
+
+  // DISALLOW_COPY_AND_ASSIGN(Heap);
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_HEAP_H__
diff --git a/src/include/fst/icu.h b/src/include/fst/icu.h
new file mode 100644
index 0000000..6b74c2e
--- /dev/null
+++ b/src/include/fst/icu.h
@@ -0,0 +1,103 @@
+// icu.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: roubert@google.com (Fredrik Roubert)
+
+// Wrapper class for UErrorCode, with conversion operators for direct use in
+// ICU C and C++ APIs.
+//
+// Features:
+// - The constructor initializes the internal UErrorCode to U_ZERO_ERROR,
+//   removing one common source of errors.
+// - Same use in C APIs taking a UErrorCode* (pointer) and C++ taking
+//   UErrorCode& (reference), via conversion operators.
+// - Automatic checking for success when it goes out of scope. On failure,
+//   the destructor will FSTERROR() an error message.
+//
+// Most of ICU will handle errors gracefully and provide sensible fallbacks.
+// Using IcuErrorCode, it is therefore possible to write very compact code
+// that does sensible things on failure and provides logging for debugging.
+//
+// Example:
+//
+// IcuErrorCode icuerrorcode;
+// return collator.compareUTF8(a, b, icuerrorcode) == UCOL_EQUAL;
+
+#ifndef FST_LIB_ICU_H_
+#define FST_LIB_ICU_H_
+
+#include <unicode/errorcode.h>
+#include <unicode/unistr.h>
+#include <unicode/ustring.h>
+#include <unicode/utf8.h>
+
+class IcuErrorCode : public icu::ErrorCode {
+ public:
+  IcuErrorCode() {}
+  virtual ~IcuErrorCode() { if (isFailure()) handleFailure(); }
+
+  // Redefine 'errorName()' in order to be compatible with ICU version 4.2
+  const char* errorName() const {
+    return u_errorName(errorCode);
+  }
+
+ protected:
+  virtual void handleFailure() const {
+    FSTERROR() << errorName();
+}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(IcuErrorCode);
+};
+
+namespace fst {
+
+template <class Label>
+bool UTF8StringToLabels(const string &str, vector<Label> *labels) {
+  const char *c_str = str.c_str();
+  int32_t length = str.size();
+  UChar32 c;
+  for (int32_t i = 0; i < length; /* no update */) {
+    U8_NEXT(c_str, i, length, c);
+    if (c < 0) {
+      LOG(ERROR) << "UTF8StringToLabels: Invalid character found: " << c;
+      return false;
+    }
+    labels->push_back(c);
+  }
+  return true;
+}
+
+template <class Label>
+bool LabelsToUTF8String(const vector<Label> &labels, string *str) {
+  icu::UnicodeString u_str;
+  char c_str[5];
+  for (size_t i = 0; i < labels.size(); ++i) {
+    u_str.setTo(labels[i]);
+    IcuErrorCode error;
+    u_strToUTF8(c_str, 5, NULL, u_str.getTerminatedBuffer(), -1, error);
+    if (error.isFailure()) {
+      LOG(ERROR) << "LabelsToUTF8String: Bad encoding: "
+                 << error.errorName();
+      return false;
+    }
+    *str += c_str;
+  }
+  return true;
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_ICU_H_
diff --git a/src/include/fst/intersect.h b/src/include/fst/intersect.h
new file mode 100644
index 0000000..f46116f
--- /dev/null
+++ b/src/include/fst/intersect.h
@@ -0,0 +1,172 @@
+// intersect.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to compute the intersection of two FSAs
+
+#ifndef FST_LIB_INTERSECT_H__
+#define FST_LIB_INTERSECT_H__
+
+#include <algorithm>
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+#include <fst/compose.h>
+
+
+namespace fst {
+
+template <class A,
+          class M = Matcher<Fst<A> >,
+          class F = SequenceComposeFilter<M>,
+          class T = GenericComposeStateTable<A, typename F::FilterState> >
+struct IntersectFstOptions : public ComposeFstOptions<A, M, F, T> {
+  explicit IntersectFstOptions(const CacheOptions &opts,
+                               M *mat1 = 0, M *mat2 = 0,
+                               F *filt = 0, T *sttable= 0)
+      : ComposeFstOptions<A, M, F, T>(opts, mat1, mat2, filt, sttable) { }
+
+  IntersectFstOptions() {}
+};
+
+// Computes the intersection (Hadamard product) of two FSAs. This
+// version is a delayed Fst.  Only strings that are in both automata
+// are retained in the result.
+//
+// The two arguments must be acceptors. One of the arguments must be
+// label-sorted.
+//
+// Complexity: same as ComposeFst.
+//
+// Caveats:  same as ComposeFst.
+template <class A>
+class IntersectFst : public ComposeFst<A> {
+ public:
+  using ComposeFst<A>::CreateBase;
+  using ComposeFst<A>::CreateBase1;
+  using ComposeFst<A>::Properties;
+  using ImplToFst< ComposeFstImplBase<A> >::GetImpl;
+  using ImplToFst< ComposeFstImplBase<A> >::SetImpl;
+
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  IntersectFst(const Fst<A> &fst1, const Fst<A> &fst2,
+               const CacheOptions opts = CacheOptions()) {
+    bool acceptors = fst1.Properties(kAcceptor, true) &&
+        fst2.Properties(kAcceptor, true);
+    SetImpl(CreateBase(fst1, fst2, opts));
+    if (!acceptors) {
+      FSTERROR() << "IntersectFst: input FSTs are not acceptors";
+      GetImpl()->SetProperties(kError);
+    }
+  }
+
+  template <class M, class F, class T>
+  IntersectFst(const Fst<A> &fst1, const Fst<A> &fst2,
+               const IntersectFstOptions<A, M, F, T> &opts) {
+    bool acceptors = fst1.Properties(kAcceptor, true) &&
+        fst2.Properties(kAcceptor, true);
+    SetImpl(CreateBase1(fst1, fst2, opts));
+    if (!acceptors) {
+      FSTERROR() << "IntersectFst: input FSTs are not acceptors";
+      GetImpl()->SetProperties(kError);
+    }
+  }
+
+  // See Fst<>::Copy() for doc.
+  IntersectFst(const IntersectFst<A> &fst, bool safe = false) :
+      ComposeFst<A>(fst, safe) {}
+
+  // Get a copy of this IntersectFst. See Fst<>::Copy() for further doc.
+  virtual IntersectFst<A> *Copy(bool safe = false) const {
+    return new IntersectFst<A>(*this, safe);
+  }
+};
+
+
+// Specialization for IntersectFst.
+template <class A>
+class StateIterator< IntersectFst<A> >
+    : public StateIterator< ComposeFst<A> > {
+ public:
+  explicit StateIterator(const IntersectFst<A> &fst)
+      : StateIterator< ComposeFst<A> >(fst) {}
+};
+
+
+// Specialization for IntersectFst.
+template <class A>
+class ArcIterator< IntersectFst<A> >
+    : public ArcIterator< ComposeFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const IntersectFst<A> &fst, StateId s)
+      : ArcIterator< ComposeFst<A> >(fst, s) {}
+};
+
+// Useful alias when using StdArc.
+typedef IntersectFst<StdArc> StdIntersectFst;
+
+
+typedef ComposeOptions IntersectOptions;
+
+
+// Computes the intersection (Hadamard product) of two FSAs. This
+// version writes the intersection to an output MurableFst. Only
+// strings that are in both automata are retained in the result.
+//
+// The two arguments must be acceptors. One of the arguments must be
+// label-sorted.
+//
+// Complexity: same as Compose.
+//
+// Caveats:  same as Compose.
+template<class Arc>
+void Intersect(const Fst<Arc> &ifst1, const Fst<Arc> &ifst2,
+             MutableFst<Arc> *ofst,
+             const IntersectOptions &opts = IntersectOptions()) {
+  typedef Matcher< Fst<Arc> > M;
+
+  if (opts.filter_type == AUTO_FILTER) {
+    CacheOptions nopts;
+    nopts.gc_limit = 0;  // Cache only the last state for fastest copy.
+    *ofst = IntersectFst<Arc>(ifst1, ifst2, nopts);
+  } else if (opts.filter_type == SEQUENCE_FILTER) {
+    IntersectFstOptions<Arc> iopts;
+    iopts.gc_limit = 0;  // Cache only the last state for fastest copy.
+    *ofst = IntersectFst<Arc>(ifst1, ifst2, iopts);
+  } else if (opts.filter_type == ALT_SEQUENCE_FILTER) {
+    IntersectFstOptions<Arc, M, AltSequenceComposeFilter<M> > iopts;
+    iopts.gc_limit = 0;  // Cache only the last state for fastest copy.
+    *ofst = IntersectFst<Arc>(ifst1, ifst2, iopts);
+  } else if (opts.filter_type == MATCH_FILTER) {
+    IntersectFstOptions<Arc, M, MatchComposeFilter<M> > iopts;
+    iopts.gc_limit = 0;  // Cache only the last state for fastest copy.
+    *ofst = IntersectFst<Arc>(ifst1, ifst2, iopts);
+  }
+
+  if (opts.connect)
+    Connect(ofst);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_INTERSECT_H__
diff --git a/src/include/fst/interval-set.h b/src/include/fst/interval-set.h
new file mode 100644
index 0000000..cf6ac54
--- /dev/null
+++ b/src/include/fst/interval-set.h
@@ -0,0 +1,381 @@
+// interval-set.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to represent and operate on sets of intervals.
+
+#ifndef FST_LIB_INTERVAL_SET_H__
+#define FST_LIB_INTERVAL_SET_H__
+
+#include <iostream>
+#include <vector>
+using std::vector;
+
+
+#include <fst/util.h>
+
+
+namespace fst {
+
+// Stores and operates on a set of half-open integral intervals [a,b)
+// of signed integers of type T.
+template <typename T>
+class IntervalSet {
+ public:
+  struct Interval {
+    T begin;
+    T end;
+
+    Interval() : begin(-1), end(-1) {}
+
+    Interval(T b, T e) : begin(b), end(e) {}
+
+    bool operator<(const Interval &i) const {
+      return begin < i.begin || (begin == i.begin && end > i.end);
+    }
+
+    bool operator==(const Interval &i) const {
+      return begin == i.begin && end == i.end;
+    }
+
+    bool operator!=(const Interval &i) const {
+      return begin != i.begin || end != i.end;
+    }
+
+    istream &Read(istream &strm) {
+      T n;
+      ReadType(strm, &n);
+      begin = n;
+      ReadType(strm, &n);
+      end = n;
+      return strm;
+    }
+
+    ostream &Write(ostream &strm) const {
+      T n = begin;
+      WriteType(strm, n);
+      n = end;
+      WriteType(strm, n);
+      return strm;
+    }
+  };
+
+  IntervalSet() : count_(-1) {}
+
+  // Returns the interval set as a vector.
+  vector<Interval> *Intervals() { return &intervals_; }
+
+  const vector<Interval> *Intervals() const { return &intervals_; }
+
+  const bool Empty() const { return intervals_.empty(); }
+
+  const T Size() const { return intervals_.size(); }
+
+  // Number of points in the intervals (undefined if not normalized).
+  const T Count() const { return count_; }
+
+  void Clear() {
+    intervals_.clear();
+    count_ = 0;
+  }
+
+  // Adds an interval set to the set. The result may not be normalized.
+  void Union(const IntervalSet<T> &iset) {
+    const vector<Interval> *intervals = iset.Intervals();
+    for (typename vector<Interval>::const_iterator it = intervals->begin();
+         it != intervals->end(); ++it)
+      intervals_.push_back(*it);
+  }
+
+  // Requires intervals be normalized.
+  bool Member(T value) const {
+    Interval interval(value, value);
+    typename vector<Interval>::const_iterator lb =
+        lower_bound(intervals_.begin(), intervals_.end(), interval);
+    if (lb == intervals_.begin())
+      return false;
+    return (--lb)->end > value;
+  }
+
+  // Requires intervals be normalized.
+  bool operator==(const IntervalSet<T>& iset) const {
+    return *(iset.Intervals()) == intervals_;
+  }
+
+  // Requires intervals be normalized.
+  bool operator!=(const IntervalSet<T>& iset) const {
+    return *(iset.Intervals()) != intervals_;
+  }
+
+  bool Singleton() const {
+    return intervals_.size() == 1 &&
+        intervals_[0].begin + 1 == intervals_[0].end;
+  }
+
+
+  // Sorts; collapses overlapping and adjacent interals; sets count.
+  void Normalize();
+
+  // Intersects an interval set with the set. Requires intervals be
+  // normalized. The result is normalized.
+  void Intersect(const IntervalSet<T> &iset, IntervalSet<T> *oset) const;
+
+  // Complements the set w.r.t [0, maxval). Requires intervals be
+  // normalized. The result is normalized.
+  void Complement(T maxval, IntervalSet<T> *oset) const;
+
+  // Subtract an interval set from the set. Requires intervals be
+  // normalized. The result is normalized.
+  void Difference(const IntervalSet<T> &iset, IntervalSet<T> *oset) const;
+
+  // Determines if an interval set overlaps with the set. Requires
+  // intervals be normalized.
+  bool Overlaps(const IntervalSet<T> &iset) const;
+
+  // Determines if an interval set overlaps with the set but neither
+  // is contained in the other. Requires intervals be normalized.
+  bool StrictlyOverlaps(const IntervalSet<T> &iset) const;
+
+  // Determines if an interval set is contained within the set. Requires
+  // intervals be normalized.
+  bool Contains(const IntervalSet<T> &iset) const;
+
+  istream &Read(istream &strm) {
+    ReadType(strm, &intervals_);
+    return ReadType(strm, &count_);
+  }
+
+  ostream &Write(ostream &strm) const {
+    WriteType(strm, intervals_);
+    return WriteType(strm, count_);
+  }
+
+ private:
+  vector<Interval> intervals_;
+  T count_;
+};
+
+// Sorts; collapses overlapping and adjacent interavls; sets count.
+template <typename T>
+void IntervalSet<T>::Normalize() {
+  sort(intervals_.begin(), intervals_.end());
+
+  count_ = 0;
+  T size = 0;
+  for (T i = 0; i < intervals_.size(); ++i) {
+    Interval &inti = intervals_[i];
+    if (inti.begin == inti.end)
+      continue;
+    for (T j = i + 1; j < intervals_.size(); ++j) {
+      Interval &intj = intervals_[j];
+      if (intj.begin > inti.end)
+        break;
+      if (intj.end > inti.end)
+        inti.end = intj.end;
+      ++i;
+    }
+    count_ += inti.end - inti.begin;
+    intervals_[size++] = inti;
+  }
+  intervals_.resize(size);
+}
+
+// Intersects an interval set with the set. Requires intervals be normalized.
+// The result is normalized.
+template <typename T>
+void IntervalSet<T>::Intersect(const IntervalSet<T> &iset,
+                               IntervalSet<T> *oset) const {
+  const vector<Interval> *iintervals = iset.Intervals();
+  vector<Interval> *ointervals = oset->Intervals();
+  typename vector<Interval>::const_iterator it1 = intervals_.begin();
+  typename vector<Interval>::const_iterator it2 = iintervals->begin();
+
+  ointervals->clear();
+  oset->count_ = 0;
+
+  while (it1 != intervals_.end() && it2 != iintervals->end()) {
+    if (it1->end <= it2->begin) {
+      ++it1;
+    } else if (it2->end <= it1->begin) {
+      ++it2;
+    } else {
+      Interval interval;
+      interval.begin = max(it1->begin, it2->begin);
+      interval.end = min(it1->end, it2->end);
+      ointervals->push_back(interval);
+      oset->count_ += interval.end - interval.begin;
+      if (it1->end < it2->end)
+        ++it1;
+      else
+        ++it2;
+    }
+  }
+}
+
+// Complements the set w.r.t [0, maxval). Requires intervals be normalized.
+// The result is normalized.
+template <typename T>
+void IntervalSet<T>::Complement(T maxval, IntervalSet<T> *oset) const {
+  vector<Interval> *ointervals = oset->Intervals();
+  ointervals->clear();
+  oset->count_ = 0;
+
+  Interval interval;
+  interval.begin = 0;
+  for (typename vector<Interval>::const_iterator it = intervals_.begin();
+       it != intervals_.end();
+       ++it) {
+    interval.end = min(it->begin, maxval);
+    if (interval.begin < interval.end) {
+      ointervals->push_back(interval);
+      oset->count_ += interval.end - interval.begin;
+    }
+    interval.begin = it->end;
+  }
+  interval.end = maxval;
+  if (interval.begin < interval.end) {
+    ointervals->push_back(interval);
+    oset->count_ += interval.end - interval.begin;
+  }
+}
+
+// Subtract an interval set from the set. Requires intervals be normalized.
+// The result is normalized.
+template <typename T>
+void IntervalSet<T>::Difference(const IntervalSet<T> &iset,
+                                IntervalSet<T> *oset) const {
+  if (intervals_.empty()) {
+    oset->Intervals()->clear();
+    oset->count_ = 0;
+  } else {
+    IntervalSet<T> cset;
+    iset.Complement(intervals_.back().end, &cset);
+    Intersect(cset, oset);
+  }
+}
+
+// Determines if an interval set overlaps with the set. Requires
+// intervals be normalized.
+template <typename T>
+bool IntervalSet<T>::Overlaps(const IntervalSet<T> &iset) const {
+  const vector<Interval> *intervals = iset.Intervals();
+  typename vector<Interval>::const_iterator it1 = intervals_.begin();
+  typename vector<Interval>::const_iterator it2 = intervals->begin();
+
+  while (it1 != intervals_.end() && it2 != intervals->end()) {
+    if (it1->end <= it2->begin) {
+      ++it1;
+    } else if (it2->end <= it1->begin) {
+      ++it2;
+    } else {
+      return true;
+    }
+  }
+  return false;
+}
+
+// Determines if an interval set overlaps with the set but neither
+// is contained in the other. Requires intervals be normalized.
+template <typename T>
+bool IntervalSet<T>::StrictlyOverlaps(const IntervalSet<T> &iset) const {
+  const vector<Interval> *intervals = iset.Intervals();
+  typename vector<Interval>::const_iterator it1 = intervals_.begin();
+  typename vector<Interval>::const_iterator it2 = intervals->begin();
+  bool only1 = false;   // point in intervals_ but not intervals
+  bool only2 = false;   // point in intervals but not intervals_
+  bool overlap = false; // point in both intervals_ and intervals
+
+  while (it1 != intervals_.end() && it2 != intervals->end()) {
+    if (it1->end <= it2->begin) {  // no overlap - it1 first
+      only1 = true;
+      ++it1;
+    } else if (it2->end <= it1->begin) {  // no overlap - it2 first
+      only2 = true;
+      ++it2;
+    } else if (it2->begin == it1->begin && it2->end == it1->end) {  // equals
+      overlap = true;
+      ++it1;
+      ++it2;
+    } else if (it2->begin <= it1->begin && it2->end >= it1->end) {  // 1 c 2
+      only2 = true;
+      overlap = true;
+      ++it1;
+    } else if (it1->begin <= it2->begin && it1->end >= it2->end) {  // 2 c 1
+      only1 = true;
+      overlap = true;
+      ++it2;
+    } else {  // strict overlap
+      only1 = true;
+      only2 = true;
+      overlap = true;
+    }
+    if (only1 == true && only2 == true && overlap == true)
+      return true;
+  }
+  if (it1 != intervals_.end())
+    only1 = true;
+  if (it2 != intervals->end())
+    only2 = true;
+
+  return only1 == true && only2 == true && overlap == true;
+}
+
+// Determines if an interval set is contained within the set. Requires
+// intervals be normalized.
+template <typename T>
+bool IntervalSet<T>::Contains(const IntervalSet<T> &iset) const {
+  if (iset.Count() > Count())
+    return false;
+
+  const vector<Interval> *intervals = iset.Intervals();
+  typename vector<Interval>::const_iterator it1 = intervals_.begin();
+  typename vector<Interval>::const_iterator it2 = intervals->begin();
+
+  while (it1 != intervals_.end() && it2 != intervals->end()) {
+    if (it1->end <= it2->begin) {  // no overlap - it1 first
+      ++it1;
+    } else if (it2->begin < it1->begin || it2->end > it1->end) {  // no C
+      return false;
+    } else if (it2->end == it1->end) {
+      ++it1;
+      ++it2;
+    } else {
+      ++it2;
+    }
+  }
+  return it2 == intervals->end();
+}
+
+template <typename T>
+ostream &operator<<(ostream &strm, const IntervalSet<T> &s)  {
+  typedef typename IntervalSet<T>::Interval Interval;
+  const vector<Interval> *intervals = s.Intervals();
+  strm << "{";
+  for (typename vector<Interval>::const_iterator it = intervals->begin();
+       it != intervals->end();
+       ++it) {
+    if (it != intervals->begin())
+      strm << ",";
+    strm << "[" << it->begin << "," << it->end << ")";
+  }
+  strm << "}";
+  return strm;
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_INTERVAL_SET_H__
diff --git a/src/include/fst/invert.h b/src/include/fst/invert.h
new file mode 100644
index 0000000..bc83a5d
--- /dev/null
+++ b/src/include/fst/invert.h
@@ -0,0 +1,125 @@
+// invert.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Functions and classes to invert an Fst.
+
+#ifndef FST_LIB_INVERT_H__
+#define FST_LIB_INVERT_H__
+
+#include <fst/arc-map.h>
+#include <fst/mutable-fst.h>
+
+
+namespace fst {
+
+// Mapper to implement inversion of an arc.
+template <class A> struct InvertMapper {
+  InvertMapper() {}
+
+  A operator()(const A &arc) {
+    return A(arc.olabel, arc.ilabel, arc.weight, arc.nextstate);
+  }
+
+  MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_CLEAR_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_CLEAR_SYMBOLS;}
+
+  uint64 Properties(uint64 props) { return InvertProperties(props); }
+};
+
+
+// Inverts the transduction corresponding to an FST by exchanging the
+// FST's input and output labels. This version modifies its input.
+//
+// Complexity:
+// - Time: O(V + E)
+// - Space: O(1)
+// where V = # of states and E = # of arcs.
+template<class Arc> inline
+void Invert(MutableFst<Arc> *fst) {
+  SymbolTable *input = fst->InputSymbols() ? fst->InputSymbols()->Copy() : 0;
+  SymbolTable *output = fst->OutputSymbols() ? fst->OutputSymbols()->Copy() : 0;
+  ArcMap(fst, InvertMapper<Arc>());
+  fst->SetInputSymbols(output);
+  fst->SetOutputSymbols(input);
+  delete input;
+  delete output;
+}
+
+
+// Inverts the transduction corresponding to an FST by exchanging the
+// FST's input and output labels.  This version is a delayed Fst.
+//
+// Complexity:
+// - Time: O(v + e)
+// - Space: O(1)
+// where v = # of states visited, e = # of arcs visited. Constant
+// time and to visit an input state or arc is assumed and exclusive
+// of caching.
+template <class A>
+class InvertFst : public ArcMapFst<A, A, InvertMapper<A> > {
+ public:
+  typedef A Arc;
+  typedef InvertMapper<A> C;
+  typedef ArcMapFstImpl< A, A, InvertMapper<A> > Impl;
+  using ImplToFst<Impl>::GetImpl;
+
+  explicit InvertFst(const Fst<A> &fst) : ArcMapFst<A, A, C>(fst, C()) {
+    GetImpl()->SetOutputSymbols(fst.InputSymbols());
+    GetImpl()->SetInputSymbols(fst.OutputSymbols());
+  }
+
+  // See Fst<>::Copy() for doc.
+  InvertFst(const InvertFst<A> &fst, bool safe = false)
+      : ArcMapFst<A, A, C>(fst, safe) {}
+
+  // Get a copy of this InvertFst. See Fst<>::Copy() for further doc.
+  virtual InvertFst<A> *Copy(bool safe = false) const {
+    return new InvertFst(*this, safe);
+  }
+};
+
+
+// Specialization for InvertFst.
+template <class A>
+class StateIterator< InvertFst<A> >
+    : public StateIterator< ArcMapFst<A, A, InvertMapper<A> > > {
+ public:
+  explicit StateIterator(const InvertFst<A> &fst)
+      : StateIterator< ArcMapFst<A, A, InvertMapper<A> > >(fst) {}
+};
+
+
+// Specialization for InvertFst.
+template <class A>
+class ArcIterator< InvertFst<A> >
+    : public ArcIterator< ArcMapFst<A, A, InvertMapper<A> > > {
+ public:
+  ArcIterator(const InvertFst<A> &fst, typename A::StateId s)
+      : ArcIterator< ArcMapFst<A, A, InvertMapper<A> > >(fst, s) {}
+};
+
+
+// Useful alias when using StdArc.
+typedef InvertFst<StdArc> StdInvertFst;
+
+}  // namespace fst
+
+#endif  // FST_LIB_INVERT_H__
diff --git a/src/include/fst/label-reachable.h b/src/include/fst/label-reachable.h
new file mode 100644
index 0000000..8f9aca8
--- /dev/null
+++ b/src/include/fst/label-reachable.h
@@ -0,0 +1,565 @@
+// label_reachable.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to determine if a non-epsilon label can be read as the
+// first non-epsilon symbol along some path from a given state.
+
+
+#ifndef FST_LIB_LABEL_REACHABLE_H__
+#define FST_LIB_LABEL_REACHABLE_H__
+
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <vector>
+using std::vector;
+
+#include <fst/accumulator.h>
+#include <fst/arcsort.h>
+#include <fst/interval-set.h>
+#include <fst/state-reachable.h>
+#include <fst/vector-fst.h>
+
+
+namespace fst {
+
+// Stores shareable data for label reachable class copies.
+template <typename L>
+class LabelReachableData {
+ public:
+  typedef L Label;
+  typedef typename IntervalSet<L>::Interval Interval;
+
+  explicit LabelReachableData(bool reach_input, bool keep_relabel_data = true)
+      : reach_input_(reach_input),
+        keep_relabel_data_(keep_relabel_data),
+        have_relabel_data_(true),
+        final_label_(kNoLabel) {}
+
+  ~LabelReachableData() {}
+
+  bool ReachInput() const { return reach_input_; }
+
+  vector< IntervalSet<L> > *IntervalSets() { return &isets_; }
+
+  unordered_map<L, L> *Label2Index() {
+    if (!have_relabel_data_)
+      FSTERROR() << "LabelReachableData: no relabeling data";
+    return &label2index_;
+  }
+
+  Label FinalLabel() {
+    if (final_label_ == kNoLabel)
+      final_label_ = label2index_[kNoLabel];
+    return final_label_;
+  }
+
+  static LabelReachableData<L> *Read(istream &istrm) {
+    LabelReachableData<L> *data = new LabelReachableData<L>();
+
+    ReadType(istrm, &data->reach_input_);
+    ReadType(istrm, &data->keep_relabel_data_);
+    data->have_relabel_data_ = data->keep_relabel_data_;
+    if (data->keep_relabel_data_)
+      ReadType(istrm, &data->label2index_);
+    ReadType(istrm, &data->final_label_);
+    ReadType(istrm, &data->isets_);
+    return data;
+  }
+
+  bool Write(ostream &ostrm) {
+    WriteType(ostrm, reach_input_);
+    WriteType(ostrm, keep_relabel_data_);
+    if (keep_relabel_data_)
+      WriteType(ostrm, label2index_);
+    WriteType(ostrm, FinalLabel());
+    WriteType(ostrm, isets_);
+    return true;
+  }
+
+  int RefCount() const { return ref_count_.count(); }
+  int IncrRefCount() { return ref_count_.Incr(); }
+  int DecrRefCount() { return ref_count_.Decr(); }
+
+ private:
+  LabelReachableData() {}
+
+  bool reach_input_;                  // Input or output labels considered?
+  bool keep_relabel_data_;            // Save label2index_ to file?
+  bool have_relabel_data_;            // Using label2index_?
+  Label final_label_;                 // Final label
+  RefCounter ref_count_;              // Reference count.
+  unordered_map<L, L> label2index_;        // Finds index for a label.
+  vector<IntervalSet <L> > isets_;    // Interval sets per state.
+
+  DISALLOW_COPY_AND_ASSIGN(LabelReachableData);
+};
+
+
+// Tests reachability of labels from a given state. If reach_input =
+// true, then input labels are considered, o.w. output labels are
+// considered. To test for reachability from a state s, first do
+// SetState(s). Then a label l can be reached from state s of FST f
+// iff Reach(r) is true where r = Relabel(l). The relabeling is
+// required to ensure a compact representation of the reachable
+// labels.
+
+// The whole FST can be relabeled instead with Relabel(&f,
+// reach_input) so that the test Reach(r) applies directly to the
+// labels of the transformed FST f. The relabeled FST will also be
+// sorted appropriately for composition.
+//
+// Reachablity of a final state from state s (via an epsilon path)
+// can be tested with ReachFinal();
+//
+// Reachability can also be tested on the set of labels specified by
+// an arc iterator, useful for FST composition.  In particular,
+// Reach(aiter, ...) is true if labels on the input (output) side of
+// the transitions of the arc iterator, when iter_input is true
+// (false), can be reached from the state s. The iterator labels must
+// have already been relabeled.
+//
+// With the arc iterator test of reachability, the begin position, end
+// position and accumulated arc weight of the matches can be
+// returned. The optional template argument controls how reachable arc
+// weights are accumulated.  The default uses the semiring
+// Plus(). Alternative ones can be used to distribute the weights in
+// composition in various ways.
+template <class A, class S = DefaultAccumulator<A> >
+class LabelReachable {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename IntervalSet<Label>::Interval Interval;
+
+  LabelReachable(const Fst<A> &fst, bool reach_input, S *s = 0,
+                 bool keep_relabel_data = true)
+      : fst_(new VectorFst<Arc>(fst)),
+        s_(kNoStateId),
+        data_(new LabelReachableData<Label>(reach_input, keep_relabel_data)),
+        accumulator_(s ? s : new S()),
+        ncalls_(0),
+        nintervals_(0),
+        error_(false) {
+    StateId ins = fst_->NumStates();
+    TransformFst();
+    FindIntervals(ins);
+    delete fst_;
+  }
+
+  explicit LabelReachable(LabelReachableData<Label> *data, S *s = 0)
+    : fst_(0),
+      s_(kNoStateId),
+      data_(data),
+      accumulator_(s ? s : new S()),
+      ncalls_(0),
+      nintervals_(0),
+      error_(false) {
+    data_->IncrRefCount();
+  }
+
+  LabelReachable(const LabelReachable<A, S> &reachable) :
+      fst_(0),
+      s_(kNoStateId),
+      data_(reachable.data_),
+      accumulator_(new S(*reachable.accumulator_)),
+      ncalls_(0),
+      nintervals_(0),
+      error_(reachable.error_) {
+    data_->IncrRefCount();
+  }
+
+  ~LabelReachable() {
+    if (!data_->DecrRefCount())
+      delete data_;
+    delete accumulator_;
+    if (ncalls_ > 0) {
+      VLOG(2) << "# of calls: " << ncalls_;
+      VLOG(2) << "# of intervals/call: " << (nintervals_ / ncalls_);
+    }
+  }
+
+  // Relabels w.r.t labels that give compact label sets.
+  Label Relabel(Label label) {
+    if (label == 0 || error_)
+      return label;
+    unordered_map<Label, Label> &label2index = *data_->Label2Index();
+    Label &relabel = label2index[label];
+    if (!relabel)  // Add new label
+      relabel = label2index.size() + 1;
+    return relabel;
+  }
+
+  // Relabels Fst w.r.t to labels that give compact label sets.
+  void Relabel(MutableFst<Arc> *fst, bool relabel_input) {
+    for (StateIterator< MutableFst<Arc> > siter(*fst);
+         !siter.Done(); siter.Next()) {
+      StateId s = siter.Value();
+      for (MutableArcIterator< MutableFst<Arc> > aiter(fst, s);
+           !aiter.Done();
+           aiter.Next()) {
+        Arc arc = aiter.Value();
+        if (relabel_input)
+          arc.ilabel = Relabel(arc.ilabel);
+        else
+          arc.olabel = Relabel(arc.olabel);
+        aiter.SetValue(arc);
+      }
+    }
+    if (relabel_input) {
+      ArcSort(fst, ILabelCompare<Arc>());
+      fst->SetInputSymbols(0);
+    } else {
+      ArcSort(fst, OLabelCompare<Arc>());
+      fst->SetOutputSymbols(0);
+    }
+  }
+
+  // Returns relabeling pairs (cf. relabel.h::Relabel()).
+  // If 'avoid_collisions' is true, extra pairs are added to
+  // ensure no collisions when relabeling automata that have
+  // labels unseen here.
+  void RelabelPairs(vector<pair<Label, Label> > *pairs,
+                    bool avoid_collisions = false) {
+    pairs->clear();
+    unordered_map<Label, Label> &label2index = *data_->Label2Index();
+    // Maps labels to their new values in [1, label2index().size()]
+    for (typename unordered_map<Label, Label>::const_iterator
+             it = label2index.begin(); it != label2index.end(); ++it)
+      if (it->second != data_->FinalLabel())
+        pairs->push_back(pair<Label, Label>(it->first, it->second));
+    if (avoid_collisions) {
+      // Ensures any label in [1, label2index().size()] is mapped either
+      // by the above step or to label2index() + 1 (to avoid collisions).
+      for (int i = 1; i <= label2index.size(); ++i) {
+        typename unordered_map<Label, Label>::const_iterator
+            it = label2index.find(i);
+        if (it == label2index.end() || it->second == data_->FinalLabel())
+          pairs->push_back(pair<Label, Label>(i, label2index.size() + 1));
+      }
+    }
+  }
+
+  // Set current state. Optionally set state associated
+  // with arc iterator to be passed to Reach.
+  void SetState(StateId s, StateId aiter_s = kNoStateId) {
+    s_ = s;
+    if (aiter_s != kNoStateId) {
+      accumulator_->SetState(aiter_s);
+      if (accumulator_->Error()) error_ = true;
+    }
+  }
+
+  // Can reach this label from current state?
+  // Original labels must be transformed by the Relabel methods above.
+  bool Reach(Label label) {
+    if (label == 0 || error_)
+      return false;
+    vector< IntervalSet<Label> > &isets = *data_->IntervalSets();
+    return isets[s_].Member(label);
+
+  }
+
+  // Can reach final state (via epsilon transitions) from this state?
+  bool ReachFinal() {
+    if (error_) return false;
+    vector< IntervalSet<Label> > &isets = *data_->IntervalSets();
+    return isets[s_].Member(data_->FinalLabel());
+  }
+
+  // Initialize with secondary FST to be used with Reach(Iterator,...).
+  // If copy is true, then 'fst' is a copy of the FST used in the
+  // previous call to this method (useful to avoid unnecessary updates).
+  template <class F>
+  void ReachInit(const F &fst, bool copy = false) {
+    accumulator_->Init(fst, copy);
+    if (accumulator_->Error()) error_ = true;
+  }
+
+  // Can reach any arc iterator label between iterator positions
+  // aiter_begin and aiter_end?  If aiter_input = true, then iterator
+  // input labels are considered, o.w. output labels are considered.
+  // Arc iterator labels must be transformed by the Relabel methods
+  // above. If compute_weight is true, user may call ReachWeight().
+  template <class Iterator>
+  bool Reach(Iterator *aiter, ssize_t aiter_begin,
+             ssize_t aiter_end, bool aiter_input, bool compute_weight) {
+    if (error_) return false;
+    vector< IntervalSet<Label> > &isets = *data_->IntervalSets();
+    const vector<Interval> *intervals = isets[s_].Intervals();
+    ++ncalls_;
+    nintervals_ += intervals->size();
+
+    reach_begin_ = -1;
+    reach_end_ = -1;
+    reach_weight_ = Weight::Zero();
+
+    uint32 flags = aiter->Flags();  // save flags to restore them on exit
+    aiter->SetFlags(kArcNoCache, kArcNoCache);  // make caching optional
+    aiter->Seek(aiter_begin);
+
+    if (2 * (aiter_end - aiter_begin) < intervals->size()) {
+      // Check each arc against intervals.
+      // Set arc iterator flags to only compute the ilabel or olabel values,
+      // since they are the only values required for most of the arcs processed.
+      aiter->SetFlags(aiter_input ? kArcILabelValue : kArcOLabelValue,
+                      kArcValueFlags);
+      Label reach_label = kNoLabel;
+      for (ssize_t aiter_pos = aiter_begin;
+           aiter_pos < aiter_end; aiter->Next(), ++aiter_pos) {
+        const A &arc = aiter->Value();
+        Label label = aiter_input ? arc.ilabel : arc.olabel;
+        if (label == reach_label || Reach(label)) {
+          reach_label = label;
+          if (reach_begin_ < 0)
+            reach_begin_ = aiter_pos;
+          reach_end_ = aiter_pos + 1;
+          if (compute_weight) {
+            if (!(aiter->Flags() & kArcWeightValue)) {
+              // If the 'arc.weight' wasn't computed by the call
+              // to 'aiter->Value()' above, we need to call
+              // 'aiter->Value()' again after having set the arc iterator
+              // flags to compute the arc weight value.
+              aiter->SetFlags(kArcWeightValue, kArcValueFlags);
+              const A &arcb = aiter->Value();
+              // Call the accumulator.
+              reach_weight_ = accumulator_->Sum(reach_weight_, arcb.weight);
+              // Only ilabel or olabel required to process the following
+              // arcs.
+              aiter->SetFlags(aiter_input ? kArcILabelValue : kArcOLabelValue,
+                              kArcValueFlags);
+            } else {
+              // Call the accumulator.
+              reach_weight_ = accumulator_->Sum(reach_weight_, arc.weight);
+            }
+          }
+        }
+      }
+    } else {
+      // Check each interval against arcs
+      ssize_t begin_low, end_low = aiter_begin;
+      for (typename vector<Interval>::const_iterator
+               iiter = intervals->begin();
+           iiter != intervals->end(); ++iiter) {
+        begin_low = LowerBound(aiter, end_low, aiter_end,
+                               aiter_input, iiter->begin);
+        end_low = LowerBound(aiter, begin_low, aiter_end,
+                             aiter_input, iiter->end);
+        if (end_low - begin_low > 0) {
+          if (reach_begin_ < 0)
+            reach_begin_ = begin_low;
+          reach_end_ = end_low;
+          if (compute_weight) {
+            aiter->SetFlags(kArcWeightValue, kArcValueFlags);
+            reach_weight_ = accumulator_->Sum(reach_weight_, aiter,
+                                              begin_low, end_low);
+          }
+        }
+      }
+    }
+
+    aiter->SetFlags(flags, kArcFlags);  // restore original flag values
+    return reach_begin_ >= 0;
+  }
+
+  // Returns iterator position of first matching arc.
+  ssize_t ReachBegin() const { return reach_begin_;  }
+
+  // Returns iterator position one past last matching arc.
+  ssize_t ReachEnd() const { return reach_end_; }
+
+  // Return the sum of the weights for matching arcs.
+  // Valid only if compute_weight was true in Reach() call.
+  Weight ReachWeight() const { return reach_weight_; }
+
+  // Access to the relabeling map. Excludes epsilon (0) label but
+  // includes kNoLabel that is used internally for super-final
+  // transitons.
+  const unordered_map<Label, Label>& Label2Index() const {
+    return *data_->Label2Index();
+  }
+
+  LabelReachableData<Label> *GetData() const { return data_; }
+
+  bool Error() const { return error_ || accumulator_->Error(); }
+
+ private:
+  // Redirects labeled arcs (input or output labels determined by
+  // ReachInput()) to new label-specific final states.  Each original
+  // final state is redirected via a transition labeled with kNoLabel
+  // to a new kNoLabel-specific final state.  Creates super-initial
+  // state for all states with zero in-degree.
+  void TransformFst() {
+    StateId ins = fst_->NumStates();
+    StateId ons = ins;
+
+    vector<ssize_t> indeg(ins, 0);
+
+    // Redirects labeled arcs to new final states.
+    for (StateId s = 0; s < ins; ++s) {
+      for (MutableArcIterator< VectorFst<Arc> > aiter(fst_, s);
+           !aiter.Done();
+           aiter.Next()) {
+        Arc arc = aiter.Value();
+        Label label = data_->ReachInput() ? arc.ilabel : arc.olabel;
+        if (label) {
+          if (label2state_.find(label) == label2state_.end()) {
+            label2state_[label] = ons;
+            indeg.push_back(0);
+            ++ons;
+          }
+          arc.nextstate = label2state_[label];
+          aiter.SetValue(arc);
+        }
+        ++indeg[arc.nextstate];      // Finds in-degrees for next step.
+      }
+
+      // Redirects final weights to new final state.
+      Weight final = fst_->Final(s);
+      if (final != Weight::Zero()) {
+        if (label2state_.find(kNoLabel) == label2state_.end()) {
+          label2state_[kNoLabel] = ons;
+          indeg.push_back(0);
+          ++ons;
+        }
+        Arc arc(kNoLabel, kNoLabel, final, label2state_[kNoLabel]);
+        fst_->AddArc(s, arc);
+        ++indeg[arc.nextstate];      // Finds in-degrees for next step.
+
+        fst_->SetFinal(s, Weight::Zero());
+      }
+    }
+
+    // Add new final states to Fst.
+    while (fst_->NumStates() < ons) {
+      StateId s = fst_->AddState();
+      fst_->SetFinal(s, Weight::One());
+    }
+
+    // Creates a super-initial state for all states with zero in-degree.
+    StateId start = fst_->AddState();
+    fst_->SetStart(start);
+    for (StateId s = 0; s < start; ++s) {
+      if (indeg[s] == 0) {
+        Arc arc(0, 0, Weight::One(), s);
+        fst_->AddArc(start, arc);
+      }
+    }
+  }
+
+  void FindIntervals(StateId ins) {
+    StateReachable<A, Label> state_reachable(*fst_);
+    if (state_reachable.Error()) {
+      error_ = true;
+      return;
+    }
+
+    vector<Label> &state2index = state_reachable.State2Index();
+    vector< IntervalSet<Label> > &isets = *data_->IntervalSets();
+    isets = state_reachable.IntervalSets();
+    isets.resize(ins);
+
+    unordered_map<Label, Label> &label2index = *data_->Label2Index();
+    for (typename unordered_map<Label, StateId>::const_iterator
+             it = label2state_.begin();
+         it != label2state_.end();
+         ++it) {
+      Label l = it->first;
+      StateId s = it->second;
+      Label i = state2index[s];
+      label2index[l] = i;
+    }
+    label2state_.clear();
+
+    double nintervals = 0;
+    ssize_t non_intervals = 0;
+    for (ssize_t s = 0; s < ins; ++s) {
+      nintervals += isets[s].Size();
+      if (isets[s].Size() > 1) {
+        ++non_intervals;
+        VLOG(3) << "state: " << s << " # of intervals: " << isets[s].Size();
+      }
+    }
+    VLOG(2) << "# of states: " << ins;
+    VLOG(2) << "# of intervals: " << nintervals;
+    VLOG(2) << "# of intervals/state: " << nintervals/ins;
+    VLOG(2) << "# of non-interval states: " << non_intervals;
+  }
+
+  template <class Iterator>
+  ssize_t LowerBound(Iterator *aiter, ssize_t aiter_begin,
+                     ssize_t aiter_end, bool aiter_input,
+                     Label match_label) const {
+    // Only need to compute the ilabel or olabel of arcs when
+    // performing the binary search.
+    aiter->SetFlags(aiter_input ?  kArcILabelValue : kArcOLabelValue,
+                    kArcValueFlags);
+    ssize_t low = aiter_begin;
+    ssize_t high = aiter_end;
+    while (low < high) {
+      ssize_t mid = (low + high) / 2;
+      aiter->Seek(mid);
+      Label label = aiter_input ?
+          aiter->Value().ilabel : aiter->Value().olabel;
+      if (label > match_label) {
+        high = mid;
+      } else if (label < match_label) {
+        low = mid + 1;
+      } else {
+        // Find first matching label (when non-deterministic)
+        for (ssize_t i = mid; i > low; --i) {
+          aiter->Seek(i - 1);
+          label = aiter_input ? aiter->Value().ilabel : aiter->Value().olabel;
+          if (label != match_label) {
+            aiter->Seek(i);
+            aiter->SetFlags(kArcValueFlags, kArcValueFlags);
+            return i;
+          }
+        }
+        aiter->SetFlags(kArcValueFlags, kArcValueFlags);
+        return low;
+      }
+    }
+    aiter->Seek(low);
+    aiter->SetFlags(kArcValueFlags, kArcValueFlags);
+    return low;
+  }
+
+  VectorFst<Arc> *fst_;
+  StateId s_;                             // Current state
+  unordered_map<Label, StateId> label2state_;  // Finds final state for a label
+
+  ssize_t reach_begin_;                   // Iterator pos of first match
+  ssize_t reach_end_;                     // Iterator pos after last match
+  Weight reach_weight_;                   // Gives weight sum of arc iterator
+                                          // arcs with reachable labels.
+  LabelReachableData<Label> *data_;       // Shareable data between copies
+  S *accumulator_;                        // Sums arc weights
+
+  double ncalls_;
+  double nintervals_;
+  bool error_;
+
+  void operator=(const LabelReachable<A, S> &);   // Disallow
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_LABEL_REACHABLE_H__
diff --git a/src/include/fst/lexicographic-weight.h b/src/include/fst/lexicographic-weight.h
new file mode 100644
index 0000000..4b55c50
--- /dev/null
+++ b/src/include/fst/lexicographic-weight.h
@@ -0,0 +1,151 @@
+// lexicographic-weight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: rws@google.com (Richard Sproat)
+//
+// \file
+// Lexicographic weight set and associated semiring operation definitions.
+//
+// A lexicographic weight is a sequence of weights, each of which must have the
+// path property and Times() must be (strongly) cancellative
+// (for all a,b,c != Zero(): Times(c, a) = Times(c, b) => a = b,
+// Times(a, c) = Times(b, c) => a = b).
+// The + operation on two weights a and b is the lexicographically
+// prior of a and b.
+
+#ifndef FST_LIB_LEXICOGRAPHIC_WEIGHT_H__
+#define FST_LIB_LEXICOGRAPHIC_WEIGHT_H__
+
+#include <string>
+
+#include <fst/pair-weight.h>
+#include <fst/weight.h>
+
+
+namespace fst {
+
+template<class W1, class W2>
+class LexicographicWeight : public PairWeight<W1, W2> {
+ public:
+  using PairWeight<W1, W2>::Value1;
+  using PairWeight<W1, W2>::Value2;
+  using PairWeight<W1, W2>::SetValue1;
+  using PairWeight<W1, W2>::SetValue2;
+  using PairWeight<W1, W2>::Zero;
+  using PairWeight<W1, W2>::One;
+  using PairWeight<W1, W2>::NoWeight;
+  using PairWeight<W1, W2>::Quantize;
+  using PairWeight<W1, W2>::Reverse;
+
+  typedef LexicographicWeight<typename W1::ReverseWeight,
+                              typename W2::ReverseWeight>
+  ReverseWeight;
+
+  LexicographicWeight() {}
+
+  LexicographicWeight(const PairWeight<W1, W2>& w)
+      : PairWeight<W1, W2>(w) {}
+
+  LexicographicWeight(W1 w1, W2 w2) : PairWeight<W1, W2>(w1, w2) {
+    uint64 props = kPath;
+    if ((W1::Properties() & props) != props) {
+      FSTERROR() << "LexicographicWeight must "
+                 << "have the path property: " << W1::Type();
+      SetValue1(W1::NoWeight());
+    }
+    if ((W2::Properties() & props) != props) {
+      FSTERROR() << "LexicographicWeight must "
+                 << "have the path property: " << W2::Type();
+      SetValue2(W2::NoWeight());
+    }
+  }
+
+  static const LexicographicWeight<W1, W2> &Zero() {
+    static const LexicographicWeight<W1, W2> zero(PairWeight<W1, W2>::Zero());
+    return zero;
+  }
+
+  static const LexicographicWeight<W1, W2> &One() {
+    static const LexicographicWeight<W1, W2> one(PairWeight<W1, W2>::One());
+    return one;
+  }
+
+  static const LexicographicWeight<W1, W2> &NoWeight() {
+    static const LexicographicWeight<W1, W2> no_weight(
+        PairWeight<W1, W2>::NoWeight());
+    return no_weight;
+  }
+
+  static const string &Type() {
+    static const string type = W1::Type() + "_LT_" + W2::Type();
+    return type;
+  }
+
+  bool Member() const {
+    if (!Value1().Member() || !Value2().Member()) return false;
+    // Lexicographic weights cannot mix zeroes and non-zeroes.
+    if (Value1() == W1::Zero() && Value2() == W2::Zero()) return true;
+    if (Value1() != W1::Zero() && Value2() != W2::Zero()) return true;
+    return false;
+  }
+
+  LexicographicWeight<W1, W2> Quantize(float delta = kDelta) const {
+    return PairWeight<W1, W2>::Quantize();
+  }
+
+  ReverseWeight Reverse() const {
+    return PairWeight<W1, W2>::Reverse();
+  }
+
+  static uint64 Properties() {
+    uint64 props1 = W1::Properties();
+    uint64 props2 = W2::Properties();
+    return props1 & props2 & (kLeftSemiring | kRightSemiring | kPath |
+                              kIdempotent | kCommutative);
+  }
+};
+
+template <class W1, class W2>
+inline LexicographicWeight<W1, W2> Plus(const LexicographicWeight<W1, W2> &w,
+                                        const LexicographicWeight<W1, W2> &v) {
+  if (!w.Member() || !v.Member())
+    return LexicographicWeight<W1, W2>::NoWeight();
+  NaturalLess<W1> less1;
+  NaturalLess<W2> less2;
+  if (less1(w.Value1(), v.Value1())) return w;
+  if (less1(v.Value1(), w.Value1())) return v;
+  if (less2(w.Value2(), v.Value2())) return w;
+  if (less2(v.Value2(), w.Value2())) return v;
+  return w;
+}
+
+template <class W1, class W2>
+inline LexicographicWeight<W1, W2> Times(const LexicographicWeight<W1, W2> &w,
+                                         const LexicographicWeight<W1, W2> &v) {
+  return LexicographicWeight<W1, W2>(Times(w.Value1(), v.Value1()),
+                                     Times(w.Value2(), v.Value2()));
+}
+
+template <class W1, class W2>
+inline LexicographicWeight<W1, W2> Divide(const LexicographicWeight<W1, W2> &w,
+                                          const LexicographicWeight<W1, W2> &v,
+                                          DivideType typ = DIVIDE_ANY) {
+  return LexicographicWeight<W1, W2>(Divide(w.Value1(), v.Value1(), typ),
+                                     Divide(w.Value2(), v.Value2(), typ));
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_LEXICOGRAPHIC_WEIGHT_H__
diff --git a/src/include/fst/lock.h b/src/include/fst/lock.h
new file mode 100644
index 0000000..3adf7df
--- /dev/null
+++ b/src/include/fst/lock.h
@@ -0,0 +1,81 @@
+// lock.h
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Google-compatibility locking declarations and inline definitions
+
+#ifndef FST_LIB_LOCK_H__
+#define FST_LIB_LOCK_H__
+
+#include <fst/compat.h>  // for DISALLOW_COPY_AND_ASSIGN
+
+namespace fst {
+
+using namespace std;
+
+//
+// Single initialization  - single-thread implementation
+//
+
+typedef int FstOnceType;
+
+static const int FST_ONCE_INIT = 1;
+
+inline int FstOnceInit(FstOnceType *once, void (*init)(void)) {
+  if (*once)
+    (*init)();
+  *once = 0;
+  return 0;
+}
+
+//
+// Thread locking - single-thread (non-)implementation
+//
+
+class Mutex {
+ public:
+  Mutex() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Mutex);
+};
+
+class MutexLock {
+ public:
+  MutexLock(Mutex *) {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(MutexLock);
+};
+
+// Reference counting - single-thread implementation
+class RefCounter {
+ public:
+  RefCounter() : count_(1) {}
+
+  int count() const { return count_; }
+  int Incr() const { return ++count_; }
+  int Decr() const {  return --count_; }
+
+ private:
+  mutable int count_;
+
+  DISALLOW_COPY_AND_ASSIGN(RefCounter);
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_LOCK_H__
diff --git a/src/include/fst/log.h b/src/include/fst/log.h
new file mode 100644
index 0000000..d1492cd
--- /dev/null
+++ b/src/include/fst/log.h
@@ -0,0 +1,66 @@
+// log.h
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Google-style logging declarations and inline definitions.
+
+#ifndef FST_LIB_LOG_H__
+#define FST_LIB_LOG_H__
+
+#include <cassert>
+#include <iostream>
+#include <string>
+
+#include <fst/types.h>
+#include <fst/flags.h>
+
+using std::string;
+
+DECLARE_int32(v);
+
+class LogMessage {
+ public:
+  LogMessage(const string &type) : fatal_(type == "FATAL") {
+    std::cerr << type << ": ";
+  }
+  ~LogMessage() {
+    std::cerr << std::endl;
+    if(fatal_)
+      exit(1);
+  }
+  std::ostream &stream() { return std::cerr; }
+
+ private:
+  bool fatal_;
+};
+
+#define LOG(type) LogMessage(#type).stream()
+#define VLOG(level) if ((level) <= FLAGS_v) LOG(INFO)
+
+// Checks
+inline void CHECK(bool x) { assert(x); }
+
+#define CHECK_EQ(x, y) CHECK((x) == (y))
+#define CHECK_LT(x, y) CHECK((x) < (y))
+#define CHECK_GT(x, y) CHECK((x) > (y))
+#define CHECK_LE(x, y) CHECK((x) <= (y))
+#define CHECK_GE(x, y) CHECK((x) >= (y))
+#define CHECK_NE(x, y) CHECK((x) != (y))
+
+// Ports
+#define ATTRIBUTE_DEPRECATED __attribute__((deprecated))
+
+#endif  // FST_LIB_LOG_H__
diff --git a/src/include/fst/lookahead-filter.h b/src/include/fst/lookahead-filter.h
new file mode 100644
index 0000000..e11c1bb
--- /dev/null
+++ b/src/include/fst/lookahead-filter.h
@@ -0,0 +1,698 @@
+// lookahead-filter.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Composition filters to support lookahead matchers, useful for improving
+// composition efficiency with certain inputs.
+
+#ifndef FST_LIB_LOOKAHEAD_FILTER_H__
+#define FST_LIB_LOOKAHEAD_FILTER_H__
+
+#include <vector>
+using std::vector;
+
+#include <fst/fst.h>
+#include <fst/lookahead-matcher.h>
+
+
+namespace fst {
+
+// Identifies and verifies the capabilities of the matcher to be used for
+// lookahead with the composition filters below. This version is passed
+// the matchers.
+template <class M1, class M2>
+MatchType LookAheadMatchType(const M1 &m1, const M2 &m2) {
+  MatchType type1 = m1.Type(false);
+  MatchType type2 = m2.Type(false);
+  if (type1 == MATCH_OUTPUT &&
+      m1.Flags() & kOutputLookAheadMatcher)
+    return MATCH_OUTPUT;
+  else if (type2 == MATCH_INPUT &&
+           m2.Flags() & kInputLookAheadMatcher)
+    return MATCH_INPUT;
+  else if (m1.Flags() & kOutputLookAheadMatcher &&
+           m1.Type(true) == MATCH_OUTPUT)
+    return MATCH_OUTPUT;
+  else if (m2.Flags() & kInputLookAheadMatcher &&
+           m2.Type(true) == MATCH_INPUT)
+    return MATCH_INPUT;
+  else
+    return MATCH_NONE;
+}
+
+// Identifies and verifies the capabilities of the matcher to be used for
+// lookahead with the composition filters below. This version uses the
+// Fst's default matchers.
+template <class Arc>
+MatchType LookAheadMatchType(const Fst<Arc> &fst1, const Fst<Arc> &fst2) {
+  LookAheadMatcher< Fst <Arc> > matcher1(fst1, MATCH_OUTPUT);
+  LookAheadMatcher< Fst <Arc> > matcher2(fst2, MATCH_INPUT);
+  return LookAheadMatchType(matcher1, matcher2);
+}
+
+//
+// LookAheadSelector - a helper class for selecting among possibly
+// distinct FST and matcher types w/o using a common base class. This
+// lets us avoid virtual function calls.
+//
+
+// Stores and returns the appropriate FST and matcher for lookahead.
+// It is templated on the matcher types.  General case has no methods
+// since not currently supported.
+template <class M1, class M2, MatchType MT>
+class LookAheadSelector {
+};
+
+// Stores and returns the appropriate FST and matcher for lookahead.
+// Specialized for two matchers of same type with the (match) 'type'
+// arg determining which is used for lookahead.
+template <class M, MatchType MT>
+class LookAheadSelector<M, M, MT> {
+ public:
+  typedef typename M::Arc Arc;
+  typedef typename M::FST F;
+
+  LookAheadSelector(M *lmatcher1, M *lmatcher2, MatchType type)
+      : lmatcher1_(lmatcher1->Copy()),
+        lmatcher2_(lmatcher2->Copy()),
+        type_(type) {}
+
+  LookAheadSelector(const LookAheadSelector<M, M, MT> &selector)
+      : lmatcher1_(selector.lmatcher1_->Copy()),
+        lmatcher2_(selector.lmatcher2_->Copy()),
+        type_(selector.type_) {}
+
+  ~LookAheadSelector() {
+    delete lmatcher1_;
+    delete lmatcher2_;
+  }
+
+  const F &GetFst() const {
+    return type_ == MATCH_OUTPUT ? lmatcher2_->GetFst() :
+        lmatcher1_->GetFst();
+  }
+
+  M *GetMatcher() const {
+    return type_ == MATCH_OUTPUT ? lmatcher1_ : lmatcher2_;
+  }
+
+ private:
+  M *lmatcher1_;
+  M *lmatcher2_;
+  MatchType type_;
+
+  void operator=(const LookAheadSelector<M, M, MT> &);  // disallow
+};
+
+// Stores and returns the appropriate FST and matcher for lookahead.
+// Specialized for lookahead on input labels.
+template <class M1, class M2>
+class LookAheadSelector<M1, M2, MATCH_INPUT> {
+ public:
+  typedef typename M1::FST F1;
+
+  LookAheadSelector(M1 *lmatcher1, M2 *lmatcher2, MatchType)
+      : fst_(lmatcher1->GetFst().Copy()),
+        lmatcher_(lmatcher2->Copy()) {}
+
+  LookAheadSelector(const LookAheadSelector<M1, M2, MATCH_INPUT> &selector)
+      : fst_(selector.fst_->Copy()),
+        lmatcher_(selector.lmatcher_->Copy()) {}
+
+  ~LookAheadSelector() {
+    delete lmatcher_;
+    delete fst_;
+  }
+
+  const F1 &GetFst() const { return *fst_; }
+
+  M2 *GetMatcher() const { return lmatcher_; }
+
+ private:
+  const F1 *fst_;
+  M2 *lmatcher_;
+
+  void operator=(const LookAheadSelector<M1, M2, MATCH_INPUT> &);  // disallow
+};
+
+
+// Stores and returns the appropriate FST and matcher for lookahead.
+// Specialized for lookahead on output labels.
+template <class M1, class M2>
+class LookAheadSelector<M1, M2, MATCH_OUTPUT> {
+ public:
+  typedef typename M2::FST F2;
+
+  LookAheadSelector(M1 *lmatcher1, M2 *lmatcher2, MatchType)
+      : fst_(lmatcher2->GetFst().Copy()),
+        lmatcher_(lmatcher1->Copy()) {}
+
+  LookAheadSelector(const LookAheadSelector<M1, M2, MATCH_OUTPUT> &selector)
+      : fst_(selector.fst_->Copy()),
+        lmatcher_(selector.lmatcher_->Copy()) {}
+
+  ~LookAheadSelector() {
+    delete lmatcher_;
+    delete fst_;
+  }
+
+  const F2 &GetFst() const { return *fst_; }
+
+  M1 *GetMatcher() const { return lmatcher_; }
+
+ private:
+  const F2 *fst_;
+  M1 *lmatcher_;
+
+  void operator=(const LookAheadSelector<M1, M2, MATCH_OUTPUT> &);  // disallow
+};
+
+// This filter uses a lookahead matcher in FilterArc(arc1, arc2) to
+// examine the future of the composition state (arc1.nextstate,
+// arc2.nextstate), blocking moving forward when its determined to be
+// non-coaccessible. It is templated on an underlying filter,
+// typically the epsilon filter.  Which matcher is the lookahead
+// matcher is determined by the template argument MT unless it is
+// MATCH_BOTH. In that case, both matcher arguments must be lookahead
+// matchers of the same type and one will be selected by
+// LookAheadMatchType() based on their capability.
+template <class F,
+          class M1 = LookAheadMatcher<typename F::FST1>,
+          class M2 = M1,
+          MatchType MT = MATCH_BOTH>
+class LookAheadComposeFilter {
+ public:
+  typedef typename F::FST1 FST1;
+  typedef typename F::FST2 FST2;
+  typedef typename F::Arc Arc;
+  typedef typename F::Matcher1 Matcher1;
+  typedef typename F::Matcher2 Matcher2;
+  typedef typename F::FilterState FilterState;
+  typedef LookAheadComposeFilter<F, M1, M2, MT> Filter;
+
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  LookAheadComposeFilter(const FST1 &fst1, const FST2 &fst2,
+                         M1 *matcher1,  M2 *matcher2)
+      : filter_(fst1, fst2, matcher1, matcher2),
+        lookahead_type_(MT == MATCH_BOTH ?
+                        LookAheadMatchType(*filter_.GetMatcher1(),
+                                           *filter_.GetMatcher2()) : MT),
+        selector_(filter_.GetMatcher1(), filter_.GetMatcher2(),
+                  lookahead_type_),
+        flags_(lookahead_type_ == MATCH_OUTPUT ?
+               filter_.GetMatcher1()->Flags() :
+               filter_.GetMatcher2()->Flags()) {
+    if (lookahead_type_ == MATCH_NONE) {
+      FSTERROR() << "LookAheadComposeFilter: 1st argument cannot "
+                 << "match/look-ahead on output labels and 2nd argument "
+                 << "cannot match/look-ahead on input labels.";
+    }
+    selector_.GetMatcher()->InitLookAheadFst(selector_.GetFst());
+  }
+
+  LookAheadComposeFilter(const LookAheadComposeFilter<F, M1, M2, MT> &filter,
+                         bool safe = false)
+      : filter_(filter.filter_, safe),
+        lookahead_type_(filter.lookahead_type_),
+        selector_(filter_.GetMatcher1(), filter_.GetMatcher2(),
+                  lookahead_type_),
+        flags_(filter.flags_) {
+    selector_.GetMatcher()->InitLookAheadFst(selector_.GetFst(), true);
+  }
+
+  FilterState Start() const {
+    return filter_.Start();
+  }
+
+  void SetState(StateId s1, StateId s2, const FilterState &f) {
+    filter_.SetState(s1, s2, f);
+  }
+
+  FilterState FilterArc(Arc *arc1, Arc *arc2) const {
+    lookahead_arc_ = false;
+
+    const FilterState &f = filter_.FilterArc(arc1, arc2);
+    if (f == FilterState::NoState())
+      return FilterState::NoState();
+
+    return LookAheadOutput() ? LookAheadFilterArc(arc1, arc2, f) :
+        LookAheadFilterArc(arc2, arc1, f);
+  }
+
+  void FilterFinal(Weight *weight1, Weight *weight2) const {
+    filter_.FilterFinal(weight1, weight2);
+  }
+
+  // Return resp matchers. Ownership stays with filter.
+  Matcher1 *GetMatcher1() { return filter_.GetMatcher1(); }
+  Matcher2 *GetMatcher2() { return filter_.GetMatcher2(); }
+
+  const LookAheadSelector<Matcher1, Matcher2, MT> &Selector() const {
+    return selector_;
+  }
+
+  uint64 Properties(uint64 inprops) const {
+    uint64 outprops = filter_.Properties(inprops);
+    if (lookahead_type_ == MATCH_NONE)
+      outprops |= kError;
+    return outprops;
+  }
+
+  uint32 LookAheadFlags() const { return flags_; }
+
+  bool LookAheadArc() const { return lookahead_arc_; }
+
+  bool LookAheadOutput() const {
+    if (MT == MATCH_OUTPUT)
+      return true;
+    else if (MT == MATCH_INPUT)
+      return false;
+    else if (lookahead_type_ == MATCH_OUTPUT)
+      return true;
+    else
+      return false;
+  }
+
+ private:
+  FilterState LookAheadFilterArc(Arc *arca, Arc *arcb,
+                                 const FilterState &f) const {
+    Label &labela = LookAheadOutput() ? arca->olabel : arca->ilabel;
+
+    if (labela != 0 && !(flags_ & kLookAheadNonEpsilons))
+      return f;
+    if (labela == 0 && !(flags_ & kLookAheadEpsilons))
+      return f;
+
+    lookahead_arc_ = true;
+    selector_.GetMatcher()->SetState(arca->nextstate);
+
+    return selector_.GetMatcher()->LookAheadFst(selector_.GetFst(),
+                                                arcb->nextstate) ? f :
+                                                FilterState::NoState();
+  }
+
+  F filter_;                    // Underlying filter
+  MatchType lookahead_type_;    // Lookahead match type
+  LookAheadSelector<Matcher1, Matcher2, MT> selector_;
+  uint32 flags_;                // Lookahead flags
+  mutable bool lookahead_arc_;  // Look-ahead performed at last FilterArc()?
+
+  void operator=(const LookAheadComposeFilter<F, M1, M2> &);  // disallow
+};
+
+
+// This filter adds weight-pushing to a lookahead composition filter
+// using the LookAheadWeight() method of matcher argument. It is
+// templated on an underlying lookahead filter, typically the basic
+// lookahead filter. Weight-pushing in composition brings weights
+// forward as much as possible based on the lookahead information.
+template <class F,
+          class M1 = LookAheadMatcher<typename F::FST1>,
+          class M2 = M1,
+          MatchType MT = MATCH_BOTH>
+class PushWeightsComposeFilter {
+ public:
+  typedef typename F::FST1 FST1;
+  typedef typename F::FST2 FST2;
+  typedef typename F::Arc Arc;
+  typedef typename F::Matcher1 Matcher1;
+  typedef typename F::Matcher2 Matcher2;
+  typedef typename F::FilterState FilterState1;
+  typedef WeightFilterState<typename Arc::Weight> FilterState2;
+  typedef PairFilterState<FilterState1, FilterState2> FilterState;
+
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  PushWeightsComposeFilter(const FST1 &fst1, const FST2 &fst2,
+                         M1 *matcher1,  M2 *matcher2)
+      : filter_(fst1, fst2, matcher1, matcher2),
+        f_(FilterState::NoState()) {}
+
+  PushWeightsComposeFilter(const PushWeightsComposeFilter<F, M1, M2, MT>
+                           &filter,
+                           bool safe = false)
+      : filter_(filter.filter_, safe),
+        f_(FilterState::NoState()) {}
+
+  FilterState Start() const {
+    return FilterState(filter_.Start(), FilterState2(Weight::One()));
+  }
+
+  void SetState(StateId s1, StateId s2, const FilterState &f) {
+    f_ = f;
+    filter_.SetState(s1, s2, f.GetState1());
+  }
+
+  FilterState FilterArc(Arc *arc1, Arc *arc2) const {
+    const FilterState1 &f1 = filter_.FilterArc(arc1, arc2);
+    if (f1 == FilterState1::NoState())
+      return FilterState::NoState();
+
+    if (!(LookAheadFlags() & kLookAheadWeight))
+      return FilterState(f1, FilterState2(Weight::One()));
+
+    const Weight &lweight = filter_.LookAheadArc() ?
+        Selector().GetMatcher()->LookAheadWeight() : Weight::One();
+    const FilterState2 &f2 = f_.GetState2();
+    const Weight &fweight = f2.GetWeight();
+
+    arc2->weight = Divide(Times(arc2->weight, lweight), fweight);
+    return FilterState(f1, FilterState2(lweight));
+  }
+
+  void FilterFinal(Weight *weight1, Weight *weight2) const {
+    filter_.FilterFinal(weight1, weight2);
+    if (!(LookAheadFlags() & kLookAheadWeight) || *weight1 == Weight::Zero())
+      return;
+
+    const FilterState2 &f2 = f_.GetState2();
+    const Weight &fweight = f2.GetWeight();
+    *weight1 = Divide(*weight1, fweight);
+  }
+  // Return resp matchers. Ownership states with filter.
+  Matcher1 *GetMatcher1() { return filter_.GetMatcher1(); }
+  Matcher2 *GetMatcher2() { return filter_.GetMatcher2(); }
+
+  const LookAheadSelector<Matcher1, Matcher2, MT> &Selector() const {
+    return filter_.Selector();
+  }
+
+  uint32 LookAheadFlags() const { return filter_.LookAheadFlags(); }
+  bool LookAheadArc() const { return filter_.LookAheadArc(); }
+  bool LookAheadOutput() const { return filter_.LookAheadOutput(); }
+
+  uint64 Properties(uint64 props) const {
+    return filter_.Properties(props) & kWeightInvariantProperties;
+  }
+
+ private:
+  F filter_;                       // Underlying filter
+  FilterState f_;                  // Current filter state
+
+  void operator=(const PushWeightsComposeFilter<F, M1, M2, MT> &);  // disallow
+};
+
+// This filter adds label-pushing to a lookahead composition filter
+// using the LookAheadPrefix() method of the matcher argument. It is
+// templated on an underlying filter, typically the basic lookahead
+// or weight-pushing lookahead filter. Label-pushing in composition
+// matches labels as early as possible based on the lookahead
+// information.
+template <class F,
+          class M1 = LookAheadMatcher<typename F::FST1>,
+          class M2 = M1,
+          MatchType MT = MATCH_BOTH>
+class PushLabelsComposeFilter {
+ public:
+  typedef typename F::FST1 FST1;
+  typedef typename F::FST2 FST2;
+  typedef typename F::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  typedef MultiEpsMatcher<typename F::Matcher1> Matcher1;
+  typedef MultiEpsMatcher<typename F::Matcher2> Matcher2;
+  typedef typename F::FilterState FilterState1;
+  typedef IntegerFilterState<typename Arc::Label> FilterState2;
+  typedef PairFilterState<FilterState1, FilterState2> FilterState;
+
+  PushLabelsComposeFilter(const FST1 &fst1, const FST2 &fst2,
+                         M1 *matcher1,  M2 *matcher2)
+      : filter_(fst1, fst2, matcher1, matcher2),
+        f_(FilterState::NoState()),
+        fst1_(filter_.GetMatcher1()->GetFst()),
+        fst2_(filter_.GetMatcher2()->GetFst()),
+        matcher1_(fst1_, MATCH_OUTPUT,
+                  filter_.LookAheadOutput() ? kMultiEpsList : kMultiEpsLoop,
+                  filter_.GetMatcher1(),
+                  false),
+        matcher2_(fst2_, MATCH_INPUT,
+                  filter_.LookAheadOutput() ? kMultiEpsLoop : kMultiEpsList,
+                  filter_.GetMatcher2(),
+                  false) {}
+
+  PushLabelsComposeFilter(const PushLabelsComposeFilter<F, M1, M2, MT> &filter,
+                          bool safe = false)
+      : filter_(filter.filter_, safe),
+        f_(FilterState::NoState()),
+        fst1_(filter_.GetMatcher1()->GetFst()),
+        fst2_(filter_.GetMatcher2()->GetFst()),
+        matcher1_(fst1_,  MATCH_OUTPUT,
+                  filter_.LookAheadOutput() ? kMultiEpsList : kMultiEpsLoop,
+                  filter_.GetMatcher1(),
+                  false),
+        matcher2_(fst2_, MATCH_INPUT,
+                  filter_.LookAheadOutput() ? kMultiEpsLoop : kMultiEpsList,
+                  filter_.GetMatcher2(),
+                  false) {
+  }
+
+  FilterState Start() const {
+    return FilterState(filter_.Start(), FilterState2(kNoLabel));
+  }
+
+  void SetState(StateId s1, StateId s2, const FilterState &f) {
+    f_ = f;
+    filter_.SetState(s1, s2, f.GetState1());
+    if (!(LookAheadFlags() & kLookAheadPrefix))
+      return;
+
+    narcsa_ = LookAheadOutput() ? internal::NumArcs(fst1_, s1)
+        : internal::NumArcs(fst2_, s2);
+
+    const FilterState2 &f2 = f_.GetState2();
+    const Label &flabel = f2.GetState();
+
+    GetMatcher1()->ClearMultiEpsLabels();
+    GetMatcher2()->ClearMultiEpsLabels();
+    if (flabel != kNoLabel) {                   // Have a lookahead label?
+      GetMatcher1()->AddMultiEpsLabel(flabel);  // Yes, make it a multi-epsilon
+      GetMatcher2()->AddMultiEpsLabel(flabel);  // label so that it matches the
+    }                                           // implicit epsilon arc to be
+  }                                             // modified below when pushing.
+
+  FilterState FilterArc(Arc *arc1, Arc *arc2) const {
+    if (!(LookAheadFlags() & kLookAheadPrefix))
+      return FilterState(filter_.FilterArc(arc1, arc2),
+                         FilterState2(kNoLabel));
+
+    const FilterState2 &f2 = f_.GetState2();
+    const Label &flabel = f2.GetState();
+    if (flabel != kNoLabel)             // Have a lookahead label?
+      return LookAheadOutput() ? PushedLabelFilterArc(arc1, arc2, flabel) :
+          PushedLabelFilterArc(arc2, arc1, flabel);
+
+    const FilterState1 &f1 = filter_.FilterArc(arc1, arc2);
+    if (f1 == FilterState1::NoState())
+      return FilterState::NoState();
+
+    if (!filter_.LookAheadArc())
+      return FilterState(f1, FilterState2(kNoLabel));
+
+    return LookAheadOutput() ? PushLabelFilterArc(arc1, arc2, f1) :
+        PushLabelFilterArc(arc2, arc1, f1);
+  }
+
+  void FilterFinal(Weight *weight1, Weight *weight2) const {
+    filter_.FilterFinal(weight1, weight2);
+    if (!(LookAheadFlags() & kLookAheadPrefix) ||
+        *weight1 == Weight::Zero())
+      return;
+
+    const FilterState2 &f2 = f_.GetState2();
+    const Label &flabel = f2.GetState();
+    if (flabel != kNoLabel)
+      *weight1 = Weight::Zero();
+  }
+
+  // Return resp matchers. Ownership states with filter.
+  Matcher1 *GetMatcher1() { return &matcher1_; }
+  Matcher2 *GetMatcher2() { return &matcher2_; }
+
+  uint64 Properties(uint64 iprops) const {
+    uint64 oprops = filter_.Properties(iprops);
+    if (LookAheadOutput())
+      return oprops & kOLabelInvariantProperties;
+    else
+      return oprops & kILabelInvariantProperties;
+  }
+
+ private:
+  const LookAheadSelector<typename F::Matcher1, typename F::Matcher2, MT>
+  &Selector() const {
+    return filter_.Selector();
+  }
+
+  // Consumes an already pushed label.
+  FilterState PushedLabelFilterArc(Arc *arca, Arc *arcb,
+                                   Label flabel) const {
+    Label &labela = LookAheadOutput() ? arca->olabel : arca->ilabel;
+    const Label &labelb = LookAheadOutput() ? arcb->ilabel : arcb->olabel;
+
+    if (labelb != kNoLabel) {
+      return FilterState::NoState();    // Block non- (multi-) epsilon label
+    } else if (labela == flabel) {
+      labela = 0;                       // Convert match to multi-eps to eps
+      return Start();
+    } else if (labela == 0) {
+      if (narcsa_ == 1)
+        return f_;                      // Take eps; keep state w/ label
+      Selector().GetMatcher()->SetState(arca->nextstate);
+      if (Selector().GetMatcher()->LookAheadLabel(flabel))
+        return f_;                      // Take eps; keep state w/ label
+      else
+        return FilterState::NoState();  // Block non-coaccessible path
+    } else {
+      return FilterState::NoState();    // Block mismatch to multi-eps label
+    }
+  }
+
+  // Pushes a label forward when possible.
+  FilterState PushLabelFilterArc(Arc *arca, Arc *arcb,
+                                 const FilterState1 &f1) const {
+    Label &labela = LookAheadOutput() ? arca->olabel : arca->ilabel;
+    const Label &labelb = LookAheadOutput() ? arcb->olabel : arcb->ilabel;
+
+    if (labelb != 0)                   // No place to push.
+      return FilterState(f1, FilterState2(kNoLabel));
+    if (labela != 0 &&                 // Wrong lookahead prefix type?
+        LookAheadFlags() & kLookAheadNonEpsilonPrefix)
+      return FilterState(f1, FilterState2(kNoLabel));
+
+    Arc larc(kNoLabel, kNoLabel, Weight::Zero(), kNoStateId);
+
+    if (Selector().GetMatcher()->LookAheadPrefix(&larc)) {  // Have prefix arc?
+      labela = LookAheadOutput() ? larc.ilabel : larc.olabel;
+      arcb->ilabel = larc.ilabel;      // Yes, go forward on that arc,
+      arcb->olabel = larc.olabel;      // thus pushing the label.
+      arcb->weight = Times(arcb->weight, larc.weight);
+      arcb->nextstate = larc.nextstate;
+      return FilterState(f1, FilterState2(labela));
+    } else {
+      return FilterState(f1, FilterState2(kNoLabel));
+    }
+  }
+
+  uint32 LookAheadFlags() const { return filter_.LookAheadFlags(); }
+  bool LookAheadArc() const { return filter_.LookAheadArc(); }
+  bool LookAheadOutput() const { return filter_.LookAheadOutput(); }
+
+  F filter_;                  // Underlying filter
+  FilterState f_ ;            // Current filter state
+  const FST1 &fst1_;
+  const FST2 &fst2_;
+  Matcher1 matcher1_;         // Multi-epsilon matcher for fst1
+  Matcher2 matcher2_;         // Multi-epsilon matcher for fst2
+  ssize_t narcsa_;            // Number of arcs leaving look-ahead match FST
+
+  void operator=(const PushLabelsComposeFilter<F, M1, M2, MT> &);  // disallow
+};
+
+//
+// CONVENIENCE CLASS useful for setting up composition with a default
+// look-ahead matcher and filter.
+//
+
+template <class A, MatchType type>  // MATCH_NONE
+class DefaultLookAhead {
+ public:
+  typedef Matcher< Fst<A> > M;
+  typedef SequenceComposeFilter<M> ComposeFilter;
+  typedef M FstMatcher;
+};
+
+// Specializes for MATCH_INPUT to allow lookahead.
+template <class A>
+class DefaultLookAhead<A, MATCH_INPUT> {
+ public:
+  typedef LookAheadMatcher< Fst<A> > M;
+  typedef SequenceComposeFilter<M> SF;
+  typedef LookAheadComposeFilter<SF, M> ComposeFilter;
+  typedef M FstMatcher;
+};
+
+// Specializes for MATCH_OUTPUT to allow lookahead.
+template <class A>
+class DefaultLookAhead<A, MATCH_OUTPUT> {
+ public:
+  typedef LookAheadMatcher< Fst<A> > M;
+  typedef AltSequenceComposeFilter<M> SF;
+  typedef LookAheadComposeFilter<SF, M> ComposeFilter;
+  typedef M FstMatcher;
+};
+
+// Specializes for StdArc to allow weight and label pushing.
+template <>
+class DefaultLookAhead<StdArc, MATCH_INPUT> {
+ public:
+  typedef StdArc A;
+  typedef LookAheadMatcher< Fst<A> > M;
+  typedef SequenceComposeFilter<M> SF;
+  typedef LookAheadComposeFilter<SF, M> LF;
+  typedef PushWeightsComposeFilter<LF, M> WF;
+  typedef PushLabelsComposeFilter<WF, M> ComposeFilter;
+  typedef M FstMatcher;
+};
+
+// Specializes for StdArc to allow weight and label pushing.
+template <>
+class DefaultLookAhead<StdArc, MATCH_OUTPUT> {
+ public:
+  typedef StdArc A;
+  typedef LookAheadMatcher< Fst<A> > M;
+  typedef AltSequenceComposeFilter<M> SF;
+  typedef LookAheadComposeFilter<SF, M>  LF;
+  typedef PushWeightsComposeFilter<LF, M> WF;
+  typedef PushLabelsComposeFilter<WF, M> ComposeFilter;
+  typedef M FstMatcher;
+};
+
+// Specializes for LogArc to allow weight and label pushing.
+template <>
+class DefaultLookAhead<LogArc, MATCH_INPUT> {
+ public:
+  typedef LogArc A;
+  typedef LookAheadMatcher< Fst<A> > M;
+  typedef SequenceComposeFilter<M> SF;
+  typedef LookAheadComposeFilter<SF, M> LF;
+  typedef PushWeightsComposeFilter<LF, M> WF;
+  typedef PushLabelsComposeFilter<WF, M> ComposeFilter;
+  typedef M FstMatcher;
+};
+
+// Specializes for LogArc to allow weight and label pushing.
+template <>
+class DefaultLookAhead<LogArc, MATCH_OUTPUT> {
+ public:
+  typedef LogArc A;
+  typedef LookAheadMatcher< Fst<A> > M;
+  typedef AltSequenceComposeFilter<M> SF;
+  typedef LookAheadComposeFilter<SF, M> LF;
+  typedef PushWeightsComposeFilter<LF, M> WF;
+  typedef PushLabelsComposeFilter<WF, M> ComposeFilter;
+  typedef M FstMatcher;
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_LOOKAHEAD_FILTER_H__
diff --git a/src/include/fst/lookahead-matcher.h b/src/include/fst/lookahead-matcher.h
new file mode 100644
index 0000000..10d9c01
--- /dev/null
+++ b/src/include/fst/lookahead-matcher.h
@@ -0,0 +1,813 @@
+// lookahead-matcher.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Classes to add lookahead to FST matchers, useful e.g. for improving
+// composition efficiency with certain inputs.
+
+#ifndef FST_LIB_LOOKAHEAD_MATCHER_H__
+#define FST_LIB_LOOKAHEAD_MATCHER_H__
+
+#include <fst/add-on.h>
+#include <fst/const-fst.h>
+#include <fst/fst.h>
+#include <fst/label-reachable.h>
+#include <fst/matcher.h>
+
+
+DECLARE_string(save_relabel_ipairs);
+DECLARE_string(save_relabel_opairs);
+
+namespace fst {
+
+// LOOKAHEAD MATCHERS - these have the interface of Matchers (see
+// matcher.h) and these additional methods:
+//
+// template <class F>
+// class LookAheadMatcher {
+//  public:
+//   typedef F FST;
+//   typedef F::Arc Arc;
+//   typedef typename Arc::StateId StateId;
+//   typedef typename Arc::Label Label;
+//   typedef typename Arc::Weight Weight;
+//
+//  // Required constructors.
+//  LookAheadMatcher(const F &fst, MatchType match_type);
+//   // If safe=true, the copy is thread-safe (except the lookahead Fst is
+//   // preserved). See Fst<>::Cop() for further doc.
+//  LookAheadMatcher(const LookAheadMatcher &matcher, bool safe = false);
+//
+//  Below are methods for looking ahead for a match to a label and
+//  more generally, to a rational set. Each returns false if there is
+//  definitely not a match and returns true if there possibly is a
+//  match.
+
+//  // LABEL LOOKAHEAD: Can 'label' be read from the current matcher state
+//  // after possibly following epsilon transitions?
+//  bool LookAheadLabel(Label label) const;
+//
+//  // RATIONAL LOOKAHEAD: The next methods allow looking ahead for an
+//  // arbitrary rational set of strings, specified by an FST and a state
+//  // from which to begin the matching. If the lookahead FST is a
+//  // transducer, this looks on the side different from the matcher
+//  // 'match_type' (cf. composition).
+//
+//  // Are there paths P from 's' in the lookahead FST that can be read from
+//  // the cur. matcher state?
+//  bool LookAheadFst(const Fst<Arc>& fst, StateId s);
+//
+//  // Gives an estimate of the combined weight of the paths P in the
+//  // lookahead and matcher FSTs for the last call to LookAheadFst.
+//  // A trivial implementation returns Weight::One(). Non-trivial
+//  // implementations are useful for weight-pushing in composition.
+//  Weight LookAheadWeight() const;
+//
+//  // Is there is a single non-epsilon arc found in the lookahead FST
+//  // that begins P (after possibly following any epsilons) in the last
+//  // call LookAheadFst? If so, return true and copy it to '*arc', o.w.
+//  // return false. A trivial implementation returns false. Non-trivial
+//  // implementations are useful for label-pushing in composition.
+//  bool LookAheadPrefix(Arc *arc);
+//
+//  // Optionally pre-specifies the lookahead FST that will be passed
+//  // to LookAheadFst() for possible precomputation. If copy is true,
+//  // then 'fst' is a copy of the FST used in the previous call to
+//  // this method (useful to avoid unnecessary updates).
+//  void InitLookAheadFst(const Fst<Arc>& fst, bool copy = false);
+//
+// };
+
+//
+// LOOK-AHEAD FLAGS (see also kMatcherFlags in matcher.h):
+//
+// Matcher is a lookahead matcher when 'match_type' is MATCH_INPUT.
+const uint32 kInputLookAheadMatcher =      0x00000001;
+
+// Matcher is a lookahead matcher when 'match_type' is MATCH_OUTPUT.
+const uint32 kOutputLookAheadMatcher =     0x00000002;
+
+// A non-trivial implementation of LookAheadWeight() method defined and
+// should be used?
+const uint32 kLookAheadWeight =            0x00000004;
+
+// A non-trivial implementation of LookAheadPrefix() method defined and
+// should be used?
+const uint32 kLookAheadPrefix =            0x00000008;
+
+// Look-ahead of matcher FST non-epsilon arcs?
+const uint32 kLookAheadNonEpsilons =       0x00000010;
+
+// Look-ahead of matcher FST epsilon arcs?
+const uint32 kLookAheadEpsilons =          0x00000020;
+
+// Ignore epsilon paths for the lookahead prefix? Note this gives
+// correct results in composition only with an appropriate composition
+// filter since it depends on the filter blocking the ignored paths.
+const uint32 kLookAheadNonEpsilonPrefix =  0x00000040;
+
+// For LabelLookAheadMatcher, save relabeling data to file
+const uint32 kLookAheadKeepRelabelData =  0x00000080;
+
+// Flags used for lookahead matchers.
+const uint32 kLookAheadFlags =            0x000000ff;
+
+// LookAhead Matcher interface, templated on the Arc definition; used
+// for lookahead matcher specializations that are returned by the
+// InitMatcher() Fst method.
+template <class A>
+class LookAheadMatcherBase : public MatcherBase<A> {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+
+  LookAheadMatcherBase()
+  : weight_(Weight::One()),
+    prefix_arc_(kNoLabel, kNoLabel, Weight::One(), kNoStateId) {}
+
+  virtual ~LookAheadMatcherBase() {}
+
+  bool LookAheadLabel(Label label) const { return LookAheadLabel_(label); }
+
+  bool LookAheadFst(const Fst<Arc> &fst, StateId s) {
+    return LookAheadFst_(fst, s);
+  }
+
+  Weight LookAheadWeight() const { return weight_; }
+
+  bool LookAheadPrefix(Arc *arc) const {
+    if (prefix_arc_.nextstate != kNoStateId) {
+      *arc = prefix_arc_;
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  virtual void InitLookAheadFst(const Fst<Arc>& fst, bool copy = false) = 0;
+
+ protected:
+  void SetLookAheadWeight(const Weight &w) { weight_ = w; }
+
+  void SetLookAheadPrefix(const Arc &arc) { prefix_arc_ = arc; }
+
+  void ClearLookAheadPrefix() { prefix_arc_.nextstate = kNoStateId; }
+
+ private:
+  virtual bool LookAheadLabel_(Label label) const = 0;
+  virtual bool LookAheadFst_(const Fst<Arc> &fst,
+                             StateId s) = 0;  // This must set l.a. weight and
+                                              // prefix if non-trivial.
+  Weight weight_;                             // Look-ahead weight
+  Arc prefix_arc_;                            // Look-ahead prefix arc
+};
+
+
+// Don't really lookahead, just declare future looks good regardless.
+template <class M>
+class TrivialLookAheadMatcher
+    : public LookAheadMatcherBase<typename M::FST::Arc> {
+ public:
+  typedef typename M::FST FST;
+  typedef typename M::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  TrivialLookAheadMatcher(const FST &fst, MatchType match_type)
+      : matcher_(fst, match_type) {}
+
+  TrivialLookAheadMatcher(const TrivialLookAheadMatcher<M> &lmatcher,
+                          bool safe = false)
+      : matcher_(lmatcher.matcher_, safe) {}
+
+  // General matcher methods
+  TrivialLookAheadMatcher<M> *Copy(bool safe = false) const {
+    return new TrivialLookAheadMatcher<M>(*this, safe);
+  }
+
+  MatchType Type(bool test) const { return matcher_.Type(test); }
+  void SetState(StateId s) { return matcher_.SetState(s); }
+  bool Find(Label label) { return matcher_.Find(label); }
+  bool Done() const { return matcher_.Done(); }
+  const Arc& Value() const { return matcher_.Value(); }
+  void Next() { matcher_.Next(); }
+  virtual const FST &GetFst() const { return matcher_.GetFst(); }
+  uint64 Properties(uint64 props) const { return matcher_.Properties(props); }
+  uint32 Flags() const {
+    return matcher_.Flags() | kInputLookAheadMatcher | kOutputLookAheadMatcher;
+  }
+
+  // Look-ahead methods.
+  bool LookAheadLabel(Label label) const { return true;  }
+  bool LookAheadFst(const Fst<Arc> &fst, StateId s) {return true; }
+  Weight LookAheadWeight() const { return Weight::One(); }
+  bool LookAheadPrefix(Arc *arc) const { return false; }
+  void InitLookAheadFst(const Fst<Arc>& fst, bool copy = false) {}
+
+ private:
+  // This allows base class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual void SetState_(StateId s) { SetState(s); }
+  virtual bool Find_(Label label) { return Find(label); }
+  virtual bool Done_() const { return Done(); }
+  virtual const Arc& Value_() const { return Value(); }
+  virtual void Next_() { Next(); }
+
+  bool LookAheadLabel_(Label l) const { return LookAheadLabel(l); }
+
+  bool LookAheadFst_(const Fst<Arc> &fst, StateId s) {
+    return LookAheadFst(fst, s);
+  }
+
+  Weight LookAheadWeight_() const { return LookAheadWeight(); }
+  bool LookAheadPrefix_(Arc *arc) const { return LookAheadPrefix(arc); }
+
+  M matcher_;
+};
+
+// Look-ahead of one transition. Template argument F accepts flags to
+// control behavior.
+template <class M, uint32 F = kLookAheadNonEpsilons | kLookAheadEpsilons |
+          kLookAheadWeight | kLookAheadPrefix>
+class ArcLookAheadMatcher
+    : public LookAheadMatcherBase<typename M::FST::Arc> {
+ public:
+  typedef typename M::FST FST;
+  typedef typename M::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+  typedef NullAddOn MatcherData;
+
+  using LookAheadMatcherBase<Arc>::LookAheadWeight;
+  using LookAheadMatcherBase<Arc>::SetLookAheadPrefix;
+  using LookAheadMatcherBase<Arc>::SetLookAheadWeight;
+  using LookAheadMatcherBase<Arc>::ClearLookAheadPrefix;
+
+  ArcLookAheadMatcher(const FST &fst, MatchType match_type,
+                      MatcherData *data = 0)
+      : matcher_(fst, match_type),
+        fst_(matcher_.GetFst()),
+        lfst_(0),
+        s_(kNoStateId) {}
+
+  ArcLookAheadMatcher(const ArcLookAheadMatcher<M, F> &lmatcher,
+                      bool safe = false)
+      : matcher_(lmatcher.matcher_, safe),
+        fst_(matcher_.GetFst()),
+        lfst_(lmatcher.lfst_),
+        s_(kNoStateId) {}
+
+  // General matcher methods
+  ArcLookAheadMatcher<M, F> *Copy(bool safe = false) const {
+    return new ArcLookAheadMatcher<M, F>(*this, safe);
+  }
+
+  MatchType Type(bool test) const { return matcher_.Type(test); }
+
+  void SetState(StateId s) {
+    s_ = s;
+    matcher_.SetState(s);
+  }
+
+  bool Find(Label label) { return matcher_.Find(label); }
+  bool Done() const { return matcher_.Done(); }
+  const Arc& Value() const { return matcher_.Value(); }
+  void Next() { matcher_.Next(); }
+  const FST &GetFst() const { return fst_; }
+  uint64 Properties(uint64 props) const { return matcher_.Properties(props); }
+  uint32 Flags() const {
+    return matcher_.Flags() | kInputLookAheadMatcher |
+        kOutputLookAheadMatcher | F;
+  }
+
+  // Writable matcher methods
+  MatcherData *GetData() const { return 0; }
+
+  // Look-ahead methods.
+  bool LookAheadLabel(Label label) const { return matcher_.Find(label); }
+
+  // Checks if there is a matching (possibly super-final) transition
+  // at (s_, s).
+  bool LookAheadFst(const Fst<Arc> &fst, StateId s);
+
+  void InitLookAheadFst(const Fst<Arc>& fst, bool copy = false) {
+    lfst_ = &fst;
+  }
+
+ private:
+  // This allows base class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual void SetState_(StateId s) { SetState(s); }
+  virtual bool Find_(Label label) { return Find(label); }
+  virtual bool Done_() const { return Done(); }
+  virtual const Arc& Value_() const { return Value(); }
+  virtual void Next_() { Next(); }
+
+  bool LookAheadLabel_(Label l) const { return LookAheadLabel(l); }
+  bool LookAheadFst_(const Fst<Arc> &fst, StateId s) {
+    return LookAheadFst(fst, s);
+  }
+
+  mutable M matcher_;
+  const FST &fst_;         // Matcher FST
+  const Fst<Arc> *lfst_;   // Look-ahead FST
+  StateId s_;              // Matcher state
+};
+
+template <class M, uint32 F>
+bool ArcLookAheadMatcher<M, F>::LookAheadFst(const Fst<Arc> &fst, StateId s) {
+  if (&fst != lfst_)
+    InitLookAheadFst(fst);
+
+  bool ret = false;
+  ssize_t nprefix = 0;
+  if (F & kLookAheadWeight)
+    SetLookAheadWeight(Weight::Zero());
+  if (F & kLookAheadPrefix)
+    ClearLookAheadPrefix();
+  if (fst_.Final(s_) != Weight::Zero() &&
+      lfst_->Final(s) != Weight::Zero()) {
+    if (!(F & (kLookAheadWeight | kLookAheadPrefix)))
+      return true;
+    ++nprefix;
+    if (F & kLookAheadWeight)
+      SetLookAheadWeight(Plus(LookAheadWeight(),
+                              Times(fst_.Final(s_), lfst_->Final(s))));
+    ret = true;
+  }
+  if (matcher_.Find(kNoLabel)) {
+    if (!(F & (kLookAheadWeight | kLookAheadPrefix)))
+      return true;
+    ++nprefix;
+    if (F & kLookAheadWeight)
+      for (; !matcher_.Done(); matcher_.Next())
+        SetLookAheadWeight(Plus(LookAheadWeight(), matcher_.Value().weight));
+    ret = true;
+  }
+  for (ArcIterator< Fst<Arc> > aiter(*lfst_, s);
+       !aiter.Done();
+       aiter.Next()) {
+    const Arc &arc = aiter.Value();
+    Label label = kNoLabel;
+    switch (matcher_.Type(false)) {
+      case MATCH_INPUT:
+        label = arc.olabel;
+        break;
+      case MATCH_OUTPUT:
+        label = arc.ilabel;
+        break;
+      default:
+        FSTERROR() << "ArcLookAheadMatcher::LookAheadFst: bad match type";
+        return true;
+    }
+    if (label == 0) {
+      if (!(F & (kLookAheadWeight | kLookAheadPrefix)))
+        return true;
+      if (!(F & kLookAheadNonEpsilonPrefix))
+        ++nprefix;
+      if (F & kLookAheadWeight)
+        SetLookAheadWeight(Plus(LookAheadWeight(), arc.weight));
+      ret = true;
+    } else if (matcher_.Find(label)) {
+      if (!(F & (kLookAheadWeight | kLookAheadPrefix)))
+        return true;
+      for (; !matcher_.Done(); matcher_.Next()) {
+        ++nprefix;
+        if (F & kLookAheadWeight)
+          SetLookAheadWeight(Plus(LookAheadWeight(),
+                                  Times(arc.weight,
+                                        matcher_.Value().weight)));
+        if ((F & kLookAheadPrefix) && nprefix == 1)
+          SetLookAheadPrefix(arc);
+      }
+      ret = true;
+    }
+  }
+  if (F & kLookAheadPrefix) {
+    if (nprefix == 1)
+      SetLookAheadWeight(Weight::One());  // Avoids double counting.
+    else
+      ClearLookAheadPrefix();
+  }
+  return ret;
+}
+
+
+// Template argument F accepts flags to control behavior.
+// It must include precisely one of KInputLookAheadMatcher or
+// KOutputLookAheadMatcher.
+template <class M, uint32 F = kLookAheadEpsilons | kLookAheadWeight |
+          kLookAheadPrefix | kLookAheadNonEpsilonPrefix |
+          kLookAheadKeepRelabelData,
+          class S = DefaultAccumulator<typename M::Arc> >
+class LabelLookAheadMatcher
+    : public LookAheadMatcherBase<typename M::FST::Arc> {
+ public:
+  typedef typename M::FST FST;
+  typedef typename M::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+  typedef LabelReachableData<Label> MatcherData;
+
+  using LookAheadMatcherBase<Arc>::LookAheadWeight;
+  using LookAheadMatcherBase<Arc>::SetLookAheadPrefix;
+  using LookAheadMatcherBase<Arc>::SetLookAheadWeight;
+  using LookAheadMatcherBase<Arc>::ClearLookAheadPrefix;
+
+  LabelLookAheadMatcher(const FST &fst, MatchType match_type,
+                        MatcherData *data = 0, S *s = 0)
+      : matcher_(fst, match_type),
+        lfst_(0),
+        label_reachable_(0),
+        s_(kNoStateId),
+        error_(false) {
+    if (!(F & (kInputLookAheadMatcher | kOutputLookAheadMatcher))) {
+      FSTERROR() << "LabelLookaheadMatcher: bad matcher flags: " << F;
+      error_ = true;
+    }
+    bool reach_input = match_type == MATCH_INPUT;
+    if (data) {
+      if (reach_input == data->ReachInput())
+        label_reachable_ = new LabelReachable<Arc, S>(data, s);
+    } else if ((reach_input && (F & kInputLookAheadMatcher)) ||
+               (!reach_input && (F & kOutputLookAheadMatcher))) {
+      label_reachable_ = new LabelReachable<Arc, S>(
+          fst, reach_input, s, F & kLookAheadKeepRelabelData);
+    }
+  }
+
+  LabelLookAheadMatcher(const LabelLookAheadMatcher<M, F, S> &lmatcher,
+                        bool safe = false)
+      : matcher_(lmatcher.matcher_, safe),
+        lfst_(lmatcher.lfst_),
+        label_reachable_(
+            lmatcher.label_reachable_ ?
+            new LabelReachable<Arc, S>(*lmatcher.label_reachable_) : 0),
+        s_(kNoStateId),
+        error_(lmatcher.error_) {}
+
+  ~LabelLookAheadMatcher() {
+    delete label_reachable_;
+  }
+
+  // General matcher methods
+  LabelLookAheadMatcher<M, F, S> *Copy(bool safe = false) const {
+    return new LabelLookAheadMatcher<M, F, S>(*this, safe);
+  }
+
+  MatchType Type(bool test) const { return matcher_.Type(test); }
+
+  void SetState(StateId s) {
+    if (s_ == s)
+      return;
+    s_ = s;
+    match_set_state_ = false;
+    reach_set_state_ = false;
+  }
+
+  bool Find(Label label) {
+    if (!match_set_state_) {
+      matcher_.SetState(s_);
+      match_set_state_ = true;
+    }
+    return matcher_.Find(label);
+  }
+
+  bool Done() const { return matcher_.Done(); }
+  const Arc& Value() const { return matcher_.Value(); }
+  void Next() { matcher_.Next(); }
+  const FST &GetFst() const { return matcher_.GetFst(); }
+
+  uint64 Properties(uint64 inprops) const {
+    uint64 outprops = matcher_.Properties(inprops);
+    if (error_ || (label_reachable_ && label_reachable_->Error()))
+      outprops |= kError;
+    return outprops;
+  }
+
+  uint32 Flags() const {
+    if (label_reachable_ && label_reachable_->GetData()->ReachInput())
+      return matcher_.Flags() | F | kInputLookAheadMatcher;
+    else if (label_reachable_ && !label_reachable_->GetData()->ReachInput())
+      return matcher_.Flags() | F | kOutputLookAheadMatcher;
+    else
+      return matcher_.Flags();
+  }
+
+  // Writable matcher methods
+  MatcherData *GetData() const {
+    return label_reachable_ ? label_reachable_->GetData() : 0;
+  };
+
+  // Look-ahead methods.
+  bool LookAheadLabel(Label label) const {
+    if (label == 0)
+      return true;
+
+    if (label_reachable_) {
+      if (!reach_set_state_) {
+        label_reachable_->SetState(s_);
+        reach_set_state_ = true;
+      }
+      return label_reachable_->Reach(label);
+    } else {
+      return true;
+    }
+  }
+
+  // Checks if there is a matching (possibly super-final) transition
+  // at (s_, s).
+  template <class L>
+  bool LookAheadFst(const L &fst, StateId s);
+
+  void InitLookAheadFst(const Fst<Arc>& fst, bool copy = false) {
+    lfst_ = &fst;
+    if (label_reachable_)
+      label_reachable_->ReachInit(fst, copy);
+  }
+
+  template <class L>
+  void InitLookAheadFst(const L& fst, bool copy = false) {
+    lfst_ = static_cast<const Fst<Arc> *>(&fst);
+    if (label_reachable_)
+      label_reachable_->ReachInit(fst, copy);
+  }
+
+ private:
+  // This allows base class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual void SetState_(StateId s) { SetState(s); }
+  virtual bool Find_(Label label) { return Find(label); }
+  virtual bool Done_() const { return Done(); }
+  virtual const Arc& Value_() const { return Value(); }
+  virtual void Next_() { Next(); }
+
+  bool LookAheadLabel_(Label l) const { return LookAheadLabel(l); }
+  bool LookAheadFst_(const Fst<Arc> &fst, StateId s) {
+    return LookAheadFst(fst, s);
+  }
+
+  mutable M matcher_;
+  const Fst<Arc> *lfst_;                     // Look-ahead FST
+  LabelReachable<Arc, S> *label_reachable_;  // Label reachability info
+  StateId s_;                                // Matcher state
+  bool match_set_state_;                     // matcher_.SetState called?
+  mutable bool reach_set_state_;             // reachable_.SetState called?
+  bool error_;
+};
+
+template <class M, uint32 F, class S>
+template <class L> inline
+bool LabelLookAheadMatcher<M, F, S>::LookAheadFst(const L &fst, StateId s) {
+  if (static_cast<const Fst<Arc> *>(&fst) != lfst_)
+    InitLookAheadFst(fst);
+
+  SetLookAheadWeight(Weight::One());
+  ClearLookAheadPrefix();
+
+  if (!label_reachable_)
+    return true;
+
+  label_reachable_->SetState(s_, s);
+  reach_set_state_ = true;
+
+  bool compute_weight = F & kLookAheadWeight;
+  bool compute_prefix = F & kLookAheadPrefix;
+
+  bool reach_input = Type(false) == MATCH_OUTPUT;
+  ArcIterator<L> aiter(fst, s);
+  bool reach_arc = label_reachable_->Reach(&aiter, 0,
+                                           internal::NumArcs(*lfst_, s),
+                                           reach_input, compute_weight);
+  if (reach_arc) {
+    ssize_t begin = label_reachable_->ReachBegin();
+    ssize_t end = label_reachable_->ReachEnd();
+    if (compute_prefix && end - begin == 1) {
+      aiter.Seek(begin);
+      SetLookAheadPrefix(aiter.Value());
+      compute_weight = false;
+    } else if (compute_weight) {
+      SetLookAheadWeight(label_reachable_->ReachWeight());
+    }
+  }
+  Weight lfinal = internal::Final(*lfst_, s);
+  bool reach_final = lfinal != Weight::Zero() &&
+      label_reachable_->ReachFinal();
+  if (reach_final && compute_weight)
+    SetLookAheadWeight(reach_arc ?
+                       Plus(LookAheadWeight(), lfinal) : lfinal);
+
+  return reach_arc || reach_final;
+}
+
+
+// Label-lookahead relabeling class.
+template <class A>
+class LabelLookAheadRelabeler {
+ public:
+  typedef typename A::Label Label;
+  typedef LabelReachableData<Label> MatcherData;
+  typedef AddOnPair<MatcherData, MatcherData> D;
+
+  // Relabels matcher Fst - initialization function object.
+  template <typename I>
+  LabelLookAheadRelabeler(I **impl);
+
+  // Relabels arbitrary Fst. Class L should be a label-lookahead Fst.
+  template <class L>
+  static void Relabel(MutableFst<A> *fst, const L &mfst,
+                      bool relabel_input) {
+    typename L::Impl *impl = mfst.GetImpl();
+    D *data = impl->GetAddOn();
+    LabelReachable<A> reachable(data->First() ?
+                                  data->First() : data->Second());
+    reachable.Relabel(fst, relabel_input);
+  }
+
+  // Returns relabeling pairs (cf. relabel.h::Relabel()).
+  // Class L should be a label-lookahead Fst.
+  // If 'avoid_collisions' is true, extra pairs are added to
+  // ensure no collisions when relabeling automata that have
+  // labels unseen here.
+  template <class L>
+  static void RelabelPairs(const L &mfst, vector<pair<Label, Label> > *pairs,
+                           bool avoid_collisions = false) {
+    typename L::Impl *impl = mfst.GetImpl();
+    D *data = impl->GetAddOn();
+    LabelReachable<A> reachable(data->First() ?
+                                  data->First() : data->Second());
+    reachable.RelabelPairs(pairs, avoid_collisions);
+  }
+};
+
+template <class A>
+template <typename I> inline
+LabelLookAheadRelabeler<A>::LabelLookAheadRelabeler(I **impl) {
+  Fst<A> &fst = (*impl)->GetFst();
+  D *data = (*impl)->GetAddOn();
+  const string name = (*impl)->Type();
+  bool is_mutable = fst.Properties(kMutable, false);
+  MutableFst<A> *mfst = 0;
+  if (is_mutable) {
+    mfst = static_cast<MutableFst<A> *>(&fst);
+  } else {
+    mfst = new VectorFst<A>(fst);
+    data->IncrRefCount();
+    delete *impl;
+  }
+  if (data->First()) {  // reach_input
+    LabelReachable<A> reachable(data->First());
+    reachable.Relabel(mfst, true);
+    if (!FLAGS_save_relabel_ipairs.empty()) {
+      vector<pair<Label, Label> > pairs;
+      reachable.RelabelPairs(&pairs, true);
+      WriteLabelPairs(FLAGS_save_relabel_ipairs, pairs);
+    }
+  } else {
+    LabelReachable<A> reachable(data->Second());
+    reachable.Relabel(mfst, false);
+    if (!FLAGS_save_relabel_opairs.empty()) {
+      vector<pair<Label, Label> > pairs;
+      reachable.RelabelPairs(&pairs, true);
+      WriteLabelPairs(FLAGS_save_relabel_opairs, pairs);
+    }
+  }
+  if (!is_mutable) {
+    *impl = new I(*mfst, name);
+    (*impl)->SetAddOn(data);
+    delete mfst;
+    data->DecrRefCount();
+  }
+}
+
+
+// Generic lookahead matcher, templated on the FST definition
+// - a wrapper around pointer to specific one.
+template <class F>
+class LookAheadMatcher {
+ public:
+  typedef F FST;
+  typedef typename F::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+  typedef LookAheadMatcherBase<Arc> LBase;
+
+  LookAheadMatcher(const F &fst, MatchType match_type) {
+    base_ = fst.InitMatcher(match_type);
+    if (!base_)
+      base_ = new SortedMatcher<F>(fst, match_type);
+    lookahead_ = false;
+  }
+
+  LookAheadMatcher(const LookAheadMatcher<F> &matcher, bool safe = false) {
+    base_ = matcher.base_->Copy(safe);
+    lookahead_ = matcher.lookahead_;
+  }
+
+  ~LookAheadMatcher() { delete base_; }
+
+  // General matcher methods
+  LookAheadMatcher<F> *Copy(bool safe = false) const {
+      return new LookAheadMatcher<F>(*this, safe);
+  }
+
+  MatchType Type(bool test) const { return base_->Type(test); }
+  void SetState(StateId s) { base_->SetState(s); }
+  bool Find(Label label) { return base_->Find(label); }
+  bool Done() const { return base_->Done(); }
+  const Arc& Value() const { return base_->Value(); }
+  void Next() { base_->Next(); }
+  const F &GetFst() const { return static_cast<const F &>(base_->GetFst()); }
+
+  uint64 Properties(uint64 props) const { return base_->Properties(props); }
+
+  uint32 Flags() const { return base_->Flags(); }
+
+  // Look-ahead methods
+  bool LookAheadLabel(Label label) const {
+    if (LookAheadCheck()) {
+      LBase *lbase = static_cast<LBase *>(base_);
+      return lbase->LookAheadLabel(label);
+    } else {
+      return true;
+    }
+  }
+
+  bool LookAheadFst(const Fst<Arc> &fst, StateId s) {
+    if (LookAheadCheck()) {
+      LBase *lbase = static_cast<LBase *>(base_);
+      return lbase->LookAheadFst(fst, s);
+    } else {
+      return true;
+    }
+  }
+
+  Weight LookAheadWeight() const {
+    if (LookAheadCheck()) {
+      LBase *lbase = static_cast<LBase *>(base_);
+      return lbase->LookAheadWeight();
+    } else {
+      return Weight::One();
+    }
+  }
+
+  bool LookAheadPrefix(Arc *arc) const {
+    if (LookAheadCheck()) {
+      LBase *lbase = static_cast<LBase *>(base_);
+      return lbase->LookAheadPrefix(arc);
+    } else {
+      return false;
+    }
+  }
+
+  void InitLookAheadFst(const Fst<Arc>& fst, bool copy = false) {
+    if (LookAheadCheck()) {
+      LBase *lbase = static_cast<LBase *>(base_);
+      lbase->InitLookAheadFst(fst, copy);
+    }
+  }
+
+ private:
+  bool LookAheadCheck() const {
+    if (!lookahead_) {
+      lookahead_ = base_->Flags() &
+          (kInputLookAheadMatcher | kOutputLookAheadMatcher);
+      if (!lookahead_) {
+        FSTERROR() << "LookAheadMatcher: No look-ahead matcher defined";
+      }
+    }
+    return lookahead_;
+  }
+
+  MatcherBase<Arc> *base_;
+  mutable bool lookahead_;
+
+  void operator=(const LookAheadMatcher<Arc> &);  // disallow
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_LOOKAHEAD_MATCHER_H__
diff --git a/src/include/fst/map.h b/src/include/fst/map.h
new file mode 100644
index 0000000..419cac4
--- /dev/null
+++ b/src/include/fst/map.h
@@ -0,0 +1,121 @@
+// map.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Compatability file for old-style Map() functions and MapFst class
+// that have been renamed to ArcMap (cf. StateMap).
+
+#ifndef FST_LIB_MAP_H__
+#define FST_LIB_MAP_H__
+
+
+#include <fst/arc-map.h>
+
+
+namespace fst {
+
+template<class A, class C>
+void Map(MutableFst<A> *fst, C* mapper) {
+  ArcMap(fst, mapper);
+}
+
+template<class A, class C>
+void Map(MutableFst<A> *fst, C mapper) {
+  ArcMap(fst, mapper);
+}
+
+template<class A, class B, class C>
+void Map(const Fst<A> &ifst, MutableFst<B> *ofst, C* mapper) {
+  ArcMap(ifst, ofst, mapper);
+}
+
+template<class A, class B, class C>
+void Map(const Fst<A> &ifst, MutableFst<B> *ofst, C mapper) {
+  ArcMap(ifst, ofst, mapper);
+}
+
+typedef ArcMapFstOptions MapFstOptions;
+
+template <class A, class B, class C>
+class MapFst : public ArcMapFst<A, B, C> {
+ public:
+  typedef B Arc;
+  typedef typename B::Weight Weight;
+  typedef typename B::StateId StateId;
+  typedef CacheState<B> State;
+
+  MapFst(const Fst<A> &fst, const C &mapper, const MapFstOptions& opts)
+      : ArcMapFst<A, B, C>(fst, mapper, opts) {}
+
+  MapFst(const Fst<A> &fst, C* mapper, const MapFstOptions& opts)
+      : ArcMapFst<A, B, C>(fst, mapper, opts) {}
+
+  MapFst(const Fst<A> &fst, const C &mapper)
+      : ArcMapFst<A, B, C>(fst, mapper) {}
+
+  MapFst(const Fst<A> &fst, C* mapper) : ArcMapFst<A, B, C>(fst, mapper) {}
+
+  // See Fst<>::Copy() for doc.
+  MapFst(const ArcMapFst<A, B, C> &fst, bool safe = false)
+      : ArcMapFst<A, B, C>(fst, safe) {}
+
+  // Get a copy of this MapFst. See Fst<>::Copy() for further doc.
+virtual MapFst<A, B, C> *Copy(bool safe = false) const {
+    return new MapFst(*this, safe);
+  }
+};
+
+
+// Specialization for MapFst.
+template <class A, class B, class C>
+class StateIterator< MapFst<A, B, C> >
+    : public StateIterator< ArcMapFst<A, B, C> > {
+ public:
+  explicit StateIterator(const ArcMapFst<A, B, C> &fst)
+      : StateIterator< ArcMapFst<A, B, C> >(fst) {}
+};
+
+
+// Specialization for MapFst.
+template <class A, class B, class C>
+class ArcIterator< MapFst<A, B, C> >
+    : public ArcIterator< ArcMapFst<A, B, C> > {
+ public:
+  ArcIterator(const ArcMapFst<A, B, C> &fst, typename A::StateId s)
+      : ArcIterator< ArcMapFst<A, B, C> >(fst, s) {}
+};
+
+
+template <class A>
+struct IdentityMapper {
+  typedef A FromArc;
+  typedef A ToArc;
+
+  A operator()(const A &arc) const { return arc; }
+
+  MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS;}
+
+  uint64 Properties(uint64 props) const { return props; }
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_MAP_H__
diff --git a/src/include/fst/matcher-fst.h b/src/include/fst/matcher-fst.h
new file mode 100644
index 0000000..73e64ad
--- /dev/null
+++ b/src/include/fst/matcher-fst.h
@@ -0,0 +1,359 @@
+// matcher-fst.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to add a matcher to an FST.
+
+#ifndef FST_LIB_MATCHER_FST_FST_H__
+#define FST_LIB_MATCHER_FST_FST_H__
+
+#include <fst/add-on.h>
+#include <fst/const-fst.h>
+#include <fst/lookahead-matcher.h>
+
+
+namespace fst {
+
+// WRITABLE MATCHERS - these have the interface of Matchers (see
+// matcher.h) and these additional methods:
+//
+// template <class F>
+// class Matcher {
+//  public:
+//   typedef ... MatcherData;  // Initialization data
+//  ...
+//   // Constructor with additional argument for external initialization
+//   // data; matcher increments its reference count on construction and
+//   // decrements the reference count, and if 0 deletes, on destruction.
+//   Matcher(const F &fst, MatchType type, MatcherData *data);
+//
+//   // Returns pointer to initialization data that can be
+//   // passed to a Matcher constructor.
+//   MatcherData *GetData() const;
+// };
+
+// The matcher initialization data class must have the form:
+// class MatcherData {
+// public:
+//   // Required copy constructor.
+//   MatcherData(const MatcherData &);
+//   //
+//   // Required I/O methods.
+//   static MatcherData *Read(istream &istrm);
+//   bool Write(ostream &ostrm);
+//
+//   // Required reference counting.
+//   int RefCount() const;
+//   int IncrRefCount();
+//   int DecrRefCount();
+// };
+
+// Default MatcherFst initializer - does nothing.
+template <class M>
+class NullMatcherFstInit {
+ public:
+  typedef AddOnPair<typename M::MatcherData, typename M::MatcherData> D;
+  typedef AddOnImpl<typename M::FST, D> Impl;
+  NullMatcherFstInit(Impl **) {}
+};
+
+// Class to add a matcher M to an Fst F. Creates a new Fst of type name N.
+// Optional function object I can be used to initialize the Fst.
+template <class F, class M, const char* N,
+          class I = NullMatcherFstInit<M> >
+class MatcherFst
+    : public ImplToExpandedFst<
+               AddOnImpl<F,
+                         AddOnPair<typename M::MatcherData,
+                                   typename M::MatcherData> > > {
+ public:
+  friend class StateIterator< MatcherFst<F, M, N, I> >;
+  friend class ArcIterator< MatcherFst<F, M, N, I> >;
+
+  typedef F FST;
+  typedef M FstMatcher;
+  typedef typename F::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef AddOnPair<typename M::MatcherData, typename M::MatcherData> D;
+  typedef AddOnImpl<F, D> Impl;
+
+  MatcherFst() : ImplToExpandedFst<Impl>(new Impl(F(), N)) {}
+
+  explicit MatcherFst(const F &fst)
+      : ImplToExpandedFst<Impl>(CreateImpl(fst, N)) {}
+
+  explicit MatcherFst(const Fst<Arc> &fst)
+      : ImplToExpandedFst<Impl>(CreateImpl(fst, N)) {}
+
+  // See Fst<>::Copy() for doc.
+  MatcherFst(const MatcherFst<F, M, N, I> &fst, bool safe = false)
+      : ImplToExpandedFst<Impl>(fst, safe) {}
+
+  // Get a copy of this MatcherFst. See Fst<>::Copy() for further doc.
+  virtual MatcherFst<F, M, N, I> *Copy(bool safe = false) const {
+    return new MatcherFst<F, M, N, I>(*this, safe);
+  }
+
+  // Read a MatcherFst from an input stream; return NULL on error
+  static MatcherFst<F, M, N, I> *Read(istream &strm,
+                                      const FstReadOptions &opts) {
+    Impl *impl = Impl::Read(strm, opts);
+    return impl ? new MatcherFst<F, M, N, I>(impl) : 0;
+  }
+
+  // Read a MatcherFst from a file; return NULL on error
+  // Empty filename reads from standard input
+  static MatcherFst<F, M, N, I> *Read(const string &filename) {
+    Impl *impl = ImplToExpandedFst<Impl>::Read(filename);
+    return impl ? new MatcherFst<F, M, N, I>(impl) : 0;
+  }
+
+  virtual bool Write(ostream &strm, const FstWriteOptions &opts) const {
+    return GetImpl()->Write(strm, opts);
+  }
+
+  virtual bool Write(const string &filename) const {
+    return Fst<Arc>::WriteFile(filename);
+  }
+
+  virtual void InitStateIterator(StateIteratorData<Arc> *data) const {
+    return GetImpl()->InitStateIterator(data);
+  }
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) const {
+    return GetImpl()->InitArcIterator(s, data);
+  }
+
+  virtual M *InitMatcher(MatchType match_type) const {
+    return new M(GetFst(), match_type, GetData(match_type));
+  }
+
+  // Allows access to MatcherFst components.
+  Impl *GetImpl() const {
+    return ImplToFst<Impl, ExpandedFst<Arc> >::GetImpl();
+  }
+
+  F& GetFst() const { return GetImpl()->GetFst(); }
+
+  typename M::MatcherData *GetData(MatchType match_type) const {
+    D *data = GetImpl()->GetAddOn();
+    return match_type == MATCH_INPUT ? data->First() : data->Second();
+  }
+
+ private:
+  static Impl *CreateImpl(const F &fst, const string &name) {
+    M imatcher(fst, MATCH_INPUT);
+    M omatcher(fst, MATCH_OUTPUT);
+    D *data = new D(imatcher.GetData(), omatcher.GetData());
+    Impl *impl = new Impl(fst, name);
+    impl->SetAddOn(data);
+    I init(&impl);
+    data->DecrRefCount();
+    return impl;
+  }
+
+  static Impl *CreateImpl(const Fst<Arc> &fst, const string &name) {
+    F ffst(fst);
+    return CreateImpl(ffst, name);
+  }
+
+  explicit MatcherFst(Impl *impl) : ImplToExpandedFst<Impl>(impl) {}
+
+  // Makes visible to friends.
+  void SetImpl(Impl *impl, bool own_impl = true) {
+    ImplToFst< Impl, ExpandedFst<Arc> >::SetImpl(impl, own_impl);
+  }
+
+  void operator=(const MatcherFst<F, M, N, I> &fst);  // disallow
+};
+
+
+// Specialization fo MatcherFst.
+template <class F, class M, const char* N, class I>
+class StateIterator< MatcherFst<F, M, N, I> > : public StateIterator<F> {
+ public:
+  explicit StateIterator(const MatcherFst<F, M, N, I> &fst) :
+      StateIterator<F>(fst.GetImpl()->GetFst()) {}
+};
+
+
+// Specialization for MatcherFst.
+template <class F, class M, const char* N, class I>
+class ArcIterator< MatcherFst<F, M, N, I> > : public ArcIterator<F> {
+ public:
+  ArcIterator(const MatcherFst<F, M, N, I> &fst, typename F::Arc::StateId s)
+      : ArcIterator<F>(fst.GetImpl()->GetFst(), s) {}
+};
+
+
+// Specialization for MatcherFst
+template <class F, class M, const char* N, class I>
+class Matcher< MatcherFst<F, M, N, I> > {
+ public:
+  typedef MatcherFst<F, M, N, I> FST;
+  typedef typename F::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+
+  Matcher(const FST &fst, MatchType match_type) {
+    matcher_ = fst.InitMatcher(match_type);
+  }
+
+  Matcher(const Matcher<FST> &matcher) {
+    matcher_ = matcher.matcher_->Copy();
+  }
+
+  ~Matcher() { delete matcher_; }
+
+  Matcher<FST> *Copy() const {
+    return new Matcher<FST>(*this);
+  }
+
+  MatchType Type(bool test) const { return matcher_->Type(test); }
+  void SetState(StateId s) { matcher_->SetState(s); }
+  bool Find(Label label) { return matcher_->Find(label); }
+  bool Done() const { return matcher_->Done(); }
+  const Arc& Value() const { return matcher_->Value(); }
+  void Next() { matcher_->Next(); }
+  uint64 Properties(uint64 props) const { return matcher_->Properties(props); }
+  uint32 Flags() const { return matcher_->Flags(); }
+
+ private:
+  M *matcher_;
+
+  void operator=(const Matcher<Arc> &);  // disallow
+};
+
+
+// Specialization for MatcherFst
+template <class F, class M, const char* N, class I>
+class LookAheadMatcher< MatcherFst<F, M, N, I> > {
+ public:
+  typedef MatcherFst<F, M, N, I> FST;
+  typedef typename F::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  LookAheadMatcher(const FST &fst, MatchType match_type) {
+    matcher_ = fst.InitMatcher(match_type);
+  }
+
+  LookAheadMatcher(const LookAheadMatcher<FST> &matcher, bool safe = false) {
+    matcher_ = matcher.matcher_->Copy(safe);
+  }
+
+  ~LookAheadMatcher() { delete matcher_; }
+
+  // General matcher methods
+  LookAheadMatcher<FST> *Copy(bool safe = false) const {
+    return new LookAheadMatcher<FST>(*this, safe);
+  }
+
+  MatchType Type(bool test) const { return matcher_->Type(test); }
+  void SetState(StateId s) { matcher_->SetState(s); }
+  bool Find(Label label) { return matcher_->Find(label); }
+  bool Done() const { return matcher_->Done(); }
+  const Arc& Value() const { return matcher_->Value(); }
+  void Next() { matcher_->Next(); }
+  const FST &GetFst() const { return matcher_->GetFst(); }
+  uint64 Properties(uint64 props) const { return matcher_->Properties(props); }
+  uint32 Flags() const { return matcher_->Flags(); }
+
+  // Look-ahead methods
+  bool LookAheadLabel(Label label) const {
+    return matcher_->LookAheadLabel(label);
+  }
+
+  bool LookAheadFst(const Fst<Arc> &fst, StateId s) {
+    return matcher_->LookAheadFst(fst, s);
+  }
+
+  Weight LookAheadWeight() const { return matcher_->LookAheadWeight(); }
+
+  bool LookAheadPrefix(Arc *arc) const {
+    return matcher_->LookAheadPrefix(arc);
+  }
+
+  void InitLookAheadFst(const Fst<Arc>& fst, bool copy = false) {
+    matcher_->InitLookAheadFst(fst, copy);
+  }
+
+ private:
+  M *matcher_;
+
+  void operator=(const LookAheadMatcher<FST> &);  // disallow
+};
+
+//
+// Useful aliases when using StdArc and LogArc.
+//
+
+// Arc look-ahead matchers
+extern const char arc_lookahead_fst_type[];
+
+typedef MatcherFst<ConstFst<StdArc>,
+                   ArcLookAheadMatcher<SortedMatcher<ConstFst<StdArc> > >,
+                   arc_lookahead_fst_type> StdArcLookAheadFst;
+
+typedef MatcherFst<ConstFst<LogArc>,
+                   ArcLookAheadMatcher<SortedMatcher<ConstFst<LogArc> > >,
+                   arc_lookahead_fst_type> LogArcLookAheadFst;
+
+
+// Label look-ahead matchers
+extern const char ilabel_lookahead_fst_type[];
+extern const char olabel_lookahead_fst_type[];
+
+static const uint32 ilabel_lookahead_flags = kInputLookAheadMatcher |
+    kLookAheadWeight | kLookAheadPrefix |
+    kLookAheadEpsilons | kLookAheadNonEpsilonPrefix;
+static const uint32 olabel_lookahead_flags = kOutputLookAheadMatcher |
+    kLookAheadWeight | kLookAheadPrefix |
+    kLookAheadEpsilons | kLookAheadNonEpsilonPrefix;
+
+typedef MatcherFst<ConstFst<StdArc>,
+                   LabelLookAheadMatcher<SortedMatcher<ConstFst<StdArc> >,
+                                         ilabel_lookahead_flags,
+                                         FastLogAccumulator<StdArc> >,
+                   ilabel_lookahead_fst_type,
+                   LabelLookAheadRelabeler<StdArc> > StdILabelLookAheadFst;
+
+typedef MatcherFst<ConstFst<LogArc>,
+                   LabelLookAheadMatcher<SortedMatcher<ConstFst<LogArc> >,
+                                         ilabel_lookahead_flags,
+                                         FastLogAccumulator<LogArc> >,
+                   ilabel_lookahead_fst_type,
+                   LabelLookAheadRelabeler<LogArc> > LogILabelLookAheadFst;
+
+typedef MatcherFst<ConstFst<StdArc>,
+                   LabelLookAheadMatcher<SortedMatcher<ConstFst<StdArc> >,
+                                         olabel_lookahead_flags,
+                                         FastLogAccumulator<StdArc> >,
+                   olabel_lookahead_fst_type,
+                   LabelLookAheadRelabeler<StdArc> > StdOLabelLookAheadFst;
+
+typedef MatcherFst<ConstFst<LogArc>,
+                   LabelLookAheadMatcher<SortedMatcher<ConstFst<LogArc> >,
+                                         olabel_lookahead_flags,
+                                         FastLogAccumulator<LogArc> >,
+                   olabel_lookahead_fst_type,
+                   LabelLookAheadRelabeler<LogArc> > LogOLabelLookAheadFst;
+
+}  // namespace fst
+
+#endif  // FST_LIB_MATCHER_FST_FST_H__
diff --git a/src/include/fst/matcher.h b/src/include/fst/matcher.h
new file mode 100644
index 0000000..a89325b
--- /dev/null
+++ b/src/include/fst/matcher.h
@@ -0,0 +1,1116 @@
+// matcher.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Classes to allow matching labels leaving FST states.
+
+#ifndef FST_LIB_MATCHER_H__
+#define FST_LIB_MATCHER_H__
+
+#include <algorithm>
+#include <set>
+
+#include <fst/mutable-fst.h>  // for all internal FST accessors
+
+
+namespace fst {
+
+// MATCHERS - these can find and iterate through requested labels at
+// FST states. In the simplest form, these are just some associative
+// map or search keyed on labels. More generally, they may
+// implement matching special labels that represent sets of labels
+// such as 'sigma' (all), 'rho' (rest), or 'phi' (fail).
+// The Matcher interface is:
+//
+// template <class F>
+// class Matcher {
+//  public:
+//   typedef F FST;
+//   typedef F::Arc Arc;
+//   typedef typename Arc::StateId StateId;
+//   typedef typename Arc::Label Label;
+//   typedef typename Arc::Weight Weight;
+//
+//   // Required constructors.
+//   Matcher(const F &fst, MatchType type);
+//   // If safe=true, the copy is thread-safe. See Fst<>::Copy()
+//   // for further doc.
+//   Matcher(const Matcher &matcher, bool safe = false);
+//
+//   // If safe=true, the copy is thread-safe. See Fst<>::Copy()
+//   // for further doc.
+//   Matcher<F> *Copy(bool safe = false) const;
+//
+//   // Returns the match type that can be provided (depending on
+//   // compatibility of the input FST). It is either
+//   // the requested match type, MATCH_NONE, or MATCH_UNKNOWN.
+//   // If 'test' is false, a constant time test is performed, but
+//   // MATCH_UNKNOWN may be returned. If 'test' is true,
+//   // a definite answer is returned, but may involve more costly
+//   // computation (e.g., visiting the Fst).
+//   MatchType Type(bool test) const;
+//   // Specifies the current state.
+//   void SetState(StateId s);
+//
+//   // This finds matches to a label at the current state.
+//   // Returns true if a match found. kNoLabel matches any
+//   // 'non-consuming' transitions, e.g., epsilon transitions,
+//   // which do not require a matching symbol.
+//   bool Find(Label label);
+//   // These iterate through any matches found:
+//   bool Done() const;         // No more matches.
+//   const A& Value() const;    // Current arc (when !Done)
+//   void Next();               // Advance to next arc (when !Done)
+//
+//   // Return matcher FST.
+//   const F& GetFst() const;
+//   // This specifies the known Fst properties as viewed from this
+//   // matcher. It takes as argument the input Fst's known properties.
+//   uint64 Properties(uint64 props) const;
+// };
+
+// Flags used for basic matchers (see also lookahead.h).
+const uint32 kMatcherFlags = 0x00000000;
+
+// Matcher interface, templated on the Arc definition; used
+// for matcher specializations that are returned by the
+// InitMatcher Fst method.
+template <class A>
+class MatcherBase {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+
+  virtual ~MatcherBase() {}
+
+  virtual MatcherBase<A> *Copy(bool safe = false) const = 0;
+  virtual MatchType Type(bool test) const = 0;
+  void SetState(StateId s) { SetState_(s); }
+  bool Find(Label label) { return Find_(label); }
+  bool Done() const { return Done_(); }
+  const A& Value() const { return Value_(); }
+  void Next() { Next_(); }
+  virtual const Fst<A> &GetFst() const = 0;
+  virtual uint64 Properties(uint64 props) const = 0;
+  virtual uint32 Flags() const { return 0; }
+ private:
+  virtual void SetState_(StateId s) = 0;
+  virtual bool Find_(Label label) = 0;
+  virtual bool Done_() const = 0;
+  virtual const A& Value_() const  = 0;
+  virtual void Next_()  = 0;
+};
+
+
+// A matcher that expects sorted labels on the side to be matched.
+// If match_type == MATCH_INPUT, epsilons match the implicit self loop
+// Arc(kNoLabel, 0, Weight::One(), current_state) as well as any
+// actual epsilon transitions. If match_type == MATCH_OUTPUT, then
+// Arc(0, kNoLabel, Weight::One(), current_state) is instead matched.
+template <class F>
+class SortedMatcher : public MatcherBase<typename F::Arc> {
+ public:
+  typedef F FST;
+  typedef typename F::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  // Labels >= binary_label will be searched for by binary search,
+  // o.w. linear search is used.
+  SortedMatcher(const F &fst, MatchType match_type,
+                Label binary_label = 1)
+      : fst_(fst.Copy()),
+        s_(kNoStateId),
+        aiter_(0),
+        match_type_(match_type),
+        binary_label_(binary_label),
+        match_label_(kNoLabel),
+        narcs_(0),
+        loop_(kNoLabel, 0, Weight::One(), kNoStateId),
+        error_(false) {
+    switch(match_type_) {
+      case MATCH_INPUT:
+      case MATCH_NONE:
+        break;
+      case MATCH_OUTPUT:
+        swap(loop_.ilabel, loop_.olabel);
+        break;
+      default:
+        FSTERROR() << "SortedMatcher: bad match type";
+        match_type_ = MATCH_NONE;
+        error_ = true;
+    }
+  }
+
+  SortedMatcher(const SortedMatcher<F> &matcher, bool safe = false)
+      : fst_(matcher.fst_->Copy(safe)),
+        s_(kNoStateId),
+        aiter_(0),
+        match_type_(matcher.match_type_),
+        binary_label_(matcher.binary_label_),
+        match_label_(kNoLabel),
+        narcs_(0),
+        loop_(matcher.loop_),
+        error_(matcher.error_) {}
+
+  virtual ~SortedMatcher() {
+    if (aiter_)
+      delete aiter_;
+    delete fst_;
+  }
+
+  virtual SortedMatcher<F> *Copy(bool safe = false) const {
+    return new SortedMatcher<F>(*this, safe);
+  }
+
+  virtual MatchType Type(bool test) const {
+    if (match_type_ == MATCH_NONE)
+      return match_type_;
+
+    uint64 true_prop =  match_type_ == MATCH_INPUT ?
+        kILabelSorted : kOLabelSorted;
+    uint64 false_prop = match_type_ == MATCH_INPUT ?
+        kNotILabelSorted : kNotOLabelSorted;
+    uint64 props = fst_->Properties(true_prop | false_prop, test);
+
+    if (props & true_prop)
+      return match_type_;
+    else if (props & false_prop)
+      return MATCH_NONE;
+    else
+      return MATCH_UNKNOWN;
+  }
+
+  void SetState(StateId s) {
+    if (s_ == s)
+      return;
+    s_ = s;
+    if (match_type_ == MATCH_NONE) {
+      FSTERROR() << "SortedMatcher: bad match type";
+      error_ = true;
+    }
+    if (aiter_)
+      delete aiter_;
+    aiter_ = new ArcIterator<F>(*fst_, s);
+    aiter_->SetFlags(kArcNoCache, kArcNoCache);
+    narcs_ = internal::NumArcs(*fst_, s);
+    loop_.nextstate = s;
+  }
+
+  bool Find(Label match_label);
+
+  bool Done() const {
+    if (current_loop_)
+      return false;
+    if (aiter_->Done())
+      return true;
+    aiter_->SetFlags(
+      match_type_ == MATCH_INPUT ? kArcILabelValue : kArcOLabelValue,
+      kArcValueFlags);
+    Label label = match_type_ == MATCH_INPUT ?
+        aiter_->Value().ilabel : aiter_->Value().olabel;
+    return label != match_label_;
+  }
+
+  const Arc& Value() const {
+    if (current_loop_) {
+      return loop_;
+    }
+    aiter_->SetFlags(kArcValueFlags, kArcValueFlags);
+    return aiter_->Value();
+  }
+
+  void Next() {
+    if (current_loop_)
+      current_loop_ = false;
+    else
+      aiter_->Next();
+  }
+
+  virtual const F &GetFst() const { return *fst_; }
+
+  virtual uint64 Properties(uint64 inprops) const {
+    uint64 outprops = inprops;
+    if (error_) outprops |= kError;
+    return outprops;
+  }
+
+ private:
+  virtual void SetState_(StateId s) { SetState(s); }
+  virtual bool Find_(Label label) { return Find(label); }
+  virtual bool Done_() const { return Done(); }
+  virtual const Arc& Value_() const { return Value(); }
+  virtual void Next_() { Next(); }
+
+  const F *fst_;
+  StateId s_;                     // Current state
+  ArcIterator<F> *aiter_;         // Iterator for current state
+  MatchType match_type_;          // Type of match to perform
+  Label binary_label_;            // Least label for binary search
+  Label match_label_;             // Current label to be matched
+  size_t narcs_;                  // Current state arc count
+  Arc loop_;                      // For non-consuming symbols
+  bool current_loop_;             // Current arc is the implicit loop
+  bool error_;                    // Error encountered
+
+  void operator=(const SortedMatcher<F> &);  // Disallow
+};
+
+template <class F> inline
+bool SortedMatcher<F>::Find(Label match_label) {
+  if (error_) {
+    current_loop_ = false;
+    match_label_ = kNoLabel;
+    return false;
+  }
+  current_loop_ = match_label == 0;
+  match_label_ = match_label == kNoLabel ? 0 : match_label;
+  aiter_->SetFlags(
+      match_type_ == MATCH_INPUT ? kArcILabelValue : kArcOLabelValue,
+      kArcValueFlags);
+  if (match_label_ >= binary_label_) {
+    // Binary search for match.
+    size_t low = 0;
+    size_t high = narcs_;
+    while (low < high) {
+      size_t mid = (low + high) / 2;
+      aiter_->Seek(mid);
+      Label label = match_type_ == MATCH_INPUT ?
+          aiter_->Value().ilabel : aiter_->Value().olabel;
+      if (label > match_label_) {
+        high = mid;
+      } else if (label < match_label_) {
+        low = mid + 1;
+      } else {
+        // find first matching label (when non-determinism)
+        for (size_t i = mid; i > low; --i) {
+          aiter_->Seek(i - 1);
+          label = match_type_ == MATCH_INPUT ? aiter_->Value().ilabel :
+              aiter_->Value().olabel;
+          if (label != match_label_) {
+            aiter_->Seek(i);
+            return true;
+          }
+        }
+        return true;
+      }
+    }
+    return current_loop_;
+  } else {
+    // Linear search for match.
+    for (aiter_->Reset(); !aiter_->Done(); aiter_->Next()) {
+      Label label = match_type_ == MATCH_INPUT ?
+          aiter_->Value().ilabel : aiter_->Value().olabel;
+      if (label == match_label_) {
+        return true;
+      }
+      if (label > match_label_)
+        break;
+    }
+    return current_loop_;
+  }
+}
+
+
+// Specifies whether during matching we rewrite both the input and output sides.
+enum MatcherRewriteMode {
+  MATCHER_REWRITE_AUTO = 0,    // Rewrites both sides iff acceptor.
+  MATCHER_REWRITE_ALWAYS,
+  MATCHER_REWRITE_NEVER
+};
+
+
+// For any requested label that doesn't match at a state, this matcher
+// considers all transitions that match the label 'rho_label' (rho =
+// 'rest').  Each such rho transition found is returned with the
+// rho_label rewritten as the requested label (both sides if an
+// acceptor, or if 'rewrite_both' is true and both input and output
+// labels of the found transition are 'rho_label').  If 'rho_label' is
+// kNoLabel, this special matching is not done.  RhoMatcher is
+// templated itself on a matcher, which is used to perform the
+// underlying matching.  By default, the underlying matcher is
+// constructed by RhoMatcher.  The user can instead pass in this
+// object; in that case, RhoMatcher takes its ownership.
+template <class M>
+class RhoMatcher : public MatcherBase<typename M::Arc> {
+ public:
+  typedef typename M::FST FST;
+  typedef typename M::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  RhoMatcher(const FST &fst,
+             MatchType match_type,
+             Label rho_label = kNoLabel,
+             MatcherRewriteMode rewrite_mode = MATCHER_REWRITE_AUTO,
+             M *matcher = 0)
+      : matcher_(matcher ? matcher : new M(fst, match_type)),
+        match_type_(match_type),
+        rho_label_(rho_label),
+        error_(false) {
+    if (match_type == MATCH_BOTH) {
+      FSTERROR() << "RhoMatcher: bad match type";
+      match_type_ = MATCH_NONE;
+      error_ = true;
+    }
+    if (rho_label == 0) {
+      FSTERROR() << "RhoMatcher: 0 cannot be used as rho_label";
+      rho_label_ = kNoLabel;
+      error_ = true;
+    }
+
+    if (rewrite_mode == MATCHER_REWRITE_AUTO)
+      rewrite_both_ = fst.Properties(kAcceptor, true);
+    else if (rewrite_mode == MATCHER_REWRITE_ALWAYS)
+      rewrite_both_ = true;
+    else
+      rewrite_both_ = false;
+  }
+
+  RhoMatcher(const RhoMatcher<M> &matcher, bool safe = false)
+      : matcher_(new M(*matcher.matcher_, safe)),
+        match_type_(matcher.match_type_),
+        rho_label_(matcher.rho_label_),
+        rewrite_both_(matcher.rewrite_both_),
+        error_(matcher.error_) {}
+
+  virtual ~RhoMatcher() {
+    delete matcher_;
+  }
+
+  virtual RhoMatcher<M> *Copy(bool safe = false) const {
+    return new RhoMatcher<M>(*this, safe);
+  }
+
+  virtual MatchType Type(bool test) const { return matcher_->Type(test); }
+
+  void SetState(StateId s) {
+    matcher_->SetState(s);
+    has_rho_ = rho_label_ != kNoLabel;
+  }
+
+  bool Find(Label match_label) {
+    if (match_label == rho_label_ && rho_label_ != kNoLabel) {
+      FSTERROR() << "RhoMatcher::Find: bad label (rho)";
+      error_ = true;
+      return false;
+    }
+    if (matcher_->Find(match_label)) {
+      rho_match_ = kNoLabel;
+      return true;
+    } else if (has_rho_ && match_label != 0 && match_label != kNoLabel &&
+               (has_rho_ = matcher_->Find(rho_label_))) {
+      rho_match_ = match_label;
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  bool Done() const { return matcher_->Done(); }
+
+  const Arc& Value() const {
+    if (rho_match_ == kNoLabel) {
+      return matcher_->Value();
+    } else {
+      rho_arc_ = matcher_->Value();
+      if (rewrite_both_) {
+        if (rho_arc_.ilabel == rho_label_)
+          rho_arc_.ilabel = rho_match_;
+        if (rho_arc_.olabel == rho_label_)
+          rho_arc_.olabel = rho_match_;
+      } else if (match_type_ == MATCH_INPUT) {
+        rho_arc_.ilabel = rho_match_;
+      } else {
+        rho_arc_.olabel = rho_match_;
+      }
+      return rho_arc_;
+    }
+  }
+
+  void Next() { matcher_->Next(); }
+
+  virtual const FST &GetFst() const { return matcher_->GetFst(); }
+
+  virtual uint64 Properties(uint64 props) const;
+
+ private:
+  virtual void SetState_(StateId s) { SetState(s); }
+  virtual bool Find_(Label label) { return Find(label); }
+  virtual bool Done_() const { return Done(); }
+  virtual const Arc& Value_() const { return Value(); }
+  virtual void Next_() { Next(); }
+
+  M *matcher_;
+  MatchType match_type_;  // Type of match requested
+  Label rho_label_;       // Label that represents the rho transition
+  bool rewrite_both_;     // Rewrite both sides when both are 'rho_label_'
+  bool has_rho_;          // Are there possibly rhos at the current state?
+  Label rho_match_;       // Current label that matches rho transition
+  mutable Arc rho_arc_;   // Arc to return when rho match
+  bool error_;            // Error encountered
+
+  void operator=(const RhoMatcher<M> &);  // Disallow
+};
+
+template <class M> inline
+uint64 RhoMatcher<M>::Properties(uint64 inprops) const {
+  uint64 outprops = matcher_->Properties(inprops);
+  if (error_) outprops |= kError;
+
+  if (match_type_ == MATCH_NONE) {
+    return outprops;
+  } else if (match_type_ == MATCH_INPUT) {
+    if (rewrite_both_) {
+      return outprops & ~(kODeterministic | kNonODeterministic | kString |
+                       kILabelSorted | kNotILabelSorted |
+                       kOLabelSorted | kNotOLabelSorted);
+    } else {
+      return outprops & ~(kODeterministic | kAcceptor | kString |
+                       kILabelSorted | kNotILabelSorted);
+    }
+  } else if (match_type_ == MATCH_OUTPUT) {
+    if (rewrite_both_) {
+      return outprops & ~(kIDeterministic | kNonIDeterministic | kString |
+                       kILabelSorted | kNotILabelSorted |
+                       kOLabelSorted | kNotOLabelSorted);
+    } else {
+      return outprops & ~(kIDeterministic | kAcceptor | kString |
+                       kOLabelSorted | kNotOLabelSorted);
+    }
+  } else {
+    // Shouldn't ever get here.
+    FSTERROR() << "RhoMatcher:: bad match type: " << match_type_;
+    return 0;
+  }
+}
+
+
+// For any requested label, this matcher considers all transitions
+// that match the label 'sigma_label' (sigma = "any"), and this in
+// additions to transitions with the requested label.  Each such sigma
+// transition found is returned with the sigma_label rewritten as the
+// requested label (both sides if an acceptor, or if 'rewrite_both' is
+// true and both input and output labels of the found transition are
+// 'sigma_label').  If 'sigma_label' is kNoLabel, this special
+// matching is not done.  SigmaMatcher is templated itself on a
+// matcher, which is used to perform the underlying matching.  By
+// default, the underlying matcher is constructed by SigmaMatcher.
+// The user can instead pass in this object; in that case,
+// SigmaMatcher takes its ownership.
+template <class M>
+class SigmaMatcher : public MatcherBase<typename M::Arc> {
+ public:
+  typedef typename M::FST FST;
+  typedef typename M::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  SigmaMatcher(const FST &fst,
+               MatchType match_type,
+               Label sigma_label = kNoLabel,
+               MatcherRewriteMode rewrite_mode = MATCHER_REWRITE_AUTO,
+               M *matcher = 0)
+      : matcher_(matcher ? matcher : new M(fst, match_type)),
+        match_type_(match_type),
+        sigma_label_(sigma_label),
+        error_(false) {
+    if (match_type == MATCH_BOTH) {
+      FSTERROR() << "SigmaMatcher: bad match type";
+      match_type_ = MATCH_NONE;
+      error_ = true;
+    }
+    if (sigma_label == 0) {
+      FSTERROR() << "SigmaMatcher: 0 cannot be used as sigma_label";
+      sigma_label_ = kNoLabel;
+      error_ = true;
+    }
+
+    if (rewrite_mode == MATCHER_REWRITE_AUTO)
+      rewrite_both_ = fst.Properties(kAcceptor, true);
+    else if (rewrite_mode == MATCHER_REWRITE_ALWAYS)
+      rewrite_both_ = true;
+    else
+      rewrite_both_ = false;
+  }
+
+  SigmaMatcher(const SigmaMatcher<M> &matcher, bool safe = false)
+      : matcher_(new M(*matcher.matcher_, safe)),
+        match_type_(matcher.match_type_),
+        sigma_label_(matcher.sigma_label_),
+        rewrite_both_(matcher.rewrite_both_),
+        error_(matcher.error_) {}
+
+  virtual ~SigmaMatcher() {
+    delete matcher_;
+  }
+
+  virtual SigmaMatcher<M> *Copy(bool safe = false) const {
+    return new SigmaMatcher<M>(*this, safe);
+  }
+
+  virtual MatchType Type(bool test) const { return matcher_->Type(test); }
+
+  void SetState(StateId s) {
+    matcher_->SetState(s);
+    has_sigma_ =
+        sigma_label_ != kNoLabel ? matcher_->Find(sigma_label_) : false;
+  }
+
+  bool Find(Label match_label) {
+    match_label_ = match_label;
+    if (match_label == sigma_label_ && sigma_label_ != kNoLabel) {
+      FSTERROR() << "SigmaMatcher::Find: bad label (sigma)";
+      error_ = true;
+      return false;
+    }
+    if (matcher_->Find(match_label)) {
+      sigma_match_ = kNoLabel;
+      return true;
+    } else if (has_sigma_ && match_label != 0 && match_label != kNoLabel &&
+               matcher_->Find(sigma_label_)) {
+      sigma_match_ = match_label;
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  bool Done() const {
+    return matcher_->Done();
+  }
+
+  const Arc& Value() const {
+    if (sigma_match_ == kNoLabel) {
+      return matcher_->Value();
+    } else {
+      sigma_arc_ = matcher_->Value();
+      if (rewrite_both_) {
+        if (sigma_arc_.ilabel == sigma_label_)
+          sigma_arc_.ilabel = sigma_match_;
+        if (sigma_arc_.olabel == sigma_label_)
+          sigma_arc_.olabel = sigma_match_;
+      } else if (match_type_ == MATCH_INPUT) {
+        sigma_arc_.ilabel = sigma_match_;
+      } else {
+        sigma_arc_.olabel = sigma_match_;
+      }
+      return sigma_arc_;
+    }
+  }
+
+  void Next() {
+    matcher_->Next();
+    if (matcher_->Done() && has_sigma_ && (sigma_match_ == kNoLabel) &&
+        (match_label_ > 0)) {
+      matcher_->Find(sigma_label_);
+      sigma_match_ = match_label_;
+    }
+  }
+
+  virtual const FST &GetFst() const { return matcher_->GetFst(); }
+
+  virtual uint64 Properties(uint64 props) const;
+
+private:
+  virtual void SetState_(StateId s) { SetState(s); }
+  virtual bool Find_(Label label) { return Find(label); }
+  virtual bool Done_() const { return Done(); }
+  virtual const Arc& Value_() const { return Value(); }
+  virtual void Next_() { Next(); }
+
+  M *matcher_;
+  MatchType match_type_;   // Type of match requested
+  Label sigma_label_;      // Label that represents the sigma transition
+  bool rewrite_both_;      // Rewrite both sides when both are 'sigma_label_'
+  bool has_sigma_;         // Are there sigmas at the current state?
+  Label sigma_match_;      // Current label that matches sigma transition
+  mutable Arc sigma_arc_;  // Arc to return when sigma match
+  Label match_label_;      // Label being matched
+  bool error_;             // Error encountered
+
+  void operator=(const SigmaMatcher<M> &);  // disallow
+};
+
+template <class M> inline
+uint64 SigmaMatcher<M>::Properties(uint64 inprops) const {
+  uint64 outprops = matcher_->Properties(inprops);
+  if (error_) outprops |= kError;
+
+  if (match_type_ == MATCH_NONE) {
+    return outprops;
+  } else if (rewrite_both_) {
+    return outprops & ~(kIDeterministic | kNonIDeterministic |
+                     kODeterministic | kNonODeterministic |
+                     kILabelSorted | kNotILabelSorted |
+                     kOLabelSorted | kNotOLabelSorted |
+                     kString);
+  } else if (match_type_ == MATCH_INPUT) {
+    return outprops & ~(kIDeterministic | kNonIDeterministic |
+                     kODeterministic | kNonODeterministic |
+                     kILabelSorted | kNotILabelSorted |
+                     kString | kAcceptor);
+  } else if (match_type_ == MATCH_OUTPUT) {
+    return outprops & ~(kIDeterministic | kNonIDeterministic |
+                     kODeterministic | kNonODeterministic |
+                     kOLabelSorted | kNotOLabelSorted |
+                     kString | kAcceptor);
+  } else {
+    // Shouldn't ever get here.
+    FSTERROR() << "SigmaMatcher:: bad match type: " << match_type_;
+    return 0;
+  }
+}
+
+
+// For any requested label that doesn't match at a state, this matcher
+// considers the *unique* transition that matches the label 'phi_label'
+// (phi = 'fail'), and recursively looks for a match at its
+// destination.  When 'phi_loop' is true, if no match is found but a
+// phi self-loop is found, then the phi transition found is returned
+// with the phi_label rewritten as the requested label (both sides if
+// an acceptor, or if 'rewrite_both' is true and both input and output
+// labels of the found transition are 'phi_label').  If 'phi_label' is
+// kNoLabel, this special matching is not done.  PhiMatcher is
+// templated itself on a matcher, which is used to perform the
+// underlying matching.  By default, the underlying matcher is
+// constructed by PhiMatcher. The user can instead pass in this
+// object; in that case, PhiMatcher takes its ownership.
+// Warning: phi non-determinism not supported (for simplicity).
+template <class M>
+class PhiMatcher : public MatcherBase<typename M::Arc> {
+ public:
+  typedef typename M::FST FST;
+  typedef typename M::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  PhiMatcher(const FST &fst,
+             MatchType match_type,
+             Label phi_label = kNoLabel,
+             bool phi_loop = true,
+             MatcherRewriteMode rewrite_mode = MATCHER_REWRITE_AUTO,
+             M *matcher = 0)
+      : matcher_(matcher ? matcher : new M(fst, match_type)),
+        match_type_(match_type),
+        phi_label_(phi_label),
+        state_(kNoStateId),
+        phi_loop_(phi_loop),
+        error_(false) {
+    if (match_type == MATCH_BOTH) {
+      FSTERROR() << "PhiMatcher: bad match type";
+      match_type_ = MATCH_NONE;
+      error_ = true;
+    }
+    if (phi_label == 0) {
+      FSTERROR() << "PhiMatcher: 0 cannot be used as phi_label";
+      phi_label_ = kNoLabel;
+      error_ = true;
+    }
+
+    if (rewrite_mode == MATCHER_REWRITE_AUTO)
+      rewrite_both_ = fst.Properties(kAcceptor, true);
+    else if (rewrite_mode == MATCHER_REWRITE_ALWAYS)
+      rewrite_both_ = true;
+    else
+      rewrite_both_ = false;
+   }
+
+  PhiMatcher(const PhiMatcher<M> &matcher, bool safe = false)
+      : matcher_(new M(*matcher.matcher_, safe)),
+        match_type_(matcher.match_type_),
+        phi_label_(matcher.phi_label_),
+        rewrite_both_(matcher.rewrite_both_),
+        state_(kNoStateId),
+        phi_loop_(matcher.phi_loop_),
+        error_(matcher.error_) {}
+
+  virtual ~PhiMatcher() {
+    delete matcher_;
+  }
+
+  virtual PhiMatcher<M> *Copy(bool safe = false) const {
+    return new PhiMatcher<M>(*this, safe);
+  }
+
+  virtual MatchType Type(bool test) const { return matcher_->Type(test); }
+
+  void SetState(StateId s) {
+    matcher_->SetState(s);
+    state_ = s;
+    has_phi_ = phi_label_ != kNoLabel;
+  }
+
+  bool Find(Label match_label);
+
+  bool Done() const { return matcher_->Done(); }
+
+  const Arc& Value() const {
+    if ((phi_match_ == kNoLabel) && (phi_weight_ == Weight::One())) {
+      return matcher_->Value();
+    } else {
+      phi_arc_ = matcher_->Value();
+      phi_arc_.weight = Times(phi_weight_, phi_arc_.weight);
+      if (phi_match_ != kNoLabel) {
+        if (rewrite_both_) {
+          if (phi_arc_.ilabel == phi_label_)
+            phi_arc_.ilabel = phi_match_;
+          if (phi_arc_.olabel == phi_label_)
+            phi_arc_.olabel = phi_match_;
+        } else if (match_type_ == MATCH_INPUT) {
+          phi_arc_.ilabel = phi_match_;
+        } else {
+          phi_arc_.olabel = phi_match_;
+        }
+      }
+      return phi_arc_;
+    }
+  }
+
+  void Next() { matcher_->Next(); }
+
+  virtual const FST &GetFst() const { return matcher_->GetFst(); }
+
+  virtual uint64 Properties(uint64 props) const;
+
+private:
+  virtual void SetState_(StateId s) { SetState(s); }
+  virtual bool Find_(Label label) { return Find(label); }
+  virtual bool Done_() const { return Done(); }
+  virtual const Arc& Value_() const { return Value(); }
+  virtual void Next_() { Next(); }
+
+  M *matcher_;
+  MatchType match_type_;  // Type of match requested
+  Label phi_label_;       // Label that represents the phi transition
+  bool rewrite_both_;     // Rewrite both sides when both are 'phi_label_'
+  bool has_phi_;          // Are there possibly phis at the current state?
+  Label phi_match_;       // Current label that matches phi loop
+  mutable Arc phi_arc_;   // Arc to return
+  StateId state_;         // State where looking for matches
+  Weight phi_weight_;     // Product of the weights of phi transitions taken
+  bool phi_loop_;         // When true, phi self-loop are allowed and treated
+                          // as rho (required for Aho-Corasick)
+  bool error_;             // Error encountered
+
+  void operator=(const PhiMatcher<M> &);  // disallow
+};
+
+template <class M> inline
+bool PhiMatcher<M>::Find(Label match_label) {
+  if (match_label == phi_label_ && phi_label_ != kNoLabel) {
+    FSTERROR() << "PhiMatcher::Find: bad label (phi)";
+    error_ = true;
+    return false;
+  }
+  matcher_->SetState(state_);
+  phi_match_ = kNoLabel;
+  phi_weight_ = Weight::One();
+  if (!has_phi_ || match_label == 0 || match_label == kNoLabel)
+    return matcher_->Find(match_label);
+  StateId state = state_;
+  while (!matcher_->Find(match_label)) {
+    if (!matcher_->Find(phi_label_))
+      return false;
+    if (phi_loop_ && matcher_->Value().nextstate == state) {
+      phi_match_ = match_label;
+      return true;
+    }
+    phi_weight_ = Times(phi_weight_, matcher_->Value().weight);
+    state = matcher_->Value().nextstate;
+    matcher_->Next();
+    if (!matcher_->Done()) {
+      FSTERROR() << "PhiMatcher: phi non-determinism not supported";
+      error_ = true;
+    }
+    matcher_->SetState(state);
+  }
+  return true;
+}
+
+template <class M> inline
+uint64 PhiMatcher<M>::Properties(uint64 inprops) const {
+  uint64 outprops = matcher_->Properties(inprops);
+  if (error_) outprops |= kError;
+
+  if (match_type_ == MATCH_NONE) {
+    return outprops;
+  } else if (match_type_ == MATCH_INPUT) {
+    if (rewrite_both_) {
+      return outprops & ~(kODeterministic | kNonODeterministic | kString |
+                       kILabelSorted | kNotILabelSorted |
+                       kOLabelSorted | kNotOLabelSorted);
+    } else {
+      return outprops & ~(kODeterministic | kAcceptor | kString |
+                       kILabelSorted | kNotILabelSorted |
+                       kOLabelSorted | kNotOLabelSorted);
+    }
+  } else if (match_type_ == MATCH_OUTPUT) {
+    if (rewrite_both_) {
+      return outprops & ~(kIDeterministic | kNonIDeterministic | kString |
+                       kILabelSorted | kNotILabelSorted |
+                       kOLabelSorted | kNotOLabelSorted);
+    } else {
+      return outprops & ~(kIDeterministic | kAcceptor | kString |
+                       kILabelSorted | kNotILabelSorted |
+                       kOLabelSorted | kNotOLabelSorted);
+    }
+  } else {
+    // Shouldn't ever get here.
+    FSTERROR() << "PhiMatcher:: bad match type: " << match_type_;
+    return 0;
+  }
+}
+
+
+//
+// MULTI-EPS MATCHER FLAGS
+//
+
+// Return multi-epsilon arcs for Find(kNoLabel).
+const uint32 kMultiEpsList =  0x00000001;
+
+// Return a kNolabel loop for Find(multi_eps).
+const uint32 kMultiEpsLoop =  0x00000002;
+
+// MultiEpsMatcher: allows treating multiple non-0 labels as
+// non-consuming labels in addition to 0 that is always
+// non-consuming. Precise behavior controlled by 'flags' argument. By
+// default, the underlying matcher is constructed by
+// MultiEpsMatcher. The user can instead pass in this object; in that
+// case, MultiEpsMatcher takes its ownership iff 'own_matcher' is
+// true.
+template <class M>
+class MultiEpsMatcher {
+ public:
+  typedef typename M::FST FST;
+  typedef typename M::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  MultiEpsMatcher(const FST &fst, MatchType match_type,
+                  uint32 flags = (kMultiEpsLoop | kMultiEpsList),
+                  M *matcher = 0, bool own_matcher = true)
+      : matcher_(matcher ? matcher : new M(fst, match_type)),
+        flags_(flags),
+        own_matcher_(matcher ?  own_matcher : true) {
+    if (match_type == MATCH_INPUT) {
+      loop_.ilabel = kNoLabel;
+      loop_.olabel = 0;
+    } else {
+      loop_.ilabel = 0;
+      loop_.olabel = kNoLabel;
+    }
+    loop_.weight = Weight::One();
+    loop_.nextstate = kNoStateId;
+  }
+
+  MultiEpsMatcher(const MultiEpsMatcher<M> &matcher, bool safe = false)
+      : matcher_(new M(*matcher.matcher_, safe)),
+        flags_(matcher.flags_),
+        own_matcher_(true),
+        multi_eps_labels_(matcher.multi_eps_labels_),
+        loop_(matcher.loop_) {
+    loop_.nextstate = kNoStateId;
+  }
+
+  ~MultiEpsMatcher() {
+    if (own_matcher_)
+      delete matcher_;
+  }
+
+  MultiEpsMatcher<M> *Copy(bool safe = false) const {
+    return new MultiEpsMatcher<M>(*this, safe);
+  }
+
+  MatchType Type(bool test) const { return matcher_->Type(test); }
+
+  void SetState(StateId s) {
+    matcher_->SetState(s);
+    loop_.nextstate = s;
+  }
+
+  bool Find(Label match_label);
+
+  bool Done() const {
+    return done_;
+  }
+
+  const Arc& Value() const {
+    return current_loop_ ? loop_ : matcher_->Value();
+  }
+
+  void Next() {
+    if (!current_loop_) {
+      matcher_->Next();
+      done_ = matcher_->Done();
+      if (done_ && multi_eps_iter_ != multi_eps_labels_.End()) {
+        ++multi_eps_iter_;
+        while ((multi_eps_iter_ != multi_eps_labels_.End()) &&
+               !matcher_->Find(*multi_eps_iter_))
+          ++multi_eps_iter_;
+        if (multi_eps_iter_ != multi_eps_labels_.End())
+          done_ = false;
+        else
+          done_ = !matcher_->Find(kNoLabel);
+
+      }
+    } else {
+      done_ = true;
+    }
+  }
+
+  const FST &GetFst() const { return matcher_->GetFst(); }
+
+  uint64 Properties(uint64 props) const { return matcher_->Properties(props); }
+
+  uint32 Flags() const { return matcher_->Flags(); }
+
+  void AddMultiEpsLabel(Label label) {
+    if (label == 0) {
+      FSTERROR() << "MultiEpsMatcher: Bad multi-eps label: 0";
+    } else {
+      multi_eps_labels_.Insert(label);
+    }
+  }
+
+  void ClearMultiEpsLabels() {
+    multi_eps_labels_.Clear();
+  }
+
+private:
+  // Specialized for 'set' - log lookup
+  bool IsMultiEps(const set<Label> &multi_eps_labels, Label label) const {
+    return multi_eps_labels.Find(label) != multi_eps_labels.end();
+  }
+
+  M *matcher_;
+  uint32 flags_;
+  bool own_matcher_;             // Does this class delete the matcher?
+
+  // Multi-eps label set
+  CompactSet<Label, kNoLabel> multi_eps_labels_;
+  typename CompactSet<Label, kNoLabel>::const_iterator multi_eps_iter_;
+
+  bool current_loop_;            // Current arc is the implicit loop
+  mutable Arc loop_;             // For non-consuming symbols
+  bool done_;                    // Matching done
+
+  void operator=(const MultiEpsMatcher<M> &);  // Disallow
+};
+
+template <class M> inline
+bool MultiEpsMatcher<M>::Find(Label match_label) {
+  multi_eps_iter_ = multi_eps_labels_.End();
+  current_loop_ = false;
+  bool ret;
+  if (match_label == 0) {
+    ret = matcher_->Find(0);
+  } else if (match_label == kNoLabel) {
+    if (flags_ & kMultiEpsList) {
+      // return all non-consuming arcs (incl. epsilon)
+      multi_eps_iter_ = multi_eps_labels_.Begin();
+      while ((multi_eps_iter_ != multi_eps_labels_.End()) &&
+             !matcher_->Find(*multi_eps_iter_))
+        ++multi_eps_iter_;
+      if (multi_eps_iter_ != multi_eps_labels_.End())
+        ret = true;
+      else
+        ret = matcher_->Find(kNoLabel);
+    } else {
+      // return all epsilon arcs
+      ret = matcher_->Find(kNoLabel);
+    }
+  } else if ((flags_ & kMultiEpsLoop) &&
+             multi_eps_labels_.Find(match_label) != multi_eps_labels_.End()) {
+    // return 'implicit' loop
+    current_loop_ = true;
+    ret = true;
+  } else {
+    ret = matcher_->Find(match_label);
+  }
+  done_ = !ret;
+  return ret;
+}
+
+
+// Generic matcher, templated on the FST definition
+// - a wrapper around pointer to specific one.
+// Here is a typical use: \code
+//   Matcher<StdFst> matcher(fst, MATCH_INPUT);
+//   matcher.SetState(state);
+//   if (matcher.Find(label))
+//     for (; !matcher.Done(); matcher.Next()) {
+//       StdArc &arc = matcher.Value();
+//       ...
+//     } \endcode
+template <class F>
+class Matcher {
+ public:
+  typedef F FST;
+  typedef typename F::Arc Arc;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  Matcher(const F &fst, MatchType match_type) {
+    base_ = fst.InitMatcher(match_type);
+    if (!base_)
+      base_ = new SortedMatcher<F>(fst, match_type);
+  }
+
+  Matcher(const Matcher<F> &matcher, bool safe = false) {
+    base_ = matcher.base_->Copy(safe);
+  }
+
+  // Takes ownership of the provided matcher
+  Matcher(MatcherBase<Arc>* base_matcher) { base_ = base_matcher; }
+
+  ~Matcher() { delete base_; }
+
+  Matcher<F> *Copy(bool safe = false) const {
+    return new Matcher<F>(*this, safe);
+  }
+
+  MatchType Type(bool test) const { return base_->Type(test); }
+  void SetState(StateId s) { base_->SetState(s); }
+  bool Find(Label label) { return base_->Find(label); }
+  bool Done() const { return base_->Done(); }
+  const Arc& Value() const { return base_->Value(); }
+  void Next() { base_->Next(); }
+  const F &GetFst() const { return static_cast<const F &>(base_->GetFst()); }
+  uint64 Properties(uint64 props) const { return base_->Properties(props); }
+  uint32 Flags() const { return base_->Flags() & kMatcherFlags; }
+
+ private:
+  MatcherBase<Arc> *base_;
+
+  void operator=(const Matcher<Arc> &);  // disallow
+};
+
+}  // namespace fst
+
+
+
+#endif  // FST_LIB_MATCHER_H__
diff --git a/src/include/fst/minimize.h b/src/include/fst/minimize.h
new file mode 100644
index 0000000..3fbe3ba
--- /dev/null
+++ b/src/include/fst/minimize.h
@@ -0,0 +1,584 @@
+// minimize.h
+// minimize.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: johans@google.com (Johan Schalkwyk)
+//
+// \file Functions and classes to minimize a finite state acceptor
+//
+
+#ifndef FST_LIB_MINIMIZE_H__
+#define FST_LIB_MINIMIZE_H__
+
+#include <cmath>
+
+#include <algorithm>
+#include <map>
+#include <queue>
+#include <vector>
+using std::vector;
+
+#include <fst/arcsort.h>
+#include <fst/connect.h>
+#include <fst/dfs-visit.h>
+#include <fst/encode.h>
+#include <fst/factor-weight.h>
+#include <fst/fst.h>
+#include <fst/mutable-fst.h>
+#include <fst/partition.h>
+#include <fst/push.h>
+#include <fst/queue.h>
+#include <fst/reverse.h>
+#include <fst/state-map.h>
+
+
+namespace fst {
+
+// comparator for creating partition based on sorting on
+// - states
+// - final weight
+// - out degree,
+// -  (input label, output label, weight, destination_block)
+template <class A>
+class StateComparator {
+ public:
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  static const uint32 kCompareFinal     = 0x00000001;
+  static const uint32 kCompareOutDegree = 0x00000002;
+  static const uint32 kCompareArcs      = 0x00000004;
+  static const uint32 kCompareAll       = 0x00000007;
+
+  StateComparator(const Fst<A>& fst,
+                  const Partition<typename A::StateId>& partition,
+                  uint32 flags = kCompareAll)
+      : fst_(fst), partition_(partition), flags_(flags) {}
+
+  // compare state x with state y based on sort criteria
+  bool operator()(const StateId x, const StateId y) const {
+    // check for final state equivalence
+    if (flags_ & kCompareFinal) {
+      const size_t xfinal = fst_.Final(x).Hash();
+      const size_t yfinal = fst_.Final(y).Hash();
+      if      (xfinal < yfinal) return true;
+      else if (xfinal > yfinal) return false;
+    }
+
+    if (flags_ & kCompareOutDegree) {
+      // check for # arcs
+      if (fst_.NumArcs(x) < fst_.NumArcs(y)) return true;
+      if (fst_.NumArcs(x) > fst_.NumArcs(y)) return false;
+
+      if (flags_ & kCompareArcs) {
+        // # arcs are equal, check for arc match
+        for (ArcIterator<Fst<A> > aiter1(fst_, x), aiter2(fst_, y);
+             !aiter1.Done() && !aiter2.Done(); aiter1.Next(), aiter2.Next()) {
+          const A& arc1 = aiter1.Value();
+          const A& arc2 = aiter2.Value();
+          if (arc1.ilabel < arc2.ilabel) return true;
+          if (arc1.ilabel > arc2.ilabel) return false;
+
+          if (partition_.class_id(arc1.nextstate) <
+              partition_.class_id(arc2.nextstate)) return true;
+          if (partition_.class_id(arc1.nextstate) >
+              partition_.class_id(arc2.nextstate)) return false;
+        }
+      }
+    }
+
+    return false;
+  }
+
+ private:
+  const Fst<A>& fst_;
+  const Partition<typename A::StateId>& partition_;
+  const uint32 flags_;
+};
+
+template <class A> const uint32 StateComparator<A>::kCompareFinal;
+template <class A> const uint32 StateComparator<A>::kCompareOutDegree;
+template <class A> const uint32 StateComparator<A>::kCompareArcs;
+template <class A> const uint32 StateComparator<A>::kCompareAll;
+
+
+// Computes equivalence classes for cyclic Fsts. For cyclic minimization
+// we use the classic HopCroft minimization algorithm, which is of
+//
+//   O(E)log(N),
+//
+// where E is the number of edges in the machine and N is number of states.
+//
+// The following paper describes the original algorithm
+//  An N Log N algorithm for minimizing states in a finite automaton
+//  by John HopCroft, January 1971
+//
+template <class A, class Queue>
+class CyclicMinimizer {
+ public:
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef typename A::StateId ClassId;
+  typedef typename A::Weight Weight;
+  typedef ReverseArc<A> RevA;
+
+  CyclicMinimizer(const ExpandedFst<A>& fst) {
+    Initialize(fst);
+    Compute(fst);
+  }
+
+  ~CyclicMinimizer() {
+    delete aiter_queue_;
+  }
+
+  const Partition<StateId>& partition() const {
+    return P_;
+  }
+
+  // helper classes
+ private:
+  typedef ArcIterator<Fst<RevA> > ArcIter;
+  class ArcIterCompare {
+   public:
+    ArcIterCompare(const Partition<StateId>& partition)
+        : partition_(partition) {}
+
+    ArcIterCompare(const ArcIterCompare& comp)
+        : partition_(comp.partition_) {}
+
+    // compare two iterators based on there input labels, and proto state
+    // (partition class Ids)
+    bool operator()(const ArcIter* x, const ArcIter* y) const {
+      const RevA& xarc = x->Value();
+      const RevA& yarc = y->Value();
+      return (xarc.ilabel > yarc.ilabel);
+    }
+
+   private:
+    const Partition<StateId>& partition_;
+  };
+
+  typedef priority_queue<ArcIter*, vector<ArcIter*>, ArcIterCompare>
+  ArcIterQueue;
+
+  // helper methods
+ private:
+  // prepartitions the space into equivalence classes with
+  //   same final weight
+  //   same # arcs per state
+  //   same outgoing arcs
+  void PrePartition(const Fst<A>& fst) {
+    VLOG(5) << "PrePartition";
+
+    typedef map<StateId, StateId, StateComparator<A> > EquivalenceMap;
+    StateComparator<A> comp(fst, P_, StateComparator<A>::kCompareFinal);
+    EquivalenceMap equiv_map(comp);
+
+    StateIterator<Fst<A> > siter(fst);
+    StateId class_id = P_.AddClass();
+    P_.Add(siter.Value(), class_id);
+    equiv_map[siter.Value()] = class_id;
+    L_.Enqueue(class_id);
+    for (siter.Next(); !siter.Done(); siter.Next()) {
+      StateId  s = siter.Value();
+      typename EquivalenceMap::const_iterator it = equiv_map.find(s);
+      if (it == equiv_map.end()) {
+        class_id = P_.AddClass();
+        P_.Add(s, class_id);
+        equiv_map[s] = class_id;
+        L_.Enqueue(class_id);
+      } else {
+        P_.Add(s, it->second);
+        equiv_map[s] = it->second;
+      }
+    }
+
+    VLOG(5) << "Initial Partition: " << P_.num_classes();
+  }
+
+  // - Create inverse transition Tr_ = rev(fst)
+  // - loop over states in fst and split on final, creating two blocks
+  //   in the partition corresponding to final, non-final
+  void Initialize(const Fst<A>& fst) {
+    // construct Tr
+    Reverse(fst, &Tr_);
+    ILabelCompare<RevA> ilabel_comp;
+    ArcSort(&Tr_, ilabel_comp);
+
+    // initial split (F, S - F)
+    P_.Initialize(Tr_.NumStates() - 1);
+
+    // prep partition
+    PrePartition(fst);
+
+    // allocate arc iterator queue
+    ArcIterCompare comp(P_);
+    aiter_queue_ = new ArcIterQueue(comp);
+  }
+
+  // partition all classes with destination C
+  void Split(ClassId C) {
+    // Prep priority queue. Open arc iterator for each state in C, and
+    // insert into priority queue.
+    for (PartitionIterator<StateId> siter(P_, C);
+         !siter.Done(); siter.Next()) {
+      StateId s = siter.Value();
+      if (Tr_.NumArcs(s + 1))
+        aiter_queue_->push(new ArcIterator<Fst<RevA> >(Tr_, s + 1));
+    }
+
+    // Now pop arc iterator from queue, split entering equivalence class
+    // re-insert updated iterator into queue.
+    Label prev_label = -1;
+    while (!aiter_queue_->empty()) {
+      ArcIterator<Fst<RevA> >* aiter = aiter_queue_->top();
+      aiter_queue_->pop();
+      if (aiter->Done()) {
+        delete aiter;
+        continue;
+     }
+
+      const RevA& arc = aiter->Value();
+      StateId from_state = aiter->Value().nextstate - 1;
+      Label   from_label = arc.ilabel;
+      if (prev_label != from_label)
+        P_.FinalizeSplit(&L_);
+
+      StateId from_class = P_.class_id(from_state);
+      if (P_.class_size(from_class) > 1)
+        P_.SplitOn(from_state);
+
+      prev_label = from_label;
+      aiter->Next();
+      if (aiter->Done())
+        delete aiter;
+      else
+        aiter_queue_->push(aiter);
+    }
+    P_.FinalizeSplit(&L_);
+  }
+
+  // Main loop for hopcroft minimization.
+  void Compute(const Fst<A>& fst) {
+    // process active classes (FIFO, or FILO)
+    while (!L_.Empty()) {
+      ClassId C = L_.Head();
+      L_.Dequeue();
+
+      // split on C, all labels in C
+      Split(C);
+    }
+  }
+
+  // helper data
+ private:
+  // Partioning of states into equivalence classes
+  Partition<StateId> P_;
+
+  // L = set of active classes to be processed in partition P
+  Queue L_;
+
+  // reverse transition function
+  VectorFst<RevA> Tr_;
+
+  // Priority queue of open arc iterators for all states in the 'splitter'
+  // equivalence class
+  ArcIterQueue* aiter_queue_;
+};
+
+
+// Computes equivalence classes for acyclic Fsts. The implementation details
+// for this algorithms is documented by the following paper.
+//
+// Minimization of acyclic deterministic automata in linear time
+//  Dominque Revuz
+//
+// Complexity O(|E|)
+//
+template <class A>
+class AcyclicMinimizer {
+ public:
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef typename A::StateId ClassId;
+  typedef typename A::Weight Weight;
+
+  AcyclicMinimizer(const ExpandedFst<A>& fst) {
+    Initialize(fst);
+    Refine(fst);
+  }
+
+  const Partition<StateId>& partition() {
+    return partition_;
+  }
+
+  // helper classes
+ private:
+  // DFS visitor to compute the height (distance) to final state.
+  class HeightVisitor {
+   public:
+    HeightVisitor() : max_height_(0), num_states_(0) { }
+
+    // invoked before dfs visit
+    void InitVisit(const Fst<A>& fst) {}
+
+    // invoked when state is discovered (2nd arg is DFS tree root)
+    bool InitState(StateId s, StateId root) {
+      // extend height array and initialize height (distance) to 0
+      for (size_t i = height_.size(); i <= s; ++i)
+        height_.push_back(-1);
+
+      if (s >= num_states_) num_states_ = s + 1;
+      return true;
+    }
+
+    // invoked when tree arc examined (to undiscoverted state)
+    bool TreeArc(StateId s, const A& arc) {
+      return true;
+    }
+
+    // invoked when back arc examined (to unfinished state)
+    bool BackArc(StateId s, const A& arc) {
+      return true;
+    }
+
+    // invoked when forward or cross arc examined (to finished state)
+    bool ForwardOrCrossArc(StateId s, const A& arc) {
+      if (height_[arc.nextstate] + 1 > height_[s])
+        height_[s] = height_[arc.nextstate] + 1;
+      return true;
+    }
+
+    // invoked when state finished (parent is kNoStateId for tree root)
+    void FinishState(StateId s, StateId parent, const A* parent_arc) {
+      if (height_[s] == -1) height_[s] = 0;
+      StateId h = height_[s] +  1;
+      if (parent >= 0) {
+        if (h > height_[parent]) height_[parent] = h;
+        if (h > max_height_)     max_height_ = h;
+      }
+    }
+
+    // invoked after DFS visit
+    void FinishVisit() {}
+
+    size_t max_height() const { return max_height_; }
+
+    const vector<StateId>& height() const { return height_; }
+
+    const size_t num_states() const { return num_states_; }
+
+   private:
+    vector<StateId> height_;
+    size_t max_height_;
+    size_t num_states_;
+  };
+
+  // helper methods
+ private:
+  // cluster states according to height (distance to final state)
+  void Initialize(const Fst<A>& fst) {
+    // compute height (distance to final state)
+    HeightVisitor hvisitor;
+    DfsVisit(fst, &hvisitor);
+
+    // create initial partition based on height
+    partition_.Initialize(hvisitor.num_states());
+    partition_.AllocateClasses(hvisitor.max_height() + 1);
+    const vector<StateId>& hstates = hvisitor.height();
+    for (size_t s = 0; s < hstates.size(); ++s)
+      partition_.Add(s, hstates[s]);
+  }
+
+  // refine states based on arc sort (out degree, arc equivalence)
+  void Refine(const Fst<A>& fst) {
+    typedef map<StateId, StateId, StateComparator<A> > EquivalenceMap;
+    StateComparator<A> comp(fst, partition_);
+
+    // start with tail (height = 0)
+    size_t height = partition_.num_classes();
+    for (size_t h = 0; h < height; ++h) {
+      EquivalenceMap equiv_classes(comp);
+
+      // sort states within equivalence class
+      PartitionIterator<StateId> siter(partition_, h);
+      equiv_classes[siter.Value()] = h;
+      for (siter.Next(); !siter.Done(); siter.Next()) {
+        const StateId s = siter.Value();
+        typename EquivalenceMap::const_iterator it = equiv_classes.find(s);
+        if (it == equiv_classes.end())
+          equiv_classes[s] = partition_.AddClass();
+        else
+          equiv_classes[s] = it->second;
+      }
+
+      // create refined partition
+      for (siter.Reset(); !siter.Done();) {
+        const StateId s = siter.Value();
+        const StateId old_class = partition_.class_id(s);
+        const StateId new_class = equiv_classes[s];
+
+        // a move operation can invalidate the iterator, so
+        // we first update the iterator to the next element
+        // before we move the current element out of the list
+        siter.Next();
+        if (old_class != new_class)
+          partition_.Move(s, new_class);
+      }
+    }
+  }
+
+ private:
+  Partition<StateId> partition_;
+};
+
+
+// Given a partition and a mutable fst, merge states of Fst inplace
+// (i.e. destructively). Merging works by taking the first state in
+// a class of the partition to be the representative state for the class.
+// Each arc is then reconnected to this state. All states in the class
+// are merged by adding there arcs to the representative state.
+template <class A>
+void MergeStates(
+    const Partition<typename A::StateId>& partition, MutableFst<A>* fst) {
+  typedef typename A::StateId StateId;
+
+  vector<StateId> state_map(partition.num_classes());
+  for (size_t i = 0; i < partition.num_classes(); ++i) {
+    PartitionIterator<StateId> siter(partition, i);
+    state_map[i] = siter.Value();  // first state in partition;
+  }
+
+  // relabel destination states
+  for (size_t c = 0; c < partition.num_classes(); ++c) {
+    for (PartitionIterator<StateId> siter(partition, c);
+         !siter.Done(); siter.Next()) {
+      StateId s = siter.Value();
+      for (MutableArcIterator<MutableFst<A> > aiter(fst, s);
+           !aiter.Done(); aiter.Next()) {
+        A arc = aiter.Value();
+        arc.nextstate = state_map[partition.class_id(arc.nextstate)];
+
+        if (s == state_map[c])  // first state just set destination
+          aiter.SetValue(arc);
+        else
+          fst->AddArc(state_map[c], arc);
+      }
+    }
+  }
+  fst->SetStart(state_map[partition.class_id(fst->Start())]);
+
+  Connect(fst);
+}
+
+template <class A>
+void AcceptorMinimize(MutableFst<A>* fst) {
+  typedef typename A::StateId StateId;
+  if (!(fst->Properties(kAcceptor | kUnweighted, true))) {
+    FSTERROR() << "FST is not an unweighted acceptor";
+    fst->SetProperties(kError, kError);
+    return;
+  }
+
+  // connect fst before minimization, handles disconnected states
+  Connect(fst);
+  if (fst->NumStates() == 0) return;
+
+  if (fst->Properties(kAcyclic, true)) {
+    // Acyclic minimization (revuz)
+    VLOG(2) << "Acyclic Minimization";
+    ArcSort(fst, ILabelCompare<A>());
+    AcyclicMinimizer<A> minimizer(*fst);
+    MergeStates(minimizer.partition(), fst);
+
+  } else {
+    // Cyclic minimizaton (hopcroft)
+    VLOG(2) << "Cyclic Minimization";
+    CyclicMinimizer<A, LifoQueue<StateId> > minimizer(*fst);
+    MergeStates(minimizer.partition(), fst);
+  }
+
+  // Merge in appropriate semiring
+  ArcUniqueMapper<A> mapper(*fst);
+  StateMap(fst, mapper);
+}
+
+
+// In place minimization of deterministic weighted automata and transducers.
+// For transducers, then the 'sfst' argument is not null, the algorithm
+// produces a compact factorization of the minimal transducer.
+//
+// In the acyclic case, we use an algorithm from Dominique Revuz that
+// is linear in the number of arcs (edges) in the machine.
+//  Complexity = O(E)
+//
+// In the cyclic case, we use the classical hopcroft minimization.
+//  Complexity = O(|E|log(|N|)
+//
+template <class A>
+void Minimize(MutableFst<A>* fst,
+              MutableFst<A>* sfst = 0,
+              float delta = kDelta) {
+  uint64 props = fst->Properties(kAcceptor | kIDeterministic|
+                                 kWeighted | kUnweighted, true);
+  if (!(props & kIDeterministic)) {
+    FSTERROR() << "FST is not deterministic";
+    fst->SetProperties(kError, kError);
+    return;
+  }
+
+  if (!(props & kAcceptor)) {  // weighted transducer
+    VectorFst< GallicArc<A, STRING_LEFT> > gfst;
+    ArcMap(*fst, &gfst, ToGallicMapper<A, STRING_LEFT>());
+    fst->DeleteStates();
+    gfst.SetProperties(kAcceptor, kAcceptor);
+    Push(&gfst, REWEIGHT_TO_INITIAL, delta);
+    ArcMap(&gfst, QuantizeMapper< GallicArc<A, STRING_LEFT> >(delta));
+    EncodeMapper< GallicArc<A, STRING_LEFT> >
+      encoder(kEncodeLabels | kEncodeWeights, ENCODE);
+    Encode(&gfst, &encoder);
+    AcceptorMinimize(&gfst);
+    Decode(&gfst, encoder);
+
+    if (sfst == 0) {
+      FactorWeightFst< GallicArc<A, STRING_LEFT>,
+        GallicFactor<typename A::Label,
+        typename A::Weight, STRING_LEFT> > fwfst(gfst);
+      SymbolTable *osyms = fst->OutputSymbols() ?
+          fst->OutputSymbols()->Copy() : 0;
+      ArcMap(fwfst, fst, FromGallicMapper<A, STRING_LEFT>());
+      fst->SetOutputSymbols(osyms);
+      delete osyms;
+    } else {
+      sfst->SetOutputSymbols(fst->OutputSymbols());
+      GallicToNewSymbolsMapper<A, STRING_LEFT> mapper(sfst);
+      ArcMap(gfst, fst, &mapper);
+      fst->SetOutputSymbols(sfst->InputSymbols());
+    }
+  } else if (props & kWeighted) {  // weighted acceptor
+    Push(fst, REWEIGHT_TO_INITIAL, delta);
+    ArcMap(fst, QuantizeMapper<A>(delta));
+    EncodeMapper<A> encoder(kEncodeLabels | kEncodeWeights, ENCODE);
+    Encode(fst, &encoder);
+    AcceptorMinimize(fst);
+    Decode(fst, encoder);
+  } else {  // unweighted acceptor
+    AcceptorMinimize(fst);
+  }
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_MINIMIZE_H__
diff --git a/src/include/fst/mutable-fst.h b/src/include/fst/mutable-fst.h
new file mode 100644
index 0000000..9afcab3
--- /dev/null
+++ b/src/include/fst/mutable-fst.h
@@ -0,0 +1,378 @@
+// mutable-fst.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Expanded FST augmented with mutators - interface class definition
+// and mutable arc iterator interface.
+//
+
+#ifndef FST_LIB_MUTABLE_FST_H__
+#define FST_LIB_MUTABLE_FST_H__
+
+#include <stddef.h>
+#include <sys/types.h>
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/expanded-fst.h>
+
+
+namespace fst {
+
+template <class A> class MutableArcIteratorData;
+
+// An expanded FST plus mutators (use MutableArcIterator to modify arcs).
+template <class A>
+class MutableFst : public ExpandedFst<A> {
+ public:
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  virtual MutableFst<A> &operator=(const Fst<A> &fst) = 0;
+
+  MutableFst<A> &operator=(const MutableFst<A> &fst) {
+    return operator=(static_cast<const Fst<A> &>(fst));
+  }
+
+  virtual void SetStart(StateId) = 0;           // Set the initial state
+  virtual void SetFinal(StateId, Weight) = 0;   // Set a state's final weight
+  virtual void SetProperties(uint64 props,
+                             uint64 mask) = 0;  // Set property bits wrt mask
+
+  virtual StateId AddState() = 0;               // Add a state, return its ID
+  virtual void AddArc(StateId, const A &arc) = 0;   // Add an arc to state
+
+  virtual void DeleteStates(const vector<StateId>&) = 0;  // Delete some states
+  virtual void DeleteStates() = 0;              // Delete all states
+  virtual void DeleteArcs(StateId, size_t n) = 0;  // Delete some arcs at state
+  virtual void DeleteArcs(StateId) = 0;         // Delete all arcs at state
+
+  virtual void ReserveStates(StateId n) { }  // Optional, best effort only.
+  virtual void ReserveArcs(StateId s, size_t n) { }  // Optional, Best effort.
+
+  // Return input label symbol table; return NULL if not specified
+  virtual const SymbolTable* InputSymbols() const = 0;
+  // Return output label symbol table; return NULL if not specified
+  virtual const SymbolTable* OutputSymbols() const = 0;
+
+  // Return input label symbol table; return NULL if not specified
+  virtual SymbolTable* MutableInputSymbols() = 0;
+  // Return output label symbol table; return NULL if not specified
+  virtual SymbolTable* MutableOutputSymbols() = 0;
+
+  // Set input label symbol table; NULL signifies not unspecified
+  virtual void SetInputSymbols(const SymbolTable* isyms) = 0;
+  // Set output label symbol table; NULL signifies not unspecified
+  virtual void SetOutputSymbols(const SymbolTable* osyms) = 0;
+
+  // Get a copy of this MutableFst. See Fst<>::Copy() for further doc.
+  virtual MutableFst<A> *Copy(bool safe = false) const = 0;
+
+  // Read an MutableFst from an input stream; return NULL on error.
+  static MutableFst<A> *Read(istream &strm, const FstReadOptions &opts) {
+    FstReadOptions ropts(opts);
+    FstHeader hdr;
+    if (ropts.header)
+      hdr = *opts.header;
+    else {
+      if (!hdr.Read(strm, opts.source))
+        return 0;
+      ropts.header = &hdr;
+    }
+    if (!(hdr.Properties() & kMutable)) {
+      LOG(ERROR) << "MutableFst::Read: Not an MutableFst: " << ropts.source;
+      return 0;
+    }
+    FstRegister<A> *registr = FstRegister<A>::GetRegister();
+    const typename FstRegister<A>::Reader reader =
+      registr->GetReader(hdr.FstType());
+    if (!reader) {
+      LOG(ERROR) << "MutableFst::Read: Unknown FST type \"" << hdr.FstType()
+                 << "\" (arc type = \"" << A::Type()
+                 << "\"): " << ropts.source;
+      return 0;
+    }
+    Fst<A> *fst = reader(strm, ropts);
+    if (!fst) return 0;
+    return static_cast<MutableFst<A> *>(fst);
+  }
+
+  // Read a MutableFst from a file; return NULL on error.
+  // Empty filename reads from standard input. If 'convert' is true,
+  // convert to a mutable FST of type 'convert_type' if file is
+  // a non-mutable FST.
+  static MutableFst<A> *Read(const string &filename, bool convert = false,
+                             const string &convert_type = "vector") {
+    if (convert == false) {
+      if (!filename.empty()) {
+        ifstream strm(filename.c_str(), ifstream::in | ifstream::binary);
+        if (!strm) {
+          LOG(ERROR) << "MutableFst::Read: Can't open file: " << filename;
+          return 0;
+        }
+        return Read(strm, FstReadOptions(filename));
+      } else {
+        return Read(std::cin, FstReadOptions("standard input"));
+      }
+    } else {  // Converts to 'convert_type' if not mutable.
+      Fst<A> *ifst = Fst<A>::Read(filename);
+      if (!ifst) return 0;
+      if (ifst->Properties(kMutable, false)) {
+        return static_cast<MutableFst *>(ifst);
+      } else {
+        Fst<A> *ofst = Convert(*ifst, convert_type);
+        delete ifst;
+        if (!ofst) return 0;
+        if (!ofst->Properties(kMutable, false))
+          LOG(ERROR) << "MutableFst: bad convert type: " << convert_type;
+        return static_cast<MutableFst *>(ofst);
+      }
+    }
+  }
+
+  // For generic mutuble arc iterator construction; not normally called
+  // directly by users.
+  virtual void InitMutableArcIterator(StateId s,
+                                      MutableArcIteratorData<A> *) = 0;
+};
+
+// Mutable arc iterator interface, templated on the Arc definition; used
+// for mutable Arc iterator specializations that are returned by
+// the InitMutableArcIterator MutableFst method.
+template <class A>
+class MutableArcIteratorBase : public ArcIteratorBase<A> {
+ public:
+  typedef A Arc;
+
+  void SetValue(const A &arc) { SetValue_(arc); }  // Set current arc's content
+
+ private:
+  virtual void SetValue_(const A &arc) = 0;
+};
+
+template <class A>
+struct MutableArcIteratorData {
+  MutableArcIteratorBase<A> *base;  // Specific iterator
+};
+
+// Generic mutable arc iterator, templated on the FST definition
+// - a wrapper around pointer to specific one.
+// Here is a typical use: \code
+//   for (MutableArcIterator<StdFst> aiter(&fst, s));
+//        !aiter.Done();
+//         aiter.Next()) {
+//     StdArc arc = aiter.Value();
+//     arc.ilabel = 7;
+//     aiter.SetValue(arc);
+//     ...
+//   } \endcode
+// This version requires function calls.
+template <class F>
+class MutableArcIterator {
+ public:
+  typedef F FST;
+  typedef typename F::Arc Arc;
+  typedef typename Arc::StateId StateId;
+
+  MutableArcIterator(F *fst, StateId s) {
+    fst->InitMutableArcIterator(s, &data_);
+  }
+  ~MutableArcIterator() { delete data_.base; }
+
+  bool Done() const { return data_.base->Done(); }
+  const Arc& Value() const { return data_.base->Value(); }
+  void Next() { data_.base->Next(); }
+  size_t Position() const { return data_.base->Position(); }
+  void Reset() { data_.base->Reset(); }
+  void Seek(size_t a) { data_.base->Seek(a); }
+  void SetValue(const Arc &a) { data_.base->SetValue(a); }
+  uint32 Flags() const { return data_.base->Flags(); }
+  void SetFlags(uint32 f, uint32 m) {
+    return data_.base->SetFlags(f, m);
+  }
+
+ private:
+  MutableArcIteratorData<Arc> data_;
+  DISALLOW_COPY_AND_ASSIGN(MutableArcIterator);
+};
+
+
+namespace internal {
+
+//  MutableFst<A> case - abstract methods.
+template <class A> inline
+typename A::Weight Final(const MutableFst<A> &fst, typename A::StateId s) {
+  return fst.Final(s);
+}
+
+template <class A> inline
+ssize_t NumArcs(const MutableFst<A> &fst, typename A::StateId s) {
+  return fst.NumArcs(s);
+}
+
+template <class A> inline
+ssize_t NumInputEpsilons(const MutableFst<A> &fst, typename A::StateId s) {
+  return fst.NumInputEpsilons(s);
+}
+
+template <class A> inline
+ssize_t NumOutputEpsilons(const MutableFst<A> &fst, typename A::StateId s) {
+  return fst.NumOutputEpsilons(s);
+}
+
+}  // namespace internal
+
+
+// A useful alias when using StdArc.
+typedef MutableFst<StdArc> StdMutableFst;
+
+
+// This is a helper class template useful for attaching a MutableFst
+// interface to its implementation, handling reference counting and
+// copy-on-write.
+template <class I, class F = MutableFst<typename I::Arc> >
+class ImplToMutableFst : public ImplToExpandedFst<I, F> {
+ public:
+  typedef typename I::Arc Arc;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  using ImplToFst<I, F>::GetImpl;
+  using ImplToFst<I, F>::SetImpl;
+
+  virtual void SetStart(StateId s) {
+    MutateCheck();
+    GetImpl()->SetStart(s);
+  }
+
+  virtual void SetFinal(StateId s, Weight w) {
+    MutateCheck();
+    GetImpl()->SetFinal(s, w);
+  }
+
+  virtual void SetProperties(uint64 props, uint64 mask) {
+    // Can skip mutate check if extrinsic properties don't change,
+    // since it is then safe to update all (shallow) copies
+    uint64 exprops = kExtrinsicProperties & mask;
+    if (GetImpl()->Properties(exprops) != (props & exprops))
+      MutateCheck();
+    GetImpl()->SetProperties(props, mask);
+  }
+
+  virtual StateId AddState() {
+    MutateCheck();
+    return GetImpl()->AddState();
+  }
+
+  virtual void AddArc(StateId s, const Arc &arc) {
+    MutateCheck();
+    GetImpl()->AddArc(s, arc);
+  }
+
+  virtual void DeleteStates(const vector<StateId> &dstates) {
+    MutateCheck();
+    GetImpl()->DeleteStates(dstates);
+  }
+
+  virtual void DeleteStates() {
+    MutateCheck();
+    GetImpl()->DeleteStates();
+  }
+
+  virtual void DeleteArcs(StateId s, size_t n) {
+    MutateCheck();
+    GetImpl()->DeleteArcs(s, n);
+  }
+
+  virtual void DeleteArcs(StateId s) {
+    MutateCheck();
+    GetImpl()->DeleteArcs(s);
+  }
+
+  virtual void ReserveStates(StateId s) {
+    MutateCheck();
+    GetImpl()->ReserveStates(s);
+  }
+
+  virtual void ReserveArcs(StateId s, size_t n) {
+    MutateCheck();
+    GetImpl()->ReserveArcs(s, n);
+  }
+
+  virtual const SymbolTable* InputSymbols() const {
+    return GetImpl()->InputSymbols();
+  }
+
+  virtual const SymbolTable* OutputSymbols() const {
+    return GetImpl()->OutputSymbols();
+  }
+
+  virtual SymbolTable* MutableInputSymbols() {
+    MutateCheck();
+    return GetImpl()->InputSymbols();
+  }
+
+  virtual SymbolTable* MutableOutputSymbols() {
+    MutateCheck();
+    return GetImpl()->OutputSymbols();
+  }
+
+  virtual void SetInputSymbols(const SymbolTable* isyms) {
+    MutateCheck();
+    GetImpl()->SetInputSymbols(isyms);
+  }
+
+  virtual void SetOutputSymbols(const SymbolTable* osyms) {
+    MutateCheck();
+    GetImpl()->SetOutputSymbols(osyms);
+  }
+
+ protected:
+  ImplToMutableFst() : ImplToExpandedFst<I, F>() {}
+
+  ImplToMutableFst(I *impl) : ImplToExpandedFst<I, F>(impl) {}
+
+
+  ImplToMutableFst(const ImplToMutableFst<I, F> &fst)
+      : ImplToExpandedFst<I, F>(fst) {}
+
+  ImplToMutableFst(const ImplToMutableFst<I, F> &fst, bool safe)
+      : ImplToExpandedFst<I, F>(fst, safe) {}
+
+  void MutateCheck() {
+    // Copy on write
+    if (GetImpl()->RefCount() > 1)
+      SetImpl(new I(*this));
+  }
+
+ private:
+  // Disallow
+  ImplToMutableFst<I, F>  &operator=(const ImplToMutableFst<I, F> &fst);
+
+  ImplToMutableFst<I, F> &operator=(const Fst<Arc> &fst) {
+    FSTERROR() << "ImplToMutableFst: Assignment operator disallowed";
+    GetImpl()->SetProperties(kError, kError);
+    return *this;
+  }
+};
+
+
+}  // namespace fst
+
+#endif  // FST_LIB_MUTABLE_FST_H__
diff --git a/src/include/fst/pair-weight.h b/src/include/fst/pair-weight.h
new file mode 100644
index 0000000..7d8aa11
--- /dev/null
+++ b/src/include/fst/pair-weight.h
@@ -0,0 +1,280 @@
+// pair-weight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: shumash@google.com (Masha Maria Shugrina)
+//
+// \file
+// Pair weight templated base class for weight classes that
+// contain two weights (e.g. Product, Lexicographic)
+
+#ifndef FST_LIB_PAIR_WEIGHT_H_
+#define FST_LIB_PAIR_WEIGHT_H_
+
+#include <climits>
+#include <stack>
+#include <string>
+
+#include <fst/weight.h>
+
+
+DECLARE_string(fst_weight_parentheses);
+DECLARE_string(fst_weight_separator);
+
+namespace fst {
+
+template<class W1, class W2> class PairWeight;
+template <class W1, class W2>
+istream &operator>>(istream &strm, PairWeight<W1, W2> &w);
+
+template<class W1, class W2>
+class PairWeight {
+ public:
+  friend istream &operator>><W1, W2>(istream&, PairWeight<W1, W2>&);
+
+  typedef PairWeight<typename W1::ReverseWeight,
+                     typename W2::ReverseWeight>
+  ReverseWeight;
+
+  PairWeight() {}
+
+  PairWeight(const PairWeight& w) : value1_(w.value1_), value2_(w.value2_) {}
+
+  PairWeight(W1 w1, W2 w2) : value1_(w1), value2_(w2) {}
+
+  static const PairWeight<W1, W2> &Zero() {
+    static const PairWeight<W1, W2> zero(W1::Zero(), W2::Zero());
+    return zero;
+  }
+
+  static const PairWeight<W1, W2> &One() {
+    static const PairWeight<W1, W2> one(W1::One(), W2::One());
+    return one;
+  }
+
+  static const PairWeight<W1, W2> &NoWeight() {
+    static const PairWeight<W1, W2> no_weight(W1::NoWeight(), W2::NoWeight());
+    return no_weight;
+  }
+
+  istream &Read(istream &strm) {
+    value1_.Read(strm);
+    return value2_.Read(strm);
+  }
+
+  ostream &Write(ostream &strm) const {
+    value1_.Write(strm);
+    return value2_.Write(strm);
+  }
+
+  PairWeight<W1, W2> &operator=(const PairWeight<W1, W2> &w) {
+    value1_ = w.Value1();
+    value2_ = w.Value2();
+    return *this;
+  }
+
+  bool Member() const { return value1_.Member() && value2_.Member(); }
+
+  size_t Hash() const {
+    size_t h1 = value1_.Hash();
+    size_t h2 = value2_.Hash();
+    const int lshift = 5;
+    const int rshift = CHAR_BIT * sizeof(size_t) - 5;
+    return h1 << lshift ^ h1 >> rshift ^ h2;
+  }
+
+  PairWeight<W1, W2> Quantize(float delta = kDelta) const {
+    return PairWeight<W1, W2>(value1_.Quantize(delta),
+                                 value2_.Quantize(delta));
+  }
+
+  ReverseWeight Reverse() const {
+    return ReverseWeight(value1_.Reverse(), value2_.Reverse());
+  }
+
+  const W1& Value1() const { return value1_; }
+
+  const W2& Value2() const { return value2_; }
+
+ protected:
+  void SetValue1(const W1 &w) { value1_ = w; }
+  void SetValue2(const W2 &w) { value2_ = w; }
+
+  // Reads PairWeight when there are not parentheses around pair terms
+  inline static istream &ReadNoParen(
+      istream &strm, PairWeight<W1, W2>& w, char separator) {
+    int c;
+    do {
+      c = strm.get();
+    } while (isspace(c));
+
+    string s1;
+    while (c != separator) {
+      if (c == EOF) {
+        strm.clear(std::ios::badbit);
+        return strm;
+      }
+      s1 += c;
+      c = strm.get();
+    }
+    istringstream strm1(s1);
+    W1 w1 = W1::Zero();
+    strm1 >> w1;
+
+    // read second element
+    W2 w2 = W2::Zero();
+    strm >> w2;
+
+    w = PairWeight<W1, W2>(w1, w2);
+    return strm;
+  }
+
+  // Reads PairWeight when there are parentheses around pair terms
+  inline static istream &ReadWithParen(
+      istream &strm, PairWeight<W1, W2>& w,
+      char separator, char open_paren, char close_paren) {
+    int c;
+    do {
+      c = strm.get();
+    } while (isspace(c));
+    if (c != open_paren) {
+      FSTERROR() << " is fst_weight_parentheses flag set correcty? ";
+      strm.clear(std::ios::failbit);
+      return strm;
+    }
+    c = strm.get();
+
+    // read first element
+    stack<int> parens;
+    string s1;
+    while (c != separator || !parens.empty()) {
+      if (c == EOF) {
+        strm.clear(std::ios::badbit);
+        return strm;
+      }
+      s1 += c;
+      // if parens encountered before separator, they must be matched
+      if (c == open_paren) {
+        parens.push(1);
+      } else if (c == close_paren) {
+        // Fail for mismatched parens
+        if (parens.empty()) {
+          strm.clear(std::ios::failbit);
+          return strm;
+        }
+        parens.pop();
+      }
+      c = strm.get();
+    }
+    istringstream strm1(s1);
+    W1 w1 = W1::Zero();
+    strm1 >> w1;
+
+    // read second element
+    string s2;
+    c = strm.get();
+    while (c != EOF) {
+      s2 += c;
+      c = strm.get();
+    }
+    if (s2.empty() || (s2[s2.size() - 1] != close_paren)) {
+      FSTERROR() << " is fst_weight_parentheses flag set correcty? ";
+      strm.clear(std::ios::failbit);
+      return strm;
+    }
+
+    s2.erase(s2.size() - 1, 1);
+    istringstream strm2(s2);
+    W2 w2 = W2::Zero();
+    strm2 >> w2;
+
+    w = PairWeight<W1, W2>(w1, w2);
+    return strm;
+  }
+
+ private:
+  W1 value1_;
+  W2 value2_;
+
+};
+
+template <class W1, class W2>
+inline bool operator==(const PairWeight<W1, W2> &w,
+                       const PairWeight<W1, W2> &v) {
+  return w.Value1() == v.Value1() && w.Value2() == v.Value2();
+}
+
+template <class W1, class W2>
+inline bool operator!=(const PairWeight<W1, W2> &w1,
+                       const PairWeight<W1, W2> &w2) {
+  return w1.Value1() != w2.Value1() || w1.Value2() != w2.Value2();
+}
+
+
+template <class W1, class W2>
+inline bool ApproxEqual(const PairWeight<W1, W2> &w1,
+                        const PairWeight<W1, W2> &w2,
+                        float delta = kDelta) {
+  return ApproxEqual(w1.Value1(), w2.Value1(), delta) &&
+      ApproxEqual(w1.Value2(), w2.Value2(), delta);
+}
+
+template <class W1, class W2>
+inline ostream &operator<<(ostream &strm, const PairWeight<W1, W2> &w) {
+  if(FLAGS_fst_weight_separator.size() != 1) {
+    FSTERROR() << "FLAGS_fst_weight_separator.size() is not equal to 1";
+    strm.clear(std::ios::badbit);
+    return strm;
+  }
+  char separator = FLAGS_fst_weight_separator[0];
+  if (FLAGS_fst_weight_parentheses.empty())
+    return strm << w.Value1() << separator << w.Value2();
+
+  if (FLAGS_fst_weight_parentheses.size() != 2) {
+    FSTERROR() << "FLAGS_fst_weight_parentheses.size() is not equal to 2";
+    strm.clear(std::ios::badbit);
+    return strm;
+  }
+  char open_paren = FLAGS_fst_weight_parentheses[0];
+  char close_paren = FLAGS_fst_weight_parentheses[1];
+  return strm << open_paren << w.Value1() << separator
+              << w.Value2() << close_paren ;
+}
+
+template <class W1, class W2>
+inline istream &operator>>(istream &strm, PairWeight<W1, W2> &w) {
+  if(FLAGS_fst_weight_separator.size() != 1) {
+    FSTERROR() << "FLAGS_fst_weight_separator.size() is not equal to 1";
+    strm.clear(std::ios::badbit);
+    return strm;
+  }
+  char separator = FLAGS_fst_weight_separator[0];
+  bool read_parens = !FLAGS_fst_weight_parentheses.empty();
+  if (read_parens) {
+    if (FLAGS_fst_weight_parentheses.size() != 2) {
+      FSTERROR() << "FLAGS_fst_weight_parentheses.size() is not equal to 2";
+      strm.clear(std::ios::badbit);
+      return strm;
+    }
+    return PairWeight<W1, W2>::ReadWithParen(
+        strm, w, separator, FLAGS_fst_weight_parentheses[0],
+        FLAGS_fst_weight_parentheses[1]);
+  } else {
+    return PairWeight<W1, W2>::ReadNoParen(strm, w, separator);
+  }
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_PAIR_WEIGHT_H_
diff --git a/src/include/fst/partition.h b/src/include/fst/partition.h
new file mode 100644
index 0000000..dcee67b
--- /dev/null
+++ b/src/include/fst/partition.h
@@ -0,0 +1,290 @@
+// partition.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: johans@google.com (Johan Schalkwyk)
+//
+// \file Functions and classes to create a partition of states
+//
+
+#ifndef FST_LIB_PARTITION_H__
+#define FST_LIB_PARTITION_H__
+
+#include <vector>
+using std::vector;
+#include <algorithm>
+
+
+#include <fst/queue.h>
+
+
+
+namespace fst {
+
+template <typename T> class PartitionIterator;
+
+// \class Partition
+// \brief Defines a partitioning of states. Typically used to represent
+//        equivalence classes for Fst operations like minimization.
+//
+template <typename T>
+class Partition {
+  friend class PartitionIterator<T>;
+
+  struct Element {
+   Element() : value(0), next(0), prev(0) {}
+   Element(T v) : value(v), next(0), prev(0) {}
+
+   T        value;
+   Element* next;
+   Element* prev;
+  };
+
+ public:
+  Partition() {}
+
+  Partition(T num_states) {
+    Initialize(num_states);
+  }
+
+  ~Partition() {
+    for (size_t i = 0; i < elements_.size(); ++i)
+      delete elements_[i];
+  }
+
+  // Create an empty partition for num_states. At initialization time
+  // all elements are not assigned to a class (i.e class_index = -1).
+  // Initialize just creates num_states of elements. All element
+  // operations are then done by simply disconnecting the element from
+  // it current class and placing it at the head of the next class.
+  void Initialize(size_t num_states) {
+    for (size_t i = 0; i < elements_.size(); ++i)
+      delete elements_[i];
+    elements_.clear();
+    classes_.clear();
+    class_index_.clear();
+
+    elements_.resize(num_states);
+    class_index_.resize(num_states, -1);
+    class_size_.reserve(num_states);
+    for (size_t i = 0; i < num_states; ++i)
+      elements_[i] = new Element(i);
+    num_states_ = num_states;
+  }
+
+  // Add a class, resize classes_ and class_size_ resource by 1.
+  size_t AddClass() {
+    size_t num_classes = classes_.size();
+    classes_.resize(num_classes + 1, 0);
+    class_size_.resize(num_classes + 1, 0);
+    class_split_.resize(num_classes + 1, 0);
+    split_size_.resize(num_classes + 1, 0);
+    return num_classes;
+  }
+
+  void AllocateClasses(T num_classes) {
+    size_t n = classes_.size() + num_classes;
+    classes_.resize(n, 0);
+    class_size_.resize(n, 0);
+    class_split_.resize(n, 0);
+    split_size_.resize(n, 0);
+  }
+
+  // Add element_id to class_id. The Add method is used to initialize
+  // partition. Once elements have been added to a class, you need to
+  // use the Move() method move an element from once class to another.
+  void Add(T element_id, T class_id) {
+    Element* element = elements_[element_id];
+
+    if (classes_[class_id])
+      classes_[class_id]->prev = element;
+    element->next = classes_[class_id];
+    element->prev = 0;
+    classes_[class_id] = element;
+
+    class_index_[element_id] = class_id;
+    class_size_[class_id]++;
+  }
+
+  // Move and element_id to class_id. Disconnects (removes) element
+  // from it current class and
+  void Move(T element_id, T class_id) {
+    T old_class_id = class_index_[element_id];
+
+    Element* element = elements_[element_id];
+    if (element->next) element->next->prev = element->prev;
+    if (element->prev) element->prev->next = element->next;
+    else               classes_[old_class_id] = element->next;
+
+    Add(element_id, class_id);
+    class_size_[old_class_id]--;
+  }
+
+  // split class on the element_id
+  void SplitOn(T element_id) {
+    T class_id = class_index_[element_id];
+    if (class_size_[class_id] == 1) return;
+
+    // first time class is split
+    if (split_size_[class_id] == 0)
+      visited_classes_.push_back(class_id);
+
+    // increment size of split (set of element at head of chain)
+    split_size_[class_id]++;
+
+    // update split point
+    if (class_split_[class_id] == 0)
+      class_split_[class_id] = classes_[class_id];
+    if (class_split_[class_id] == elements_[element_id])
+      class_split_[class_id] = elements_[element_id]->next;
+
+    // move to head of chain in same class
+    Move(element_id, class_id);
+  }
+
+  // Finalize class_id, split if required, and update class_splits,
+  // class indices of the newly created class. Returns the new_class id
+  // or -1 if no new class was created.
+  T SplitRefine(T class_id) {
+    // only split if necessary
+    if (class_size_[class_id] == split_size_[class_id]) {
+      class_split_[class_id] = 0;
+      split_size_[class_id] = 0;
+      return -1;
+    } else {
+
+      T new_class = AddClass();
+      size_t remainder = class_size_[class_id] - split_size_[class_id];
+      if (remainder < split_size_[class_id]) {  // add smaller
+        Element* split_el   = class_split_[class_id];
+        classes_[new_class] = split_el;
+        class_size_[class_id] = split_size_[class_id];
+        class_size_[new_class] = remainder;
+        split_el->prev->next = 0;
+        split_el->prev = 0;
+      } else {
+        Element* split_el   = class_split_[class_id];
+        classes_[new_class] = classes_[class_id];
+        class_size_[class_id] = remainder;
+        class_size_[new_class] = split_size_[class_id];
+        split_el->prev->next = 0;
+        split_el->prev = 0;
+        classes_[class_id] = split_el;
+      }
+
+      // update class index for element in new class
+      for (Element* el = classes_[new_class]; el; el = el->next)
+        class_index_[el->value] = new_class;
+
+      class_split_[class_id] = 0;
+      split_size_[class_id] = 0;
+
+      return new_class;
+    }
+  }
+
+  // Once all states have been processed for a particular class C, we
+  // can finalize the split. FinalizeSplit() will update each block in the
+  // partition, create new once and update the queue of active classes
+  // that require further refinement.
+  template <class Queue>
+  void FinalizeSplit(Queue* L) {
+    for (size_t i = 0; i < visited_classes_.size(); ++i) {
+      T new_class = SplitRefine(visited_classes_[i]);
+      if (new_class != -1 && L)
+        L->Enqueue(new_class);
+    }
+    visited_classes_.clear();
+  }
+
+
+  const T class_id(T element_id) const {
+    return class_index_[element_id];
+  }
+
+  const vector<T>& class_sizes() const {
+    return class_size_;
+  }
+
+  const size_t class_size(T class_id)  const {
+    return class_size_[class_id];
+  }
+
+  const T num_classes() const {
+    return classes_.size();
+  }
+
+
+ private:
+  int num_states_;
+
+  // container of all elements (owner of ptrs)
+  vector<Element*> elements_;
+
+  // linked list of elements belonging to class
+  vector<Element*> classes_;
+
+  // pointer to split point for each class
+  vector<Element*> class_split_;
+
+  // class index of element
+  vector<T> class_index_;
+
+  // class sizes
+  vector<T> class_size_;
+
+  // size of split for each class
+  vector<T> split_size_;
+
+  // set of visited classes to be used in split refine
+  vector<T> visited_classes_;
+};
+
+
+// iterate over members of a class in a partition
+template <typename T>
+class PartitionIterator {
+  typedef typename Partition<T>::Element Element;
+ public:
+  PartitionIterator(const Partition<T>& partition, T class_id)
+      : p_(partition),
+        element_(p_.classes_[class_id]),
+        class_id_(class_id) {}
+
+  bool Done() {
+    return (element_ == 0);
+  }
+
+  const T Value() {
+    return (element_->value);
+  }
+
+  void Next() {
+    element_ = element_->next;
+  }
+
+  void Reset() {
+    element_ = p_.classes_[class_id_];
+  }
+
+ private:
+  const Partition<T>& p_;
+
+  const Element* element_;
+
+  T class_id_;
+};
+}  // namespace fst
+
+#endif  // FST_LIB_PARTITION_H__
diff --git a/src/include/fst/power-weight.h b/src/include/fst/power-weight.h
new file mode 100644
index 0000000..256928d
--- /dev/null
+++ b/src/include/fst/power-weight.h
@@ -0,0 +1,159 @@
+// power-weight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Cartesian power weight semiring operation definitions.
+
+#ifndef FST_LIB_POWER_WEIGHT_H__
+#define FST_LIB_POWER_WEIGHT_H__
+
+#include <fst/tuple-weight.h>
+#include <fst/weight.h>
+
+
+namespace fst {
+
+// Cartesian power semiring: W ^ n
+// Forms:
+//  - a left semimodule when W is a left semiring,
+//  - a right semimodule when W is a right semiring,
+//  - a bisemimodule when W is a semiring,
+//    the free semimodule of rank n over W
+// The Times operation is overloaded to provide the
+// left and right scalar products.
+template <class W, unsigned int n>
+class PowerWeight : public TupleWeight<W, n> {
+ public:
+  using TupleWeight<W, n>::Zero;
+  using TupleWeight<W, n>::One;
+  using TupleWeight<W, n>::NoWeight;
+  using TupleWeight<W, n>::Quantize;
+  using TupleWeight<W, n>::Reverse;
+
+  typedef PowerWeight<typename W::ReverseWeight, n> ReverseWeight;
+
+  PowerWeight() {}
+
+  PowerWeight(const TupleWeight<W, n> &w) : TupleWeight<W, n>(w) {}
+
+  template <class Iterator>
+  PowerWeight(Iterator begin, Iterator end) : TupleWeight<W, n>(begin, end) {}
+
+  static const PowerWeight<W, n> &Zero() {
+    static const PowerWeight<W, n> zero(TupleWeight<W, n>::Zero());
+    return zero;
+  }
+
+  static const PowerWeight<W, n> &One() {
+    static const PowerWeight<W, n> one(TupleWeight<W, n>::One());
+    return one;
+  }
+
+  static const PowerWeight<W, n> &NoWeight() {
+    static const PowerWeight<W, n> no_weight(TupleWeight<W, n>::NoWeight());
+    return no_weight;
+  }
+
+  static const string &Type() {
+    static string type;
+    if (type.empty()) {
+      string power;
+      Int64ToStr(n, &power);
+      type = W::Type() + "_^" + power;
+    }
+    return type;
+  }
+
+  static uint64 Properties() {
+    uint64 props = W::Properties();
+    return props & (kLeftSemiring | kRightSemiring |
+                    kCommutative | kIdempotent);
+  }
+
+  PowerWeight<W, n> Quantize(float delta = kDelta) const {
+    return TupleWeight<W, n>::Quantize(delta);
+  }
+
+  ReverseWeight Reverse() const {
+    return TupleWeight<W, n>::Reverse();
+  }
+};
+
+
+// Semiring plus operation
+template <class W, unsigned int n>
+inline PowerWeight<W, n> Plus(const PowerWeight<W, n> &w1,
+                              const PowerWeight<W, n> &w2) {
+  PowerWeight<W, n> w;
+  for (size_t i = 0; i < n; ++i)
+    w.SetValue(i, Plus(w1.Value(i), w2.Value(i)));
+  return w;
+}
+
+// Semiring times operation
+template <class W, unsigned int n>
+inline PowerWeight<W, n> Times(const PowerWeight<W, n> &w1,
+                               const PowerWeight<W, n> &w2) {
+  PowerWeight<W, n> w;
+  for (size_t i = 0; i < n; ++i)
+    w.SetValue(i, Times(w1.Value(i), w2.Value(i)));
+  return w;
+}
+
+// Semiring divide operation
+template <class W, unsigned int n>
+inline PowerWeight<W, n> Divide(const PowerWeight<W, n> &w1,
+                                const PowerWeight<W, n> &w2,
+                                DivideType type = DIVIDE_ANY) {
+  PowerWeight<W, n> w;
+  for (size_t i = 0; i < n; ++i)
+    w.SetValue(i, Divide(w1.Value(i), w2.Value(i), type));
+  return w;
+}
+
+// Semimodule left scalar product
+template <class W, unsigned int n>
+inline PowerWeight<W, n> Times(const W &s, const PowerWeight<W, n> &w) {
+  PowerWeight<W, n> sw;
+  for (size_t i = 0; i < n; ++i)
+    sw.SetValue(i, Times(s, w.Value(i)));
+  return w;
+}
+
+// Semimodule right scalar product
+template <class W, unsigned int n>
+inline PowerWeight<W, n> Times(const PowerWeight<W, n> &w, const W &s) {
+  PowerWeight<W, n> ws;
+  for (size_t i = 0; i < n; ++i)
+    ws.SetValue(i, Times(w.Value(i), s));
+  return w;
+}
+
+// Semimodule dot product
+template <class W, unsigned int n>
+inline W DotProduct(const PowerWeight<W, n> &w1,
+                    const PowerWeight<W, n> &w2) {
+  W w = W::Zero();
+  for (size_t i = 0; i < n; ++i)
+    w = Plus(w, Times(w1.Value(i), w2.Value(i)));
+  return w;
+}
+
+
+}  // namespace fst
+
+#endif  // FST_LIB_POWER_WEIGHT_H__
diff --git a/src/include/fst/product-weight.h b/src/include/fst/product-weight.h
new file mode 100644
index 0000000..16dede8
--- /dev/null
+++ b/src/include/fst/product-weight.h
@@ -0,0 +1,115 @@
+// product-weight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Product weight set and associated semiring operation definitions.
+
+#ifndef FST_LIB_PRODUCT_WEIGHT_H__
+#define FST_LIB_PRODUCT_WEIGHT_H__
+
+#include <stack>
+#include <string>
+
+#include <fst/pair-weight.h>
+#include <fst/weight.h>
+
+
+namespace fst {
+
+// Product semiring: W1 * W2
+template<class W1, class W2>
+class ProductWeight : public PairWeight<W1, W2> {
+ public:
+  using PairWeight<W1, W2>::Zero;
+  using PairWeight<W1, W2>::One;
+  using PairWeight<W1, W2>::NoWeight;
+  using PairWeight<W1, W2>::Quantize;
+  using PairWeight<W1, W2>::Reverse;
+
+  typedef ProductWeight<typename W1::ReverseWeight, typename W2::ReverseWeight>
+  ReverseWeight;
+
+  ProductWeight() {}
+
+  ProductWeight(const PairWeight<W1, W2>& w) : PairWeight<W1, W2>(w) {}
+
+  ProductWeight(W1 w1, W2 w2) : PairWeight<W1, W2>(w1, w2) {}
+
+  static const ProductWeight<W1, W2> &Zero() {
+    static const ProductWeight<W1, W2> zero(PairWeight<W1, W2>::Zero());
+    return zero;
+  }
+
+  static const ProductWeight<W1, W2> &One() {
+    static const ProductWeight<W1, W2> one(PairWeight<W1, W2>::One());
+    return one;
+  }
+
+  static const ProductWeight<W1, W2> &NoWeight() {
+    static const ProductWeight<W1, W2> no_weight(
+        PairWeight<W1, W2>::NoWeight());
+    return no_weight;
+  }
+
+  static const string &Type() {
+    static const string type = W1::Type() + "_X_" + W2::Type();
+    return type;
+  }
+
+  static uint64 Properties() {
+    uint64 props1 = W1::Properties();
+    uint64 props2 = W2::Properties();
+    return props1 & props2 & (kLeftSemiring | kRightSemiring |
+                              kCommutative | kIdempotent);
+  }
+
+  ProductWeight<W1, W2> Quantize(float delta = kDelta) const {
+    return PairWeight<W1, W2>::Quantize(delta);
+  }
+
+  ReverseWeight Reverse() const {
+    return PairWeight<W1, W2>::Reverse();
+  }
+
+
+};
+
+template <class W1, class W2>
+inline ProductWeight<W1, W2> Plus(const ProductWeight<W1, W2> &w,
+                                  const ProductWeight<W1, W2> &v) {
+  return ProductWeight<W1, W2>(Plus(w.Value1(), v.Value1()),
+                               Plus(w.Value2(), v.Value2()));
+}
+
+template <class W1, class W2>
+inline ProductWeight<W1, W2> Times(const ProductWeight<W1, W2> &w,
+                                   const ProductWeight<W1, W2> &v) {
+  return ProductWeight<W1, W2>(Times(w.Value1(), v.Value1()),
+                               Times(w.Value2(), v.Value2()));
+}
+
+template <class W1, class W2>
+inline ProductWeight<W1, W2> Divide(const ProductWeight<W1, W2> &w,
+                                    const ProductWeight<W1, W2> &v,
+                                    DivideType typ = DIVIDE_ANY) {
+  return ProductWeight<W1, W2>(Divide(w.Value1(), v.Value1(), typ),
+                               Divide(w.Value2(), v.Value2(), typ));
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_PRODUCT_WEIGHT_H__
diff --git a/src/include/fst/project.h b/src/include/fst/project.h
new file mode 100644
index 0000000..07946c3
--- /dev/null
+++ b/src/include/fst/project.h
@@ -0,0 +1,148 @@
+// project.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Functions and classes to project an Fst on to its domain or range.
+
+#ifndef FST_LIB_PROJECT_H__
+#define FST_LIB_PROJECT_H__
+
+#include <fst/arc-map.h>
+#include <fst/mutable-fst.h>
+
+
+namespace fst {
+
+// This specifies whether to project on input or output.
+enum ProjectType { PROJECT_INPUT = 1, PROJECT_OUTPUT = 2 };
+
+
+// Mapper to implement projection per arc.
+template <class A> class ProjectMapper {
+ public:
+  explicit ProjectMapper(ProjectType project_type)
+      : project_type_(project_type) {}
+
+  A operator()(const A &arc) {
+    typename A::Label label = project_type_ == PROJECT_INPUT
+                              ? arc.ilabel : arc.olabel;
+    return A(label, label, arc.weight, arc.nextstate);
+  }
+
+  MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; }
+
+  MapSymbolsAction InputSymbolsAction() const {
+    return project_type_ == PROJECT_INPUT ? MAP_COPY_SYMBOLS :
+        MAP_CLEAR_SYMBOLS;
+  }
+
+  MapSymbolsAction OutputSymbolsAction() const {
+    return project_type_ == PROJECT_OUTPUT ? MAP_COPY_SYMBOLS :
+        MAP_CLEAR_SYMBOLS;
+  }
+
+  uint64 Properties(uint64 props) {
+    return ProjectProperties(props, project_type_ == PROJECT_INPUT);
+  }
+
+
+ private:
+  ProjectType project_type_;
+};
+
+
+// Projects an FST onto its domain or range by either copying each arcs'
+// input label to the output label or vice versa. This version modifies
+// its input.
+//
+// Complexity:
+// - Time: O(V + E)
+// - Space: O(1)
+// where V = # of states and E = # of arcs.
+template<class Arc> inline
+void Project(MutableFst<Arc> *fst, ProjectType project_type) {
+  ArcMap(fst, ProjectMapper<Arc>(project_type));
+  if (project_type == PROJECT_INPUT)
+    fst->SetOutputSymbols(fst->InputSymbols());
+  if (project_type == PROJECT_OUTPUT)
+    fst->SetInputSymbols(fst->OutputSymbols());
+}
+
+
+// Projects an FST onto its domain or range by either copying each arc's
+// input label to the output label or vice versa. This version is a delayed
+// Fst.
+//
+// Complexity:
+// - Time: O(v + e)
+// - Space: O(1)
+// where v = # of states visited, e = # of arcs visited. Constant
+// time and to visit an input state or arc is assumed and exclusive
+// of caching.
+template <class A>
+class ProjectFst : public ArcMapFst<A, A, ProjectMapper<A> > {
+ public:
+  typedef A Arc;
+  typedef ProjectMapper<A> C;
+  typedef ArcMapFstImpl< A, A, ProjectMapper<A> > Impl;
+  using ImplToFst<Impl>::GetImpl;
+
+  ProjectFst(const Fst<A> &fst, ProjectType project_type)
+      : ArcMapFst<A, A, C>(fst, C(project_type)) {
+    if (project_type == PROJECT_INPUT)
+      GetImpl()->SetOutputSymbols(fst.InputSymbols());
+    if (project_type == PROJECT_OUTPUT)
+      GetImpl()->SetInputSymbols(fst.OutputSymbols());
+  }
+
+  // See Fst<>::Copy() for doc.
+  ProjectFst(const ProjectFst<A> &fst, bool safe = false)
+      : ArcMapFst<A, A, C>(fst, safe) {}
+
+  // Get a copy of this ProjectFst. See Fst<>::Copy() for further doc.
+  virtual ProjectFst<A> *Copy(bool safe = false) const {
+    return new ProjectFst(*this, safe);
+  }
+};
+
+
+// Specialization for ProjectFst.
+template <class A>
+class StateIterator< ProjectFst<A> >
+    : public StateIterator< ArcMapFst<A, A, ProjectMapper<A> > > {
+ public:
+  explicit StateIterator(const ProjectFst<A> &fst)
+      : StateIterator< ArcMapFst<A, A, ProjectMapper<A> > >(fst) {}
+};
+
+
+// Specialization for ProjectFst.
+template <class A>
+class ArcIterator< ProjectFst<A> >
+    : public ArcIterator< ArcMapFst<A, A, ProjectMapper<A> > > {
+ public:
+  ArcIterator(const ProjectFst<A> &fst, typename A::StateId s)
+      : ArcIterator< ArcMapFst<A, A, ProjectMapper<A> > >(fst, s) {}
+};
+
+
+// Useful alias when using StdArc.
+typedef ProjectFst<StdArc> StdProjectFst;
+
+}  // namespace fst
+
+#endif  // FST_LIB_PROJECT_H__
diff --git a/src/include/fst/properties.h b/src/include/fst/properties.h
new file mode 100644
index 0000000..8fab16f
--- /dev/null
+++ b/src/include/fst/properties.h
@@ -0,0 +1,460 @@
+// properties.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: Michael Riley <riley@google.com>
+// \file
+// FST property bits.
+
+#ifndef FST_LIB_PROPERTIES_H__
+#define FST_LIB_PROPERTIES_H__
+
+#include <sys/types.h>
+#include <vector>
+using std::vector;
+
+#include <fst/compat.h>
+
+namespace fst {
+
+// The property bits here assert facts about an FST. If individual
+// bits are added, then the composite properties below, the property
+// functions and property names in properties.cc, and
+// TestProperties() in test-properties.h should be updated.
+
+//
+// BINARY PROPERTIES
+//
+// For each property below, there is a single bit. If it is set,
+// the property is true. If it is not set, the property is false.
+//
+
+// The Fst is an ExpandedFst
+const uint64 kExpanded =          0x0000000000000001ULL;
+
+// The Fst is a MutableFst
+const uint64 kMutable =           0x0000000000000002ULL;
+
+// An error was detected while constructing/using the FST
+const uint64 kError =             0x0000000000000004ULL;
+
+//
+// TRINARY PROPERTIES
+//
+// For each of these properties below there is a pair of property bits
+// - one positive and one negative. If the positive bit is set, the
+// property is true. If the negative bit is set, the property is
+// false. If neither is set, the property has unknown value. Both
+// should never be simultaneously set. The individual positive and
+// negative bit pairs should be adjacent with the positive bit
+// at an odd and lower position.
+
+// ilabel == olabel for each arc
+const uint64 kAcceptor =          0x0000000000010000ULL;
+// ilabel != olabel for some arc
+const uint64 kNotAcceptor =       0x0000000000020000ULL;
+
+// ilabels unique leaving each state
+const uint64 kIDeterministic =    0x0000000000040000ULL;
+// ilabels not unique leaving some state
+const uint64 kNonIDeterministic = 0x0000000000080000ULL;
+
+// olabels unique leaving each state
+const uint64 kODeterministic =    0x0000000000100000ULL;
+// olabels not unique leaving some state
+const uint64 kNonODeterministic = 0x0000000000200000ULL;
+
+// FST has input/output epsilons
+const uint64 kEpsilons =          0x0000000000400000ULL;
+// FST has no input/output epsilons
+const uint64 kNoEpsilons =        0x0000000000800000ULL;
+
+// FST has input epsilons
+const uint64 kIEpsilons =         0x0000000001000000ULL;
+// FST has no input epsilons
+const uint64 kNoIEpsilons =       0x0000000002000000ULL;
+
+// FST has output epsilons
+const uint64 kOEpsilons =         0x0000000004000000ULL;
+// FST has no output epsilons
+const uint64 kNoOEpsilons =       0x0000000008000000ULL;
+
+// ilabels sorted wrt < for each state
+const uint64 kILabelSorted =      0x0000000010000000ULL;
+// ilabels not sorted wrt < for some state
+const uint64 kNotILabelSorted =   0x0000000020000000ULL;
+
+// olabels sorted wrt < for each state
+const uint64 kOLabelSorted =      0x0000000040000000ULL;
+// olabels not sorted wrt < for some state
+const uint64 kNotOLabelSorted =   0x0000000080000000ULL;
+
+// Non-trivial arc or final weights
+const uint64 kWeighted =          0x0000000100000000ULL;
+// Only trivial arc and final weights
+const uint64 kUnweighted =        0x0000000200000000ULL;
+
+// FST has cycles
+const uint64 kCyclic =            0x0000000400000000ULL;
+// FST has no cycles
+const uint64 kAcyclic =           0x0000000800000000ULL;
+
+// FST has cycles containing the initial state
+const uint64 kInitialCyclic =     0x0000001000000000ULL;
+// FST has no cycles containing the initial state
+const uint64 kInitialAcyclic =    0x0000002000000000ULL;
+
+// FST is topologically sorted
+const uint64 kTopSorted =         0x0000004000000000ULL;
+// FST is not topologically sorted
+const uint64 kNotTopSorted =      0x0000008000000000ULL;
+
+// All states reachable from the initial state
+const uint64 kAccessible =        0x0000010000000000ULL;
+// Not all states reachable from the initial state
+const uint64 kNotAccessible =     0x0000020000000000ULL;
+
+// All states can reach a final state
+const uint64 kCoAccessible =      0x0000040000000000ULL;
+// Not all states can reach a final state
+const uint64 kNotCoAccessible =   0x0000080000000000ULL;
+
+// If NumStates() > 0, then state 0 is initial, state NumStates()-1 is
+// final, there is a transition from each non-final state i to
+// state i+1, and there are no other transitions.
+const uint64 kString =            0x0000100000000000ULL;
+
+// Not a string FST
+const uint64 kNotString =         0x0000200000000000ULL;
+
+//
+// COMPOSITE PROPERTIES
+//
+
+// Properties of an empty machine
+const uint64 kNullProperties
+  = kAcceptor | kIDeterministic | kODeterministic | kNoEpsilons |
+    kNoIEpsilons | kNoOEpsilons | kILabelSorted | kOLabelSorted |
+    kUnweighted | kAcyclic | kInitialAcyclic | kTopSorted |
+    kAccessible | kCoAccessible | kString;
+
+// Properties that are preserved when an FST is copied
+const uint64 kCopyProperties
+  = kError | kAcceptor | kNotAcceptor | kIDeterministic | kNonIDeterministic |
+    kODeterministic | kNonODeterministic | kEpsilons | kNoEpsilons |
+    kIEpsilons | kNoIEpsilons | kOEpsilons | kNoOEpsilons |
+    kILabelSorted | kNotILabelSorted | kOLabelSorted |
+    kNotOLabelSorted | kWeighted | kUnweighted | kCyclic | kAcyclic |
+    kInitialCyclic | kInitialAcyclic | kTopSorted | kNotTopSorted |
+    kAccessible | kNotAccessible | kCoAccessible | kNotCoAccessible |
+    kString | kNotString;
+
+// Properites that are intrinsic to the FST
+const uint64 kIntrinsicProperties
+  = kExpanded | kMutable | kAcceptor | kNotAcceptor | kIDeterministic |
+    kNonIDeterministic | kODeterministic | kNonODeterministic |
+    kEpsilons | kNoEpsilons | kIEpsilons | kNoIEpsilons | kOEpsilons |
+    kNoOEpsilons | kILabelSorted | kNotILabelSorted | kOLabelSorted |
+    kNotOLabelSorted | kWeighted | kUnweighted | kCyclic | kAcyclic |
+    kInitialCyclic | kInitialAcyclic | kTopSorted | kNotTopSorted |
+    kAccessible | kNotAccessible | kCoAccessible | kNotCoAccessible |
+    kString | kNotString;
+
+// Properites that are (potentially) extrinsic to the FST
+const uint64 kExtrinsicProperties = kError;
+
+// Properties that are preserved when an FST start state is set
+const uint64 kSetStartProperties
+  = kExpanded | kMutable | kError | kAcceptor | kNotAcceptor |
+    kIDeterministic | kNonIDeterministic | kODeterministic |
+    kNonODeterministic | kEpsilons | kNoEpsilons | kIEpsilons |
+    kNoIEpsilons | kOEpsilons | kNoOEpsilons | kILabelSorted |
+    kNotILabelSorted | kOLabelSorted | kNotOLabelSorted | kWeighted |
+    kUnweighted | kCyclic | kAcyclic | kTopSorted | kNotTopSorted |
+    kCoAccessible | kNotCoAccessible;
+
+// Properties that are preserved when an FST final weight is set
+const uint64 kSetFinalProperties
+  = kExpanded | kMutable | kError | kAcceptor | kNotAcceptor |
+    kIDeterministic | kNonIDeterministic | kODeterministic |
+    kNonODeterministic | kEpsilons | kNoEpsilons | kIEpsilons |
+    kNoIEpsilons | kOEpsilons | kNoOEpsilons | kILabelSorted |
+    kNotILabelSorted | kOLabelSorted | kNotOLabelSorted | kCyclic |
+    kAcyclic | kInitialCyclic | kInitialAcyclic | kTopSorted |
+    kNotTopSorted | kAccessible | kNotAccessible;
+
+// Properties that are preserved when an FST state is added
+const uint64 kAddStateProperties
+  = kExpanded | kMutable | kError | kAcceptor | kNotAcceptor |
+    kIDeterministic | kNonIDeterministic | kODeterministic |
+    kNonODeterministic | kEpsilons | kNoEpsilons | kIEpsilons |
+    kNoIEpsilons | kOEpsilons | kNoOEpsilons | kILabelSorted |
+    kNotILabelSorted | kOLabelSorted | kNotOLabelSorted | kWeighted |
+    kUnweighted | kCyclic | kAcyclic | kInitialCyclic |
+    kInitialAcyclic | kTopSorted | kNotTopSorted | kNotAccessible |
+    kNotCoAccessible | kNotString;
+
+// Properties that are preserved when an FST arc is added
+const uint64 kAddArcProperties = kExpanded | kMutable | kError | kNotAcceptor |
+    kNonIDeterministic | kNonODeterministic | kEpsilons | kIEpsilons |
+    kOEpsilons | kNotILabelSorted | kNotOLabelSorted | kWeighted |
+    kCyclic | kInitialCyclic | kNotTopSorted | kAccessible | kCoAccessible;
+
+// Properties that are preserved when an FST arc is set
+const uint64 kSetArcProperties = kExpanded | kMutable | kError;
+
+// Properties that are preserved when FST states are deleted
+const uint64 kDeleteStatesProperties
+  = kExpanded | kMutable | kError | kAcceptor | kIDeterministic |
+    kODeterministic | kNoEpsilons | kNoIEpsilons | kNoOEpsilons |
+    kILabelSorted | kOLabelSorted | kUnweighted | kAcyclic |
+    kInitialAcyclic | kTopSorted;
+
+// Properties that are preserved when FST arcs are deleted
+const uint64 kDeleteArcsProperties
+  = kExpanded | kMutable | kError | kAcceptor | kIDeterministic |
+    kODeterministic | kNoEpsilons | kNoIEpsilons | kNoOEpsilons |
+    kILabelSorted | kOLabelSorted | kUnweighted | kAcyclic |
+    kInitialAcyclic | kTopSorted |  kNotAccessible | kNotCoAccessible;
+
+// Properties that are preserved when an FST's states are reordered
+const uint64 kStateSortProperties = kExpanded | kMutable | kError | kAcceptor |
+    kNotAcceptor | kIDeterministic | kNonIDeterministic |
+    kODeterministic | kNonODeterministic | kEpsilons | kNoEpsilons |
+    kIEpsilons | kNoIEpsilons | kOEpsilons | kNoOEpsilons |
+    kILabelSorted | kNotILabelSorted | kOLabelSorted | kNotOLabelSorted
+    | kWeighted | kUnweighted | kCyclic | kAcyclic | kInitialCyclic |
+    kInitialAcyclic | kAccessible | kNotAccessible | kCoAccessible |
+    kNotCoAccessible;
+
+// Properties that are preserved when an FST's arcs are reordered
+const uint64 kArcSortProperties =
+  kExpanded | kMutable | kError | kAcceptor | kNotAcceptor | kIDeterministic |
+  kNonIDeterministic | kODeterministic | kNonODeterministic |
+  kEpsilons | kNoEpsilons | kIEpsilons | kNoIEpsilons | kOEpsilons |
+  kNoOEpsilons | kWeighted | kUnweighted | kCyclic | kAcyclic |
+  kInitialCyclic | kInitialAcyclic | kTopSorted | kNotTopSorted |
+  kAccessible | kNotAccessible | kCoAccessible | kNotCoAccessible |
+  kString | kNotString;
+
+// Properties that are preserved when an FST's input labels are changed.
+const uint64 kILabelInvariantProperties =
+  kExpanded | kMutable | kError | kODeterministic | kNonODeterministic |
+  kOEpsilons | kNoOEpsilons | kOLabelSorted | kNotOLabelSorted |
+  kWeighted | kUnweighted | kCyclic | kAcyclic | kInitialCyclic |
+  kInitialAcyclic | kTopSorted | kNotTopSorted | kAccessible |
+  kNotAccessible | kCoAccessible | kNotCoAccessible | kString | kNotString;
+
+// Properties that are preserved when an FST's output labels are changed.
+const uint64 kOLabelInvariantProperties =
+  kExpanded | kMutable | kError | kIDeterministic | kNonIDeterministic |
+  kIEpsilons | kNoIEpsilons | kILabelSorted | kNotILabelSorted |
+  kWeighted | kUnweighted | kCyclic | kAcyclic | kInitialCyclic |
+  kInitialAcyclic | kTopSorted | kNotTopSorted | kAccessible |
+  kNotAccessible | kCoAccessible | kNotCoAccessible | kString | kNotString;
+
+// Properties that are preserved when an FST's weights are changed.
+// This assumes that the set of states that are non-final is not changed.
+const uint64 kWeightInvariantProperties =
+  kExpanded | kMutable | kError | kAcceptor | kNotAcceptor | kIDeterministic |
+  kNonIDeterministic | kODeterministic | kNonODeterministic |
+  kEpsilons | kNoEpsilons | kIEpsilons | kNoIEpsilons | kOEpsilons |
+  kNoOEpsilons | kILabelSorted | kNotILabelSorted | kOLabelSorted |
+  kNotOLabelSorted | kCyclic | kAcyclic | kInitialCyclic | kInitialAcyclic |
+  kTopSorted | kNotTopSorted | kAccessible | kNotAccessible | kCoAccessible |
+  kNotCoAccessible | kString | kNotString;
+
+// Properties that are preserved when a superfinal state is added
+// and an FSTs final weights are directed to it via new transitions.
+const uint64 kAddSuperFinalProperties  = kExpanded | kMutable | kError |
+    kAcceptor | kNotAcceptor | kNonIDeterministic | kNonODeterministic |
+    kEpsilons | kIEpsilons | kOEpsilons | kNotILabelSorted | kNotOLabelSorted |
+    kWeighted | kUnweighted | kCyclic | kAcyclic | kInitialCyclic |
+    kInitialAcyclic | kNotTopSorted | kNotAccessible | kCoAccessible |
+    kNotCoAccessible | kNotString;
+
+// Properties that are preserved when a superfinal state is removed
+// and the epsilon transitions directed to it are made final weights.
+const uint64 kRmSuperFinalProperties  = kExpanded | kMutable | kError |
+    kAcceptor | kNotAcceptor | kIDeterministic | kODeterministic |
+    kNoEpsilons | kNoIEpsilons | kNoOEpsilons | kILabelSorted | kOLabelSorted |
+    kWeighted | kUnweighted | kCyclic | kAcyclic | kInitialCyclic |
+    kInitialAcyclic | kTopSorted | kAccessible | kCoAccessible |
+    kNotCoAccessible | kString;
+
+// All binary properties
+const uint64 kBinaryProperties =  0x0000000000000007ULL;
+
+// All trinary properties
+const uint64 kTrinaryProperties = 0x00003fffffff0000ULL;
+
+//
+// COMPUTED PROPERTIES
+//
+
+// 1st bit of trinary properties
+const uint64 kPosTrinaryProperties =
+  kTrinaryProperties & 0x5555555555555555ULL;
+
+// 2nd bit of trinary properties
+const uint64 kNegTrinaryProperties =
+  kTrinaryProperties & 0xaaaaaaaaaaaaaaaaULL;
+
+// All properties
+const uint64 kFstProperties = kBinaryProperties | kTrinaryProperties;
+
+//
+// PROPERTY FUNCTIONS and STRING NAMES (defined in properties.cc)
+//
+
+// Below are functions for getting property bit vectors when executing
+// mutating fst operations.
+inline uint64 SetStartProperties(uint64 inprops);
+template <typename Weight>
+uint64 SetFinalProperties(uint64 inprops, Weight old_weight,
+                          Weight new_weight);
+inline uint64 AddStateProperties(uint64 inprops);
+template <typename A>
+uint64 AddArcProperties(uint64 inprops, typename A::StateId s, const A &arc,
+                           const A *prev_arc);
+inline uint64 DeleteStatesProperties(uint64 inprops);
+inline uint64 DeleteAllStatesProperties(uint64 inprops, uint64 staticProps);
+inline uint64 DeleteArcsProperties(uint64 inprops);
+
+uint64 ClosureProperties(uint64 inprops, bool star, bool delayed = false);
+uint64 ComplementProperties(uint64 inprops);
+uint64 ComposeProperties(uint64 inprops1, uint64 inprops2);
+uint64 ConcatProperties(uint64 inprops1, uint64 inprops2,
+                        bool delayed = false);
+uint64 DeterminizeProperties(uint64 inprops, bool has_subsequential_label);
+uint64 FactorWeightProperties(uint64 inprops);
+uint64 InvertProperties(uint64 inprops);
+uint64 ProjectProperties(uint64 inprops, bool project_input);
+uint64 RandGenProperties(uint64 inprops, bool weighted);
+uint64 RelabelProperties(uint64 inprops);
+uint64 ReplaceProperties(const vector<uint64>& inprops,
+                         ssize_t root,
+                         bool epsilon_on_replace,
+                         bool no_empty_fst);
+uint64 ReverseProperties(uint64 inprops);
+uint64 ReweightProperties(uint64 inprops);
+uint64 RmEpsilonProperties(uint64 inprops, bool delayed = false);
+uint64 ShortestPathProperties(uint64 props);
+uint64 SynchronizeProperties(uint64 inprops);
+uint64 UnionProperties(uint64 inprops1, uint64 inprops2, bool delayed = false);
+
+// Definitions of inlined functions.
+
+uint64 SetStartProperties(uint64 inprops) {
+  uint64 outprops = inprops & kSetStartProperties;
+  if (inprops & kAcyclic) {
+    outprops |= kInitialAcyclic;
+  }
+  return outprops;
+}
+
+uint64 AddStateProperties(uint64 inprops) {
+  return inprops & kAddStateProperties;
+}
+
+uint64 DeleteStatesProperties(uint64 inprops) {
+  return inprops & kDeleteStatesProperties;
+}
+
+uint64 DeleteAllStatesProperties(uint64 inprops, uint64 staticprops) {
+  uint64 outprops = inprops & kError;
+  return outprops | kNullProperties | staticprops;
+}
+
+uint64 DeleteArcsProperties(uint64 inprops) {
+  return inprops & kDeleteArcsProperties;
+}
+
+// Definitions of template functions.
+
+//
+template <typename Weight>
+uint64 SetFinalProperties(uint64 inprops, Weight old_weight,
+                          Weight new_weight) {
+  uint64 outprops = inprops;
+  if (old_weight != Weight::Zero() && old_weight != Weight::One()) {
+    outprops &= ~kWeighted;
+  }
+  if (new_weight != Weight::Zero() && new_weight != Weight::One()) {
+    outprops |= kWeighted;
+    outprops &= ~kUnweighted;
+  }
+  outprops &= kSetFinalProperties | kWeighted | kUnweighted;
+  return outprops;
+}
+
+/// Gets the properties for the MutableFst::AddArc method.
+///
+/// \param inprops  the current properties of the fst
+/// \param s        the id of the state to which an arc is being added
+/// \param arc      the arc being added to the state with the specified id
+/// \param prev_arc the previously-added (or "last") arc of state s, or NULL if
+///                 s currently has no arcs
+template <typename A>
+uint64 AddArcProperties(uint64 inprops, typename A::StateId s,
+                        const A &arc, const A *prev_arc) {
+  uint64 outprops = inprops;
+  if (arc.ilabel != arc.olabel) {
+    outprops |= kNotAcceptor;
+    outprops &= ~kAcceptor;
+  }
+  if (arc.ilabel == 0) {
+    outprops |= kIEpsilons;
+    outprops &= ~kNoIEpsilons;
+    if (arc.olabel == 0) {
+      outprops |= kEpsilons;
+      outprops &= ~kNoEpsilons;
+    }
+  }
+  if (arc.olabel == 0) {
+    outprops |= kOEpsilons;
+    outprops &= ~kNoOEpsilons;
+  }
+  if (prev_arc != 0) {
+    if (prev_arc->ilabel > arc.ilabel) {
+      outprops |= kNotILabelSorted;
+      outprops &= ~kILabelSorted;
+    }
+    if (prev_arc->olabel > arc.olabel) {
+      outprops |= kNotOLabelSorted;
+      outprops &= ~kOLabelSorted;
+    }
+  }
+  if (arc.weight != A::Weight::Zero() && arc.weight != A::Weight::One()) {
+    outprops |= kWeighted;
+    outprops &= ~kUnweighted;
+  }
+  if (arc.nextstate <= s) {
+    outprops |= kNotTopSorted;
+    outprops &= ~kTopSorted;
+  }
+  outprops &= kAddArcProperties | kAcceptor |
+              kNoEpsilons | kNoIEpsilons | kNoOEpsilons |
+              kILabelSorted | kOLabelSorted | kUnweighted | kTopSorted;
+  if (outprops & kTopSorted) {
+    outprops |= kAcyclic | kInitialAcyclic;
+  }
+  return outprops;
+}
+
+extern const char *PropertyNames[];
+
+}  // namespace fst
+
+#endif  // FST_LIB_PROPERTIES_H__
diff --git a/src/include/fst/prune.h b/src/include/fst/prune.h
new file mode 100644
index 0000000..5ea5b4d
--- /dev/null
+++ b/src/include/fst/prune.h
@@ -0,0 +1,339 @@
+// prune.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Functions implementing pruning.
+
+#ifndef FST_LIB_PRUNE_H__
+#define FST_LIB_PRUNE_H__
+
+#include <vector>
+using std::vector;
+
+#include <fst/arcfilter.h>
+#include <fst/heap.h>
+#include <fst/shortest-distance.h>
+
+
+namespace fst {
+
+template <class A, class ArcFilter>
+class PruneOptions {
+ public:
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  // Pruning weight threshold.
+  Weight weight_threshold;
+  // Pruning state threshold.
+  StateId state_threshold;
+  // Arc filter.
+  ArcFilter filter;
+  // If non-zero, passes in pre-computed shortest distance to final states.
+  const vector<Weight> *distance;
+  // Determines the degree of convergence required when computing shortest
+  // distances.
+  float delta;
+
+  explicit PruneOptions(const Weight& w, StateId s, ArcFilter f,
+                        vector<Weight> *d = 0, float e = kDelta)
+      : weight_threshold(w),
+        state_threshold(s),
+        filter(f),
+        distance(d),
+        delta(e) {}
+ private:
+  PruneOptions();  // disallow
+};
+
+
+template <class S, class W>
+class PruneCompare {
+ public:
+  typedef S StateId;
+  typedef W Weight;
+
+  PruneCompare(const vector<Weight> &idistance,
+               const vector<Weight> &fdistance)
+      : idistance_(idistance), fdistance_(fdistance) {}
+
+  bool operator()(const StateId x, const StateId y) const {
+    Weight wx = Times(x < idistance_.size() ? idistance_[x] : Weight::Zero(),
+                      x < fdistance_.size() ? fdistance_[x] : Weight::Zero());
+    Weight wy = Times(y < idistance_.size() ? idistance_[y] : Weight::Zero(),
+                      y < fdistance_.size() ? fdistance_[y] : Weight::Zero());
+    return less_(wx, wy);
+  }
+
+ private:
+  const vector<Weight> &idistance_;
+  const vector<Weight> &fdistance_;
+  NaturalLess<Weight> less_;
+};
+
+
+
+// Pruning algorithm: this version modifies its input and it takes an
+// options class as an argment. Delete states and arcs in 'fst' that
+// do not belong to a successful path whose weight is no more than
+// the weight of the shortest path Times() 'opts.weight_threshold'.
+// When 'opts.state_threshold != kNoStateId', the resulting transducer
+// will restricted further to have at most 'opts.state_threshold'
+// states. Weights need to be commutative and have the path
+// property. The weight 'w' of any cycle needs to be bounded, i.e.,
+// 'Plus(w, W::One()) = One()'.
+template <class Arc, class ArcFilter>
+void Prune(MutableFst<Arc> *fst,
+           const PruneOptions<Arc, ArcFilter> &opts) {
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  if ((Weight::Properties() & (kPath | kCommutative))
+      != (kPath | kCommutative)) {
+    FSTERROR() << "Prune: Weight needs to have the path property and"
+               << " be commutative: "
+               << Weight::Type();
+    fst->SetProperties(kError, kError);
+    return;
+  }
+  StateId ns = fst->NumStates();
+  if (ns == 0) return;
+  vector<Weight> idistance(ns, Weight::Zero());
+  vector<Weight> tmp;
+  if (!opts.distance) {
+    tmp.reserve(ns);
+    ShortestDistance(*fst, &tmp, true, opts.delta);
+  }
+  const vector<Weight> *fdistance = opts.distance ? opts.distance : &tmp;
+
+  if ((opts.state_threshold == 0) ||
+      (fdistance->size() <= fst->Start()) ||
+      ((*fdistance)[fst->Start()] == Weight::Zero())) {
+    fst->DeleteStates();
+    return;
+  }
+  PruneCompare<StateId, Weight> compare(idistance, *fdistance);
+  Heap< StateId, PruneCompare<StateId, Weight>, false> heap(compare);
+  vector<bool> visited(ns, false);
+  vector<size_t> enqueued(ns, kNoKey);
+  vector<StateId> dead;
+  dead.push_back(fst->AddState());
+  NaturalLess<Weight> less;
+  Weight limit = Times((*fdistance)[fst->Start()], opts.weight_threshold);
+
+  StateId num_visited = 0;
+  StateId s = fst->Start();
+  if (!less(limit, (*fdistance)[s])) {
+    idistance[s] = Weight::One();
+    enqueued[s] = heap.Insert(s);
+    ++num_visited;
+  }
+
+  while (!heap.Empty()) {
+    s = heap.Top();
+    heap.Pop();
+    enqueued[s] = kNoKey;
+    visited[s] = true;
+    if (less(limit, Times(idistance[s], fst->Final(s))))
+      fst->SetFinal(s, Weight::Zero());
+    for (MutableArcIterator< MutableFst<Arc> > ait(fst, s);
+         !ait.Done();
+         ait.Next()) {
+      Arc arc = ait.Value();
+      if (!opts.filter(arc)) continue;
+      Weight weight = Times(Times(idistance[s], arc.weight),
+                            arc.nextstate < fdistance->size()
+                            ? (*fdistance)[arc.nextstate]
+                            : Weight::Zero());
+      if (less(limit, weight)) {
+        arc.nextstate = dead[0];
+        ait.SetValue(arc);
+        continue;
+      }
+      if (less(Times(idistance[s], arc.weight), idistance[arc.nextstate]))
+        idistance[arc.nextstate] = Times(idistance[s], arc.weight);
+      if (visited[arc.nextstate]) continue;
+      if ((opts.state_threshold != kNoStateId) &&
+          (num_visited >= opts.state_threshold))
+        continue;
+      if (enqueued[arc.nextstate] == kNoKey) {
+        enqueued[arc.nextstate] = heap.Insert(arc.nextstate);
+        ++num_visited;
+      } else {
+        heap.Update(enqueued[arc.nextstate], arc.nextstate);
+      }
+    }
+  }
+  for (size_t i = 0; i < visited.size(); ++i)
+    if (!visited[i]) dead.push_back(i);
+  fst->DeleteStates(dead);
+}
+
+
+// Pruning algorithm: this version modifies its input and simply takes
+// the pruning threshold as an argument. Delete states and arcs in
+// 'fst' that do not belong to a successful path whose weight is no
+// more than the weight of the shortest path Times()
+// 'weight_threshold'.  When 'state_threshold != kNoStateId', the
+// resulting transducer will be restricted further to have at most
+// 'opts.state_threshold' states. Weights need to be commutative and
+// have the path property. The weight 'w' of any cycle needs to be
+// bounded, i.e., 'Plus(w, W::One()) = One()'.
+template <class Arc>
+void Prune(MutableFst<Arc> *fst,
+           typename Arc::Weight weight_threshold,
+           typename Arc::StateId state_threshold = kNoStateId,
+           double delta = kDelta) {
+  PruneOptions<Arc, AnyArcFilter<Arc> > opts(weight_threshold, state_threshold,
+                                             AnyArcFilter<Arc>(), 0, delta);
+  Prune(fst, opts);
+}
+
+
+// Pruning algorithm: this version writes the pruned input Fst to an
+// output MutableFst and it takes an options class as an argument.
+// 'ofst' contains states and arcs that belong to a successful path in
+// 'ifst' whose weight is no more than the weight of the shortest path
+// Times() 'opts.weight_threshold'. When 'opts.state_threshold !=
+// kNoStateId', 'ofst' will be restricted further to have at most
+// 'opts.state_threshold' states. Weights need to be commutative and
+// have the path property. The weight 'w' of any cycle needs to be
+// bounded, i.e., 'Plus(w, W::One()) = One()'.
+template <class Arc, class ArcFilter>
+void Prune(const Fst<Arc> &ifst,
+           MutableFst<Arc> *ofst,
+           const PruneOptions<Arc, ArcFilter> &opts) {
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  if ((Weight::Properties() & (kPath | kCommutative))
+      != (kPath | kCommutative)) {
+    FSTERROR() << "Prune: Weight needs to have the path property and"
+               << " be commutative: "
+               << Weight::Type();
+    ofst->SetProperties(kError, kError);
+    return;
+  }
+  ofst->DeleteStates();
+  ofst->SetInputSymbols(ifst.InputSymbols());
+  ofst->SetOutputSymbols(ifst.OutputSymbols());
+  if (ifst.Start() == kNoStateId)
+    return;
+  NaturalLess<Weight> less;
+  if (less(opts.weight_threshold, Weight::One()) ||
+      (opts.state_threshold == 0))
+    return;
+  vector<Weight> idistance;
+  vector<Weight> tmp;
+  if (!opts.distance)
+    ShortestDistance(ifst, &tmp, true, opts.delta);
+  const vector<Weight> *fdistance = opts.distance ? opts.distance : &tmp;
+
+  if ((fdistance->size() <= ifst.Start()) ||
+      ((*fdistance)[ifst.Start()] == Weight::Zero())) {
+    return;
+  }
+  PruneCompare<StateId, Weight> compare(idistance, *fdistance);
+  Heap< StateId, PruneCompare<StateId, Weight>, false> heap(compare);
+  vector<StateId> copy;
+  vector<size_t> enqueued;
+  vector<bool> visited;
+
+  StateId s = ifst.Start();
+  Weight limit = Times(s < fdistance->size() ? (*fdistance)[s] : Weight::Zero(),
+                         opts.weight_threshold);
+  while (copy.size() <= s)
+    copy.push_back(kNoStateId);
+  copy[s] = ofst->AddState();
+  ofst->SetStart(copy[s]);
+  while (idistance.size() <= s)
+    idistance.push_back(Weight::Zero());
+  idistance[s] = Weight::One();
+  while (enqueued.size() <= s) {
+    enqueued.push_back(kNoKey);
+    visited.push_back(false);
+  }
+  enqueued[s] = heap.Insert(s);
+
+  while (!heap.Empty()) {
+    s = heap.Top();
+    heap.Pop();
+    enqueued[s] = kNoKey;
+    visited[s] = true;
+    if (!less(limit, Times(idistance[s], ifst.Final(s))))
+      ofst->SetFinal(copy[s], ifst.Final(s));
+    for (ArcIterator< Fst<Arc> > ait(ifst, s);
+         !ait.Done();
+         ait.Next()) {
+      const Arc &arc = ait.Value();
+      if (!opts.filter(arc)) continue;
+      Weight weight = Times(Times(idistance[s], arc.weight),
+                            arc.nextstate < fdistance->size()
+                            ? (*fdistance)[arc.nextstate]
+                            : Weight::Zero());
+      if (less(limit, weight)) continue;
+      if ((opts.state_threshold != kNoStateId) &&
+          (ofst->NumStates() >= opts.state_threshold))
+        continue;
+      while (idistance.size() <= arc.nextstate)
+        idistance.push_back(Weight::Zero());
+      if (less(Times(idistance[s], arc.weight),
+               idistance[arc.nextstate]))
+        idistance[arc.nextstate] = Times(idistance[s], arc.weight);
+      while (copy.size() <= arc.nextstate)
+        copy.push_back(kNoStateId);
+      if (copy[arc.nextstate] == kNoStateId)
+        copy[arc.nextstate] = ofst->AddState();
+      ofst->AddArc(copy[s], Arc(arc.ilabel, arc.olabel, arc.weight,
+                                copy[arc.nextstate]));
+      while (enqueued.size() <= arc.nextstate) {
+        enqueued.push_back(kNoKey);
+        visited.push_back(false);
+      }
+      if (visited[arc.nextstate]) continue;
+      if (enqueued[arc.nextstate] == kNoKey)
+        enqueued[arc.nextstate] = heap.Insert(arc.nextstate);
+      else
+        heap.Update(enqueued[arc.nextstate], arc.nextstate);
+    }
+  }
+}
+
+
+// Pruning algorithm: this version writes the pruned input Fst to an
+// output MutableFst and simply takes the pruning threshold as an
+// argument.  'ofst' contains states and arcs that belong to a
+// successful path in 'ifst' whose weight is no more than
+// the weight of the shortest path Times() 'weight_threshold'. When
+// 'state_threshold != kNoStateId', 'ofst' will be restricted further
+// to have at most 'opts.state_threshold' states. Weights need to be
+// commutative and have the path property. The weight 'w' of any cycle
+// needs to be bounded, i.e., 'Plus(w, W::One()) = W::One()'.
+template <class Arc>
+void Prune(const Fst<Arc> &ifst,
+           MutableFst<Arc> *ofst,
+           typename Arc::Weight weight_threshold,
+           typename Arc::StateId state_threshold = kNoStateId,
+           float delta = kDelta) {
+  PruneOptions<Arc, AnyArcFilter<Arc> > opts(weight_threshold, state_threshold,
+                                             AnyArcFilter<Arc>(), 0, delta);
+  Prune(ifst, ofst, opts);
+}
+
+}  // namespace fst
+
+#endif // FST_LIB_PRUNE_H_
diff --git a/src/include/fst/push.h b/src/include/fst/push.h
new file mode 100644
index 0000000..1f7a8fa
--- /dev/null
+++ b/src/include/fst/push.h
@@ -0,0 +1,175 @@
+// push.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Class to reweight/push an FST.
+
+#ifndef FST_LIB_PUSH_H__
+#define FST_LIB_PUSH_H__
+
+#include <vector>
+using std::vector;
+
+#include <fst/factor-weight.h>
+#include <fst/fst.h>
+#include <fst/arc-map.h>
+#include <fst/reweight.h>
+#include <fst/shortest-distance.h>
+
+
+namespace fst {
+
+// Private helper functions for Push
+namespace internal {
+
+// Compute the total weight (sum of the weights of all accepting paths) from
+// the output of ShortestDistance. 'distance' is the shortest distance from the
+// initial state when 'reverse == false' and to the final states when
+// 'reverse == true'.
+template <class Arc>
+typename Arc::Weight ComputeTotalWeight(
+    const Fst<Arc> &fst,
+    const vector<typename Arc::Weight> &distance,
+    bool reverse) {
+  if (reverse)
+    return fst.Start() < distance.size() ?
+        distance[fst.Start()] : Arc::Weight::Zero();
+
+  typename Arc::Weight sum = Arc::Weight::Zero();
+  for (typename Arc::StateId s = 0; s < distance.size(); ++s)
+    sum = Plus(sum, Times(distance[s], fst.Final(s)));
+  return sum;
+}
+
+// Divide the weight of every accepting path by 'w'. The weight 'w' is
+// divided at the final states if 'at_final == true' and at the
+// initial state otherwise.
+template <class Arc>
+void RemoveWeight(MutableFst<Arc> *fst, typename Arc::Weight w, bool at_final) {
+  if ((w == Arc::Weight::One()) || (w == Arc::Weight::Zero()))
+      return;
+
+  if (at_final) {
+    // Remove 'w' from the final states
+    for (StateIterator< MutableFst<Arc> > sit(*fst);
+         !sit.Done();
+         sit.Next())
+      fst->SetFinal(sit.Value(),
+                    Divide(fst->Final(sit.Value()), w,  DIVIDE_RIGHT));
+  } else {  // at_final == false
+    // Remove 'w' from the initial state
+    typename Arc::StateId start = fst->Start();
+    for (MutableArcIterator<MutableFst<Arc> > ait(fst, start);
+         !ait.Done();
+         ait.Next()) {
+      Arc arc = ait.Value();
+      arc.weight = Divide(arc.weight, w, DIVIDE_LEFT);
+      ait.SetValue(arc);
+    }
+    fst->SetFinal(start, Divide(fst->Final(start), w, DIVIDE_LEFT));
+  }
+}
+}  // namespace internal
+
+// Pushes the weights in FST in the direction defined by TYPE.  If
+// pushing towards the initial state, the sum of the weight of the
+// outgoing transitions and final weight at a non-initial state is
+// equal to One() in the resulting machine.  If pushing towards the
+// final state, the same property holds on the reverse machine.
+//
+// Weight needs to be left distributive when pushing towards the
+// initial state and right distributive when pushing towards the final
+// states.
+template <class Arc>
+void Push(MutableFst<Arc> *fst,
+          ReweightType type,
+          float delta = kDelta,
+          bool remove_total_weight = false) {
+  vector<typename Arc::Weight> distance;
+  ShortestDistance(*fst, &distance, type == REWEIGHT_TO_INITIAL, delta);
+  typename Arc::Weight total_weight = Arc::Weight::One();
+  if (remove_total_weight)
+    total_weight = internal::ComputeTotalWeight(*fst, distance,
+                                                type == REWEIGHT_TO_INITIAL);
+  Reweight(fst, distance, type);
+  if (remove_total_weight)
+    internal::RemoveWeight(fst, total_weight, type == REWEIGHT_TO_FINAL);
+}
+
+const uint32 kPushWeights = 0x0001;
+const uint32 kPushLabels =  0x0002;
+const uint32 kPushRemoveTotalWeight = 0x0004;
+const uint32 kPushRemoveCommonAffix = 0x0008;
+
+// OFST obtained from IFST by pushing weights and/or labels according
+// to PTYPE in the direction defined by RTYPE.  Weight needs to be
+// left distributive when pushing weights towards the initial state
+// and right distributive when pushing weights towards the final
+// states.
+template <class Arc, ReweightType rtype>
+void Push(const Fst<Arc> &ifst,
+          MutableFst<Arc> *ofst,
+          uint32 ptype,
+          float delta = kDelta) {
+
+  if ((ptype & (kPushWeights | kPushLabels)) == kPushWeights) {
+    *ofst = ifst;
+    Push(ofst, rtype, delta, ptype & kPushRemoveTotalWeight);
+  } else if (ptype & kPushLabels) {
+    const StringType stype = rtype == REWEIGHT_TO_INITIAL
+                             ? STRING_LEFT
+                             : STRING_RIGHT;
+    vector<typename GallicArc<Arc, stype>::Weight> gdistance;
+    VectorFst<GallicArc<Arc, stype> > gfst;
+    ArcMap(ifst, &gfst, ToGallicMapper<Arc, stype>());
+    if (ptype & kPushWeights ) {
+      ShortestDistance(gfst, &gdistance, rtype == REWEIGHT_TO_INITIAL, delta);
+    } else {
+      ArcMapFst<Arc, Arc, RmWeightMapper<Arc> >
+        uwfst(ifst, RmWeightMapper<Arc>());
+      ArcMapFst<Arc, GallicArc<Arc, stype>, ToGallicMapper<Arc, stype> >
+        guwfst(uwfst, ToGallicMapper<Arc, stype>());
+      ShortestDistance(guwfst, &gdistance, rtype == REWEIGHT_TO_INITIAL, delta);
+    }
+    typename GallicArc<Arc, stype>::Weight total_weight =
+        GallicArc<Arc, stype>::Weight::One();
+    if (ptype & (kPushRemoveTotalWeight | kPushRemoveCommonAffix)) {
+      total_weight = internal::ComputeTotalWeight(
+          gfst, gdistance, rtype == REWEIGHT_TO_INITIAL);
+      total_weight = typename GallicArc<Arc, stype>::Weight(
+          ptype & kPushRemoveCommonAffix ? total_weight.Value1()
+          : StringWeight<typename Arc::Label, stype>::One(),
+          ptype & kPushRemoveTotalWeight ? total_weight.Value2()
+          : Arc::Weight::One());
+    }
+    Reweight(&gfst, gdistance, rtype);
+    if (ptype & (kPushRemoveTotalWeight | kPushRemoveCommonAffix))
+      internal::RemoveWeight(&gfst, total_weight, rtype == REWEIGHT_TO_FINAL);
+    FactorWeightFst< GallicArc<Arc, stype>, GallicFactor<typename Arc::Label,
+      typename Arc::Weight, stype> > fwfst(gfst);
+    ArcMap(fwfst, ofst, FromGallicMapper<Arc, stype>());
+    ofst->SetOutputSymbols(ifst.OutputSymbols());
+  } else {
+    LOG(WARNING) << "Push: pushing type is set to 0: "
+                 << "pushing neither labels nor weights.";
+    *ofst = ifst;
+  }
+}
+
+}  // namespace fst
+
+#endif /* FST_LIB_PUSH_H_ */
diff --git a/src/include/fst/queue.h b/src/include/fst/queue.h
new file mode 100644
index 0000000..707dffc
--- /dev/null
+++ b/src/include/fst/queue.h
@@ -0,0 +1,889 @@
+// queue.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Functions and classes for various Fst state queues with
+// a unified interface.
+
+#ifndef FST_LIB_QUEUE_H__
+#define FST_LIB_QUEUE_H__
+
+#include <deque>
+#include <vector>
+using std::vector;
+
+#include <fst/arcfilter.h>
+#include <fst/connect.h>
+#include <fst/heap.h>
+#include <fst/topsort.h>
+
+
+namespace fst {
+
+// template <class S>
+// class Queue {
+//  public:
+//   typedef typename S StateId;
+//
+//   // Ctr: may need args (e.g., Fst, comparator) for some queues
+//   Queue(...);
+//   // Returns the head of the queue
+//   StateId Head() const;
+//   // Inserts a state
+//   void Enqueue(StateId s);
+//   // Removes the head of the queue
+//   void Dequeue();
+//   // Updates ordering of state s when weight changes, if necessary
+//   void Update(StateId s);
+//   // Does the queue contain no elements?
+//   bool Empty() const;
+//   // Remove all states from queue
+//   void Clear();
+// };
+
+// State queue types.
+enum QueueType {
+  TRIVIAL_QUEUE = 0,         // Single state queue
+  FIFO_QUEUE = 1,            // First-in, first-out queue
+  LIFO_QUEUE = 2,            // Last-in, first-out queue
+  SHORTEST_FIRST_QUEUE = 3,  // Shortest-first queue
+  TOP_ORDER_QUEUE = 4,       // Topologically-ordered queue
+  STATE_ORDER_QUEUE = 5,     // State-ID ordered queue
+  SCC_QUEUE = 6,             // Component graph top-ordered meta-queue
+  AUTO_QUEUE = 7,            // Auto-selected queue
+  OTHER_QUEUE = 8
+ };
+
+
+// QueueBase, templated on the StateId, is the base class shared by the
+// queues considered by AutoQueue.
+template <class S>
+class QueueBase {
+ public:
+  typedef S StateId;
+
+  QueueBase(QueueType type) : queue_type_(type), error_(false) {}
+  virtual ~QueueBase() {}
+  StateId Head() const { return Head_(); }
+  void Enqueue(StateId s) { Enqueue_(s); }
+  void Dequeue() { Dequeue_(); }
+  void Update(StateId s) { Update_(s); }
+  bool Empty() const { return Empty_(); }
+  void Clear() { Clear_(); }
+  QueueType Type() { return queue_type_; }
+  bool Error() const { return error_; }
+  void SetError(bool error) { error_ = error; }
+
+ private:
+  // This allows base-class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual StateId Head_() const = 0;
+  virtual void Enqueue_(StateId s) = 0;
+  virtual void Dequeue_() = 0;
+  virtual void Update_(StateId s) = 0;
+  virtual bool Empty_() const = 0;
+  virtual void Clear_() = 0;
+
+  QueueType queue_type_;
+  bool error_;
+};
+
+
+// Trivial queue discipline, templated on the StateId. You may enqueue
+// at most one state at a time. It is used for strongly connected components
+// with only one state and no self loops.
+template <class S>
+class TrivialQueue : public QueueBase<S> {
+public:
+  typedef S StateId;
+
+  TrivialQueue() : QueueBase<S>(TRIVIAL_QUEUE), front_(kNoStateId) {}
+  StateId Head() const { return front_; }
+  void Enqueue(StateId s) { front_ = s; }
+  void Dequeue() { front_ = kNoStateId; }
+  void Update(StateId s) {}
+  bool Empty() const { return front_ == kNoStateId; }
+  void Clear() { front_ = kNoStateId; }
+
+
+private:
+  // This allows base-class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual StateId Head_() const { return Head(); }
+  virtual void Enqueue_(StateId s) { Enqueue(s); }
+  virtual void Dequeue_() { Dequeue(); }
+  virtual void Update_(StateId s) { Update(s); }
+  virtual bool Empty_() const { return Empty(); }
+  virtual void Clear_() { return Clear(); }
+
+  StateId front_;
+};
+
+
+// First-in, first-out queue discipline, templated on the StateId.
+template <class S>
+class FifoQueue : public QueueBase<S>, public deque<S> {
+ public:
+  using deque<S>::back;
+  using deque<S>::push_front;
+  using deque<S>::pop_back;
+  using deque<S>::empty;
+  using deque<S>::clear;
+
+  typedef S StateId;
+
+  FifoQueue() : QueueBase<S>(FIFO_QUEUE) {}
+  StateId Head() const { return back(); }
+  void Enqueue(StateId s) { push_front(s); }
+  void Dequeue() { pop_back(); }
+  void Update(StateId s) {}
+  bool Empty() const { return empty(); }
+  void Clear() { clear(); }
+
+ private:
+  // This allows base-class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual StateId Head_() const { return Head(); }
+  virtual void Enqueue_(StateId s) { Enqueue(s); }
+  virtual void Dequeue_() { Dequeue(); }
+  virtual void Update_(StateId s) { Update(s); }
+  virtual bool Empty_() const { return Empty(); }
+  virtual void Clear_() { return Clear(); }
+};
+
+
+// Last-in, first-out queue discipline, templated on the StateId.
+template <class S>
+class LifoQueue : public QueueBase<S>, public deque<S> {
+ public:
+  using deque<S>::front;
+  using deque<S>::push_front;
+  using deque<S>::pop_front;
+  using deque<S>::empty;
+  using deque<S>::clear;
+
+  typedef S StateId;
+
+  LifoQueue() : QueueBase<S>(LIFO_QUEUE) {}
+  StateId Head() const { return front(); }
+  void Enqueue(StateId s) { push_front(s); }
+  void Dequeue() { pop_front(); }
+  void Update(StateId s) {}
+  bool Empty() const { return empty(); }
+  void Clear() { clear(); }
+
+ private:
+  // This allows base-class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual StateId Head_() const { return Head(); }
+  virtual void Enqueue_(StateId s) { Enqueue(s); }
+  virtual void Dequeue_() { Dequeue(); }
+  virtual void Update_(StateId s) { Update(s); }
+  virtual bool Empty_() const { return Empty(); }
+  virtual void Clear_() { return Clear(); }
+};
+
+
+// Shortest-first queue discipline, templated on the StateId and
+// comparison function object.  Comparison function object COMP is
+// used to compare two StateIds. If a (single) state's order changes,
+// it can be reordered in the queue with a call to Update().
+// If 'update == false', call to Update() does not reorder the queue.
+template <typename S, typename C, bool update = true>
+class ShortestFirstQueue : public QueueBase<S> {
+ public:
+  typedef S StateId;
+  typedef C Compare;
+
+  ShortestFirstQueue(C comp)
+      : QueueBase<S>(SHORTEST_FIRST_QUEUE), heap_(comp) {}
+
+  StateId Head() const { return heap_.Top(); }
+
+  void Enqueue(StateId s) {
+    if (update) {
+      for (StateId i = key_.size(); i <= s; ++i)
+        key_.push_back(kNoKey);
+      key_[s] = heap_.Insert(s);
+    } else {
+      heap_.Insert(s);
+    }
+  }
+
+  void Dequeue() {
+    if (update)
+      key_[heap_.Pop()] = kNoKey;
+    else
+      heap_.Pop();
+  }
+
+  void Update(StateId s) {
+    if (!update)
+      return;
+    if (s >= key_.size() || key_[s] == kNoKey) {
+      Enqueue(s);
+    } else {
+      heap_.Update(key_[s], s);
+    }
+  }
+
+  bool Empty() const { return heap_.Empty(); }
+
+  void Clear() {
+    heap_.Clear();
+    if (update) key_.clear();
+  }
+
+ private:
+  Heap<S, C, false> heap_;
+  vector<ssize_t> key_;
+
+  // This allows base-class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual StateId Head_() const { return Head(); }
+  virtual void Enqueue_(StateId s) { Enqueue(s); }
+  virtual void Dequeue_() { Dequeue(); }
+  virtual void Update_(StateId s) { Update(s); }
+  virtual bool Empty_() const { return Empty(); }
+  virtual void Clear_() { return Clear(); }
+};
+
+
+// Given a vector that maps from states to weights and a Less
+// comparison function object between weights, this class defines a
+// comparison function object between states.
+template <typename S, typename L>
+class StateWeightCompare {
+ public:
+  typedef L Less;
+  typedef typename L::Weight Weight;
+  typedef S StateId;
+
+  StateWeightCompare(const vector<Weight>& weights, const L &less)
+      : weights_(weights), less_(less) {}
+
+  bool operator()(const S x, const S y) const {
+    return less_(weights_[x], weights_[y]);
+  }
+
+ private:
+  const vector<Weight>& weights_;
+  L less_;
+};
+
+
+// Shortest-first queue discipline, templated on the StateId and Weight, is
+// specialized to use the weight's natural order for the comparison function.
+template <typename S, typename W>
+class NaturalShortestFirstQueue :
+      public ShortestFirstQueue<S, StateWeightCompare<S, NaturalLess<W> > > {
+ public:
+  typedef StateWeightCompare<S, NaturalLess<W> > C;
+
+  NaturalShortestFirstQueue(const vector<W> &distance) :
+      ShortestFirstQueue<S, C>(C(distance, less_)) {}
+
+ private:
+  NaturalLess<W> less_;
+};
+
+// Topological-order queue discipline, templated on the StateId.
+// States are ordered in the queue topologically. The FST must be acyclic.
+template <class S>
+class TopOrderQueue : public QueueBase<S> {
+ public:
+  typedef S StateId;
+
+  // This constructor computes the top. order. It accepts an arc filter
+  // to limit the transitions considered in that computation (e.g., only
+  // the epsilon graph).
+  template <class Arc, class ArcFilter>
+  TopOrderQueue(const Fst<Arc> &fst, ArcFilter filter)
+      : QueueBase<S>(TOP_ORDER_QUEUE), front_(0), back_(kNoStateId),
+        order_(0), state_(0) {
+    bool acyclic;
+    TopOrderVisitor<Arc> top_order_visitor(&order_, &acyclic);
+    DfsVisit(fst, &top_order_visitor, filter);
+    if (!acyclic) {
+      FSTERROR() << "TopOrderQueue: fst is not acyclic.";
+      QueueBase<S>::SetError(true);
+    }
+    state_.resize(order_.size(), kNoStateId);
+  }
+
+  // This constructor is passed the top. order, useful when we know it
+  // beforehand.
+  TopOrderQueue(const vector<StateId> &order)
+      : QueueBase<S>(TOP_ORDER_QUEUE), front_(0), back_(kNoStateId),
+        order_(order), state_(order.size(), kNoStateId) {}
+
+  StateId Head() const { return state_[front_]; }
+
+  void Enqueue(StateId s) {
+    if (front_ > back_) front_ = back_ = order_[s];
+    else if (order_[s] > back_) back_ = order_[s];
+    else if (order_[s] < front_) front_ = order_[s];
+    state_[order_[s]] = s;
+  }
+
+  void Dequeue() {
+    state_[front_] = kNoStateId;
+    while ((front_ <= back_) && (state_[front_] == kNoStateId)) ++front_;
+  }
+
+  void Update(StateId s) {}
+
+  bool Empty() const { return front_ > back_; }
+
+  void Clear() {
+    for (StateId i = front_; i <= back_; ++i) state_[i] = kNoStateId;
+    back_ = kNoStateId;
+    front_ = 0;
+  }
+
+ private:
+  StateId front_;
+  StateId back_;
+  vector<StateId> order_;
+  vector<StateId> state_;
+
+  // This allows base-class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual StateId Head_() const { return Head(); }
+  virtual void Enqueue_(StateId s) { Enqueue(s); }
+  virtual void Dequeue_() { Dequeue(); }
+  virtual void Update_(StateId s) { Update(s); }
+  virtual bool Empty_() const { return Empty(); }
+  virtual void Clear_() { return Clear(); }
+};
+
+
+// State order queue discipline, templated on the StateId.
+// States are ordered in the queue by state Id.
+template <class S>
+class StateOrderQueue : public QueueBase<S> {
+public:
+  typedef S StateId;
+
+  StateOrderQueue()
+      : QueueBase<S>(STATE_ORDER_QUEUE), front_(0), back_(kNoStateId) {}
+
+  StateId Head() const { return front_; }
+
+  void Enqueue(StateId s) {
+    if (front_ > back_) front_ = back_ = s;
+    else if (s > back_) back_ = s;
+    else if (s < front_) front_ = s;
+    while (enqueued_.size() <= s) enqueued_.push_back(false);
+    enqueued_[s] = true;
+  }
+
+  void Dequeue() {
+    enqueued_[front_] = false;
+    while ((front_ <= back_) && (enqueued_[front_] == false)) ++front_;
+  }
+
+  void Update(StateId s) {}
+
+  bool Empty() const { return front_ > back_; }
+
+  void Clear() {
+        for (StateId i = front_; i <= back_; ++i) enqueued_[i] = false;
+        front_ = 0;
+        back_ = kNoStateId;
+  }
+
+private:
+  StateId front_;
+  StateId back_;
+  vector<bool> enqueued_;
+
+  // This allows base-class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual StateId Head_() const { return Head(); }
+  virtual void Enqueue_(StateId s) { Enqueue(s); }
+  virtual void Dequeue_() { Dequeue(); }
+  virtual void Update_(StateId s) { Update(s); }
+  virtual bool Empty_() const { return Empty(); }
+  virtual void Clear_() { return Clear(); }
+
+};
+
+
+// SCC topological-order meta-queue discipline, templated on the StateId S
+// and a queue Q, which is used inside each SCC.  It visits the SCC's
+// of an FST in topological order. Its constructor is passed the queues to
+// to use within an SCC.
+template <class S, class Q>
+class SccQueue : public QueueBase<S> {
+ public:
+  typedef S StateId;
+  typedef Q Queue;
+
+  // Constructor takes a vector specifying the SCC number per state
+  // and a vector giving the queue to use per SCC number.
+  SccQueue(const vector<StateId> &scc, vector<Queue*> *queue)
+    : QueueBase<S>(SCC_QUEUE), queue_(queue), scc_(scc), front_(0),
+      back_(kNoStateId) {}
+
+  StateId Head() const {
+    while ((front_ <= back_) &&
+           (((*queue_)[front_] && (*queue_)[front_]->Empty())
+            || (((*queue_)[front_] == 0) &&
+                ((front_ > trivial_queue_.size())
+                 || (trivial_queue_[front_] == kNoStateId)))))
+      ++front_;
+    if ((*queue_)[front_])
+      return (*queue_)[front_]->Head();
+    else
+      return trivial_queue_[front_];
+  }
+
+  void Enqueue(StateId s) {
+    if (front_ > back_) front_ = back_ = scc_[s];
+    else if (scc_[s] > back_) back_ = scc_[s];
+    else if (scc_[s] < front_) front_ = scc_[s];
+    if ((*queue_)[scc_[s]]) {
+      (*queue_)[scc_[s]]->Enqueue(s);
+    } else {
+      while (trivial_queue_.size() <= scc_[s])
+        trivial_queue_.push_back(kNoStateId);
+      trivial_queue_[scc_[s]] = s;
+    }
+  }
+
+  void Dequeue() {
+    if ((*queue_)[front_])
+      (*queue_)[front_]->Dequeue();
+    else if (front_ < trivial_queue_.size())
+      trivial_queue_[front_] = kNoStateId;
+  }
+
+  void Update(StateId s) {
+    if ((*queue_)[scc_[s]])
+      (*queue_)[scc_[s]]->Update(s);
+  }
+
+  bool Empty() const {
+    if (front_ < back_)  // Queue scc # back_ not empty unless back_==front_
+      return false;
+    else if (front_ > back_)
+      return true;
+    else if ((*queue_)[front_])
+      return (*queue_)[front_]->Empty();
+    else
+      return (front_ > trivial_queue_.size())
+        || (trivial_queue_[front_] == kNoStateId);
+  }
+
+  void Clear() {
+    for (StateId i = front_; i <= back_; ++i)
+      if ((*queue_)[i])
+        (*queue_)[i]->Clear();
+      else if (i < trivial_queue_.size())
+        trivial_queue_[i] = kNoStateId;
+    front_ = 0;
+    back_ = kNoStateId;
+  }
+
+private:
+  vector<Queue*> *queue_;
+  const vector<StateId> &scc_;
+  mutable StateId front_;
+  StateId back_;
+  vector<StateId> trivial_queue_;
+
+  // This allows base-class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual StateId Head_() const { return Head(); }
+  virtual void Enqueue_(StateId s) { Enqueue(s); }
+  virtual void Dequeue_() { Dequeue(); }
+  virtual void Update_(StateId s) { Update(s); }
+  virtual bool Empty_() const { return Empty(); }
+  virtual void Clear_() { return Clear(); }
+
+  DISALLOW_COPY_AND_ASSIGN(SccQueue);
+};
+
+
+// Automatic queue discipline, templated on the StateId. It selects a
+// queue discipline for a given FST based on its properties.
+template <class S>
+class AutoQueue : public QueueBase<S> {
+public:
+  typedef S StateId;
+
+  // This constructor takes a state distance vector that, if non-null and if
+  // the Weight type has the path property, will entertain the
+  // shortest-first queue using the natural order w.r.t to the distance.
+  template <class Arc, class ArcFilter>
+  AutoQueue(const Fst<Arc> &fst, const vector<typename Arc::Weight> *distance,
+            ArcFilter filter) : QueueBase<S>(AUTO_QUEUE) {
+    typedef typename Arc::Weight Weight;
+    typedef StateWeightCompare< StateId, NaturalLess<Weight> > Compare;
+
+    //  First check if the FST is known to have these properties.
+    uint64 props = fst.Properties(kAcyclic | kCyclic |
+                                  kTopSorted | kUnweighted, false);
+    if ((props & kTopSorted) || fst.Start() == kNoStateId) {
+      queue_ = new StateOrderQueue<StateId>();
+      VLOG(2) << "AutoQueue: using state-order discipline";
+    } else if (props & kAcyclic) {
+      queue_ = new TopOrderQueue<StateId>(fst, filter);
+      VLOG(2) << "AutoQueue: using top-order discipline";
+    } else if ((props & kUnweighted) && (Weight::Properties() & kIdempotent)) {
+      queue_ = new LifoQueue<StateId>();
+      VLOG(2) << "AutoQueue: using LIFO discipline";
+    } else {
+      uint64 properties;
+      // Decompose into strongly-connected components.
+      SccVisitor<Arc> scc_visitor(&scc_, 0, 0, &properties);
+      DfsVisit(fst, &scc_visitor, filter);
+      StateId nscc = *max_element(scc_.begin(), scc_.end()) + 1;
+      vector<QueueType> queue_types(nscc);
+      NaturalLess<Weight> *less = 0;
+      Compare *comp = 0;
+      if (distance && (Weight::Properties() & kPath)) {
+        less = new NaturalLess<Weight>;
+        comp = new Compare(*distance, *less);
+      }
+      // Find the queue type to use per SCC.
+      bool unweighted;
+      bool all_trivial;
+      SccQueueType(fst, scc_, &queue_types, filter, less, &all_trivial,
+                                      &unweighted);
+      // If unweighted and semiring is idempotent, use lifo queue.
+      if (unweighted) {
+          queue_ = new LifoQueue<StateId>();
+          VLOG(2) << "AutoQueue: using LIFO discipline";
+          delete comp;
+          delete less;
+          return;
+      }
+      // If all the scc are trivial, FST is acyclic and the scc# gives
+      // the topological order.
+      if (all_trivial) {
+          queue_ = new TopOrderQueue<StateId>(scc_);
+          VLOG(2) << "AutoQueue: using top-order discipline";
+          delete comp;
+          delete less;
+          return;
+      }
+      VLOG(2) << "AutoQueue: using SCC meta-discipline";
+      queues_.resize(nscc);
+      for (StateId i = 0; i < nscc; ++i) {
+        switch(queue_types[i]) {
+          case TRIVIAL_QUEUE:
+            queues_[i] = 0;
+            VLOG(3) << "AutoQueue: SCC #" << i
+                    << ": using trivial discipline";
+            break;
+          case SHORTEST_FIRST_QUEUE:
+            queues_[i] = new ShortestFirstQueue<StateId, Compare, false>(*comp);
+            VLOG(3) << "AutoQueue: SCC #" << i <<
+              ": using shortest-first discipline";
+            break;
+          case LIFO_QUEUE:
+            queues_[i] = new LifoQueue<StateId>();
+            VLOG(3) << "AutoQueue: SCC #" << i
+                    << ": using LIFO disciplle";
+            break;
+          case FIFO_QUEUE:
+          default:
+            queues_[i] = new FifoQueue<StateId>();
+            VLOG(3) << "AutoQueue: SCC #" << i
+                    << ": using FIFO disciplle";
+            break;
+        }
+      }
+      queue_ = new SccQueue< StateId, QueueBase<StateId> >(scc_, &queues_);
+      delete comp;
+      delete less;
+    }
+  }
+
+  ~AutoQueue() {
+    for (StateId i = 0; i < queues_.size(); ++i)
+      delete queues_[i];
+    delete queue_;
+  }
+
+  StateId Head() const { return queue_->Head(); }
+
+  void Enqueue(StateId s) { queue_->Enqueue(s); }
+
+  void Dequeue() { queue_->Dequeue(); }
+
+  void Update(StateId s) { queue_->Update(s); }
+
+  bool Empty() const { return queue_->Empty(); }
+
+  void Clear() { queue_->Clear(); }
+
+
+ private:
+  QueueBase<StateId> *queue_;
+  vector< QueueBase<StateId>* > queues_;
+  vector<StateId> scc_;
+
+  template <class Arc, class ArcFilter, class Less>
+  static void SccQueueType(const Fst<Arc> &fst,
+                           const vector<StateId> &scc,
+                           vector<QueueType> *queue_types,
+                           ArcFilter filter, Less *less,
+                           bool *all_trivial, bool *unweighted);
+
+  // This allows base-class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual StateId Head_() const { return Head(); }
+
+  virtual void Enqueue_(StateId s) { Enqueue(s); }
+
+  virtual void Dequeue_() { Dequeue(); }
+
+  virtual void Update_(StateId s) { Update(s); }
+
+  virtual bool Empty_() const { return Empty(); }
+
+  virtual void Clear_() { return Clear(); }
+
+  DISALLOW_COPY_AND_ASSIGN(AutoQueue);
+};
+
+
+// Examines the states in an Fst's strongly connected components and
+// determines which type of queue to use per SCC. Stores result in
+// vector QUEUE_TYPES, which is assumed to have length equal to the
+// number of SCCs. An arc filter is used to limit the transitions
+// considered (e.g., only the epsilon graph).  ALL_TRIVIAL is set
+// to true if every queue is the trivial queue. UNWEIGHTED is set to
+// true if the semiring is idempotent and all the arc weights are equal to
+// Zero() or One().
+template <class StateId>
+template <class A, class ArcFilter, class Less>
+void AutoQueue<StateId>::SccQueueType(const Fst<A> &fst,
+                                      const vector<StateId> &scc,
+                                      vector<QueueType> *queue_type,
+                                      ArcFilter filter, Less *less,
+                                      bool *all_trivial, bool *unweighted) {
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  *all_trivial = true;
+  *unweighted = true;
+
+  for (StateId i = 0; i < queue_type->size(); ++i)
+    (*queue_type)[i] = TRIVIAL_QUEUE;
+
+  for (StateIterator< Fst<Arc> > sit(fst); !sit.Done(); sit.Next()) {
+    StateId state = sit.Value();
+    for (ArcIterator< Fst<Arc> > ait(fst, state);
+	 !ait.Done();
+	 ait.Next()) {
+      const Arc &arc = ait.Value();
+      if (!filter(arc)) continue;
+      if (scc[state] == scc[arc.nextstate]) {
+        QueueType &type = (*queue_type)[scc[state]];
+        if (!less || ((*less)(arc.weight, Weight::One())))
+          type = FIFO_QUEUE;
+        else if ((type == TRIVIAL_QUEUE) || (type == LIFO_QUEUE)) {
+          if (!(Weight::Properties() & kIdempotent) ||
+              (arc.weight != Weight::Zero() && arc.weight != Weight::One()))
+            type = SHORTEST_FIRST_QUEUE;
+          else
+            type = LIFO_QUEUE;
+        }
+        if (type != TRIVIAL_QUEUE) *all_trivial = false;
+      }
+      if (!(Weight::Properties() & kIdempotent) ||
+          (arc.weight != Weight::Zero() && arc.weight != Weight::One()))
+        *unweighted = false;
+    }
+  }
+}
+
+
+// An A* estimate is a function object that maps from a state ID to a
+// an estimate of the shortest distance to the final states.
+// The trivial A* estimate is always One().
+template <typename S, typename W>
+struct TrivialAStarEstimate {
+  W operator()(S s) const { return W::One(); }
+};
+
+
+// Given a vector that maps from states to weights representing the
+// shortest distance from the initial state, a Less comparison
+// function object between weights, and an estimate E of the
+// shortest distance to the final states, this class defines a
+// comparison function object between states.
+template <typename S, typename L, typename E>
+class AStarWeightCompare {
+ public:
+  typedef L Less;
+  typedef typename L::Weight Weight;
+  typedef S StateId;
+
+  AStarWeightCompare(const vector<Weight>& weights, const L &less,
+                     const E &estimate)
+      : weights_(weights), less_(less), estimate_(estimate) {}
+
+  bool operator()(const S x, const S y) const {
+    Weight wx = Times(weights_[x], estimate_(x));
+    Weight wy = Times(weights_[y], estimate_(y));
+    return less_(wx, wy);
+  }
+
+ private:
+  const vector<Weight>& weights_;
+  L less_;
+  const E &estimate_;
+};
+
+
+// A* queue discipline, templated on the StateId, Weight and an
+// estimate E of the shortest distance to the final states, is specialized
+// to use the weight's natural order for the comparison function.
+template <typename S, typename W, typename E>
+class NaturalAStarQueue :
+      public ShortestFirstQueue<S, AStarWeightCompare<S, NaturalLess<W>, E> > {
+ public:
+  typedef AStarWeightCompare<S, NaturalLess<W>, E> C;
+
+  NaturalAStarQueue(const vector<W> &distance, const E &estimate) :
+      ShortestFirstQueue<S, C>(C(distance, less_, estimate)) {}
+
+ private:
+  NaturalLess<W> less_;
+};
+
+
+// A state equivalence class is a function object that
+// maps from a state ID to an equivalence class (state) ID.
+// The trivial equivalence class maps a state to itself.
+template <typename S>
+struct TrivialStateEquivClass {
+  S operator()(S s) const { return s; }
+};
+
+
+// Pruning queue discipline: Enqueues a state 's' only when its
+// shortest distance (so far), as specified by 'distance', is less
+// than (as specified by 'comp') the shortest distance Times() the
+// 'threshold' to any state in the same equivalence class, as
+// specified by the function object 'class_func'. The underlying
+// queue discipline is specified by 'queue'. The ownership of 'queue'
+// is given to this class.
+template <typename Q, typename L, typename C>
+class PruneQueue : public QueueBase<typename Q::StateId> {
+ public:
+  typedef typename Q::StateId StateId;
+  typedef typename L::Weight Weight;
+
+  PruneQueue(const vector<Weight> &distance, Q *queue, L comp,
+	     const C &class_func, Weight threshold)
+    : QueueBase<StateId>(OTHER_QUEUE),
+      distance_(distance),
+      queue_(queue),
+      less_(comp),
+      class_func_(class_func),
+      threshold_(threshold) {}
+
+  ~PruneQueue() { delete queue_; }
+
+  StateId Head() const { return queue_->Head(); }
+
+  void Enqueue(StateId s) {
+    StateId c = class_func_(s);
+    if (c >= class_distance_.size())
+      class_distance_.resize(c + 1, Weight::Zero());
+    if (less_(distance_[s], class_distance_[c]))
+      class_distance_[c] = distance_[s];
+
+    // Enqueue only if below threshold limit
+    Weight limit = Times(class_distance_[c], threshold_);
+    if (less_(distance_[s], limit))
+      queue_->Enqueue(s);
+  }
+
+  void Dequeue() { queue_->Dequeue(); }
+
+  void Update(StateId s) {
+    StateId c = class_func_(s);
+    if (less_(distance_[s], class_distance_[c]))
+      class_distance_[c] = distance_[s];
+    queue_->Update(s);
+  }
+
+  bool Empty() const { return queue_->Empty(); }
+  void Clear() { queue_->Clear(); }
+
+ private:
+  // This allows base-class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual StateId Head_() const { return Head(); }
+  virtual void Enqueue_(StateId s) { Enqueue(s); }
+  virtual void Dequeue_() { Dequeue(); }
+  virtual void Update_(StateId s) { Update(s); }
+  virtual bool Empty_() const { return Empty(); }
+  virtual void Clear_() { return Clear(); }
+
+  const vector<Weight> &distance_;         // shortest distance to state
+  Q *queue_;
+  L less_;
+  const C &class_func_;                    // eqv. class function object
+  Weight threshold_;                       // pruning weight threshold
+  vector<Weight> class_distance_;          // shortest distance to class
+
+  DISALLOW_COPY_AND_ASSIGN(PruneQueue);
+};
+
+
+// Pruning queue discipline (see above) using the weight's natural
+// order for the comparison function. The ownership of 'queue' is
+// given to this class.
+template <typename Q, typename W, typename C>
+class NaturalPruneQueue :
+      public PruneQueue<Q, NaturalLess<W>, C> {
+ public:
+  typedef typename Q::StateId StateId;
+  typedef W Weight;
+
+  NaturalPruneQueue(const vector<W> &distance, Q *queue,
+                    const C &class_func_, Weight threshold) :
+      PruneQueue<Q, NaturalLess<W>, C>(distance, queue, less_,
+                                       class_func_, threshold) {}
+
+ private:
+  NaturalLess<W> less_;
+};
+
+
+}  // namespace fst
+
+#endif
diff --git a/src/include/fst/randequivalent.h b/src/include/fst/randequivalent.h
new file mode 100644
index 0000000..1aaccf7
--- /dev/null
+++ b/src/include/fst/randequivalent.h
@@ -0,0 +1,135 @@
+// randequivalent.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Tests if two FSTS are equivalent by checking if random
+// strings from one FST are transduced the same by both FSTs.
+
+#ifndef FST_RANDEQUIVALENT_H__
+#define FST_RANDEQUIVALENT_H__
+
+#include <fst/arcsort.h>
+#include <fst/compose.h>
+#include <fst/project.h>
+#include <fst/randgen.h>
+#include <fst/shortest-distance.h>
+#include <fst/vector-fst.h>
+
+
+namespace fst {
+
+// Test if two FSTs are equivalent by randomly generating 'num_paths'
+// paths (as specified by the RandGenOptions 'opts') in these FSTs.
+//
+// For each randomly generated path, the algorithm computes for each
+// of the two FSTs the sum of the weights of all the successful paths
+// sharing the same input and output labels as the considered randomly
+// generated path and checks that these two values are within
+// 'delta'. Returns optional error value (when FLAGS_error_fatal = false).
+template<class Arc, class ArcSelector>
+bool RandEquivalent(const Fst<Arc> &fst1, const Fst<Arc> &fst2,
+                    ssize_t num_paths, float delta,
+                    const RandGenOptions<ArcSelector> &opts,
+                    bool *error = 0) {
+  typedef typename Arc::Weight Weight;
+  if (error) *error = false;
+
+  // Check that the symbol table are compatible
+  if (!CompatSymbols(fst1.InputSymbols(), fst2.InputSymbols()) ||
+      !CompatSymbols(fst1.OutputSymbols(), fst2.OutputSymbols())) {
+    FSTERROR() << "RandEquivalent: input/output symbol tables of 1st "
+               << "argument do not match input/output symbol tables of 2nd "
+               << "argument";
+    if (error) *error = true;
+    return false;
+  }
+
+  ILabelCompare<Arc> icomp;
+  OLabelCompare<Arc> ocomp;
+  VectorFst<Arc> sfst1(fst1);
+  VectorFst<Arc> sfst2(fst2);
+  Connect(&sfst1);
+  Connect(&sfst2);
+  ArcSort(&sfst1, icomp);
+  ArcSort(&sfst2, icomp);
+
+  bool ret = true;
+  for (ssize_t n = 0; n < num_paths; ++n) {
+    VectorFst<Arc> path;
+    const Fst<Arc> &fst = rand() % 2 ? sfst1 : sfst2;
+    RandGen(fst, &path, opts);
+
+    VectorFst<Arc> ipath(path);
+    VectorFst<Arc> opath(path);
+    Project(&ipath, PROJECT_INPUT);
+    Project(&opath, PROJECT_OUTPUT);
+
+    VectorFst<Arc> cfst1, pfst1;
+    Compose(ipath, sfst1, &cfst1);
+    ArcSort(&cfst1, ocomp);
+    Compose(cfst1, opath, &pfst1);
+    // Give up if there are epsilon cycles in a non-idempotent semiring
+    if (!(Weight::Properties() & kIdempotent) &&
+        pfst1.Properties(kCyclic, true))
+      continue;
+    Weight sum1 = ShortestDistance(pfst1);
+
+    VectorFst<Arc> cfst2, pfst2;
+    Compose(ipath, sfst2, &cfst2);
+    ArcSort(&cfst2, ocomp);
+    Compose(cfst2, opath, &pfst2);
+    // Give up if there are epsilon cycles in a non-idempotent semiring
+    if (!(Weight::Properties() & kIdempotent) &&
+        pfst2.Properties(kCyclic, true))
+      continue;
+    Weight sum2 = ShortestDistance(pfst2);
+
+    if (!ApproxEqual(sum1, sum2, delta)) {
+        VLOG(1) << "Sum1 = " << sum1;
+        VLOG(1) << "Sum2 = " << sum2;
+        ret = false;
+        break;
+    }
+  }
+
+  if (fst1.Properties(kError, false) || fst2.Properties(kError, false)) {
+    if (error) *error = true;
+    return false;
+  }
+
+  return ret;
+}
+
+
+// Test if two FSTs are equivalent by randomly generating 'num_paths' paths
+// of length no more than 'path_length' using the seed 'seed' in these FSTs.
+// Returns optional error value (when FLAGS_error_fatal = false).
+template <class Arc>
+bool RandEquivalent(const Fst<Arc> &fst1, const Fst<Arc> &fst2,
+                    ssize_t num_paths, float delta = kDelta,
+                    int seed = time(0), int path_length = INT_MAX,
+                    bool *error = 0) {
+  UniformArcSelector<Arc> uniform_selector(seed);
+  RandGenOptions< UniformArcSelector<Arc> >
+      opts(uniform_selector, path_length);
+  return RandEquivalent(fst1, fst2, num_paths, delta, opts, error);
+}
+
+
+}  // namespace fst
+
+#endif  // FST_LIB_RANDEQUIVALENT_H__
diff --git a/src/include/fst/randgen.h b/src/include/fst/randgen.h
new file mode 100644
index 0000000..82ddffa
--- /dev/null
+++ b/src/include/fst/randgen.h
@@ -0,0 +1,712 @@
+// randgen.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Classes and functions to generate random paths through an FST.
+
+#ifndef FST_LIB_RANDGEN_H__
+#define FST_LIB_RANDGEN_H__
+
+#include <cmath>
+#include <cstdlib>
+#include <ctime>
+#include <map>
+
+#include <fst/accumulator.h>
+#include <fst/cache.h>
+#include <fst/dfs-visit.h>
+#include <fst/mutable-fst.h>
+
+namespace fst {
+
+//
+// ARC SELECTORS - these function objects are used to select a random
+// transition to take from an FST's state. They should return a number
+// N s.t. 0 <= N <= NumArcs(). If N < NumArcs(), then the N-th
+// transition is selected. If N == NumArcs(), then the final weight at
+// that state is selected (i.e., the 'super-final' transition is selected).
+// It can be assumed these will not be called unless either there
+// are transitions leaving the state and/or the state is final.
+//
+
+// Randomly selects a transition using the uniform distribution.
+template <class A>
+struct UniformArcSelector {
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  UniformArcSelector(int seed = time(0)) { srand(seed); }
+
+  size_t operator()(const Fst<A> &fst, StateId s) const {
+    double r = rand()/(RAND_MAX + 1.0);
+    size_t n = fst.NumArcs(s);
+    if (fst.Final(s) != Weight::Zero())
+      ++n;
+    return static_cast<size_t>(r * n);
+  }
+};
+
+
+// Randomly selects a transition w.r.t. the weights treated as negative
+// log probabilities after normalizing for the total weight leaving
+// the state. Weight::zero transitions are disregarded.
+// Assumes Weight::Value() accesses the floating point
+// representation of the weight.
+template <class A>
+class LogProbArcSelector {
+ public:
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  LogProbArcSelector(int seed = time(0)) { srand(seed); }
+
+  size_t operator()(const Fst<A> &fst, StateId s) const {
+    // Find total weight leaving state
+    double sum = 0.0;
+    for (ArcIterator< Fst<A> > aiter(fst, s); !aiter.Done();
+         aiter.Next()) {
+      const A &arc = aiter.Value();
+      sum += exp(-to_log_weight_(arc.weight).Value());
+    }
+    sum += exp(-to_log_weight_(fst.Final(s)).Value());
+
+    double r = rand()/(RAND_MAX + 1.0);
+    double p = 0.0;
+    int n = 0;
+    for (ArcIterator< Fst<A> > aiter(fst, s); !aiter.Done();
+         aiter.Next(), ++n) {
+      const A &arc = aiter.Value();
+      p += exp(-to_log_weight_(arc.weight).Value());
+      if (p > r * sum) return n;
+    }
+    return n;
+  }
+
+ private:
+  WeightConvert<Weight, Log64Weight> to_log_weight_;
+};
+
+// Convenience definitions
+typedef LogProbArcSelector<StdArc> StdArcSelector;
+typedef LogProbArcSelector<LogArc> LogArcSelector;
+
+
+// Same as LogProbArcSelector but use CacheLogAccumulator to cache
+// the cummulative weight computations.
+template <class A>
+class FastLogProbArcSelector : public LogProbArcSelector<A> {
+ public:
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+  using LogProbArcSelector<A>::operator();
+
+  FastLogProbArcSelector(int seed = time(0))
+      : LogProbArcSelector<A>(seed),
+        seed_(seed) {}
+
+  size_t operator()(const Fst<A> &fst, StateId s,
+                    CacheLogAccumulator<A> *accumulator) const {
+    accumulator->SetState(s);
+    ArcIterator< Fst<A> > aiter(fst, s);
+    // Find total weight leaving state
+    double sum = to_log_weight_(accumulator->Sum(fst.Final(s), &aiter, 0,
+                                                 fst.NumArcs(s))).Value();
+    double r = -log(rand()/(RAND_MAX + 1.0));
+    return accumulator->LowerBound(r + sum, &aiter);
+  }
+
+  int Seed() const { return seed_; }
+ private:
+  int seed_;
+  WeightConvert<Weight, Log64Weight> to_log_weight_;
+};
+
+// Random path state info maintained by RandGenFst and passed to samplers.
+template <typename A>
+struct RandState {
+  typedef typename A::StateId StateId;
+
+  StateId state_id;              // current input FST state
+  size_t nsamples;               // # of samples to be sampled at this state
+  size_t length;                 // length of path to this random state
+  size_t select;                 // previous sample arc selection
+  const RandState<A> *parent;    // previous random state on this path
+
+  RandState(StateId s, size_t n, size_t l, size_t k, const RandState<A> *p)
+      : state_id(s), nsamples(n), length(l), select(k), parent(p) {}
+
+  RandState()
+      : state_id(kNoStateId), nsamples(0), length(0), select(0), parent(0) {}
+};
+
+// This class, given an arc selector, samples, with raplacement,
+// multiple random transitions from an FST's state. This is a generic
+// version with a straight-forward use of the arc selector.
+// Specializations may be defined for arc selectors for greater
+// efficiency or special behavior.
+template <class A, class S>
+class ArcSampler {
+ public:
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  // The 'max_length' may be interpreted (including ignored) by a
+  // sampler as it chooses. This generic version interprets this literally.
+  ArcSampler(const Fst<A> &fst, const S &arc_selector,
+             int max_length = INT_MAX)
+      : fst_(fst),
+        arc_selector_(arc_selector),
+        max_length_(max_length) {}
+
+  // Allow updating Fst argument; pass only if changed.
+  ArcSampler(const ArcSampler<A, S> &sampler, const Fst<A> *fst = 0)
+      : fst_(fst ? *fst : sampler.fst_),
+        arc_selector_(sampler.arc_selector_),
+        max_length_(sampler.max_length_) {
+    Reset();
+  }
+
+  // Samples 'rstate.nsamples' from state 'state_id'. The 'rstate.length' is
+  // the length of the path to 'rstate'. Returns true if samples were
+  // collected.  No samples may be collected if either there are no (including
+  // 'super-final') transitions leaving that state or if the
+  // 'max_length' has been deemed reached. Use the iterator members to
+  // read the samples. The samples will be in their original order.
+  bool Sample(const RandState<A> &rstate) {
+    sample_map_.clear();
+    if ((fst_.NumArcs(rstate.state_id) == 0 &&
+         fst_.Final(rstate.state_id) == Weight::Zero()) ||
+        rstate.length == max_length_) {
+      Reset();
+      return false;
+    }
+
+    for (size_t i = 0; i < rstate.nsamples; ++i)
+      ++sample_map_[arc_selector_(fst_, rstate.state_id)];
+    Reset();
+    return true;
+  }
+
+  // More samples?
+  bool Done() const { return sample_iter_ == sample_map_.end(); }
+
+  // Gets the next sample.
+  void Next() { ++sample_iter_; }
+
+  // Returns a pair (N, K) where 0 <= N <= NumArcs(s) and 0 < K <= nsamples.
+  // If N < NumArcs(s), then the N-th transition is specified.
+  // If N == NumArcs(s), then the final weight at that state is
+  // specified (i.e., the 'super-final' transition is specified).
+  // For the specified transition, K repetitions have been sampled.
+  pair<size_t, size_t> Value() const { return *sample_iter_; }
+
+  void Reset() { sample_iter_ = sample_map_.begin(); }
+
+  bool Error() const { return false; }
+
+ private:
+  const Fst<A> &fst_;
+  const S &arc_selector_;
+  int max_length_;
+
+  // Stores (N, K) as described for Value().
+  map<size_t, size_t> sample_map_;
+  map<size_t, size_t>::const_iterator sample_iter_;
+
+  // disallow
+  ArcSampler<A, S> & operator=(const ArcSampler<A, S> &s);
+};
+
+
+// Specialization for FastLogProbArcSelector.
+template <class A>
+class ArcSampler<A, FastLogProbArcSelector<A> > {
+ public:
+  typedef FastLogProbArcSelector<A> S;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+  typedef CacheLogAccumulator<A> C;
+
+  ArcSampler(const Fst<A> &fst, const S &arc_selector, int max_length = INT_MAX)
+      : fst_(fst),
+        arc_selector_(arc_selector),
+        max_length_(max_length),
+        accumulator_(new C()) {
+    accumulator_->Init(fst);
+  }
+
+  ArcSampler(const ArcSampler<A, S> &sampler, const Fst<A> *fst = 0)
+      : fst_(fst ? *fst : sampler.fst_),
+        arc_selector_(sampler.arc_selector_),
+        max_length_(sampler.max_length_) {
+    if (fst) {
+      accumulator_ = new C();
+      accumulator_->Init(*fst);
+    } else {  // shallow copy
+      accumulator_ = new C(*sampler.accumulator_);
+    }
+  }
+
+  ~ArcSampler() {
+    delete accumulator_;
+  }
+
+  bool Sample(const RandState<A> &rstate) {
+    sample_map_.clear();
+    if ((fst_.NumArcs(rstate.state_id) == 0 &&
+         fst_.Final(rstate.state_id) == Weight::Zero()) ||
+        rstate.length == max_length_) {
+      Reset();
+      return false;
+    }
+
+    for (size_t i = 0; i < rstate.nsamples; ++i)
+      ++sample_map_[arc_selector_(fst_, rstate.state_id, accumulator_)];
+    Reset();
+    return true;
+  }
+
+  bool Done() const { return sample_iter_ == sample_map_.end(); }
+  void Next() { ++sample_iter_; }
+  pair<size_t, size_t> Value() const { return *sample_iter_; }
+  void Reset() { sample_iter_ = sample_map_.begin(); }
+
+  bool Error() const { return accumulator_->Error(); }
+
+ private:
+  const Fst<A> &fst_;
+  const S &arc_selector_;
+  int max_length_;
+
+  // Stores (N, K) as described for Value().
+  map<size_t, size_t> sample_map_;
+  map<size_t, size_t>::const_iterator sample_iter_;
+  C *accumulator_;
+
+  // disallow
+  ArcSampler<A, S> & operator=(const ArcSampler<A, S> &s);
+};
+
+
+// Options for random path generation with RandGenFst. The template argument
+// is an arc sampler, typically class 'ArcSampler' above.  Ownership of
+// the sampler is taken by RandGenFst.
+template <class S>
+struct RandGenFstOptions : public CacheOptions {
+  S *arc_sampler;            // How to sample transitions at a state
+  size_t npath;              // # of paths to generate
+  bool weighted;             // Output tree weighted by path count; o.w.
+                             // output unweighted DAG
+  bool remove_total_weight;  // Remove total weight when output is weighted.
+
+  RandGenFstOptions(const CacheOptions &copts, S *samp,
+                    size_t n = 1, bool w = true, bool rw = false)
+      : CacheOptions(copts),
+        arc_sampler(samp),
+        npath(n),
+        weighted(w),
+        remove_total_weight(rw) {}
+};
+
+
+// Implementation of RandGenFst.
+template <class A, class B, class S>
+class RandGenFstImpl : public CacheImpl<B> {
+ public:
+  using FstImpl<B>::SetType;
+  using FstImpl<B>::SetProperties;
+  using FstImpl<B>::SetInputSymbols;
+  using FstImpl<B>::SetOutputSymbols;
+
+  using CacheBaseImpl< CacheState<B> >::AddArc;
+  using CacheBaseImpl< CacheState<B> >::HasArcs;
+  using CacheBaseImpl< CacheState<B> >::HasFinal;
+  using CacheBaseImpl< CacheState<B> >::HasStart;
+  using CacheBaseImpl< CacheState<B> >::SetArcs;
+  using CacheBaseImpl< CacheState<B> >::SetFinal;
+  using CacheBaseImpl< CacheState<B> >::SetStart;
+
+  typedef B Arc;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  RandGenFstImpl(const Fst<A> &fst, const RandGenFstOptions<S> &opts)
+      : CacheImpl<B>(opts),
+        fst_(fst.Copy()),
+        arc_sampler_(opts.arc_sampler),
+        npath_(opts.npath),
+        weighted_(opts.weighted),
+        remove_total_weight_(opts.remove_total_weight),
+        superfinal_(kNoLabel) {
+    SetType("randgen");
+
+    uint64 props = fst.Properties(kFstProperties, false);
+    SetProperties(RandGenProperties(props, weighted_), kCopyProperties);
+
+    SetInputSymbols(fst.InputSymbols());
+    SetOutputSymbols(fst.OutputSymbols());
+  }
+
+  RandGenFstImpl(const RandGenFstImpl &impl)
+    : CacheImpl<B>(impl),
+      fst_(impl.fst_->Copy(true)),
+      arc_sampler_(new S(*impl.arc_sampler_, fst_)),
+      npath_(impl.npath_),
+      weighted_(impl.weighted_),
+      superfinal_(kNoLabel) {
+    SetType("randgen");
+    SetProperties(impl.Properties(), kCopyProperties);
+    SetInputSymbols(impl.InputSymbols());
+    SetOutputSymbols(impl.OutputSymbols());
+  }
+
+  ~RandGenFstImpl() {
+    for (int i = 0; i < state_table_.size(); ++i)
+      delete state_table_[i];
+    delete fst_;
+    delete arc_sampler_;
+  }
+
+  StateId Start() {
+    if (!HasStart()) {
+      StateId s = fst_->Start();
+      if (s == kNoStateId)
+        return kNoStateId;
+      StateId start = state_table_.size();
+      SetStart(start);
+      RandState<A> *rstate = new RandState<A>(s, npath_, 0, 0, 0);
+      state_table_.push_back(rstate);
+    }
+    return CacheImpl<B>::Start();
+  }
+
+  Weight Final(StateId s) {
+    if (!HasFinal(s)) {
+      Expand(s);
+    }
+    return CacheImpl<B>::Final(s);
+  }
+
+  size_t NumArcs(StateId s) {
+    if (!HasArcs(s)) {
+      Expand(s);
+    }
+    return CacheImpl<B>::NumArcs(s);
+  }
+
+  size_t NumInputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<B>::NumInputEpsilons(s);
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<B>::NumOutputEpsilons(s);
+  }
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if ((mask & kError) &&
+        (fst_->Properties(kError, false) || arc_sampler_->Error())) {
+      SetProperties(kError, kError);
+    }
+    return FstImpl<Arc>::Properties(mask);
+  }
+
+  void InitArcIterator(StateId s, ArcIteratorData<B> *data) {
+    if (!HasArcs(s))
+      Expand(s);
+    CacheImpl<B>::InitArcIterator(s, data);
+  }
+
+  // Computes the outgoing transitions from a state, creating new destination
+  // states as needed.
+  void Expand(StateId s) {
+    if (s == superfinal_) {
+      SetFinal(s, Weight::One());
+      SetArcs(s);
+      return;
+    }
+
+    SetFinal(s, Weight::Zero());
+    const RandState<A> &rstate = *state_table_[s];
+    arc_sampler_->Sample(rstate);
+    ArcIterator< Fst<A> > aiter(*fst_, rstate.state_id);
+    size_t narcs = fst_->NumArcs(rstate.state_id);
+    for (;!arc_sampler_->Done(); arc_sampler_->Next()) {
+      const pair<size_t, size_t> &sample_pair = arc_sampler_->Value();
+      size_t pos = sample_pair.first;
+      size_t count = sample_pair.second;
+      double prob = static_cast<double>(count)/rstate.nsamples;
+      if (pos < narcs) {  // regular transition
+        aiter.Seek(sample_pair.first);
+        const A &aarc = aiter.Value();
+        Weight weight = weighted_ ? to_weight_(-log(prob)) : Weight::One();
+        B barc(aarc.ilabel, aarc.olabel, weight, state_table_.size());
+        AddArc(s, barc);
+        RandState<A> *nrstate =
+            new RandState<A>(aarc.nextstate, count, rstate.length + 1,
+                             pos, &rstate);
+        state_table_.push_back(nrstate);
+      } else {            // super-final transition
+        if (weighted_) {
+          Weight weight = remove_total_weight_ ?
+              to_weight_(-log(prob)) : to_weight_(-log(prob * npath_));
+          SetFinal(s, weight);
+        } else {
+          if (superfinal_ == kNoLabel) {
+            superfinal_ = state_table_.size();
+            RandState<A> *nrstate = new RandState<A>(kNoStateId, 0, 0, 0, 0);
+            state_table_.push_back(nrstate);
+          }
+          for (size_t n = 0; n < count; ++n) {
+            B barc(0, 0, Weight::One(), superfinal_);
+            AddArc(s, barc);
+          }
+        }
+      }
+    }
+    SetArcs(s);
+  }
+
+ private:
+  Fst<A> *fst_;
+  S *arc_sampler_;
+  size_t npath_;
+  vector<RandState<A> *> state_table_;
+  bool weighted_;
+  bool remove_total_weight_;
+  StateId superfinal_;
+  WeightConvert<Log64Weight, Weight> to_weight_;
+
+  void operator=(const RandGenFstImpl<A, B, S> &);  // disallow
+};
+
+
+// Fst class to randomly generate paths through an FST; details controlled
+// by RandGenOptionsFst. Output format is a tree weighted by the
+// path count.
+template <class A, class B, class S>
+class RandGenFst : public ImplToFst< RandGenFstImpl<A, B, S> > {
+ public:
+  friend class ArcIterator< RandGenFst<A, B, S> >;
+  friend class StateIterator< RandGenFst<A, B, S> >;
+  typedef B Arc;
+  typedef S Sampler;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef CacheState<B> State;
+  typedef RandGenFstImpl<A, B, S> Impl;
+
+  RandGenFst(const Fst<A> &fst, const RandGenFstOptions<S> &opts)
+    : ImplToFst<Impl>(new Impl(fst, opts)) {}
+
+  // See Fst<>::Copy() for doc.
+ RandGenFst(const RandGenFst<A, B, S> &fst, bool safe = false)
+    : ImplToFst<Impl>(fst, safe) {}
+
+  // Get a copy of this RandGenFst. See Fst<>::Copy() for further doc.
+  virtual RandGenFst<A, B, S> *Copy(bool safe = false) const {
+    return new RandGenFst<A, B, S>(*this, safe);
+  }
+
+  virtual inline void InitStateIterator(StateIteratorData<B> *data) const;
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<B> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+ private:
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const RandGenFst<A, B, S> &fst);  // Disallow
+};
+
+
+
+// Specialization for RandGenFst.
+template <class A, class B, class S>
+class StateIterator< RandGenFst<A, B, S> >
+    : public CacheStateIterator< RandGenFst<A, B, S> > {
+ public:
+  explicit StateIterator(const RandGenFst<A, B, S> &fst)
+    : CacheStateIterator< RandGenFst<A, B, S> >(fst, fst.GetImpl()) {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(StateIterator);
+};
+
+
+// Specialization for RandGenFst.
+template <class A, class B, class S>
+class ArcIterator< RandGenFst<A, B, S> >
+    : public CacheArcIterator< RandGenFst<A, B, S> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const RandGenFst<A, B, S> &fst, StateId s)
+      : CacheArcIterator< RandGenFst<A, B, S> >(fst.GetImpl(), s) {
+    if (!fst.GetImpl()->HasArcs(s))
+      fst.GetImpl()->Expand(s);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+
+template <class A, class B, class S> inline
+void RandGenFst<A, B, S>::InitStateIterator(StateIteratorData<B> *data) const
+{
+  data->base = new StateIterator< RandGenFst<A, B, S> >(*this);
+}
+
+// Options for random path generation.
+template <class S>
+struct RandGenOptions {
+  const S &arc_selector;     // How an arc is selected at a state
+  int max_length;            // Maximum path length
+  size_t npath;              // # of paths to generate
+  bool weighted;             // Output is tree weighted by path count; o.w.
+                             // output unweighted union of paths.
+  bool remove_total_weight;  // Remove total weight when output is weighted.
+
+  RandGenOptions(const S &sel, int len = INT_MAX, size_t n = 1,
+                 bool w = false, bool rw = false)
+      : arc_selector(sel),
+        max_length(len),
+        npath(n),
+        weighted(w),
+        remove_total_weight(rw) {}
+};
+
+
+template <class IArc, class OArc>
+class RandGenVisitor {
+ public:
+  typedef typename IArc::Weight Weight;
+  typedef typename IArc::StateId StateId;
+
+  RandGenVisitor(MutableFst<OArc> *ofst) : ofst_(ofst) {}
+
+  void InitVisit(const Fst<IArc> &ifst) {
+    ifst_ = &ifst;
+
+    ofst_->DeleteStates();
+    ofst_->SetInputSymbols(ifst.InputSymbols());
+    ofst_->SetOutputSymbols(ifst.OutputSymbols());
+    if (ifst.Properties(kError, false))
+      ofst_->SetProperties(kError, kError);
+    path_.clear();
+  }
+
+  bool InitState(StateId s, StateId root) { return true; }
+
+  bool TreeArc(StateId s, const IArc &arc) {
+    if (ifst_->Final(arc.nextstate) == Weight::Zero()) {
+      path_.push_back(arc);
+    } else {
+      OutputPath();
+    }
+    return true;
+  }
+
+  bool BackArc(StateId s, const IArc &arc) {
+    FSTERROR() << "RandGenVisitor: cyclic input";
+    ofst_->SetProperties(kError, kError);
+    return false;
+  }
+
+  bool ForwardOrCrossArc(StateId s, const IArc &arc) {
+    OutputPath();
+    return true;
+  }
+
+  void FinishState(StateId s, StateId p, const IArc *) {
+    if (p != kNoStateId && ifst_->Final(s) == Weight::Zero())
+      path_.pop_back();
+  }
+
+  void FinishVisit() {}
+
+ private:
+  void OutputPath() {
+    if (ofst_->Start() == kNoStateId) {
+      StateId start = ofst_->AddState();
+      ofst_->SetStart(start);
+    }
+
+    StateId src = ofst_->Start();
+    for (size_t i = 0; i < path_.size(); ++i) {
+      StateId dest = ofst_->AddState();
+      OArc arc(path_[i].ilabel, path_[i].olabel, Weight::One(), dest);
+      ofst_->AddArc(src, arc);
+      src = dest;
+    }
+    ofst_->SetFinal(src, Weight::One());
+  }
+
+  const Fst<IArc> *ifst_;
+  MutableFst<OArc> *ofst_;
+  vector<OArc> path_;
+
+  DISALLOW_COPY_AND_ASSIGN(RandGenVisitor);
+};
+
+
+// Randomly generate paths through an FST; details controlled by
+// RandGenOptions.
+template<class IArc, class OArc, class Selector>
+void RandGen(const Fst<IArc> &ifst, MutableFst<OArc> *ofst,
+             const RandGenOptions<Selector> &opts) {
+  typedef ArcSampler<IArc, Selector> Sampler;
+  typedef RandGenFst<IArc, OArc, Sampler> RandFst;
+  typedef typename OArc::StateId StateId;
+  typedef typename OArc::Weight Weight;
+
+  Sampler* arc_sampler = new Sampler(ifst, opts.arc_selector, opts.max_length);
+  RandGenFstOptions<Sampler> fopts(CacheOptions(true, 0), arc_sampler,
+                                   opts.npath, opts.weighted,
+                                   opts.remove_total_weight);
+  RandFst rfst(ifst, fopts);
+  if (opts.weighted) {
+    *ofst = rfst;
+  } else {
+    RandGenVisitor<IArc, OArc> rand_visitor(ofst);
+    DfsVisit(rfst, &rand_visitor);
+  }
+}
+
+// Randomly generate a path through an FST with the uniform distribution
+// over the transitions.
+template<class IArc, class OArc>
+void RandGen(const Fst<IArc> &ifst, MutableFst<OArc> *ofst) {
+  UniformArcSelector<IArc> uniform_selector;
+  RandGenOptions< UniformArcSelector<IArc> > opts(uniform_selector);
+  RandGen(ifst, ofst, opts);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_RANDGEN_H__
diff --git a/src/include/fst/random-weight.h b/src/include/fst/random-weight.h
new file mode 100644
index 0000000..0ccd95d
--- /dev/null
+++ b/src/include/fst/random-weight.h
@@ -0,0 +1,348 @@
+// random-weight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Function objects to generate random weights in various semirings
+// for testing purposes.
+
+#ifndef FST_LIB_RANDOM_WEIGHT_H__
+#define FST_LIB_RANDOM_WEIGHT_H__
+
+#include <cstdlib>
+#include <ctime>
+#include <vector>
+using std::vector;
+
+
+#include <fst/float-weight.h>
+#include <fst/product-weight.h>
+#include <fst/string-weight.h>
+#include <fst/lexicographic-weight.h>
+#include <fst/power-weight.h>
+#include <fst/signed-log-weight.h>
+#include <fst/sparse-power-weight.h>
+
+
+namespace fst {
+
+// The boolean 'allow_zero' below determines whether Zero() and zero
+// divisors should be returned in the random weight generation.
+
+// This function object returns TropicalWeightTpl<T>'s that are random integers
+// chosen from [0, kNumRandomWeights).
+template <class T>
+class TropicalWeightGenerator_ {
+ public:
+  typedef TropicalWeightTpl<T> Weight;
+
+  TropicalWeightGenerator_(int seed = time(0), bool allow_zero = true)
+      : allow_zero_(allow_zero) {
+    srand(seed);
+  }
+
+  Weight operator() () const {
+    int n = rand() % (kNumRandomWeights + allow_zero_);
+    if (allow_zero_ && n == kNumRandomWeights)
+      return Weight::Zero();
+
+    return Weight(static_cast<T>(n));
+  }
+
+ private:
+  // The number of alternative random weights.
+  static const int kNumRandomWeights = 5;
+
+  bool allow_zero_;  // permit Zero() and zero divisors
+};
+
+template <class T> const int TropicalWeightGenerator_<T>::kNumRandomWeights;
+
+typedef TropicalWeightGenerator_<float> TropicalWeightGenerator;
+
+
+// This function object returns LogWeightTpl<T>'s that are random integers
+// chosen from [0, kNumRandomWeights).
+template <class T>
+class LogWeightGenerator_ {
+ public:
+  typedef LogWeightTpl<T> Weight;
+
+  LogWeightGenerator_(int seed = time(0), bool allow_zero = true)
+      : allow_zero_(allow_zero) {
+    srand(seed);
+  }
+
+  Weight operator() () const {
+    int n = rand() % (kNumRandomWeights + allow_zero_);
+    if (allow_zero_ && n == kNumRandomWeights)
+      return Weight::Zero();
+
+    return Weight(static_cast<T>(n));
+  }
+
+ private:
+  // Number of alternative random weights.
+  static const int kNumRandomWeights = 5;
+
+  bool allow_zero_;  // permit Zero() and zero divisors
+};
+
+template <class T> const int LogWeightGenerator_<T>::kNumRandomWeights;
+
+typedef LogWeightGenerator_<float> LogWeightGenerator;
+
+
+// This function object returns MinMaxWeightTpl<T>'s that are random integers
+// chosen from (-kNumRandomWeights, kNumRandomWeights) in addition to
+// One(), and Zero() if zero is allowed.
+template <class T>
+class MinMaxWeightGenerator_ {
+ public:
+  typedef MinMaxWeightTpl<T> Weight;
+
+  MinMaxWeightGenerator_(int seed = time(0), bool allow_zero = true)
+      : allow_zero_(allow_zero) {
+    srand(seed);
+  }
+
+  Weight operator() () const {
+    int n = (rand() % (2*kNumRandomWeights + allow_zero_)) - kNumRandomWeights;
+    if (allow_zero_ && n == kNumRandomWeights)
+      return Weight::Zero();
+    else if (n == -kNumRandomWeights)
+      return Weight::One();
+
+    return Weight(static_cast<T>(n));
+  }
+
+ private:
+  // Parameters controlling the number of alternative random weights.
+  static const int kNumRandomWeights = 5;
+
+  bool allow_zero_;  // permit Zero() and zero divisors
+};
+
+template <class T> const int MinMaxWeightGenerator_<T>::kNumRandomWeights;
+
+typedef MinMaxWeightGenerator_<float> MinMaxWeightGenerator;
+
+
+// This function object returns StringWeights that are random integer
+// strings chosen from {1,...,kAlphabetSize}^{0,kMaxStringLength} U { Zero }
+template <typename L, StringType S = STRING_LEFT>
+class StringWeightGenerator {
+ public:
+  typedef StringWeight<L, S> Weight;
+
+  StringWeightGenerator(int seed = time(0), bool allow_zero = true)
+      : allow_zero_(allow_zero) {
+     srand(seed);
+  }
+
+  Weight operator() () const {
+    int n = rand() % (kMaxStringLength + allow_zero_);
+    if (allow_zero_ && n == kMaxStringLength)
+      return Weight::Zero();
+
+    vector<L> v;
+    for (int i = 0; i < n; ++i)
+      v.push_back(rand() % kAlphabetSize + 1);
+    return Weight(v.begin(), v.end());
+  }
+
+ private:
+  // Alphabet size for random weights.
+  static const int kAlphabetSize = 5;
+  // Number of alternative random weights.
+  static const int kMaxStringLength = 5;
+
+  bool allow_zero_;  // permit Zero() and zero
+};
+
+template <typename L, StringType S>
+const int StringWeightGenerator<L, S>::kAlphabetSize;
+template <typename L, StringType S>
+const int StringWeightGenerator<L, S>::kMaxStringLength;
+
+
+// This function object returns a weight generator over the product of the
+// weights (by default) for the generators G1 and G2.
+template <class G1, class G2,
+  class W = ProductWeight<typename G1::Weight, typename G2::Weight> >
+class ProductWeightGenerator {
+ public:
+  typedef typename G1::Weight W1;
+  typedef typename G2::Weight W2;
+  typedef W Weight;
+
+  ProductWeightGenerator(int seed = time(0), bool allow_zero = true)
+      : generator1_(seed, allow_zero), generator2_(seed, allow_zero) {}
+
+  Weight operator() () const {
+    W1 w1 = generator1_();
+    W2 w2 = generator2_();
+    return Weight(w1, w2);
+  }
+
+ private:
+  G1 generator1_;
+  G2 generator2_;
+};
+
+
+// This function object returns a weight generator for a lexicographic weight
+// composed out of weights for the generators G1 and G2. For lexicographic
+// weights, we cannot generate zeroes for the two subweights separately:
+// weights are members iff both members are zero or both members are non-zero.
+template <class G1, class G2>
+class LexicographicWeightGenerator {
+ public:
+  typedef typename G1::Weight W1;
+  typedef typename G2::Weight W2;
+  typedef LexicographicWeight<W1, W2> Weight;
+
+  LexicographicWeightGenerator(int seed = time(0), bool allow_zero = true)
+      : generator1_(seed, false), generator2_(seed, false),
+        allow_zero_(allow_zero) {}
+
+  Weight operator() () const {
+    if (allow_zero_) {
+      int n = rand() % (kNumRandomWeights + allow_zero_);
+      if (n == kNumRandomWeights)
+        return Weight(W1::Zero(), W2::Zero());
+    }
+    W1 w1 = generator1_();
+    W2 w2 = generator2_();
+    return Weight(w1, w2);
+  }
+
+ private:
+  G1 generator1_;
+  G2 generator2_;
+  static const int kNumRandomWeights = 5;
+  bool allow_zero_;
+};
+
+template <class G1, class G2>
+const int LexicographicWeightGenerator<G1, G2>::kNumRandomWeights;
+
+
+// Product generator of a string weight generator and an
+// arbitrary weight generator.
+template <class L, class G, StringType S = STRING_LEFT>
+class GallicWeightGenerator
+    : public ProductWeightGenerator<StringWeightGenerator<L, S>, G> {
+
+ public:
+  typedef ProductWeightGenerator<StringWeightGenerator<L, S>, G> PG;
+  typedef typename G::Weight W;
+  typedef GallicWeight<L, W, S> Weight;
+
+  GallicWeightGenerator(int seed = time(0), bool allow_zero = true)
+      : PG(seed, allow_zero) {}
+
+  GallicWeightGenerator(const PG &pg) : PG(pg) {}
+};
+
+// This function object returms a weight generator over the catersian power
+// of rank n of the weights for the generator G.
+template <class G, unsigned int n>
+class PowerWeightGenerator {
+ public:
+  typedef typename G::Weight W;
+  typedef PowerWeight<W, n> Weight;
+
+  PowerWeightGenerator(int seed = time(0), bool allow_zero = true)
+      : generator_(seed, allow_zero) {}
+
+  Weight operator()() const {
+    Weight w;
+    for (size_t i = 0; i < n; ++i) {
+      W r = generator_();
+      w.SetValue(i, r);
+    }
+    return w;
+  }
+
+ private:
+  G generator_;
+};
+
+// This function object returns SignedLogWeightTpl<T>'s that are
+// random integers chosen from [0, kNumRandomWeights).
+// The sign is randomly chosen as well.
+template <class T>
+class SignedLogWeightGenerator_ {
+ public:
+  typedef SignedLogWeightTpl<T> Weight;
+
+  SignedLogWeightGenerator_(int seed = time(0), bool allow_zero = true)
+  : allow_zero_(allow_zero) {
+    srand(seed);
+  }
+
+  Weight operator() () const {
+    int m = rand() % 2;
+    int n = rand() % (kNumRandomWeights + allow_zero_);
+
+    return SignedLogWeightTpl<T>(
+      (m == 0) ?
+        TropicalWeight(-1.0) :
+        TropicalWeight(1.0),
+      (allow_zero_ && n == kNumRandomWeights) ?
+        LogWeightTpl<T>::Zero() :
+        LogWeightTpl<T>(static_cast<T>(n)));
+  }
+
+ private:
+  // Number of alternative random weights.
+  static const int kNumRandomWeights = 5;
+  bool allow_zero_;  // permit Zero() and zero divisors
+};
+
+template <class T> const int SignedLogWeightGenerator_<T>::kNumRandomWeights;
+
+typedef SignedLogWeightGenerator_<float> SignedLogWeightGenerator;
+
+// This function object returms a weight generator over the catersian power
+// of rank n of the weights for the generator G.
+template <class G, class K, unsigned int n>
+class SparsePowerWeightGenerator {
+ public:
+  typedef typename G::Weight W;
+  typedef SparsePowerWeight<W, K> Weight;
+
+  SparsePowerWeightGenerator(int seed = time(0), bool allow_zero = true)
+      : generator_(seed, allow_zero) {}
+
+  Weight operator()() const {
+    Weight w;
+    for (size_t i = 1; i <= n; ++i) {
+      W r = generator_();
+      K p = i;
+      w.Push(p, r, true);
+    }
+    return w;
+  }
+
+ private:
+  G generator_;
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_RANDOM_WEIGHT_H__
diff --git a/src/include/fst/rational.h b/src/include/fst/rational.h
new file mode 100644
index 0000000..96aa00d
--- /dev/null
+++ b/src/include/fst/rational.h
@@ -0,0 +1,330 @@
+// rational.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// An Fst implementation and base interface for delayed unions,
+// concatenations and closures.
+
+#ifndef FST_LIB_RATIONAL_H__
+#define FST_LIB_RATIONAL_H__
+
+#include <algorithm>
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/mutable-fst.h>
+#include <fst/replace.h>
+#include <fst/test-properties.h>
+
+
+namespace fst {
+
+typedef CacheOptions RationalFstOptions;
+
+// This specifies whether to add the empty string.
+enum ClosureType { CLOSURE_STAR = 0,    // T* -> add the empty string
+                   CLOSURE_PLUS = 1 };  // T+ -> don't add the empty string
+
+template <class A> class RationalFst;
+template <class A> void Union(RationalFst<A> *fst1, const Fst<A> &fst2);
+template <class A> void Concat(RationalFst<A> *fst1, const Fst<A> &fst2);
+template <class A> void Concat(const Fst<A> &fst1, RationalFst<A> *fst2);
+template <class A> void Closure(RationalFst<A> *fst, ClosureType closure_type);
+
+
+// Implementation class for delayed unions, concatenations and closures.
+template<class A>
+class RationalFstImpl : public FstImpl<A> {
+ public:
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::WriteHeader;
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+
+  explicit RationalFstImpl(const RationalFstOptions &opts)
+      : nonterminals_(0),
+        replace_(0),
+        replace_options_(opts, 0) {
+    SetType("rational");
+    fst_tuples_.push_back(pair<Label, const Fst<A>*>(0, 0));
+  }
+
+  RationalFstImpl(const RationalFstImpl<A> &impl)
+      : rfst_(impl.rfst_),
+        nonterminals_(impl.nonterminals_),
+
+        replace_(impl.replace_ ? impl.replace_->Copy(true) : 0),
+        replace_options_(impl.replace_options_) {
+    SetType("rational");
+    fst_tuples_.reserve(impl.fst_tuples_.size());
+    for (size_t i = 0; i < impl.fst_tuples_.size(); ++i)
+      fst_tuples_.push_back(make_pair(impl.fst_tuples_[i].first,
+                                      impl.fst_tuples_[i].second
+                                      ? impl.fst_tuples_[i].second->Copy(true)
+                                      : 0));
+  }
+
+  virtual ~RationalFstImpl() {
+    for (size_t i = 0; i < fst_tuples_.size(); ++i)
+      if (fst_tuples_[i].second)
+        delete fst_tuples_[i].second;
+    if (replace_)
+      delete replace_;
+  }
+
+  StateId Start() { return Replace()->Start(); }
+
+  Weight Final(StateId s) { return Replace()->Final(s); }
+
+  size_t NumArcs(StateId s) { return Replace()->NumArcs(s); }
+
+  size_t NumInputEpsilons(StateId s) {
+    return Replace()->NumInputEpsilons(s);
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    return Replace()->NumOutputEpsilons(s);
+  }
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if ((mask & kError) && Replace()->Properties(kError, false))
+      SetProperties(kError, kError);
+    return FstImpl<Arc>::Properties(mask);
+  }
+
+  // Implementation of UnionFst(fst1,fst2)
+  void InitUnion(const Fst<A> &fst1, const Fst<A> &fst2) {
+    if (replace_)
+      delete replace_;
+    uint64 props1 = fst1.Properties(kFstProperties, false);
+    uint64 props2 = fst2.Properties(kFstProperties, false);
+    SetInputSymbols(fst1.InputSymbols());
+    SetOutputSymbols(fst1.OutputSymbols());
+    rfst_.AddState();
+    rfst_.AddState();
+    rfst_.SetStart(0);
+    rfst_.SetFinal(1, Weight::One());
+    rfst_.SetInputSymbols(fst1.InputSymbols());
+    rfst_.SetOutputSymbols(fst1.OutputSymbols());
+    nonterminals_ = 2;
+    rfst_.AddArc(0, A(0, -1, Weight::One(), 1));
+    rfst_.AddArc(0, A(0, -2, Weight::One(), 1));
+    fst_tuples_.push_back(make_pair(-1, fst1.Copy()));
+    fst_tuples_.push_back(make_pair(-2, fst2.Copy()));
+    SetProperties(UnionProperties(props1, props2, true), kCopyProperties);
+  }
+
+  // Implementation of ConcatFst(fst1,fst2)
+  void InitConcat(const Fst<A> &fst1, const Fst<A> &fst2) {
+    if (replace_)
+      delete replace_;
+    uint64 props1 = fst1.Properties(kFstProperties, false);
+    uint64 props2 = fst2.Properties(kFstProperties, false);
+    SetInputSymbols(fst1.InputSymbols());
+    SetOutputSymbols(fst1.OutputSymbols());
+    rfst_.AddState();
+    rfst_.AddState();
+    rfst_.AddState();
+    rfst_.SetStart(0);
+    rfst_.SetFinal(2, Weight::One());
+    rfst_.SetInputSymbols(fst1.InputSymbols());
+    rfst_.SetOutputSymbols(fst1.OutputSymbols());
+    nonterminals_ = 2;
+    rfst_.AddArc(0, A(0, -1, Weight::One(), 1));
+    rfst_.AddArc(1, A(0, -2, Weight::One(), 2));
+    fst_tuples_.push_back(make_pair(-1, fst1.Copy()));
+    fst_tuples_.push_back(make_pair(-2, fst2.Copy()));
+    SetProperties(ConcatProperties(props1, props2, true), kCopyProperties);
+  }
+
+  // Implementation of ClosureFst(fst, closure_type)
+  void InitClosure(const Fst<A> &fst, ClosureType closure_type) {
+    if (replace_)
+      delete replace_;
+    uint64 props = fst.Properties(kFstProperties, false);
+    SetInputSymbols(fst.InputSymbols());
+    SetOutputSymbols(fst.OutputSymbols());
+    if (closure_type == CLOSURE_STAR) {
+      rfst_.AddState();
+      rfst_.SetStart(0);
+      rfst_.SetFinal(0, Weight::One());
+      rfst_.AddArc(0, A(0, -1, Weight::One(), 0));
+    } else {
+      rfst_.AddState();
+      rfst_.AddState();
+      rfst_.SetStart(0);
+      rfst_.SetFinal(1, Weight::One());
+      rfst_.AddArc(0, A(0, -1, Weight::One(), 1));
+      rfst_.AddArc(1, A(0, 0, Weight::One(), 0));
+    }
+    rfst_.SetInputSymbols(fst.InputSymbols());
+    rfst_.SetOutputSymbols(fst.OutputSymbols());
+    fst_tuples_.push_back(make_pair(-1, fst.Copy()));
+    nonterminals_ = 1;
+    SetProperties(ClosureProperties(props, closure_type == CLOSURE_STAR, true),
+                  kCopyProperties);
+  }
+
+  // Implementation of Union(Fst &, RationalFst *)
+  void AddUnion(const Fst<A> &fst) {
+    if (replace_)
+      delete replace_;
+    uint64 props1 = FstImpl<A>::Properties();
+    uint64 props2 = fst.Properties(kFstProperties, false);
+    VectorFst<A> afst;
+    afst.AddState();
+    afst.AddState();
+    afst.SetStart(0);
+    afst.SetFinal(1, Weight::One());
+    ++nonterminals_;
+    afst.AddArc(0, A(0, -nonterminals_, Weight::One(), 1));
+    Union(&rfst_, afst);
+    fst_tuples_.push_back(make_pair(-nonterminals_, fst.Copy()));
+    SetProperties(UnionProperties(props1, props2, true), kCopyProperties);
+  }
+
+  // Implementation of Concat(Fst &, RationalFst *)
+  void AddConcat(const Fst<A> &fst, bool append) {
+    if (replace_)
+      delete replace_;
+    uint64 props1 = FstImpl<A>::Properties();
+    uint64 props2 = fst.Properties(kFstProperties, false);
+    VectorFst<A> afst;
+    afst.AddState();
+    afst.AddState();
+    afst.SetStart(0);
+    afst.SetFinal(1, Weight::One());
+    ++nonterminals_;
+    afst.AddArc(0, A(0, -nonterminals_, Weight::One(), 1));
+    if (append)
+      Concat(&rfst_, afst);
+    else
+      Concat(afst, &rfst_);
+    fst_tuples_.push_back(make_pair(-nonterminals_, fst.Copy()));
+    SetProperties(ConcatProperties(props1, props2, true), kCopyProperties);
+  }
+
+  // Implementation of Closure(RationalFst *, closure_type)
+  void AddClosure(ClosureType closure_type) {
+    if (replace_)
+      delete replace_;
+    uint64 props = FstImpl<A>::Properties();
+    Closure(&rfst_, closure_type);
+    SetProperties(ClosureProperties(props, closure_type == CLOSURE_STAR, true),
+                  kCopyProperties);
+  }
+
+  // Returns the underlying ReplaceFst.
+  ReplaceFst<A> *Replace() const {
+    if (!replace_) {
+      fst_tuples_[0].second = rfst_.Copy();
+      replace_ = new ReplaceFst<A>(fst_tuples_, replace_options_);
+    }
+    return replace_;
+  }
+
+ private:
+  VectorFst<A> rfst_;   // rational topology machine; uses neg. nonterminals
+  Label nonterminals_;  // # of nonterminals used
+  // Contains the nonterminals and their corresponding FSTs.
+  mutable vector<pair<Label, const Fst<A>*> > fst_tuples_;
+  mutable ReplaceFst<A> *replace_;        // Underlying ReplaceFst
+  ReplaceFstOptions<A> replace_options_;  // Options for creating 'replace_'
+
+  void operator=(const RationalFstImpl<A> &impl);    // disallow
+};
+
+// Parent class for the delayed rational operations - delayed union,
+// concatenation, and closure.
+//
+// This class attaches interface to implementation and handles
+// reference counting, delegating most methods to ImplToFst.
+template <class A>
+class RationalFst : public ImplToFst< RationalFstImpl<A> > {
+ public:
+  friend class StateIterator< RationalFst<A> >;
+  friend class ArcIterator< RationalFst<A> >;
+  friend void Union<>(RationalFst<A> *fst1, const Fst<A> &fst2);
+  friend void Concat<>(RationalFst<A> *fst1, const Fst<A> &fst2);
+  friend void Concat<>(const Fst<A> &fst1, RationalFst<A> *fst2);
+  friend void Closure<>(RationalFst<A> *fst, ClosureType closure_type);
+
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef RationalFstImpl<A> Impl;
+
+  virtual void InitStateIterator(StateIteratorData<A> *data) const {
+    GetImpl()->Replace()->InitStateIterator(data);
+  }
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<A> *data) const {
+    GetImpl()->Replace()->InitArcIterator(s, data);
+  }
+
+ protected:
+  RationalFst()
+      : ImplToFst<Impl>(new Impl(RationalFstOptions())) {}
+
+  explicit RationalFst(const RationalFstOptions &opts)
+      : ImplToFst<Impl>(new Impl(opts)) {}
+
+  // See Fst<>::Copy() for doc.
+  RationalFst(const RationalFst<A> &fst , bool safe = false)
+      : ImplToFst<Impl>(fst, safe) {}
+
+ private:
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const RationalFst<A> &fst);  // disallow
+};
+
+
+// Specialization for RationalFst.
+template <class A>
+class StateIterator< RationalFst<A> >
+    : public StateIterator< ReplaceFst<A> > {
+ public:
+  explicit StateIterator(const RationalFst<A> &fst)
+      : StateIterator< ReplaceFst<A> >(*(fst.GetImpl()->Replace())) {}
+};
+
+
+// Specialization for RationalFst.
+template <class A>
+class ArcIterator< RationalFst<A> >
+    : public CacheArcIterator< ReplaceFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const RationalFst<A> &fst, StateId s)
+      : ArcIterator< ReplaceFst<A> >(*(fst.GetImpl()->Replace()), s) {}
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_RATIONAL_H__
diff --git a/src/include/fst/register.h b/src/include/fst/register.h
new file mode 100644
index 0000000..55651cd
--- /dev/null
+++ b/src/include/fst/register.h
@@ -0,0 +1,132 @@
+// register.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley), jpr@google.com (Jake Ratkiewicz)
+//
+// \file
+// Classes for registering derived Fsts for generic reading
+//
+
+#ifndef FST_LIB_REGISTER_H__
+#define FST_LIB_REGISTER_H__
+
+#include <string>
+
+
+#include <fst/compat.h>
+#include <iostream>
+#include <fstream>
+#include <fst/util.h>
+#include <fst/generic-register.h>
+
+
+#include <fst/types.h>
+
+namespace fst {
+
+template <class A> class Fst;
+struct FstReadOptions;
+
+// This class represents a single entry in a FstRegister
+template<class A>
+struct FstRegisterEntry {
+  typedef Fst<A> *(*Reader)(istream &strm, const FstReadOptions &opts);
+  typedef Fst<A> *(*Converter)(const Fst<A> &fst);
+
+  Reader reader;
+  Converter converter;
+  FstRegisterEntry() : reader(0), converter(0) {}
+  FstRegisterEntry(Reader r, Converter c) : reader(r), converter(c) { }
+};
+
+// This class maintains the correspondence between a string describing
+// an FST type, and its reader and converter.
+template<class A>
+class FstRegister : public GenericRegister<string, FstRegisterEntry<A>,
+                                           FstRegister<A> > {
+ public:
+  typedef typename FstRegisterEntry<A>::Reader Reader;
+  typedef typename FstRegisterEntry<A>::Converter Converter;
+
+  const Reader GetReader(const string &type) const {
+    return this->GetEntry(type).reader;
+  }
+
+  const Converter GetConverter(const string &type) const {
+    return this->GetEntry(type).converter;
+  }
+
+ protected:
+  virtual string ConvertKeyToSoFilename(const string& key) const {
+    string legal_type(key);
+
+    ConvertToLegalCSymbol(&legal_type);
+
+    return legal_type + "-fst.so";
+  }
+};
+
+
+// This class registers an Fst type for generic reading and creating.
+// The Fst type must have a default constructor and a copy constructor
+// from 'Fst<Arc>' for this to work.
+template <class F>
+class FstRegisterer
+  : public GenericRegisterer<FstRegister<typename F::Arc> > {
+ public:
+  typedef typename F::Arc Arc;
+  typedef typename FstRegister<Arc>::Entry Entry;
+  typedef typename FstRegister<Arc>::Reader Reader;
+
+  FstRegisterer() :
+      GenericRegisterer<FstRegister<typename F::Arc> >(
+          F().Type(), BuildEntry()) {  }
+
+ private:
+  Entry BuildEntry() {
+    F *(*reader)(istream &strm,
+                 const FstReadOptions &opts) = &F::Read;
+
+    return Entry(reinterpret_cast<Reader>(reader),
+                 &FstRegisterer<F>::Convert);
+  }
+
+  static Fst<Arc> *Convert(const Fst<Arc> &fst) { return new F(fst); }
+};
+
+
+// Convenience macro to generate static FstRegisterer instance.
+#define REGISTER_FST(F, A) \
+static fst::FstRegisterer< F<A> > F ## _ ## A ## _registerer
+
+
+// Converts an fst to type 'type'.
+template <class A>
+Fst<A> *Convert(const Fst<A> &fst, const string &ftype) {
+  FstRegister<A> *registr = FstRegister<A>::GetRegister();
+  const typename FstRegister<A>::Converter
+      converter = registr->GetConverter(ftype);
+  if (!converter) {
+    string atype = A::Type();
+    LOG(ERROR) << "Fst::Convert: Unknown FST type \"" << ftype
+               << "\" (arc type = \"" << atype << "\")";
+    return 0;
+  }
+  return converter(fst);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_REGISTER_H__
diff --git a/src/include/fst/relabel.h b/src/include/fst/relabel.h
new file mode 100644
index 0000000..fbb8942
--- /dev/null
+++ b/src/include/fst/relabel.h
@@ -0,0 +1,524 @@
+// relabel.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: johans@google.com (Johan Schalkwyk)
+//
+// \file
+// Functions and classes to relabel an Fst (either on input or output)
+//
+#ifndef FST_LIB_RELABEL_H__
+#define FST_LIB_RELABEL_H__
+
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <string>
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+#include <fst/test-properties.h>
+
+
+namespace fst {
+
+//
+// Relabels either the input labels or output labels. The old to
+// new labels are specified using a vector of pair<Label,Label>.
+// Any label associations not specified are assumed to be identity
+// mapping.
+//
+// \param fst input fst, must be mutable
+// \param ipairs vector of input label pairs indicating old to new mapping
+// \param opairs vector of output label pairs indicating old to new mapping
+//
+template <class A>
+void Relabel(
+    MutableFst<A> *fst,
+    const vector<pair<typename A::Label, typename A::Label> >& ipairs,
+    const vector<pair<typename A::Label, typename A::Label> >& opairs) {
+  typedef typename A::StateId StateId;
+  typedef typename A::Label   Label;
+
+  uint64 props = fst->Properties(kFstProperties, false);
+
+  // construct label to label hash.
+  unordered_map<Label, Label> input_map;
+  for (size_t i = 0; i < ipairs.size(); ++i) {
+    input_map[ipairs[i].first] = ipairs[i].second;
+  }
+
+  unordered_map<Label, Label> output_map;
+  for (size_t i = 0; i < opairs.size(); ++i) {
+    output_map[opairs[i].first] = opairs[i].second;
+  }
+
+  for (StateIterator<MutableFst<A> > siter(*fst);
+       !siter.Done(); siter.Next()) {
+    StateId s = siter.Value();
+    for (MutableArcIterator<MutableFst<A> > aiter(fst, s);
+         !aiter.Done(); aiter.Next()) {
+      A arc = aiter.Value();
+
+      // relabel input
+      // only relabel if relabel pair defined
+      typename unordered_map<Label, Label>::iterator it =
+        input_map.find(arc.ilabel);
+      if (it != input_map.end()) {
+        if (it->second == kNoLabel) {
+          FSTERROR() << "Input symbol id " << arc.ilabel
+                     << " missing from target vocabulary";
+          fst->SetProperties(kError, kError);
+          return;
+        }
+        arc.ilabel = it->second;
+      }
+
+      // relabel output
+      it = output_map.find(arc.olabel);
+      if (it != output_map.end()) {
+        if (it->second == kNoLabel) {
+          FSTERROR() << "Output symbol id " << arc.olabel
+                     << " missing from target vocabulary";
+          fst->SetProperties(kError, kError);
+          return;
+        }
+        arc.olabel = it->second;
+      }
+
+      aiter.SetValue(arc);
+    }
+  }
+
+  fst->SetProperties(RelabelProperties(props), kFstProperties);
+}
+
+//
+// Relabels either the input labels or output labels. The old to
+// new labels mappings are specified using an input Symbol set.
+// Any label associations not specified are assumed to be identity
+// mapping.
+//
+// \param fst input fst, must be mutable
+// \param new_isymbols symbol set indicating new mapping of input symbols
+// \param new_osymbols symbol set indicating new mapping of output symbols
+//
+template<class A>
+void Relabel(MutableFst<A> *fst,
+             const SymbolTable* new_isymbols,
+             const SymbolTable* new_osymbols) {
+  Relabel(fst,
+          fst->InputSymbols(), new_isymbols, true,
+          fst->OutputSymbols(), new_osymbols, true);
+}
+
+template<class A>
+void Relabel(MutableFst<A> *fst,
+             const SymbolTable* old_isymbols,
+             const SymbolTable* new_isymbols,
+             bool attach_new_isymbols,
+             const SymbolTable* old_osymbols,
+             const SymbolTable* new_osymbols,
+             bool attach_new_osymbols) {
+  typedef typename A::StateId StateId;
+  typedef typename A::Label   Label;
+
+  vector<pair<Label, Label> > ipairs;
+  if (old_isymbols && new_isymbols) {
+    for (SymbolTableIterator syms_iter(*old_isymbols); !syms_iter.Done();
+         syms_iter.Next()) {
+      string isymbol = syms_iter.Symbol();
+      int isymbol_val = syms_iter.Value();
+      int new_isymbol_val = new_isymbols->Find(isymbol);
+      ipairs.push_back(make_pair(isymbol_val, new_isymbol_val));
+    }
+    if (attach_new_isymbols)
+      fst->SetInputSymbols(new_isymbols);
+  }
+
+  vector<pair<Label, Label> > opairs;
+  if (old_osymbols && new_osymbols) {
+    for (SymbolTableIterator syms_iter(*old_osymbols); !syms_iter.Done();
+         syms_iter.Next()) {
+      string osymbol = syms_iter.Symbol();
+      int osymbol_val = syms_iter.Value();
+      int new_osymbol_val = new_osymbols->Find(osymbol);
+      opairs.push_back(make_pair(osymbol_val, new_osymbol_val));
+    }
+    if (attach_new_osymbols)
+      fst->SetOutputSymbols(new_osymbols);
+  }
+
+  // call relabel using vector of relabel pairs.
+  Relabel(fst, ipairs, opairs);
+}
+
+
+typedef CacheOptions RelabelFstOptions;
+
+template <class A> class RelabelFst;
+
+//
+// \class RelabelFstImpl
+// \brief Implementation for delayed relabeling
+//
+// Relabels an FST from one symbol set to another. Relabeling
+// can either be on input or output space. RelabelFst implements
+// a delayed version of the relabel. Arcs are relabeled on the fly
+// and not cached. I.e each request is recomputed.
+//
+template<class A>
+class RelabelFstImpl : public CacheImpl<A> {
+  friend class StateIterator< RelabelFst<A> >;
+ public:
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::WriteHeader;
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+
+  using CacheImpl<A>::PushArc;
+  using CacheImpl<A>::HasArcs;
+  using CacheImpl<A>::HasFinal;
+  using CacheImpl<A>::HasStart;
+  using CacheImpl<A>::SetArcs;
+  using CacheImpl<A>::SetFinal;
+  using CacheImpl<A>::SetStart;
+
+  typedef A Arc;
+  typedef typename A::Label   Label;
+  typedef typename A::Weight  Weight;
+  typedef typename A::StateId StateId;
+  typedef CacheState<A> State;
+
+  RelabelFstImpl(const Fst<A>& fst,
+                 const vector<pair<Label, Label> >& ipairs,
+                 const vector<pair<Label, Label> >& opairs,
+                 const RelabelFstOptions &opts)
+      : CacheImpl<A>(opts), fst_(fst.Copy()),
+        relabel_input_(false), relabel_output_(false) {
+    uint64 props = fst.Properties(kCopyProperties, false);
+    SetProperties(RelabelProperties(props));
+    SetType("relabel");
+
+    // create input label map
+    if (ipairs.size() > 0) {
+      for (size_t i = 0; i < ipairs.size(); ++i) {
+        input_map_[ipairs[i].first] = ipairs[i].second;
+      }
+      relabel_input_ = true;
+    }
+
+    // create output label map
+    if (opairs.size() > 0) {
+      for (size_t i = 0; i < opairs.size(); ++i) {
+        output_map_[opairs[i].first] = opairs[i].second;
+      }
+      relabel_output_ = true;
+    }
+  }
+
+  RelabelFstImpl(const Fst<A>& fst,
+                 const SymbolTable* old_isymbols,
+                 const SymbolTable* new_isymbols,
+                 const SymbolTable* old_osymbols,
+                 const SymbolTable* new_osymbols,
+                 const RelabelFstOptions &opts)
+      : CacheImpl<A>(opts), fst_(fst.Copy()),
+        relabel_input_(false), relabel_output_(false) {
+    SetType("relabel");
+
+    uint64 props = fst.Properties(kCopyProperties, false);
+    SetProperties(RelabelProperties(props));
+    SetInputSymbols(old_isymbols);
+    SetOutputSymbols(old_osymbols);
+
+    if (old_isymbols && new_isymbols &&
+        old_isymbols->LabeledCheckSum() != new_isymbols->LabeledCheckSum()) {
+      for (SymbolTableIterator syms_iter(*old_isymbols); !syms_iter.Done();
+           syms_iter.Next()) {
+        input_map_[syms_iter.Value()] = new_isymbols->Find(syms_iter.Symbol());
+      }
+      SetInputSymbols(new_isymbols);
+      relabel_input_ = true;
+    }
+
+    if (old_osymbols && new_osymbols &&
+        old_osymbols->LabeledCheckSum() != new_osymbols->LabeledCheckSum()) {
+      for (SymbolTableIterator syms_iter(*old_osymbols); !syms_iter.Done();
+           syms_iter.Next()) {
+        output_map_[syms_iter.Value()] =
+          new_osymbols->Find(syms_iter.Symbol());
+      }
+      SetOutputSymbols(new_osymbols);
+      relabel_output_ = true;
+    }
+  }
+
+  RelabelFstImpl(const RelabelFstImpl<A>& impl)
+      : CacheImpl<A>(impl),
+        fst_(impl.fst_->Copy(true)),
+        input_map_(impl.input_map_),
+        output_map_(impl.output_map_),
+        relabel_input_(impl.relabel_input_),
+        relabel_output_(impl.relabel_output_) {
+    SetType("relabel");
+    SetProperties(impl.Properties(), kCopyProperties);
+    SetInputSymbols(impl.InputSymbols());
+    SetOutputSymbols(impl.OutputSymbols());
+  }
+
+  ~RelabelFstImpl() { delete fst_; }
+
+  StateId Start() {
+    if (!HasStart()) {
+      StateId s = fst_->Start();
+      SetStart(s);
+    }
+    return CacheImpl<A>::Start();
+  }
+
+  Weight Final(StateId s) {
+    if (!HasFinal(s)) {
+      SetFinal(s, fst_->Final(s));
+    }
+    return CacheImpl<A>::Final(s);
+  }
+
+  size_t NumArcs(StateId s) {
+    if (!HasArcs(s)) {
+      Expand(s);
+    }
+    return CacheImpl<A>::NumArcs(s);
+  }
+
+  size_t NumInputEpsilons(StateId s) {
+    if (!HasArcs(s)) {
+      Expand(s);
+    }
+    return CacheImpl<A>::NumInputEpsilons(s);
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    if (!HasArcs(s)) {
+      Expand(s);
+    }
+    return CacheImpl<A>::NumOutputEpsilons(s);
+  }
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if ((mask & kError) && fst_->Properties(kError, false))
+      SetProperties(kError, kError);
+    return FstImpl<Arc>::Properties(mask);
+  }
+
+  void InitArcIterator(StateId s, ArcIteratorData<A>* data) {
+    if (!HasArcs(s)) {
+      Expand(s);
+    }
+    CacheImpl<A>::InitArcIterator(s, data);
+  }
+
+  void Expand(StateId s) {
+    for (ArcIterator<Fst<A> > aiter(*fst_, s); !aiter.Done(); aiter.Next()) {
+      A arc = aiter.Value();
+
+      // relabel input
+      if (relabel_input_) {
+        typename unordered_map<Label, Label>::iterator it =
+          input_map_.find(arc.ilabel);
+        if (it != input_map_.end()) { arc.ilabel = it->second; }
+      }
+
+      // relabel output
+      if (relabel_output_) {
+        typename unordered_map<Label, Label>::iterator it =
+          output_map_.find(arc.olabel);
+        if (it != output_map_.end()) { arc.olabel = it->second; }
+      }
+
+      PushArc(s, arc);
+    }
+    SetArcs(s);
+  }
+
+
+ private:
+  const Fst<A> *fst_;
+
+  unordered_map<Label, Label> input_map_;
+  unordered_map<Label, Label> output_map_;
+  bool relabel_input_;
+  bool relabel_output_;
+
+  void operator=(const RelabelFstImpl<A> &);  // disallow
+};
+
+
+//
+// \class RelabelFst
+// \brief Delayed implementation of arc relabeling
+//
+// This class attaches interface to implementation and handles
+// reference counting, delegating most methods to ImplToFst.
+template <class A>
+class RelabelFst : public ImplToFst< RelabelFstImpl<A> > {
+ public:
+  friend class ArcIterator< RelabelFst<A> >;
+  friend class StateIterator< RelabelFst<A> >;
+
+  typedef A Arc;
+  typedef typename A::Label   Label;
+  typedef typename A::Weight  Weight;
+  typedef typename A::StateId StateId;
+  typedef CacheState<A> State;
+  typedef RelabelFstImpl<A> Impl;
+
+  RelabelFst(const Fst<A>& fst,
+             const vector<pair<Label, Label> >& ipairs,
+             const vector<pair<Label, Label> >& opairs)
+      : ImplToFst<Impl>(new Impl(fst, ipairs, opairs, RelabelFstOptions())) {}
+
+  RelabelFst(const Fst<A>& fst,
+             const vector<pair<Label, Label> >& ipairs,
+             const vector<pair<Label, Label> >& opairs,
+             const RelabelFstOptions &opts)
+      : ImplToFst<Impl>(new Impl(fst, ipairs, opairs, opts)) {}
+
+  RelabelFst(const Fst<A>& fst,
+             const SymbolTable* new_isymbols,
+             const SymbolTable* new_osymbols)
+      : ImplToFst<Impl>(new Impl(fst, fst.InputSymbols(), new_isymbols,
+                                 fst.OutputSymbols(), new_osymbols,
+                                 RelabelFstOptions())) {}
+
+  RelabelFst(const Fst<A>& fst,
+             const SymbolTable* new_isymbols,
+             const SymbolTable* new_osymbols,
+             const RelabelFstOptions &opts)
+      : ImplToFst<Impl>(new Impl(fst, fst.InputSymbols(), new_isymbols,
+                                 fst.OutputSymbols(), new_osymbols, opts)) {}
+
+  RelabelFst(const Fst<A>& fst,
+             const SymbolTable* old_isymbols,
+             const SymbolTable* new_isymbols,
+             const SymbolTable* old_osymbols,
+             const SymbolTable* new_osymbols)
+    : ImplToFst<Impl>(new Impl(fst, old_isymbols, new_isymbols, old_osymbols,
+                               new_osymbols, RelabelFstOptions())) {}
+
+  RelabelFst(const Fst<A>& fst,
+             const SymbolTable* old_isymbols,
+             const SymbolTable* new_isymbols,
+             const SymbolTable* old_osymbols,
+             const SymbolTable* new_osymbols,
+             const RelabelFstOptions &opts)
+    : ImplToFst<Impl>(new Impl(fst, old_isymbols, new_isymbols, old_osymbols,
+                               new_osymbols, opts)) {}
+
+  // See Fst<>::Copy() for doc.
+  RelabelFst(const RelabelFst<A> &fst, bool safe = false)
+    : ImplToFst<Impl>(fst, safe) {}
+
+  // Get a copy of this RelabelFst. See Fst<>::Copy() for further doc.
+  virtual RelabelFst<A> *Copy(bool safe = false) const {
+    return new RelabelFst<A>(*this, safe);
+  }
+
+  virtual void InitStateIterator(StateIteratorData<A> *data) const;
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<A> *data) const {
+    return GetImpl()->InitArcIterator(s, data);
+  }
+
+ private:
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const RelabelFst<A> &fst);  // disallow
+};
+
+// Specialization for RelabelFst.
+template<class A>
+class StateIterator< RelabelFst<A> > : public StateIteratorBase<A> {
+ public:
+  typedef typename A::StateId StateId;
+
+  explicit StateIterator(const RelabelFst<A> &fst)
+      : impl_(fst.GetImpl()), siter_(*impl_->fst_), s_(0) {}
+
+  bool Done() const { return siter_.Done(); }
+
+  StateId Value() const { return s_; }
+
+  void Next() {
+    if (!siter_.Done()) {
+      ++s_;
+      siter_.Next();
+    }
+  }
+
+  void Reset() {
+    s_ = 0;
+    siter_.Reset();
+  }
+
+ private:
+  bool Done_() const { return Done(); }
+  StateId Value_() const { return Value(); }
+  void Next_() { Next(); }
+  void Reset_() { Reset(); }
+
+  const RelabelFstImpl<A> *impl_;
+  StateIterator< Fst<A> > siter_;
+  StateId s_;
+
+  DISALLOW_COPY_AND_ASSIGN(StateIterator);
+};
+
+
+// Specialization for RelabelFst.
+template <class A>
+class ArcIterator< RelabelFst<A> >
+    : public CacheArcIterator< RelabelFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const RelabelFst<A> &fst, StateId s)
+      : CacheArcIterator< RelabelFst<A> >(fst.GetImpl(), s) {
+    if (!fst.GetImpl()->HasArcs(s))
+      fst.GetImpl()->Expand(s);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+template <class A> inline
+void RelabelFst<A>::InitStateIterator(StateIteratorData<A> *data) const {
+  data->base = new StateIterator< RelabelFst<A> >(*this);
+}
+
+// Useful alias when using StdArc.
+typedef RelabelFst<StdArc> StdRelabelFst;
+
+}  // namespace fst
+
+#endif  // FST_LIB_RELABEL_H__
diff --git a/src/include/fst/replace-util.h b/src/include/fst/replace-util.h
new file mode 100644
index 0000000..f4a9c05
--- /dev/null
+++ b/src/include/fst/replace-util.h
@@ -0,0 +1,550 @@
+// replace-util.h
+
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+
+// \file
+// Utility classes for the recursive replacement of Fsts (RTNs).
+
+#ifndef FST_LIB_REPLACE_UTIL_H__
+#define FST_LIB_REPLACE_UTIL_H__
+
+#include <vector>
+using std::vector;
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <unordered_set>
+using std::tr1::unordered_set;
+using std::tr1::unordered_multiset;
+#include <map>
+
+#include <fst/connect.h>
+#include <fst/mutable-fst.h>
+#include <fst/topsort.h>
+
+
+namespace fst {
+
+template <class Arc>
+void Replace(const vector<pair<typename Arc::Label, const Fst<Arc>* > >&,
+             MutableFst<Arc> *, typename Arc::Label, bool);
+
+
+// Utility class for the recursive replacement of Fsts (RTNs). The
+// user provides a set of Label, Fst pairs at construction. These are
+// used by methods for testing cyclic dependencies and connectedness
+// and doing RTN connection and specific Fst replacement by label or
+// for various optimization properties. The modified results can be
+// obtained with the GetFstPairs() or GetMutableFstPairs() methods.
+template <class Arc>
+class ReplaceUtil {
+ public:
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  typedef pair<Label, const Fst<Arc>*> FstPair;
+  typedef pair<Label, MutableFst<Arc>*> MutableFstPair;
+  typedef unordered_map<Label, Label> NonTerminalHash;
+
+  // Constructs from mutable Fsts; Fst ownership given to ReplaceUtil.
+  ReplaceUtil(const vector<MutableFstPair> &fst_pairs,
+              Label root_label, bool epsilon_on_replace = false);
+
+  // Constructs from Fsts; Fst ownership retained by caller.
+  ReplaceUtil(const vector<FstPair> &fst_pairs,
+              Label root_label, bool epsilon_on_replace = false);
+
+  // Constructs from ReplaceFst internals; ownership retained by caller.
+  ReplaceUtil(const vector<const Fst<Arc> *> &fst_array,
+              const NonTerminalHash &nonterminal_hash, Label root_fst,
+              bool epsilon_on_replace = false);
+
+  ~ReplaceUtil() {
+    for (Label i = 0; i < fst_array_.size(); ++i)
+      delete fst_array_[i];
+  }
+
+  // True if the non-terminal dependencies are cyclic. Cyclic
+  // dependencies will result in an unexpandable replace fst.
+  bool CyclicDependencies() const {
+    GetDependencies(false);
+    return depprops_ & kCyclic;
+  }
+
+  // Returns true if no useless Fsts, states or transitions.
+  bool Connected() const {
+    GetDependencies(false);
+    uint64 props = kAccessible | kCoAccessible;
+    for (Label i = 0; i < fst_array_.size(); ++i) {
+      if (!fst_array_[i])
+        continue;
+      if (fst_array_[i]->Properties(props, true) != props || !depaccess_[i])
+        return false;
+    }
+    return true;
+  }
+
+  // Removes useless Fsts, states and transitions.
+  void Connect();
+
+  // Replaces Fsts specified by labels.
+  // Does nothing if there are cyclic dependencies.
+  void ReplaceLabels(const vector<Label> &labels);
+
+  // Replaces Fsts that have at most 'nstates' states, 'narcs' arcs and
+  // 'nnonterm' non-terminals (updating in reverse dependency order).
+  // Does nothing if there are cyclic dependencies.
+  void ReplaceBySize(size_t nstates, size_t narcs, size_t nnonterms);
+
+  // Replaces singleton Fsts.
+  // Does nothing if there are cyclic dependencies.
+  void ReplaceTrivial() { ReplaceBySize(2, 1, 1); }
+
+  // Replaces non-terminals that have at most 'ninstances' instances
+  // (updating in dependency order).
+  // Does nothing if there are cyclic dependencies.
+  void ReplaceByInstances(size_t ninstances);
+
+  // Replaces non-terminals that have only one instance.
+  // Does nothing if there are cyclic dependencies.
+  void ReplaceUnique() { ReplaceByInstances(1); }
+
+  // Returns Label, Fst pairs; Fst ownership retained by ReplaceUtil.
+  void GetFstPairs(vector<FstPair> *fst_pairs);
+
+  // Returns Label, MutableFst pairs; Fst ownership given to caller.
+  void GetMutableFstPairs(vector<MutableFstPair> *mutable_fst_pairs);
+
+ private:
+  // Per Fst statistics
+  struct ReplaceStats {
+    StateId nstates;    // # of states
+    StateId nfinal;     // # of final states
+    size_t narcs;       // # of arcs
+    Label nnonterms;    // # of non-terminals in Fst
+    size_t nref;        // # of non-terminal instances referring to this Fst
+
+    // # of times that ith Fst references this Fst
+    map<Label, size_t> inref;
+    // # of times that this Fst references the ith Fst
+    map<Label, size_t> outref;
+
+    ReplaceStats()
+        : nstates(0),
+          nfinal(0),
+          narcs(0),
+          nnonterms(0),
+          nref(0) {}
+  };
+
+  // Check Mutable Fsts exist o.w. create them.
+  void CheckMutableFsts();
+
+  // Computes the dependency graph of the replace Fsts.
+  // If 'stats' is true, dependency statistics computed as well.
+  void GetDependencies(bool stats) const;
+
+  void ClearDependencies() const {
+    depfst_.DeleteStates();
+    stats_.clear();
+    depprops_ = 0;
+    have_stats_ = false;
+  }
+
+  // Get topological order of dependencies. Returns false with cyclic input.
+  bool GetTopOrder(const Fst<Arc> &fst, vector<Label> *toporder) const;
+
+  // Update statistics assuming that jth Fst will be replaced.
+  void UpdateStats(Label j);
+
+  Label root_label_;                              // root non-terminal
+  Label root_fst_;                                // root Fst ID
+  bool epsilon_on_replace_;                       // see Replace()
+  vector<const Fst<Arc> *> fst_array_;            // Fst per ID
+  vector<MutableFst<Arc> *> mutable_fst_array_;   // MutableFst per ID
+  vector<Label> nonterminal_array_;               // Fst ID to non-terminal
+  NonTerminalHash nonterminal_hash_;              // non-terminal to Fst ID
+  mutable VectorFst<Arc> depfst_;                 // Fst ID dependencies
+  mutable vector<bool> depaccess_;                // Fst ID accessibility
+  mutable uint64 depprops_;                       // dependency Fst props
+  mutable bool have_stats_;                       // have dependency statistics
+  mutable vector<ReplaceStats> stats_;            // Per Fst statistics
+  DISALLOW_COPY_AND_ASSIGN(ReplaceUtil);
+};
+
+template <class Arc>
+ReplaceUtil<Arc>::ReplaceUtil(
+    const vector<MutableFstPair> &fst_pairs,
+    Label root_label, bool epsilon_on_replace)
+    : root_label_(root_label),
+      epsilon_on_replace_(epsilon_on_replace),
+      depprops_(0),
+      have_stats_(false) {
+  fst_array_.push_back(0);
+  mutable_fst_array_.push_back(0);
+  nonterminal_array_.push_back(kNoLabel);
+  for (Label i = 0; i < fst_pairs.size(); ++i) {
+    Label label = fst_pairs[i].first;
+    MutableFst<Arc> *fst = fst_pairs[i].second;
+    nonterminal_hash_[label] = fst_array_.size();
+    nonterminal_array_.push_back(label);
+    fst_array_.push_back(fst);
+    mutable_fst_array_.push_back(fst);
+  }
+  root_fst_ = nonterminal_hash_[root_label_];
+  if (!root_fst_)
+    FSTERROR() << "ReplaceUtil: no root FST for label: " << root_label_;
+}
+
+template <class Arc>
+ReplaceUtil<Arc>::ReplaceUtil(
+    const vector<FstPair> &fst_pairs,
+    Label root_label, bool epsilon_on_replace)
+    : root_label_(root_label),
+      epsilon_on_replace_(epsilon_on_replace),
+      depprops_(0),
+      have_stats_(false) {
+  fst_array_.push_back(0);
+  nonterminal_array_.push_back(kNoLabel);
+  for (Label i = 0; i < fst_pairs.size(); ++i) {
+    Label label = fst_pairs[i].first;
+    const Fst<Arc> *fst = fst_pairs[i].second;
+    nonterminal_hash_[label] = fst_array_.size();
+    nonterminal_array_.push_back(label);
+    fst_array_.push_back(fst->Copy());
+  }
+  root_fst_ = nonterminal_hash_[root_label];
+  if (!root_fst_)
+    FSTERROR() << "ReplaceUtil: no root FST for label: " << root_label_;
+}
+
+template <class Arc>
+ReplaceUtil<Arc>::ReplaceUtil(
+    const vector<const Fst<Arc> *> &fst_array,
+    const NonTerminalHash &nonterminal_hash, Label root_fst,
+    bool epsilon_on_replace)
+    : root_fst_(root_fst),
+      epsilon_on_replace_(epsilon_on_replace),
+      nonterminal_array_(fst_array.size()),
+      nonterminal_hash_(nonterminal_hash),
+      depprops_(0),
+      have_stats_(false) {
+  fst_array_.push_back(0);
+  for (Label i = 1; i < fst_array.size(); ++i)
+    fst_array_.push_back(fst_array[i]->Copy());
+  for (typename NonTerminalHash::const_iterator it =
+           nonterminal_hash.begin(); it != nonterminal_hash.end(); ++it)
+    nonterminal_array_[it->second] = it->first;
+  root_label_ = nonterminal_array_[root_fst_];
+}
+
+template <class Arc>
+void ReplaceUtil<Arc>::GetDependencies(bool stats) const {
+  if (depfst_.NumStates() > 0) {
+    if (stats && !have_stats_)
+      ClearDependencies();
+    else
+      return;
+  }
+
+  have_stats_ = stats;
+  if (have_stats_)
+    stats_.reserve(fst_array_.size());
+
+  for (Label i = 0; i < fst_array_.size(); ++i) {
+    depfst_.AddState();
+    depfst_.SetFinal(i, Weight::One());
+    if (have_stats_)
+      stats_.push_back(ReplaceStats());
+  }
+  depfst_.SetStart(root_fst_);
+
+  // An arc from each state (representing the fst) to the
+  // state representing the fst being replaced
+  for (Label i = 0; i < fst_array_.size(); ++i) {
+    const Fst<Arc> *ifst = fst_array_[i];
+    if (!ifst)
+      continue;
+    for (StateIterator<Fst<Arc> > siter(*ifst); !siter.Done(); siter.Next()) {
+      StateId s = siter.Value();
+      if (have_stats_) {
+        ++stats_[i].nstates;
+        if (ifst->Final(s) != Weight::Zero())
+          ++stats_[i].nfinal;
+      }
+      for (ArcIterator<Fst<Arc> > aiter(*ifst, s);
+           !aiter.Done(); aiter.Next()) {
+        if (have_stats_)
+          ++stats_[i].narcs;
+        const Arc& arc = aiter.Value();
+
+        typename NonTerminalHash::const_iterator it =
+            nonterminal_hash_.find(arc.olabel);
+        if (it != nonterminal_hash_.end()) {
+          Label j = it->second;
+          depfst_.AddArc(i, Arc(arc.olabel, arc.olabel, Weight::One(), j));
+          if (have_stats_) {
+            ++stats_[i].nnonterms;
+            ++stats_[j].nref;
+            ++stats_[j].inref[i];
+            ++stats_[i].outref[j];
+          }
+        }
+      }
+    }
+  }
+
+  // Gets accessibility info
+  SccVisitor<Arc> scc_visitor(0, &depaccess_, 0, &depprops_);
+  DfsVisit(depfst_, &scc_visitor);
+}
+
+template <class Arc>
+void ReplaceUtil<Arc>::UpdateStats(Label j) {
+  if (!have_stats_) {
+    FSTERROR() << "ReplaceUtil::UpdateStats: stats not available";
+    return;
+  }
+
+  if (j == root_fst_)  // can't replace root
+    return;
+
+  typedef typename map<Label, size_t>::iterator Iter;
+  for (Iter in = stats_[j].inref.begin();
+       in != stats_[j].inref.end();
+       ++in) {
+    Label i = in->first;
+    size_t ni = in->second;
+    stats_[i].nstates += stats_[j].nstates * ni;
+    stats_[i].narcs += (stats_[j].narcs + 1) * ni;  // narcs - 1 + 2 (eps)
+    stats_[i].nnonterms += (stats_[j].nnonterms - 1) * ni;
+    stats_[i].outref.erase(stats_[i].outref.find(j));
+    for (Iter out = stats_[j].outref.begin();
+         out != stats_[j].outref.end();
+         ++out) {
+      Label k = out->first;
+      size_t nk = out->second;
+      stats_[i].outref[k] += ni * nk;
+    }
+  }
+
+  for (Iter out = stats_[j].outref.begin();
+       out != stats_[j].outref.end();
+       ++out) {
+    Label k = out->first;
+    size_t nk = out->second;
+    stats_[k].nref -= nk;
+    stats_[k].inref.erase(stats_[k].inref.find(j));
+    for (Iter in = stats_[j].inref.begin();
+         in != stats_[j].inref.end();
+         ++in) {
+      Label i = in->first;
+      size_t ni = in->second;
+      stats_[k].inref[i] += ni * nk;
+      stats_[k].nref += ni * nk;
+    }
+  }
+}
+
+template <class Arc>
+void ReplaceUtil<Arc>::CheckMutableFsts() {
+  if (mutable_fst_array_.size() == 0) {
+    for (Label i = 0; i < fst_array_.size(); ++i) {
+      if (!fst_array_[i]) {
+        mutable_fst_array_.push_back(0);
+      } else {
+        mutable_fst_array_.push_back(new VectorFst<Arc>(*fst_array_[i]));
+        delete fst_array_[i];
+        fst_array_[i] = mutable_fst_array_[i];
+      }
+    }
+  }
+}
+
+template <class Arc>
+void ReplaceUtil<Arc>::Connect() {
+  CheckMutableFsts();
+  uint64 props = kAccessible | kCoAccessible;
+  for (Label i = 0; i < mutable_fst_array_.size(); ++i) {
+    if (!mutable_fst_array_[i])
+      continue;
+    if (mutable_fst_array_[i]->Properties(props, false) != props)
+      fst::Connect(mutable_fst_array_[i]);
+  }
+  GetDependencies(false);
+  for (Label i = 0; i < mutable_fst_array_.size(); ++i) {
+    MutableFst<Arc> *fst = mutable_fst_array_[i];
+    if (fst && !depaccess_[i]) {
+      delete fst;
+      fst_array_[i] = 0;
+      mutable_fst_array_[i] = 0;
+    }
+  }
+  ClearDependencies();
+}
+
+template <class Arc>
+bool ReplaceUtil<Arc>::GetTopOrder(const Fst<Arc> &fst,
+                                   vector<Label> *toporder) const {
+  // Finds topological order of dependencies.
+  vector<StateId> order;
+  bool acyclic = false;
+
+  TopOrderVisitor<Arc> top_order_visitor(&order, &acyclic);
+  DfsVisit(fst, &top_order_visitor);
+  if (!acyclic) {
+    LOG(WARNING) << "ReplaceUtil::GetTopOrder: Cyclical label dependencies";
+    return false;
+  }
+
+  toporder->resize(order.size());
+  for (Label i = 0; i < order.size(); ++i)
+    (*toporder)[order[i]] = i;
+
+  return true;
+}
+
+template <class Arc>
+void ReplaceUtil<Arc>::ReplaceLabels(const vector<Label> &labels) {
+  CheckMutableFsts();
+  unordered_set<Label> label_set;
+  for (Label i = 0; i < labels.size(); ++i)
+    if (labels[i] != root_label_)  // can't replace root
+      label_set.insert(labels[i]);
+
+  // Finds Fst dependencies restricted to the labels requested.
+  GetDependencies(false);
+  VectorFst<Arc> pfst(depfst_);
+  for (StateId i = 0; i < pfst.NumStates(); ++i) {
+    vector<Arc> arcs;
+    for (ArcIterator< VectorFst<Arc> > aiter(pfst, i);
+         !aiter.Done(); aiter.Next()) {
+      const Arc &arc = aiter.Value();
+      Label label = nonterminal_array_[arc.nextstate];
+      if (label_set.count(label) > 0)
+        arcs.push_back(arc);
+    }
+    pfst.DeleteArcs(i);
+    for (size_t j = 0; j < arcs.size(); ++j)
+      pfst.AddArc(i, arcs[j]);
+  }
+
+  vector<Label> toporder;
+  if (!GetTopOrder(pfst, &toporder)) {
+    ClearDependencies();
+    return;
+  }
+
+  // Visits Fsts in reverse topological order of dependencies and
+  // performs replacements.
+  for (Label o = toporder.size() - 1; o >= 0;  --o) {
+    vector<FstPair> fst_pairs;
+    StateId s = toporder[o];
+    for (ArcIterator< VectorFst<Arc> > aiter(pfst, s);
+         !aiter.Done(); aiter.Next()) {
+      const Arc &arc = aiter.Value();
+      Label label = nonterminal_array_[arc.nextstate];
+      const Fst<Arc> *fst = fst_array_[arc.nextstate];
+      fst_pairs.push_back(make_pair(label, fst));
+    }
+    if (fst_pairs.empty())
+        continue;
+    Label label = nonterminal_array_[s];
+    const Fst<Arc> *fst = fst_array_[s];
+    fst_pairs.push_back(make_pair(label, fst));
+
+    Replace(fst_pairs, mutable_fst_array_[s], label, epsilon_on_replace_);
+  }
+  ClearDependencies();
+}
+
+template <class Arc>
+void ReplaceUtil<Arc>::ReplaceBySize(size_t nstates, size_t narcs,
+                                     size_t nnonterms) {
+  vector<Label> labels;
+  GetDependencies(true);
+
+  vector<Label> toporder;
+  if (!GetTopOrder(depfst_, &toporder)) {
+    ClearDependencies();
+    return;
+  }
+
+  for (Label o = toporder.size() - 1; o >= 0; --o) {
+    Label j = toporder[o];
+    if (stats_[j].nstates <= nstates &&
+        stats_[j].narcs <= narcs &&
+        stats_[j].nnonterms <= nnonterms) {
+      labels.push_back(nonterminal_array_[j]);
+      UpdateStats(j);
+    }
+  }
+  ReplaceLabels(labels);
+}
+
+template <class Arc>
+void ReplaceUtil<Arc>::ReplaceByInstances(size_t ninstances) {
+  vector<Label> labels;
+  GetDependencies(true);
+
+  vector<Label> toporder;
+  if (!GetTopOrder(depfst_, &toporder)) {
+    ClearDependencies();
+    return;
+  }
+  for (Label o = 0; o < toporder.size(); ++o) {
+    Label j = toporder[o];
+    if (stats_[j].nref <= ninstances) {
+      labels.push_back(nonterminal_array_[j]);
+      UpdateStats(j);
+    }
+  }
+  ReplaceLabels(labels);
+}
+
+template <class Arc>
+void ReplaceUtil<Arc>::GetFstPairs(vector<FstPair> *fst_pairs) {
+  CheckMutableFsts();
+  fst_pairs->clear();
+  for (Label i = 0; i < fst_array_.size(); ++i) {
+    Label label = nonterminal_array_[i];
+    const Fst<Arc> *fst = fst_array_[i];
+    if (!fst)
+      continue;
+    fst_pairs->push_back(make_pair(label, fst));
+  }
+}
+
+template <class Arc>
+void ReplaceUtil<Arc>::GetMutableFstPairs(
+    vector<MutableFstPair> *mutable_fst_pairs) {
+  CheckMutableFsts();
+  mutable_fst_pairs->clear();
+  for (Label i = 0; i < mutable_fst_array_.size(); ++i) {
+    Label label = nonterminal_array_[i];
+    MutableFst<Arc> *fst = mutable_fst_array_[i];
+    if (!fst)
+      continue;
+    mutable_fst_pairs->push_back(make_pair(label, fst->Copy()));
+  }
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_REPLACE_UTIL_H__
diff --git a/src/include/fst/replace.h b/src/include/fst/replace.h
new file mode 100644
index 0000000..d08c0ea
--- /dev/null
+++ b/src/include/fst/replace.h
@@ -0,0 +1,1453 @@
+// replace.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: johans@google.com (Johan Schalkwyk)
+//
+// \file
+// Functions and classes for the recursive replacement of Fsts.
+//
+
+#ifndef FST_LIB_REPLACE_H__
+#define FST_LIB_REPLACE_H__
+
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <set>
+#include <string>
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+#include <fst/expanded-fst.h>
+#include <fst/fst.h>
+#include <fst/matcher.h>
+#include <fst/replace-util.h>
+#include <fst/state-table.h>
+#include <fst/test-properties.h>
+
+namespace fst {
+
+//
+// REPLACE STATE TUPLES AND TABLES
+//
+// The replace state table has the form
+//
+// template <class A, class P>
+// class ReplaceStateTable {
+//  public:
+//   typedef A Arc;
+//   typedef P PrefixId;
+//   typedef typename A::StateId StateId;
+//   typedef ReplaceStateTuple<StateId, PrefixId> StateTuple;
+//   typedef typename A::Label Label;
+//
+//   // Required constuctor
+//   ReplaceStateTable(const vector<pair<Label, const Fst<A>*> > &fst_tuples,
+//                     Label root);
+//
+//   // Required copy constructor that does not copy state
+//   ReplaceStateTable(const ReplaceStateTable<A,P> &table);
+//
+//   // Lookup state ID by tuple. If it doesn't exist, then add it.
+//   StateId FindState(const StateTuple &tuple);
+//
+//   // Lookup state tuple by ID.
+//   const StateTuple &Tuple(StateId id) const;
+// };
+
+
+// \struct ReplaceStateTuple
+// \brief Tuple of information that uniquely defines a state in replace
+template <class S, class P>
+struct ReplaceStateTuple {
+  typedef S StateId;
+  typedef P PrefixId;
+
+  ReplaceStateTuple()
+      : prefix_id(-1), fst_id(kNoStateId), fst_state(kNoStateId) {}
+
+  ReplaceStateTuple(PrefixId p, StateId f, StateId s)
+      : prefix_id(p), fst_id(f), fst_state(s) {}
+
+  PrefixId prefix_id;  // index in prefix table
+  StateId fst_id;      // current fst being walked
+  StateId fst_state;   // current state in fst being walked, not to be
+                       // confused with the state_id of the combined fst
+};
+
+
+// Equality of replace state tuples.
+template <class S, class P>
+inline bool operator==(const ReplaceStateTuple<S, P>& x,
+                       const ReplaceStateTuple<S, P>& y) {
+  return x.prefix_id == y.prefix_id &&
+      x.fst_id == y.fst_id &&
+      x.fst_state == y.fst_state;
+}
+
+
+// \class ReplaceRootSelector
+// Functor returning true for tuples corresponding to states in the root FST
+template <class S, class P>
+class ReplaceRootSelector {
+ public:
+  bool operator()(const ReplaceStateTuple<S, P> &tuple) const {
+    return tuple.prefix_id == 0;
+  }
+};
+
+
+// \class ReplaceFingerprint
+// Fingerprint for general replace state tuples.
+template <class S, class P>
+class ReplaceFingerprint {
+ public:
+  ReplaceFingerprint(const vector<uint64> *size_array)
+      : cumulative_size_array_(size_array) {}
+
+  uint64 operator()(const ReplaceStateTuple<S, P> &tuple) const {
+    return tuple.prefix_id * (cumulative_size_array_->back()) +
+        cumulative_size_array_->at(tuple.fst_id - 1) +
+        tuple.fst_state;
+  }
+
+ private:
+  const vector<uint64> *cumulative_size_array_;
+};
+
+
+// \class ReplaceFstStateFingerprint
+// Useful when the fst_state uniquely define the tuple.
+template <class S, class P>
+class ReplaceFstStateFingerprint {
+ public:
+  uint64 operator()(const ReplaceStateTuple<S, P>& tuple) const {
+    return tuple.fst_state;
+  }
+};
+
+
+// \class ReplaceHash
+// A generic hash function for replace state tuples.
+template <typename S, typename P>
+class ReplaceHash {
+ public:
+  size_t operator()(const ReplaceStateTuple<S, P>& t) const {
+    return t.prefix_id + t.fst_id * kPrime0 + t.fst_state * kPrime1;
+  }
+ private:
+  static const size_t kPrime0;
+  static const size_t kPrime1;
+};
+
+template <typename S, typename P>
+const size_t ReplaceHash<S, P>::kPrime0 = 7853;
+
+template <typename S, typename P>
+const size_t ReplaceHash<S, P>::kPrime1 = 7867;
+
+template <class A, class T> class ReplaceFstMatcher;
+
+
+// \class VectorHashReplaceStateTable
+// A two-level state table for replace.
+// Warning: calls CountStates to compute the number of states of each
+// component Fst.
+template <class A, class P = ssize_t>
+class VectorHashReplaceStateTable {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef P PrefixId;
+  typedef ReplaceStateTuple<StateId, P> StateTuple;
+  typedef VectorHashStateTable<ReplaceStateTuple<StateId, P>,
+                               ReplaceRootSelector<StateId, P>,
+                               ReplaceFstStateFingerprint<StateId, P>,
+                               ReplaceFingerprint<StateId, P> > StateTable;
+
+  VectorHashReplaceStateTable(
+      const vector<pair<Label, const Fst<A>*> > &fst_tuples,
+      Label root) : root_size_(0) {
+    cumulative_size_array_.push_back(0);
+    for (size_t i = 0; i < fst_tuples.size(); ++i) {
+      if (fst_tuples[i].first == root) {
+        root_size_ = CountStates(*(fst_tuples[i].second));
+        cumulative_size_array_.push_back(cumulative_size_array_.back());
+      } else {
+        cumulative_size_array_.push_back(cumulative_size_array_.back() +
+                                         CountStates(*(fst_tuples[i].second)));
+      }
+    }
+    state_table_ = new StateTable(
+        new ReplaceRootSelector<StateId, P>,
+        new ReplaceFstStateFingerprint<StateId, P>,
+        new ReplaceFingerprint<StateId, P>(&cumulative_size_array_),
+        root_size_,
+        root_size_ + cumulative_size_array_.back());
+  }
+
+  VectorHashReplaceStateTable(const VectorHashReplaceStateTable<A, P> &table)
+      : root_size_(table.root_size_),
+        cumulative_size_array_(table.cumulative_size_array_) {
+    state_table_ = new StateTable(
+        new ReplaceRootSelector<StateId, P>,
+        new ReplaceFstStateFingerprint<StateId, P>,
+        new ReplaceFingerprint<StateId, P>(&cumulative_size_array_),
+        root_size_,
+        root_size_ + cumulative_size_array_.back());
+  }
+
+  ~VectorHashReplaceStateTable() {
+    delete state_table_;
+  }
+
+  StateId FindState(const StateTuple &tuple) {
+    return state_table_->FindState(tuple);
+  }
+
+  const StateTuple &Tuple(StateId id) const {
+    return state_table_->Tuple(id);
+  }
+
+ private:
+  StateId root_size_;
+  vector<uint64> cumulative_size_array_;
+  StateTable *state_table_;
+};
+
+
+// \class DefaultReplaceStateTable
+// Default replace state table
+template <class A, class P = ssize_t>
+class DefaultReplaceStateTable : public CompactHashStateTable<
+  ReplaceStateTuple<typename A::StateId, P>,
+  ReplaceHash<typename A::StateId, P> > {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef P PrefixId;
+  typedef ReplaceStateTuple<StateId, P> StateTuple;
+  typedef CompactHashStateTable<StateTuple,
+                                ReplaceHash<StateId, PrefixId> > StateTable;
+
+  using StateTable::FindState;
+  using StateTable::Tuple;
+
+  DefaultReplaceStateTable(
+      const vector<pair<Label, const Fst<A>*> > &fst_tuples,
+      Label root) {}
+
+  DefaultReplaceStateTable(const DefaultReplaceStateTable<A, P> &table)
+      : StateTable() {}
+};
+
+//
+// REPLACE FST CLASS
+//
+
+// By default ReplaceFst will copy the input label of the 'replace arc'.
+// For acceptors we do not want this behaviour. Instead we need to
+// create an epsilon arc when recursing into the appropriate Fst.
+// The 'epsilon_on_replace' option can be used to toggle this behaviour.
+template <class A, class T = DefaultReplaceStateTable<A> >
+struct ReplaceFstOptions : CacheOptions {
+  int64 root;    // root rule for expansion
+  bool  epsilon_on_replace;
+  bool  take_ownership;  // take ownership of input Fst(s)
+  T*    state_table;
+
+  ReplaceFstOptions(const CacheOptions &opts, int64 r)
+      : CacheOptions(opts),
+        root(r),
+        epsilon_on_replace(false),
+        take_ownership(false),
+        state_table(0) {}
+  explicit ReplaceFstOptions(int64 r)
+      : root(r),
+        epsilon_on_replace(false),
+        take_ownership(false),
+        state_table(0) {}
+  ReplaceFstOptions(int64 r, bool epsilon_replace_arc)
+      : root(r),
+        epsilon_on_replace(epsilon_replace_arc),
+        take_ownership(false),
+        state_table(0) {}
+  ReplaceFstOptions()
+      : root(kNoLabel),
+        epsilon_on_replace(false),
+        take_ownership(false),
+        state_table(0) {}
+};
+
+
+// \class ReplaceFstImpl
+// \brief Implementation class for replace class Fst
+//
+// The replace implementation class supports a dynamic
+// expansion of a recursive transition network represented as Fst
+// with dynamic replacable arcs.
+//
+template <class A, class T>
+class ReplaceFstImpl : public CacheImpl<A> {
+  friend class ReplaceFstMatcher<A, T>;
+
+ public:
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::WriteHeader;
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+  using FstImpl<A>::InputSymbols;
+  using FstImpl<A>::OutputSymbols;
+
+  using CacheImpl<A>::PushArc;
+  using CacheImpl<A>::HasArcs;
+  using CacheImpl<A>::HasFinal;
+  using CacheImpl<A>::HasStart;
+  using CacheImpl<A>::SetArcs;
+  using CacheImpl<A>::SetFinal;
+  using CacheImpl<A>::SetStart;
+
+  typedef typename A::Label   Label;
+  typedef typename A::Weight  Weight;
+  typedef typename A::StateId StateId;
+  typedef CacheState<A> State;
+  typedef A Arc;
+  typedef unordered_map<Label, Label> NonTerminalHash;
+
+  typedef T StateTable;
+  typedef typename T::PrefixId PrefixId;
+  typedef ReplaceStateTuple<StateId, PrefixId> StateTuple;
+
+  // constructor for replace class implementation.
+  // \param fst_tuples array of label/fst tuples, one for each non-terminal
+  ReplaceFstImpl(const vector< pair<Label, const Fst<A>* > >& fst_tuples,
+                 const ReplaceFstOptions<A, T> &opts)
+      : CacheImpl<A>(opts),
+        epsilon_on_replace_(opts.epsilon_on_replace),
+        state_table_(opts.state_table ? opts.state_table :
+                     new StateTable(fst_tuples, opts.root)) {
+
+    SetType("replace");
+
+    if (fst_tuples.size() > 0) {
+      SetInputSymbols(fst_tuples[0].second->InputSymbols());
+      SetOutputSymbols(fst_tuples[0].second->OutputSymbols());
+    }
+
+    bool all_negative = true;  // all nonterminals are negative?
+    bool dense_range = true;   // all nonterminals are positive
+                               // and form a dense range containing 1?
+    for (size_t i = 0; i < fst_tuples.size(); ++i) {
+      Label nonterminal = fst_tuples[i].first;
+      if (nonterminal >= 0)
+        all_negative = false;
+      if (nonterminal > fst_tuples.size() || nonterminal <= 0)
+        dense_range = false;
+    }
+
+    vector<uint64> inprops;
+    bool all_ilabel_sorted = true;
+    bool all_olabel_sorted = true;
+    bool all_non_empty = true;
+    fst_array_.push_back(0);
+    for (size_t i = 0; i < fst_tuples.size(); ++i) {
+      Label label = fst_tuples[i].first;
+      const Fst<A> *fst = fst_tuples[i].second;
+      nonterminal_hash_[label] = fst_array_.size();
+      nonterminal_set_.insert(label);
+      fst_array_.push_back(opts.take_ownership ? fst : fst->Copy());
+      if (fst->Start() == kNoStateId)
+        all_non_empty = false;
+      if(!fst->Properties(kILabelSorted, false))
+        all_ilabel_sorted = false;
+      if(!fst->Properties(kOLabelSorted, false))
+        all_olabel_sorted = false;
+      inprops.push_back(fst->Properties(kCopyProperties, false));
+      if (i) {
+        if (!CompatSymbols(InputSymbols(), fst->InputSymbols())) {
+          FSTERROR() << "ReplaceFstImpl: input symbols of Fst " << i
+                     << " does not match input symbols of base Fst (0'th fst)";
+          SetProperties(kError, kError);
+        }
+        if (!CompatSymbols(OutputSymbols(), fst->OutputSymbols())) {
+          FSTERROR() << "ReplaceFstImpl: output symbols of Fst " << i
+                     << " does not match output symbols of base Fst "
+                     << "(0'th fst)";
+          SetProperties(kError, kError);
+        }
+      }
+    }
+    Label nonterminal = nonterminal_hash_[opts.root];
+    if ((nonterminal == 0) && (fst_array_.size() > 1)) {
+      FSTERROR() << "ReplaceFstImpl: no Fst corresponding to root label '"
+                 << opts.root << "' in the input tuple vector";
+      SetProperties(kError, kError);
+    }
+    root_ = (nonterminal > 0) ? nonterminal : 1;
+
+    SetProperties(ReplaceProperties(inprops, root_ - 1, epsilon_on_replace_,
+                                    all_non_empty));
+    // We assume that all terminals are positive.  The resulting
+    // ReplaceFst is known to be kILabelSorted when all sub-FSTs are
+    // kILabelSorted and one of the 3 following conditions is satisfied:
+    //  1. 'epsilon_on_replace' is false, or
+    //  2. all non-terminals are negative, or
+    //  3. all non-terninals are positive and form a dense range containing 1.
+    if (all_ilabel_sorted &&
+        (!epsilon_on_replace_ || all_negative || dense_range))
+      SetProperties(kILabelSorted, kILabelSorted);
+    // Similarly, the resulting ReplaceFst is known to be
+    // kOLabelSorted when all sub-FSTs are kOLabelSorted and one of
+    // the 2 following conditions is satisfied:
+    //  1. all non-terminals are negative, or
+    //  2. all non-terninals are positive and form a dense range containing 1.
+    if (all_olabel_sorted && (all_negative || dense_range))
+      SetProperties(kOLabelSorted, kOLabelSorted);
+
+    // Enable optional caching as long as sorted and all non empty.
+    if (Properties(kILabelSorted | kOLabelSorted) && all_non_empty)
+      always_cache_ = false;
+    else
+      always_cache_ = true;
+    VLOG(2) << "ReplaceFstImpl::ReplaceFstImpl: always_cache = "
+            << (always_cache_ ? "true" : "false");
+  }
+
+  ReplaceFstImpl(const ReplaceFstImpl& impl)
+      : CacheImpl<A>(impl),
+        epsilon_on_replace_(impl.epsilon_on_replace_),
+        always_cache_(impl.always_cache_),
+        state_table_(new StateTable(*(impl.state_table_))),
+        nonterminal_set_(impl.nonterminal_set_),
+        nonterminal_hash_(impl.nonterminal_hash_),
+        root_(impl.root_) {
+    SetType("replace");
+    SetProperties(impl.Properties(), kCopyProperties);
+    SetInputSymbols(impl.InputSymbols());
+    SetOutputSymbols(impl.OutputSymbols());
+    fst_array_.reserve(impl.fst_array_.size());
+    fst_array_.push_back(0);
+    for (size_t i = 1; i < impl.fst_array_.size(); ++i) {
+      fst_array_.push_back(impl.fst_array_[i]->Copy(true));
+    }
+  }
+
+  ~ReplaceFstImpl() {
+    VLOG(2) << "~ReplaceFstImpl: gc = "
+            << (CacheImpl<A>::GetCacheGc() ? "true" : "false")
+            << ", gc_size = " << CacheImpl<A>::GetCacheSize()
+            << ", gc_limit = " << CacheImpl<A>::GetCacheLimit();
+
+    delete state_table_;
+    for (size_t i = 1; i < fst_array_.size(); ++i) {
+      delete fst_array_[i];
+    }
+  }
+
+  // Computes the dependency graph of the replace class and returns
+  // true if the dependencies are cyclic. Cyclic dependencies will result
+  // in an un-expandable replace fst.
+  bool CyclicDependencies() const {
+    ReplaceUtil<A> replace_util(fst_array_, nonterminal_hash_, root_);
+    return replace_util.CyclicDependencies();
+  }
+
+  // Return or compute start state of replace fst
+  StateId Start() {
+    if (!HasStart()) {
+      if (fst_array_.size() == 1) {      // no fsts defined for replace
+        SetStart(kNoStateId);
+        return kNoStateId;
+      } else {
+        const Fst<A>* fst = fst_array_[root_];
+        StateId fst_start = fst->Start();
+        if (fst_start == kNoStateId)  // root Fst is empty
+          return kNoStateId;
+
+        PrefixId prefix = GetPrefixId(StackPrefix());
+        StateId start = state_table_->FindState(
+            StateTuple(prefix, root_, fst_start));
+        SetStart(start);
+        return start;
+      }
+    } else {
+      return CacheImpl<A>::Start();
+    }
+  }
+
+  // return final weight of state (kInfWeight means state is not final)
+  Weight Final(StateId s) {
+    if (!HasFinal(s)) {
+      const StateTuple& tuple  = state_table_->Tuple(s);
+      const StackPrefix& stack = stackprefix_array_[tuple.prefix_id];
+      const Fst<A>* fst = fst_array_[tuple.fst_id];
+      StateId fst_state = tuple.fst_state;
+
+      if (fst->Final(fst_state) != Weight::Zero() && stack.Depth() == 0)
+        SetFinal(s, fst->Final(fst_state));
+      else
+        SetFinal(s, Weight::Zero());
+    }
+    return CacheImpl<A>::Final(s);
+  }
+
+  size_t NumArcs(StateId s) {
+    if (HasArcs(s)) {  // If state cached, use the cached value.
+      return CacheImpl<A>::NumArcs(s);
+    } else if (always_cache_) {  // If always caching, expand and cache state.
+      Expand(s);
+      return CacheImpl<A>::NumArcs(s);
+    } else {  // Otherwise compute the number of arcs without expanding.
+      StateTuple tuple  = state_table_->Tuple(s);
+      if (tuple.fst_state == kNoStateId)
+        return 0;
+
+      const Fst<A>* fst = fst_array_[tuple.fst_id];
+      size_t num_arcs = fst->NumArcs(tuple.fst_state);
+      if (ComputeFinalArc(tuple, 0))
+        num_arcs++;
+
+      return num_arcs;
+    }
+  }
+
+  // Returns whether a given label is a non terminal
+  bool IsNonTerminal(Label l) const {
+    // TODO(allauzen): be smarter and take advantage of
+    // all_dense or all_negative.
+    // Use also in ComputeArc, this would require changes to replace
+    // so that recursing into an empty fst lead to a non co-accessible
+    // state instead of deleting the arc as done currently.
+    // Current use correct, since i/olabel sorted iff all_non_empty.
+    typename NonTerminalHash::const_iterator it =
+        nonterminal_hash_.find(l);
+    return it != nonterminal_hash_.end();
+  }
+
+  size_t NumInputEpsilons(StateId s) {
+    if (HasArcs(s)) {
+      // If state cached, use the cached value.
+      return CacheImpl<A>::NumInputEpsilons(s);
+    } else if (always_cache_ || !Properties(kILabelSorted)) {
+      // If always caching or if the number of input epsilons is too expensive
+      // to compute without caching (i.e. not ilabel sorted),
+      // then expand and cache state.
+      Expand(s);
+      return CacheImpl<A>::NumInputEpsilons(s);
+    } else {
+      // Otherwise, compute the number of input epsilons without caching.
+      StateTuple tuple  = state_table_->Tuple(s);
+      if (tuple.fst_state == kNoStateId)
+        return 0;
+      const Fst<A>* fst = fst_array_[tuple.fst_id];
+      size_t num  = 0;
+      if (!epsilon_on_replace_) {
+        // If epsilon_on_replace is false, all input epsilon arcs
+        // are also input epsilons arcs in the underlying machine.
+        fst->NumInputEpsilons(tuple.fst_state);
+      } else {
+        // Otherwise, one need to consider that all non-terminal arcs
+        // in the underlying machine also become input epsilon arc.
+        ArcIterator<Fst<A> > aiter(*fst, tuple.fst_state);
+        for (; !aiter.Done() &&
+                 ((aiter.Value().ilabel == 0) ||
+                  IsNonTerminal(aiter.Value().olabel));
+             aiter.Next())
+          ++num;
+      }
+      if (ComputeFinalArc(tuple, 0))
+        num++;
+      return num;
+    }
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    if (HasArcs(s)) {
+      // If state cached, use the cached value.
+      return CacheImpl<A>::NumOutputEpsilons(s);
+    } else if(always_cache_ || !Properties(kOLabelSorted)) {
+      // If always caching or if the number of output epsilons is too expensive
+      // to compute without caching (i.e. not olabel sorted),
+      // then expand and cache state.
+      Expand(s);
+      return CacheImpl<A>::NumOutputEpsilons(s);
+    } else {
+      // Otherwise, compute the number of output epsilons without caching.
+      StateTuple tuple  = state_table_->Tuple(s);
+      if (tuple.fst_state == kNoStateId)
+        return 0;
+      const Fst<A>* fst = fst_array_[tuple.fst_id];
+      size_t num  = 0;
+      ArcIterator<Fst<A> > aiter(*fst, tuple.fst_state);
+      for (; !aiter.Done() &&
+               ((aiter.Value().olabel == 0) ||
+                IsNonTerminal(aiter.Value().olabel));
+           aiter.Next())
+        ++num;
+      if (ComputeFinalArc(tuple, 0))
+        num++;
+      return num;
+    }
+  }
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if (mask & kError) {
+      for (size_t i = 1; i < fst_array_.size(); ++i) {
+        if (fst_array_[i]->Properties(kError, false))
+          SetProperties(kError, kError);
+      }
+    }
+    return FstImpl<Arc>::Properties(mask);
+  }
+
+  // return the base arc iterator, if arcs have not been computed yet,
+  // extend/recurse for new arcs.
+  void InitArcIterator(StateId s, ArcIteratorData<A> *data) {
+    if (!HasArcs(s))
+      Expand(s);
+    CacheImpl<A>::InitArcIterator(s, data);
+    // TODO(allauzen): Set behaviour of generic iterator
+    // Warning: ArcIterator<ReplaceFst<A> >::InitCache()
+    // relies on current behaviour.
+  }
+
+
+  // Extend current state (walk arcs one level deep)
+  void Expand(StateId s) {
+    StateTuple tuple = state_table_->Tuple(s);
+
+    // If local fst is empty
+    if (tuple.fst_state == kNoStateId) {
+      SetArcs(s);
+      return;
+    }
+
+    ArcIterator< Fst<A> > aiter(
+        *(fst_array_[tuple.fst_id]), tuple.fst_state);
+    Arc arc;
+
+    // Create a final arc when needed
+    if (ComputeFinalArc(tuple, &arc))
+      PushArc(s, arc);
+
+    // Expand all arcs leaving the state
+    for (;!aiter.Done(); aiter.Next()) {
+      if (ComputeArc(tuple, aiter.Value(), &arc))
+        PushArc(s, arc);
+    }
+
+    SetArcs(s);
+  }
+
+  void Expand(StateId s, const StateTuple &tuple,
+              const ArcIteratorData<A> &data) {
+     // If local fst is empty
+    if (tuple.fst_state == kNoStateId) {
+      SetArcs(s);
+      return;
+    }
+
+    ArcIterator< Fst<A> > aiter(data);
+    Arc arc;
+
+    // Create a final arc when needed
+    if (ComputeFinalArc(tuple, &arc))
+      AddArc(s, arc);
+
+    // Expand all arcs leaving the state
+    for (; !aiter.Done(); aiter.Next()) {
+      if (ComputeArc(tuple, aiter.Value(), &arc))
+        AddArc(s, arc);
+    }
+
+    SetArcs(s);
+  }
+
+  // If arcp == 0, only returns if a final arc is required, does not
+  // actually compute it.
+  bool ComputeFinalArc(const StateTuple &tuple, A* arcp,
+                       uint32 flags = kArcValueFlags) {
+    const Fst<A>* fst = fst_array_[tuple.fst_id];
+    StateId fst_state = tuple.fst_state;
+    if (fst_state == kNoStateId)
+      return false;
+
+   // if state is final, pop up stack
+    const StackPrefix& stack = stackprefix_array_[tuple.prefix_id];
+    if (fst->Final(fst_state) != Weight::Zero() && stack.Depth()) {
+      if (arcp) {
+        arcp->ilabel = 0;
+        arcp->olabel = 0;
+        if (flags & kArcNextStateValue) {
+          PrefixId prefix_id = PopPrefix(stack);
+          const PrefixTuple& top = stack.Top();
+          arcp->nextstate = state_table_->FindState(
+              StateTuple(prefix_id, top.fst_id, top.nextstate));
+        }
+        if (flags & kArcWeightValue)
+          arcp->weight = fst->Final(fst_state);
+      }
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  // Compute the arc in the replace fst corresponding to a given
+  // in the underlying machine. Returns false if the underlying arc
+  // corresponds to no arc in the replace.
+  bool ComputeArc(const StateTuple &tuple, const A &arc, A* arcp,
+                  uint32 flags = kArcValueFlags) {
+    if (!epsilon_on_replace_ &&
+        (flags == (flags & (kArcILabelValue | kArcWeightValue)))) {
+      *arcp = arc;
+      return true;
+    }
+
+    if (arc.olabel == 0) {  // expand local fst
+      StateId nextstate = flags & kArcNextStateValue
+          ? state_table_->FindState(
+              StateTuple(tuple.prefix_id, tuple.fst_id, arc.nextstate))
+          : kNoStateId;
+      *arcp = A(arc.ilabel, arc.olabel, arc.weight, nextstate);
+    } else {
+      // check for non terminal
+      typename NonTerminalHash::const_iterator it =
+          nonterminal_hash_.find(arc.olabel);
+      if (it != nonterminal_hash_.end()) {  // recurse into non terminal
+        Label nonterminal = it->second;
+        const Fst<A>* nt_fst = fst_array_[nonterminal];
+        PrefixId nt_prefix = PushPrefix(stackprefix_array_[tuple.prefix_id],
+                                        tuple.fst_id, arc.nextstate);
+
+        // if start state is valid replace, else arc is implicitly
+        // deleted
+        StateId nt_start = nt_fst->Start();
+        if (nt_start != kNoStateId) {
+          StateId nt_nextstate =  flags & kArcNextStateValue
+              ? state_table_->FindState(
+                  StateTuple(nt_prefix, nonterminal, nt_start))
+              : kNoStateId;
+          Label ilabel = (epsilon_on_replace_) ? 0 : arc.ilabel;
+          *arcp = A(ilabel, 0, arc.weight, nt_nextstate);
+        } else {
+          return false;
+        }
+      } else {
+        StateId nextstate = flags & kArcNextStateValue
+            ? state_table_->FindState(
+                StateTuple(tuple.prefix_id, tuple.fst_id, arc.nextstate))
+            : kNoStateId;
+        *arcp = A(arc.ilabel, arc.olabel, arc.weight, nextstate);
+      }
+    }
+    return true;
+  }
+
+  // Returns the arc iterator flags supported by this Fst.
+  uint32 ArcIteratorFlags() const {
+    uint32 flags = kArcValueFlags;
+    if (!always_cache_)
+      flags |= kArcNoCache;
+    return flags;
+  }
+
+  T* GetStateTable() const {
+    return state_table_;
+  }
+
+  const Fst<A>* GetFst(Label fst_id) const {
+    return fst_array_[fst_id];
+  }
+
+  bool EpsilonOnReplace() const { return epsilon_on_replace_; }
+
+  // private helper classes
+ private:
+  static const size_t kPrime0;
+
+  // \class PrefixTuple
+  // \brief Tuple of fst_id and destination state (entry in stack prefix)
+  struct PrefixTuple {
+    PrefixTuple(Label f, StateId s) : fst_id(f), nextstate(s) {}
+
+    Label   fst_id;
+    StateId nextstate;
+  };
+
+  // \class StackPrefix
+  // \brief Container for stack prefix.
+  class StackPrefix {
+   public:
+    StackPrefix() {}
+
+    // copy constructor
+    StackPrefix(const StackPrefix& x) :
+        prefix_(x.prefix_) {
+    }
+
+    void Push(StateId fst_id, StateId nextstate) {
+      prefix_.push_back(PrefixTuple(fst_id, nextstate));
+    }
+
+    void Pop() {
+      prefix_.pop_back();
+    }
+
+    const PrefixTuple& Top() const {
+      return prefix_[prefix_.size()-1];
+    }
+
+    size_t Depth() const {
+      return prefix_.size();
+    }
+
+   public:
+    vector<PrefixTuple> prefix_;
+  };
+
+
+  // \class StackPrefixEqual
+  // \brief Compare two stack prefix classes for equality
+  class StackPrefixEqual {
+   public:
+    bool operator()(const StackPrefix& x, const StackPrefix& y) const {
+      if (x.prefix_.size() != y.prefix_.size()) return false;
+      for (size_t i = 0; i < x.prefix_.size(); ++i) {
+        if (x.prefix_[i].fst_id    != y.prefix_[i].fst_id ||
+           x.prefix_[i].nextstate != y.prefix_[i].nextstate) return false;
+      }
+      return true;
+    }
+  };
+
+  //
+  // \class StackPrefixKey
+  // \brief Hash function for stack prefix to prefix id
+  class StackPrefixKey {
+   public:
+    size_t operator()(const StackPrefix& x) const {
+      size_t sum = 0;
+      for (size_t i = 0; i < x.prefix_.size(); ++i) {
+        sum += x.prefix_[i].fst_id + x.prefix_[i].nextstate*kPrime0;
+      }
+      return sum;
+    }
+  };
+
+  typedef unordered_map<StackPrefix, PrefixId, StackPrefixKey, StackPrefixEqual>
+  StackPrefixHash;
+
+  // private methods
+ private:
+  // hash stack prefix (return unique index into stackprefix array)
+  PrefixId GetPrefixId(const StackPrefix& prefix) {
+    typename StackPrefixHash::iterator it = prefix_hash_.find(prefix);
+    if (it == prefix_hash_.end()) {
+      PrefixId prefix_id = stackprefix_array_.size();
+      stackprefix_array_.push_back(prefix);
+      prefix_hash_[prefix] = prefix_id;
+      return prefix_id;
+    } else {
+      return it->second;
+    }
+  }
+
+  // prefix id after a stack pop
+  PrefixId PopPrefix(StackPrefix prefix) {
+    prefix.Pop();
+    return GetPrefixId(prefix);
+  }
+
+  // prefix id after a stack push
+  PrefixId PushPrefix(StackPrefix prefix, Label fst_id, StateId nextstate) {
+    prefix.Push(fst_id, nextstate);
+    return GetPrefixId(prefix);
+  }
+
+
+  // private data
+ private:
+  // runtime options
+  bool epsilon_on_replace_;
+  bool always_cache_;  // Optionally caching arc iterator disabled when true
+
+  // state table
+  StateTable *state_table_;
+
+  // cross index of unique stack prefix
+  // could potentially have one copy of prefix array
+  StackPrefixHash prefix_hash_;
+  vector<StackPrefix> stackprefix_array_;
+
+  set<Label> nonterminal_set_;
+  NonTerminalHash nonterminal_hash_;
+  vector<const Fst<A>*> fst_array_;
+  Label root_;
+
+  void operator=(const ReplaceFstImpl<A, T> &);  // disallow
+};
+
+
+template <class A, class T>
+const size_t ReplaceFstImpl<A, T>::kPrime0 = 7853;
+
+//
+// \class ReplaceFst
+// \brief Recursivively replaces arcs in the root Fst with other Fsts.
+// This version is a delayed Fst.
+//
+// ReplaceFst supports dynamic replacement of arcs in one Fst with
+// another Fst. This replacement is recursive.  ReplaceFst can be used
+// to support a variety of delayed constructions such as recursive
+// transition networks, union, or closure.  It is constructed with an
+// array of Fst(s). One Fst represents the root (or topology)
+// machine. The root Fst refers to other Fsts by recursively replacing
+// arcs labeled as non-terminals with the matching non-terminal
+// Fst. Currently the ReplaceFst uses the output symbols of the arcs
+// to determine whether the arc is a non-terminal arc or not. A
+// non-terminal can be any label that is not a non-zero terminal label
+// in the output alphabet.
+//
+// Note that the constructor uses a vector of pair<>. These correspond
+// to the tuple of non-terminal Label and corresponding Fst. For example
+// to implement the closure operation we need 2 Fsts. The first root
+// Fst is a single Arc on the start State that self loops, it references
+// the particular machine for which we are performing the closure operation.
+//
+// The ReplaceFst class supports an optionally caching arc iterator:
+//    ArcIterator< ReplaceFst<A> >
+// The ReplaceFst need to be built such that it is known to be ilabel
+// or olabel sorted (see usage below).
+//
+// Observe that Matcher<Fst<A> > will use the optionally caching arc
+// iterator when available (Fst is ilabel sorted and matching on the
+// input, or Fst is olabel sorted and matching on the output).
+// In order to obtain the most efficient behaviour, it is recommended
+// to set 'epsilon_on_replace' to false (this means constructing acceptors
+// as transducers with epsilons on the input side of nonterminal arcs)
+// and matching on the input side.
+//
+// This class attaches interface to implementation and handles
+// reference counting, delegating most methods to ImplToFst.
+template <class A, class T = DefaultReplaceStateTable<A> >
+class ReplaceFst : public ImplToFst< ReplaceFstImpl<A, T> > {
+ public:
+  friend class ArcIterator< ReplaceFst<A, T> >;
+  friend class StateIterator< ReplaceFst<A, T> >;
+  friend class ReplaceFstMatcher<A, T>;
+
+  typedef A Arc;
+  typedef typename A::Label   Label;
+  typedef typename A::Weight  Weight;
+  typedef typename A::StateId StateId;
+  typedef CacheState<A> State;
+  typedef ReplaceFstImpl<A, T> Impl;
+
+  using ImplToFst<Impl>::Properties;
+
+  ReplaceFst(const vector<pair<Label, const Fst<A>* > >& fst_array,
+             Label root)
+      : ImplToFst<Impl>(new Impl(fst_array, ReplaceFstOptions<A, T>(root))) {}
+
+  ReplaceFst(const vector<pair<Label, const Fst<A>* > >& fst_array,
+             const ReplaceFstOptions<A, T> &opts)
+      : ImplToFst<Impl>(new Impl(fst_array, opts)) {}
+
+  // See Fst<>::Copy() for doc.
+  ReplaceFst(const ReplaceFst<A, T>& fst, bool safe = false)
+      : ImplToFst<Impl>(fst, safe) {}
+
+  // Get a copy of this ReplaceFst. See Fst<>::Copy() for further doc.
+  virtual ReplaceFst<A, T> *Copy(bool safe = false) const {
+    return new ReplaceFst<A, T>(*this, safe);
+  }
+
+  virtual inline void InitStateIterator(StateIteratorData<A> *data) const;
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<A> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+  virtual MatcherBase<A> *InitMatcher(MatchType match_type) const {
+    if ((GetImpl()->ArcIteratorFlags() & kArcNoCache) &&
+        ((match_type == MATCH_INPUT && Properties(kILabelSorted, false)) ||
+         (match_type == MATCH_OUTPUT && Properties(kOLabelSorted, false)))) {
+      return new ReplaceFstMatcher<A, T>(*this, match_type);
+    }
+    else {
+      VLOG(2) << "Not using replace matcher";
+      return 0;
+    }
+  }
+
+  bool CyclicDependencies() const {
+    return GetImpl()->CyclicDependencies();
+  }
+
+ private:
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const ReplaceFst<A> &fst);  // disallow
+};
+
+
+// Specialization for ReplaceFst.
+template<class A, class T>
+class StateIterator< ReplaceFst<A, T> >
+    : public CacheStateIterator< ReplaceFst<A, T> > {
+ public:
+  explicit StateIterator(const ReplaceFst<A, T> &fst)
+      : CacheStateIterator< ReplaceFst<A, T> >(fst, fst.GetImpl()) {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(StateIterator);
+};
+
+
+// Specialization for ReplaceFst.
+// Implements optional caching. It can be used as follows:
+//
+//   ReplaceFst<A> replace;
+//   ArcIterator< ReplaceFst<A> > aiter(replace, s);
+//   // Note: ArcIterator< Fst<A> > is always a caching arc iterator.
+//   aiter.SetFlags(kArcNoCache, kArcNoCache);
+//   // Use the arc iterator, no arc will be cached, no state will be expanded.
+//   // The varied 'kArcValueFlags' can be used to decide which part
+//   // of arc values needs to be computed.
+//   aiter.SetFlags(kArcILabelValue, kArcValueFlags);
+//   // Only want the ilabel for this arc
+//   aiter.Value();  // Does not compute the destination state.
+//   aiter.Next();
+//   aiter.SetFlags(kArcNextStateValue, kArcNextStateValue);
+//   // Want both ilabel and nextstate for that arc
+//   aiter.Value();  // Does compute the destination state and inserts it
+//                   // in the replace state table.
+//   // No Arc has been cached at that point.
+//
+template <class A, class T>
+class ArcIterator< ReplaceFst<A, T> > {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const ReplaceFst<A, T> &fst, StateId s)
+      : fst_(fst), state_(s), pos_(0), offset_(0), flags_(0), arcs_(0),
+        data_flags_(0), final_flags_(0) {
+    cache_data_.ref_count = 0;
+    local_data_.ref_count = 0;
+
+    // If FST does not support optional caching, force caching.
+    if(!(fst_.GetImpl()->ArcIteratorFlags() & kArcNoCache) &&
+       !(fst_.GetImpl()->HasArcs(state_)))
+       fst_.GetImpl()->Expand(state_);
+
+    // If state is already cached, use cached arcs array.
+    if (fst_.GetImpl()->HasArcs(state_)) {
+      (fst_.GetImpl())->template CacheImpl<A>::InitArcIterator(state_,
+                                                               &cache_data_);
+      num_arcs_ = cache_data_.narcs;
+      arcs_ = cache_data_.arcs;      // 'arcs_' is a ptr to the cached arcs.
+      data_flags_ = kArcValueFlags;  // All the arc member values are valid.
+    } else {  // Otherwise delay decision until Value() is called.
+      tuple_ = fst_.GetImpl()->GetStateTable()->Tuple(state_);
+      if (tuple_.fst_state == kNoStateId) {
+        num_arcs_ = 0;
+      } else {
+        // The decision to cache or not to cache has been defered
+        // until Value() or SetFlags() is called. However, the arc
+        // iterator is set up now to be ready for non-caching in order
+        // to keep the Value() method simple and efficient.
+        const Fst<A>* fst = fst_.GetImpl()->GetFst(tuple_.fst_id);
+        fst->InitArcIterator(tuple_.fst_state, &local_data_);
+        // 'arcs_' is a pointer to the arcs in the underlying machine.
+        arcs_ = local_data_.arcs;
+        // Compute the final arc (but not its destination state)
+        // if a final arc is required.
+        bool has_final_arc = fst_.GetImpl()->ComputeFinalArc(
+            tuple_,
+            &final_arc_,
+            kArcValueFlags & ~kArcNextStateValue);
+        // Set the arc value flags that hold for 'final_arc_'.
+        final_flags_ = kArcValueFlags & ~kArcNextStateValue;
+        // Compute the number of arcs.
+        num_arcs_ = local_data_.narcs;
+        if (has_final_arc)
+          ++num_arcs_;
+        // Set the offset between the underlying arc positions and
+        // the positions in the arc iterator.
+        offset_ = num_arcs_ - local_data_.narcs;
+        // Defers the decision to cache or not until Value() or
+        // SetFlags() is called.
+        data_flags_ = 0;
+      }
+    }
+  }
+
+  ~ArcIterator() {
+    if (cache_data_.ref_count)
+      --(*cache_data_.ref_count);
+    if (local_data_.ref_count)
+      --(*local_data_.ref_count);
+  }
+
+  void ExpandAndCache() const   {
+    // TODO(allauzen): revisit this
+    // fst_.GetImpl()->Expand(state_, tuple_, local_data_);
+    // (fst_.GetImpl())->CacheImpl<A>*>::InitArcIterator(state_,
+    //                                               &cache_data_);
+    //
+    fst_.InitArcIterator(state_, &cache_data_);  // Expand and cache state.
+    arcs_ = cache_data_.arcs;  // 'arcs_' is a pointer to the cached arcs.
+    data_flags_ = kArcValueFlags;  // All the arc member values are valid.
+    offset_ = 0;  // No offset
+
+  }
+
+  void Init() {
+    if (flags_ & kArcNoCache) {  // If caching is disabled
+      // 'arcs_' is a pointer to the arcs in the underlying machine.
+      arcs_ = local_data_.arcs;
+      // Set the arcs value flags that hold for 'arcs_'.
+      data_flags_ = kArcWeightValue;
+      if (!fst_.GetImpl()->EpsilonOnReplace())
+          data_flags_ |= kArcILabelValue;
+      // Set the offset between the underlying arc positions and
+      // the positions in the arc iterator.
+      offset_ = num_arcs_ - local_data_.narcs;
+    } else {  // Otherwise, expand and cache
+      ExpandAndCache();
+    }
+  }
+
+  bool Done() const { return pos_ >= num_arcs_; }
+
+  const A& Value() const {
+    // If 'data_flags_' was set to 0, non-caching was not requested
+    if (!data_flags_) {
+      // TODO(allauzen): revisit this.
+      if (flags_ & kArcNoCache) {
+        // Should never happen.
+        FSTERROR() << "ReplaceFst: inconsistent arc iterator flags";
+      }
+      ExpandAndCache();  // Expand and cache.
+    }
+
+    if (pos_ - offset_ >= 0) {  // The requested arc is not the 'final' arc.
+      const A& arc = arcs_[pos_ - offset_];
+      if ((data_flags_ & flags_) == (flags_ & kArcValueFlags)) {
+        // If the value flags for 'arc' match the recquired value flags
+        // then return 'arc'.
+        return arc;
+      } else {
+        // Otherwise, compute the corresponding arc on-the-fly.
+        fst_.GetImpl()->ComputeArc(tuple_, arc, &arc_, flags_ & kArcValueFlags);
+        return arc_;
+      }
+    } else {  // The requested arc is the 'final' arc.
+      if ((final_flags_ & flags_) != (flags_ & kArcValueFlags)) {
+        // If the arc value flags that hold for the final arc
+        // do not match the requested value flags, then
+        // 'final_arc_' needs to be updated.
+        fst_.GetImpl()->ComputeFinalArc(tuple_, &final_arc_,
+                                    flags_ & kArcValueFlags);
+        final_flags_ = flags_ & kArcValueFlags;
+      }
+      return final_arc_;
+    }
+  }
+
+  void Next() { ++pos_; }
+
+  size_t Position() const { return pos_; }
+
+  void Reset() { pos_ = 0;  }
+
+  void Seek(size_t pos) { pos_ = pos; }
+
+  uint32 Flags() const { return flags_; }
+
+  void SetFlags(uint32 f, uint32 mask) {
+    // Update the flags taking into account what flags are supported
+    // by the Fst.
+    flags_ &= ~mask;
+    flags_ |= (f & fst_.GetImpl()->ArcIteratorFlags());
+    // If non-caching is not requested (and caching has not already
+    // been performed), then flush 'data_flags_' to request caching
+    // during the next call to Value().
+    if (!(flags_ & kArcNoCache) && data_flags_ != kArcValueFlags) {
+      if (!fst_.GetImpl()->HasArcs(state_))
+         data_flags_ = 0;
+    }
+    // If 'data_flags_' has been flushed but non-caching is requested
+    // before calling Value(), then set up the iterator for non-caching.
+    if ((f & kArcNoCache) && (!data_flags_))
+      Init();
+  }
+
+ private:
+  const ReplaceFst<A, T> &fst_;           // Reference to the FST
+  StateId state_;                         // State in the FST
+  mutable typename T::StateTuple tuple_;  // Tuple corresponding to state_
+
+  ssize_t pos_;             // Current position
+  mutable ssize_t offset_;  // Offset between position in iterator and in arcs_
+  ssize_t num_arcs_;        // Number of arcs at state_
+  uint32 flags_;            // Behavorial flags for the arc iterator
+  mutable Arc arc_;         // Memory to temporarily store computed arcs
+
+  mutable ArcIteratorData<Arc> cache_data_;  // Arc iterator data in cache
+  mutable ArcIteratorData<Arc> local_data_;  // Arc iterator data in local fst
+
+  mutable const A* arcs_;       // Array of arcs
+  mutable uint32 data_flags_;   // Arc value flags valid for data in arcs_
+  mutable Arc final_arc_;       // Final arc (when required)
+  mutable uint32 final_flags_;  // Arc value flags valid for final_arc_
+
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+
+template <class A, class T>
+class ReplaceFstMatcher : public MatcherBase<A> {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef MultiEpsMatcher<Matcher<Fst<A> > > LocalMatcher;
+
+  ReplaceFstMatcher(const ReplaceFst<A, T> &fst, fst::MatchType match_type)
+      : fst_(fst),
+        impl_(fst_.GetImpl()),
+        s_(fst::kNoStateId),
+        match_type_(match_type),
+        current_loop_(false),
+        final_arc_(false),
+        loop_(fst::kNoLabel, 0, A::Weight::One(), fst::kNoStateId) {
+    if (match_type_ == fst::MATCH_OUTPUT)
+      swap(loop_.ilabel, loop_.olabel);
+    InitMatchers();
+  }
+
+  ReplaceFstMatcher(const ReplaceFstMatcher<A, T> &matcher, bool safe = false)
+      : fst_(matcher.fst_),
+        impl_(fst_.GetImpl()),
+        s_(fst::kNoStateId),
+        match_type_(matcher.match_type_),
+        current_loop_(false),
+        loop_(fst::kNoLabel, 0, A::Weight::One(), fst::kNoStateId) {
+    if (match_type_ == fst::MATCH_OUTPUT)
+      swap(loop_.ilabel, loop_.olabel);
+    InitMatchers();
+  }
+
+  // Create a local matcher for each component Fst of replace.
+  // LocalMatcher is a multi epsilon wrapper matcher. MultiEpsilonMatcher
+  // is used to match each non-terminal arc, since these non-terminal
+  // turn into epsilons on recursion.
+  void InitMatchers() {
+    const vector<const Fst<A>*>& fst_array = impl_->fst_array_;
+    matcher_.resize(fst_array.size(), 0);
+    for (size_t i = 0; i < fst_array.size(); ++i) {
+      if (fst_array[i]) {
+        matcher_[i] =
+            new LocalMatcher(*fst_array[i], match_type_, kMultiEpsList);
+
+        typename set<Label>::iterator it = impl_->nonterminal_set_.begin();
+        for (; it != impl_->nonterminal_set_.end(); ++it) {
+          matcher_[i]->AddMultiEpsLabel(*it);
+        }
+      }
+    }
+  }
+
+  virtual ReplaceFstMatcher<A, T> *Copy(bool safe = false) const {
+    return new ReplaceFstMatcher<A, T>(*this, safe);
+  }
+
+  virtual ~ReplaceFstMatcher() {
+    for (size_t i = 0; i < matcher_.size(); ++i)
+      delete matcher_[i];
+  }
+
+  virtual MatchType Type(bool test) const {
+    if (match_type_ == MATCH_NONE)
+      return match_type_;
+
+    uint64 true_prop =  match_type_ == MATCH_INPUT ?
+        kILabelSorted : kOLabelSorted;
+    uint64 false_prop = match_type_ == MATCH_INPUT ?
+        kNotILabelSorted : kNotOLabelSorted;
+    uint64 props = fst_.Properties(true_prop | false_prop, test);
+
+    if (props & true_prop)
+      return match_type_;
+    else if (props & false_prop)
+      return MATCH_NONE;
+    else
+      return MATCH_UNKNOWN;
+  }
+
+  virtual const Fst<A> &GetFst() const {
+    return fst_;
+  }
+
+  virtual uint64 Properties(uint64 props) const {
+    return props;
+  }
+
+ private:
+  // Set the sate from which our matching happens.
+  virtual void SetState_(StateId s) {
+    if (s_ == s) return;
+
+    s_ = s;
+    tuple_ = impl_->GetStateTable()->Tuple(s_);
+    if (tuple_.fst_state == kNoStateId) {
+      done_ = true;
+      return;
+    }
+    // Get current matcher. Used for non epsilon matching
+    current_matcher_ = matcher_[tuple_.fst_id];
+    current_matcher_->SetState(tuple_.fst_state);
+    loop_.nextstate = s_;
+
+    final_arc_ = false;
+  }
+
+  // Search for label, from previous set state. If label == 0, first
+  // hallucinate and epsilon loop, else use the underlying matcher to
+  // search for the label or epsilons.
+  // - Note since the ReplaceFST recursion on non-terminal arcs causes
+  //   epsilon transitions to be created we use the MultiEpsilonMatcher
+  //   to search for possible matches of non terminals.
+  // - If the component Fst reaches a final state we also need to add
+  //   the exiting final arc.
+  virtual bool Find_(Label label) {
+    bool found = false;
+    label_ = label;
+    if (label_ == 0 || label_ == kNoLabel) {
+      // Compute loop directly, saving Replace::ComputeArc
+      if (label_ == 0) {
+        current_loop_ = true;
+        found = true;
+      }
+      // Search for matching multi epsilons
+      final_arc_ = impl_->ComputeFinalArc(tuple_, 0);
+      found = current_matcher_->Find(kNoLabel) || final_arc_ || found;
+    } else {
+      // Search on sub machine directly using sub machine matcher.
+      found = current_matcher_->Find(label_);
+    }
+    return found;
+  }
+
+  virtual bool Done_() const {
+    return !current_loop_ && !final_arc_ && current_matcher_->Done();
+  }
+
+  virtual const Arc& Value_() const {
+    if (current_loop_) {
+      return loop_;
+    }
+    if (final_arc_) {
+      impl_->ComputeFinalArc(tuple_, &arc_);
+      return arc_;
+    }
+    const Arc& component_arc = current_matcher_->Value();
+    impl_->ComputeArc(tuple_, component_arc, &arc_);
+    return arc_;
+  }
+
+  virtual void Next_() {
+    if (current_loop_) {
+      current_loop_ = false;
+      return;
+    }
+    if (final_arc_) {
+      final_arc_ = false;
+      return;
+    }
+    current_matcher_->Next();
+  }
+
+  const ReplaceFst<A, T>& fst_;
+  ReplaceFstImpl<A, T> *impl_;
+  LocalMatcher* current_matcher_;
+  vector<LocalMatcher*> matcher_;
+
+  StateId s_;                        // Current state
+  Label label_;                      // Current label
+
+  MatchType match_type_;             // Supplied by caller
+  mutable bool done_;
+  mutable bool current_loop_;        // Current arc is the implicit loop
+  mutable bool final_arc_;           // Current arc for exiting recursion
+  mutable typename T::StateTuple tuple_;  // Tuple corresponding to state_
+  mutable Arc arc_;
+  Arc loop_;
+};
+
+template <class A, class T> inline
+void ReplaceFst<A, T>::InitStateIterator(StateIteratorData<A> *data) const {
+  data->base = new StateIterator< ReplaceFst<A, T> >(*this);
+}
+
+typedef ReplaceFst<StdArc> StdReplaceFst;
+
+
+// // Recursivively replaces arcs in the root Fst with other Fsts.
+// This version writes the result of replacement to an output MutableFst.
+//
+// Replace supports replacement of arcs in one Fst with another
+// Fst. This replacement is recursive.  Replace takes an array of
+// Fst(s). One Fst represents the root (or topology) machine. The root
+// Fst refers to other Fsts by recursively replacing arcs labeled as
+// non-terminals with the matching non-terminal Fst. Currently Replace
+// uses the output symbols of the arcs to determine whether the arc is
+// a non-terminal arc or not. A non-terminal can be any label that is
+// not a non-zero terminal label in the output alphabet.  Note that
+// input argument is a vector of pair<>. These correspond to the tuple
+// of non-terminal Label and corresponding Fst.
+template<class Arc>
+void Replace(const vector<pair<typename Arc::Label,
+             const Fst<Arc>* > >& ifst_array,
+             MutableFst<Arc> *ofst, typename Arc::Label root,
+             bool epsilon_on_replace) {
+  ReplaceFstOptions<Arc> opts(root, epsilon_on_replace);
+  opts.gc_limit = 0;  // Cache only the last state for fastest copy.
+  *ofst = ReplaceFst<Arc>(ifst_array, opts);
+}
+
+template<class Arc>
+void Replace(const vector<pair<typename Arc::Label,
+             const Fst<Arc>* > >& ifst_array,
+             MutableFst<Arc> *ofst, typename Arc::Label root) {
+  Replace(ifst_array, ofst, root, false);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_REPLACE_H__
diff --git a/src/include/fst/reverse.h b/src/include/fst/reverse.h
new file mode 100644
index 0000000..4d4c75c
--- /dev/null
+++ b/src/include/fst/reverse.h
@@ -0,0 +1,91 @@
+// reverse.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Functions and classes to sort arcs in an FST.
+
+#ifndef FST_LIB_REVERSE_H__
+#define FST_LIB_REVERSE_H__
+
+#include <algorithm>
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+
+
+namespace fst {
+
+// Reverses an FST. The reversed result is written to an output
+// MutableFst.  If A transduces string x to y with weight a, then the
+// reverse of A transduces the reverse of x to the reverse of y with
+// weight a.Reverse().
+//
+// Typically, a = a.Reverse() and Arc = RevArc (e.g. for
+// TropicalWeight or LogWeight).  In general, e.g. when the weights
+// only form a left or right semiring, the output arc type must match
+// the input arc type except having the reversed Weight type.
+template<class Arc, class RevArc>
+void Reverse(const Fst<Arc> &ifst, MutableFst<RevArc> *ofst) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef typename RevArc::Weight RevWeight;
+
+  ofst->DeleteStates();
+  ofst->SetInputSymbols(ifst.InputSymbols());
+  ofst->SetOutputSymbols(ifst.OutputSymbols());
+  if (ifst.Properties(kExpanded, false))
+    ofst->ReserveStates(CountStates(ifst) + 1);
+  StateId istart = ifst.Start();
+  StateId ostart = ofst->AddState();
+  ofst->SetStart(ostart);
+
+  for (StateIterator< Fst<Arc> > siter(ifst);
+       !siter.Done();
+       siter.Next()) {
+    StateId is = siter.Value();
+    StateId os = is + 1;
+    while (ofst->NumStates() <= os)
+      ofst->AddState();
+    if (is == istart)
+      ofst->SetFinal(os, RevWeight::One());
+
+    Weight final = ifst.Final(is);
+    if (final != Weight::Zero()) {
+      RevArc oarc(0, 0, final.Reverse(), os);
+      ofst->AddArc(0, oarc);
+    }
+
+    for (ArcIterator< Fst<Arc> > aiter(ifst, is);
+         !aiter.Done();
+         aiter.Next()) {
+      const Arc &iarc = aiter.Value();
+      RevArc oarc(iarc.ilabel, iarc.olabel, iarc.weight.Reverse(), os);
+      StateId nos = iarc.nextstate + 1;
+      while (ofst->NumStates() <= nos)
+        ofst->AddState();
+      ofst->AddArc(nos, oarc);
+    }
+  }
+  uint64 iprops = ifst.Properties(kCopyProperties, false);
+  uint64 oprops = ofst->Properties(kFstProperties, false);
+  ofst->SetProperties(ReverseProperties(iprops) | oprops, kFstProperties);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_REVERSE_H__
diff --git a/src/include/fst/reweight.h b/src/include/fst/reweight.h
new file mode 100644
index 0000000..c051c2a
--- /dev/null
+++ b/src/include/fst/reweight.h
@@ -0,0 +1,146 @@
+// reweight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Function to reweight an FST.
+
+#ifndef FST_LIB_REWEIGHT_H__
+#define FST_LIB_REWEIGHT_H__
+
+#include <vector>
+using std::vector;
+
+#include <fst/mutable-fst.h>
+
+
+namespace fst {
+
+enum ReweightType { REWEIGHT_TO_INITIAL, REWEIGHT_TO_FINAL };
+
+// Reweight FST according to the potentials defined by the POTENTIAL
+// vector in the direction defined by TYPE. Weight needs to be left
+// distributive when reweighting towards the initial state and right
+// distributive when reweighting towards the final states.
+//
+// An arc of weight w, with an origin state of potential p and
+// destination state of potential q, is reweighted by p\wq when
+// reweighting towards the initial state and by pw/q when reweighting
+// towards the final states.
+template <class Arc>
+void Reweight(MutableFst<Arc> *fst,
+              const vector<typename Arc::Weight> &potential,
+              ReweightType type) {
+  typedef typename Arc::Weight Weight;
+
+  if (fst->NumStates() == 0)
+    return;
+
+  if (type == REWEIGHT_TO_FINAL && !(Weight::Properties() & kRightSemiring)) {
+    FSTERROR() << "Reweight: Reweighting to the final states requires "
+               << "Weight to be right distributive: "
+               << Weight::Type();
+    fst->SetProperties(kError, kError);
+    return;
+  }
+
+  if (type == REWEIGHT_TO_INITIAL && !(Weight::Properties() & kLeftSemiring)) {
+    FSTERROR() << "Reweight: Reweighting to the initial state requires "
+               << "Weight to be left distributive: "
+               << Weight::Type();
+    fst->SetProperties(kError, kError);
+    return;
+  }
+
+  StateIterator< MutableFst<Arc> > sit(*fst);
+  for (; !sit.Done(); sit.Next()) {
+    typename Arc::StateId state = sit.Value();
+    if (state == potential.size())
+      break;
+    typename Arc::Weight weight = potential[state];
+    if (weight != Weight::Zero()) {
+      for (MutableArcIterator< MutableFst<Arc> > ait(fst, state);
+           !ait.Done();
+           ait.Next()) {
+        Arc arc = ait.Value();
+        if (arc.nextstate >= potential.size())
+          continue;
+        typename Arc::Weight nextweight = potential[arc.nextstate];
+        if (nextweight == Weight::Zero())
+          continue;
+        if (type == REWEIGHT_TO_INITIAL)
+          arc.weight = Divide(Times(arc.weight, nextweight), weight,
+                              DIVIDE_LEFT);
+        if (type == REWEIGHT_TO_FINAL)
+          arc.weight = Divide(Times(weight, arc.weight), nextweight,
+                              DIVIDE_RIGHT);
+        ait.SetValue(arc);
+      }
+      if (type == REWEIGHT_TO_INITIAL)
+        fst->SetFinal(state, Divide(fst->Final(state), weight, DIVIDE_LEFT));
+    }
+    if (type == REWEIGHT_TO_FINAL)
+      fst->SetFinal(state, Times(weight, fst->Final(state)));
+  }
+
+  // This handles elements past the end of the potentials array.
+  for (; !sit.Done(); sit.Next()) {
+    typename Arc::StateId state = sit.Value();
+    if (type == REWEIGHT_TO_FINAL)
+      fst->SetFinal(state, Times(Weight::Zero(), fst->Final(state)));
+  }
+
+  typename Arc::Weight startweight = fst->Start() < potential.size() ?
+      potential[fst->Start()] : Weight::Zero();
+  if ((startweight != Weight::One()) && (startweight != Weight::Zero())) {
+    if (fst->Properties(kInitialAcyclic, true) & kInitialAcyclic) {
+      typename Arc::StateId state = fst->Start();
+      for (MutableArcIterator< MutableFst<Arc> > ait(fst, state);
+           !ait.Done();
+           ait.Next()) {
+        Arc arc = ait.Value();
+        if (type == REWEIGHT_TO_INITIAL)
+          arc.weight = Times(startweight, arc.weight);
+        else
+          arc.weight = Times(
+              Divide(Weight::One(), startweight, DIVIDE_RIGHT),
+              arc.weight);
+        ait.SetValue(arc);
+      }
+      if (type == REWEIGHT_TO_INITIAL)
+        fst->SetFinal(state, Times(startweight, fst->Final(state)));
+      else
+        fst->SetFinal(state, Times(Divide(Weight::One(), startweight,
+                                          DIVIDE_RIGHT),
+                                   fst->Final(state)));
+    } else {
+      typename Arc::StateId state = fst->AddState();
+      Weight w = type == REWEIGHT_TO_INITIAL ?  startweight :
+                 Divide(Weight::One(), startweight, DIVIDE_RIGHT);
+      Arc arc(0, 0, w, fst->Start());
+      fst->AddArc(state, arc);
+      fst->SetStart(state);
+    }
+  }
+
+  fst->SetProperties(ReweightProperties(
+                         fst->Properties(kFstProperties, false)),
+                     kFstProperties);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_REWEIGHT_H_
diff --git a/src/include/fst/rmepsilon.h b/src/include/fst/rmepsilon.h
new file mode 100644
index 0000000..ee9753e
--- /dev/null
+++ b/src/include/fst/rmepsilon.h
@@ -0,0 +1,601 @@
+// rmepsilon.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Functions and classes that implemement epsilon-removal.
+
+#ifndef FST_LIB_RMEPSILON_H__
+#define FST_LIB_RMEPSILON_H__
+
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <fst/slist.h>
+#include <stack>
+#include <string>
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+#include <fst/arcfilter.h>
+#include <fst/cache.h>
+#include <fst/connect.h>
+#include <fst/factor-weight.h>
+#include <fst/invert.h>
+#include <fst/prune.h>
+#include <fst/queue.h>
+#include <fst/shortest-distance.h>
+#include <fst/topsort.h>
+
+
+namespace fst {
+
+template <class Arc, class Queue>
+class RmEpsilonOptions
+    : public ShortestDistanceOptions<Arc, Queue, EpsilonArcFilter<Arc> > {
+ public:
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+
+  bool connect;              // Connect output
+  Weight weight_threshold;   // Pruning weight threshold.
+  StateId state_threshold;   // Pruning state threshold.
+
+  explicit RmEpsilonOptions(Queue *q, float d = kDelta, bool c = true,
+                            Weight w = Weight::Zero(),
+                            StateId n = kNoStateId)
+      : ShortestDistanceOptions< Arc, Queue, EpsilonArcFilter<Arc> >(
+          q, EpsilonArcFilter<Arc>(), kNoStateId, d),
+        connect(c), weight_threshold(w), state_threshold(n) {}
+ private:
+  RmEpsilonOptions();  // disallow
+};
+
+// Computation state of the epsilon-removal algorithm.
+template <class Arc, class Queue>
+class RmEpsilonState {
+ public:
+  typedef typename Arc::Label Label;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+
+  RmEpsilonState(const Fst<Arc> &fst,
+                 vector<Weight> *distance,
+                 const RmEpsilonOptions<Arc, Queue> &opts)
+      : fst_(fst), distance_(distance), sd_state_(fst_, distance, opts, true),
+        expand_id_(0) {}
+
+  // Compute arcs and final weight for state 's'
+  void Expand(StateId s);
+
+  // Returns arcs of expanded state.
+  vector<Arc> &Arcs() { return arcs_; }
+
+  // Returns final weight of expanded state.
+  const Weight &Final() const { return final_; }
+
+  // Return true if an error has occured.
+  bool Error() const { return sd_state_.Error(); }
+
+ private:
+  static const size_t kPrime0 = 7853;
+  static const size_t kPrime1 = 7867;
+
+  struct Element {
+    Label ilabel;
+    Label olabel;
+    StateId nextstate;
+
+    Element() {}
+
+    Element(Label i, Label o, StateId s)
+        : ilabel(i), olabel(o), nextstate(s) {}
+  };
+
+  class ElementKey {
+   public:
+    size_t operator()(const Element& e) const {
+      return static_cast<size_t>(e.nextstate);
+      return static_cast<size_t>(e.nextstate +
+                                 e.ilabel * kPrime0 +
+                                 e.olabel * kPrime1);
+    }
+
+   private:
+  };
+
+  class ElementEqual {
+   public:
+    bool operator()(const Element &e1, const Element &e2) const {
+      return (e1.ilabel == e2.ilabel) &&  (e1.olabel == e2.olabel)
+                         && (e1.nextstate == e2.nextstate);
+    }
+  };
+
+  typedef unordered_map<Element, pair<StateId, size_t>,
+                   ElementKey, ElementEqual> ElementMap;
+
+  const Fst<Arc> &fst_;
+  // Distance from state being expanded in epsilon-closure.
+  vector<Weight> *distance_;
+  // Shortest distance algorithm computation state.
+  ShortestDistanceState<Arc, Queue, EpsilonArcFilter<Arc> > sd_state_;
+  // Maps an element 'e' to a pair 'p' corresponding to a position
+  // in the arcs vector of the state being expanded. 'e' corresponds
+  // to the position 'p.second' in the 'arcs_' vector if 'p.first' is
+  // equal to the state being expanded.
+  ElementMap element_map_;
+  EpsilonArcFilter<Arc> eps_filter_;
+  stack<StateId> eps_queue_;      // Queue used to visit the epsilon-closure
+  vector<bool> visited_;          // '[i] = true' if state 'i' has been visited
+  slist<StateId> visited_states_; // List of visited states
+  vector<Arc> arcs_;              // Arcs of state being expanded
+  Weight final_;                  // Final weight of state being expanded
+  StateId expand_id_;             // Unique ID for each call to Expand
+
+  DISALLOW_COPY_AND_ASSIGN(RmEpsilonState);
+};
+
+template <class Arc, class Queue>
+const size_t RmEpsilonState<Arc, Queue>::kPrime0;
+template <class Arc, class Queue>
+const size_t RmEpsilonState<Arc, Queue>::kPrime1;
+
+
+template <class Arc, class Queue>
+void RmEpsilonState<Arc,Queue>::Expand(typename Arc::StateId source) {
+   final_ = Weight::Zero();
+   arcs_.clear();
+   sd_state_.ShortestDistance(source);
+   if (sd_state_.Error())
+     return;
+   eps_queue_.push(source);
+
+   while (!eps_queue_.empty()) {
+     StateId state = eps_queue_.top();
+     eps_queue_.pop();
+
+     while (visited_.size() <= state) visited_.push_back(false);
+     if (visited_[state]) continue;
+     visited_[state] = true;
+     visited_states_.push_front(state);
+
+     for (ArcIterator< Fst<Arc> > ait(fst_, state);
+          !ait.Done();
+          ait.Next()) {
+       Arc arc = ait.Value();
+       arc.weight = Times((*distance_)[state], arc.weight);
+
+       if (eps_filter_(arc)) {
+         while (visited_.size() <= arc.nextstate)
+           visited_.push_back(false);
+         if (!visited_[arc.nextstate])
+           eps_queue_.push(arc.nextstate);
+       } else {
+          Element element(arc.ilabel, arc.olabel, arc.nextstate);
+          typename ElementMap::iterator it = element_map_.find(element);
+          if (it == element_map_.end()) {
+            element_map_.insert(
+                pair<Element, pair<StateId, size_t> >
+                (element, pair<StateId, size_t>(expand_id_, arcs_.size())));
+            arcs_.push_back(arc);
+          } else {
+            if (((*it).second).first == expand_id_) {
+              Weight &w = arcs_[((*it).second).second].weight;
+              w = Plus(w, arc.weight);
+            } else {
+              ((*it).second).first = expand_id_;
+              ((*it).second).second = arcs_.size();
+              arcs_.push_back(arc);
+            }
+          }
+        }
+     }
+     final_ = Plus(final_, Times((*distance_)[state], fst_.Final(state)));
+   }
+
+   while (!visited_states_.empty()) {
+     visited_[visited_states_.front()] = false;
+     visited_states_.pop_front();
+   }
+   ++expand_id_;
+}
+
+// Removes epsilon-transitions (when both the input and output label
+// are an epsilon) from a transducer. The result will be an equivalent
+// FST that has no such epsilon transitions.  This version modifies
+// its input. It allows fine control via the options argument; see
+// below for a simpler interface.
+//
+// The vector 'distance' will be used to hold the shortest distances
+// during the epsilon-closure computation. The state queue discipline
+// and convergence delta are taken in the options argument.
+template <class Arc, class Queue>
+void RmEpsilon(MutableFst<Arc> *fst,
+               vector<typename Arc::Weight> *distance,
+               const RmEpsilonOptions<Arc, Queue> &opts) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::Label Label;
+
+  if (fst->Start() == kNoStateId) {
+    return;
+  }
+
+  // 'noneps_in[s]' will be set to true iff 's' admits a non-epsilon
+  // incoming transition or is the start state.
+  vector<bool> noneps_in(fst->NumStates(), false);
+  noneps_in[fst->Start()] = true;
+  for (StateId i = 0; i < fst->NumStates(); ++i) {
+    for (ArcIterator<Fst<Arc> > aiter(*fst, i);
+         !aiter.Done();
+         aiter.Next()) {
+      if (aiter.Value().ilabel != 0 || aiter.Value().olabel != 0)
+        noneps_in[aiter.Value().nextstate] = true;
+    }
+  }
+
+  // States sorted in topological order when (acyclic) or generic
+  // topological order (cyclic).
+  vector<StateId> states;
+  states.reserve(fst->NumStates());
+
+  if (fst->Properties(kTopSorted, false) & kTopSorted) {
+    for (StateId i = 0; i < fst->NumStates(); i++)
+      states.push_back(i);
+  } else if (fst->Properties(kAcyclic, false) & kAcyclic) {
+    vector<StateId> order;
+    bool acyclic;
+    TopOrderVisitor<Arc> top_order_visitor(&order, &acyclic);
+    DfsVisit(*fst, &top_order_visitor, EpsilonArcFilter<Arc>());
+    // Sanity check: should be acyclic if property bit is set.
+    if(!acyclic) {
+      FSTERROR() << "RmEpsilon: inconsistent acyclic property bit";
+      fst->SetProperties(kError, kError);
+      return;
+    }
+    states.resize(order.size());
+    for (StateId i = 0; i < order.size(); i++)
+      states[order[i]] = i;
+  } else {
+     uint64 props;
+     vector<StateId> scc;
+     SccVisitor<Arc> scc_visitor(&scc, 0, 0, &props);
+     DfsVisit(*fst, &scc_visitor, EpsilonArcFilter<Arc>());
+     vector<StateId> first(scc.size(), kNoStateId);
+     vector<StateId> next(scc.size(), kNoStateId);
+     for (StateId i = 0; i < scc.size(); i++) {
+       if (first[scc[i]] != kNoStateId)
+         next[i] = first[scc[i]];
+       first[scc[i]] = i;
+     }
+     for (StateId i = 0; i < first.size(); i++)
+       for (StateId j = first[i]; j != kNoStateId; j = next[j])
+         states.push_back(j);
+  }
+
+  RmEpsilonState<Arc, Queue>
+    rmeps_state(*fst, distance, opts);
+
+  while (!states.empty()) {
+    StateId state = states.back();
+    states.pop_back();
+    if (!noneps_in[state])
+      continue;
+    rmeps_state.Expand(state);
+    fst->SetFinal(state, rmeps_state.Final());
+    fst->DeleteArcs(state);
+    vector<Arc> &arcs = rmeps_state.Arcs();
+    fst->ReserveArcs(state, arcs.size());
+    while (!arcs.empty()) {
+      fst->AddArc(state, arcs.back());
+      arcs.pop_back();
+    }
+  }
+
+  for (StateId s = 0; s < fst->NumStates(); ++s) {
+    if (!noneps_in[s])
+      fst->DeleteArcs(s);
+  }
+
+  if(rmeps_state.Error())
+    fst->SetProperties(kError, kError);
+  fst->SetProperties(
+      RmEpsilonProperties(fst->Properties(kFstProperties, false)),
+      kFstProperties);
+
+  if (opts.weight_threshold != Weight::Zero() ||
+      opts.state_threshold != kNoStateId)
+    Prune(fst, opts.weight_threshold, opts.state_threshold);
+  if (opts.connect && (opts.weight_threshold == Weight::Zero() ||
+                       opts.state_threshold != kNoStateId))
+    Connect(fst);
+}
+
+// Removes epsilon-transitions (when both the input and output label
+// are an epsilon) from a transducer. The result will be an equivalent
+// FST that has no such epsilon transitions. This version modifies its
+// input. It has a simplified interface; see above for a version that
+// allows finer control.
+//
+// Complexity:
+// - Time:
+//   - Unweighted: O(V2 + V E)
+//   - Acyclic: O(V2 + V E)
+//   - Tropical semiring: O(V2 log V + V E)
+//   - General: exponential
+// - Space: O(V E)
+// where V = # of states visited, E = # of arcs.
+//
+// References:
+// - Mehryar Mohri. Generic Epsilon-Removal and Input
+//   Epsilon-Normalization Algorithms for Weighted Transducers,
+//   "International Journal of Computer Science", 13(1):129-143 (2002).
+template <class Arc>
+void RmEpsilon(MutableFst<Arc> *fst,
+               bool connect = true,
+               typename Arc::Weight weight_threshold = Arc::Weight::Zero(),
+               typename Arc::StateId state_threshold = kNoStateId,
+               float delta = kDelta) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::Label Label;
+
+  vector<Weight> distance;
+  AutoQueue<StateId> state_queue(*fst, &distance, EpsilonArcFilter<Arc>());
+  RmEpsilonOptions<Arc, AutoQueue<StateId> >
+      opts(&state_queue, delta, connect, weight_threshold, state_threshold);
+
+  RmEpsilon(fst, &distance, opts);
+}
+
+
+struct RmEpsilonFstOptions : CacheOptions {
+  float delta;
+
+  RmEpsilonFstOptions(const CacheOptions &opts, float delta = kDelta)
+      : CacheOptions(opts), delta(delta) {}
+
+  explicit RmEpsilonFstOptions(float delta = kDelta) : delta(delta) {}
+};
+
+
+// Implementation of delayed RmEpsilonFst.
+template <class A>
+class RmEpsilonFstImpl : public CacheImpl<A> {
+ public:
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+
+  using CacheBaseImpl< CacheState<A> >::PushArc;
+  using CacheBaseImpl< CacheState<A> >::HasArcs;
+  using CacheBaseImpl< CacheState<A> >::HasFinal;
+  using CacheBaseImpl< CacheState<A> >::HasStart;
+  using CacheBaseImpl< CacheState<A> >::SetArcs;
+  using CacheBaseImpl< CacheState<A> >::SetFinal;
+  using CacheBaseImpl< CacheState<A> >::SetStart;
+
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef CacheState<A> State;
+
+  RmEpsilonFstImpl(const Fst<A>& fst, const RmEpsilonFstOptions &opts)
+      : CacheImpl<A>(opts),
+        fst_(fst.Copy()),
+        delta_(opts.delta),
+        rmeps_state_(
+            *fst_,
+            &distance_,
+            RmEpsilonOptions<A, FifoQueue<StateId> >(&queue_, delta_, false)) {
+    SetType("rmepsilon");
+    uint64 props = fst.Properties(kFstProperties, false);
+    SetProperties(RmEpsilonProperties(props, true), kCopyProperties);
+    SetInputSymbols(fst.InputSymbols());
+    SetOutputSymbols(fst.OutputSymbols());
+  }
+
+  RmEpsilonFstImpl(const RmEpsilonFstImpl &impl)
+      : CacheImpl<A>(impl),
+        fst_(impl.fst_->Copy(true)),
+        delta_(impl.delta_),
+        rmeps_state_(
+            *fst_,
+            &distance_,
+            RmEpsilonOptions<A, FifoQueue<StateId> >(&queue_, delta_, false)) {
+    SetType("rmepsilon");
+    SetProperties(impl.Properties(), kCopyProperties);
+    SetInputSymbols(impl.InputSymbols());
+    SetOutputSymbols(impl.OutputSymbols());
+  }
+
+  ~RmEpsilonFstImpl() {
+    delete fst_;
+  }
+
+  StateId Start() {
+    if (!HasStart()) {
+      SetStart(fst_->Start());
+    }
+    return CacheImpl<A>::Start();
+  }
+
+  Weight Final(StateId s) {
+    if (!HasFinal(s)) {
+      Expand(s);
+    }
+    return CacheImpl<A>::Final(s);
+  }
+
+  size_t NumArcs(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumArcs(s);
+  }
+
+  size_t NumInputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumInputEpsilons(s);
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumOutputEpsilons(s);
+  }
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if ((mask & kError) &&
+        (fst_->Properties(kError, false) || rmeps_state_.Error()))
+      SetProperties(kError, kError);
+    return FstImpl<A>::Properties(mask);
+  }
+
+  void InitArcIterator(StateId s, ArcIteratorData<A> *data) {
+    if (!HasArcs(s))
+      Expand(s);
+    CacheImpl<A>::InitArcIterator(s, data);
+  }
+
+  void Expand(StateId s) {
+    rmeps_state_.Expand(s);
+    SetFinal(s, rmeps_state_.Final());
+    vector<A> &arcs = rmeps_state_.Arcs();
+    while (!arcs.empty()) {
+      PushArc(s, arcs.back());
+      arcs.pop_back();
+    }
+    SetArcs(s);
+  }
+
+ private:
+  const Fst<A> *fst_;
+  float delta_;
+  vector<Weight> distance_;
+  FifoQueue<StateId> queue_;
+  RmEpsilonState<A, FifoQueue<StateId> > rmeps_state_;
+
+  void operator=(const RmEpsilonFstImpl<A> &);  // disallow
+};
+
+
+// Removes epsilon-transitions (when both the input and output label
+// are an epsilon) from a transducer. The result will be an equivalent
+// FST that has no such epsilon transitions.  This version is a
+// delayed Fst.
+//
+// Complexity:
+// - Time:
+//   - Unweighted: O(v^2 + v e)
+//   - General: exponential
+// - Space: O(v e)
+// where v = # of states visited, e = # of arcs visited. Constant time
+// to visit an input state or arc is assumed and exclusive of caching.
+//
+// References:
+// - Mehryar Mohri. Generic Epsilon-Removal and Input
+//   Epsilon-Normalization Algorithms for Weighted Transducers,
+//   "International Journal of Computer Science", 13(1):129-143 (2002).
+//
+// This class attaches interface to implementation and handles
+// reference counting, delegating most methods to ImplToFst.
+template <class A>
+class RmEpsilonFst : public ImplToFst< RmEpsilonFstImpl<A> > {
+ public:
+  friend class ArcIterator< RmEpsilonFst<A> >;
+  friend class StateIterator< RmEpsilonFst<A> >;
+
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef CacheState<A> State;
+  typedef RmEpsilonFstImpl<A> Impl;
+
+  RmEpsilonFst(const Fst<A> &fst)
+      : ImplToFst<Impl>(new Impl(fst, RmEpsilonFstOptions())) {}
+
+  RmEpsilonFst(const Fst<A> &fst, const RmEpsilonFstOptions &opts)
+      : ImplToFst<Impl>(new Impl(fst, opts)) {}
+
+  // See Fst<>::Copy() for doc.
+  RmEpsilonFst(const RmEpsilonFst<A> &fst, bool safe = false)
+      : ImplToFst<Impl>(fst, safe) {}
+
+  // Get a copy of this RmEpsilonFst. See Fst<>::Copy() for further doc.
+  virtual RmEpsilonFst<A> *Copy(bool safe = false) const {
+    return new RmEpsilonFst<A>(*this, safe);
+  }
+
+  virtual inline void InitStateIterator(StateIteratorData<A> *data) const;
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+ private:
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const RmEpsilonFst<A> &fst);  // disallow
+};
+
+// Specialization for RmEpsilonFst.
+template<class A>
+class StateIterator< RmEpsilonFst<A> >
+    : public CacheStateIterator< RmEpsilonFst<A> > {
+ public:
+  explicit StateIterator(const RmEpsilonFst<A> &fst)
+      : CacheStateIterator< RmEpsilonFst<A> >(fst, fst.GetImpl()) {}
+};
+
+
+// Specialization for RmEpsilonFst.
+template <class A>
+class ArcIterator< RmEpsilonFst<A> >
+    : public CacheArcIterator< RmEpsilonFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const RmEpsilonFst<A> &fst, StateId s)
+      : CacheArcIterator< RmEpsilonFst<A> >(fst.GetImpl(), s) {
+    if (!fst.GetImpl()->HasArcs(s))
+      fst.GetImpl()->Expand(s);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+
+template <class A> inline
+void RmEpsilonFst<A>::InitStateIterator(StateIteratorData<A> *data) const {
+  data->base = new StateIterator< RmEpsilonFst<A> >(*this);
+}
+
+
+// Useful alias when using StdArc.
+typedef RmEpsilonFst<StdArc> StdRmEpsilonFst;
+
+}  // namespace fst
+
+#endif  // FST_LIB_RMEPSILON_H__
diff --git a/src/include/fst/rmfinalepsilon.h b/src/include/fst/rmfinalepsilon.h
new file mode 100644
index 0000000..236d1a7
--- /dev/null
+++ b/src/include/fst/rmfinalepsilon.h
@@ -0,0 +1,107 @@
+// rmfinalepsilon.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: johans@google.com (Johan Schalkwyk)
+//
+// \file
+// Function to remove of final states that have epsilon only input arcs.
+
+#ifndef FST_LIB_RMFINALEPSILON_H__
+#define FST_LIB_RMFINALEPSILON_H__
+
+#include <unordered_set>
+using std::tr1::unordered_set;
+using std::tr1::unordered_multiset;
+#include <vector>
+using std::vector;
+
+#include <fst/connect.h>
+#include <fst/mutable-fst.h>
+
+
+namespace fst {
+
+template<class A>
+void RmFinalEpsilon(MutableFst<A>* fst) {
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  // Determine the coaccesibility of states.
+  vector<bool> access;
+  vector<bool> coaccess;
+  uint64 props = 0;
+  SccVisitor<A> scc_visitor(0, &access, &coaccess, &props);
+  DfsVisit(*fst, &scc_visitor);
+
+  // Find potential list of removable final states. These are final states
+  // that have no outgoing transitions or final states that have a
+  // non-coaccessible future. Complexity O(S)
+  unordered_set<StateId> finals;
+  for (StateIterator<Fst<A> > siter(*fst); !siter.Done(); siter.Next()) {
+    StateId s = siter.Value();
+    if (fst->Final(s) != Weight::Zero()) {
+      bool future_coaccess = false;
+      for (ArcIterator<Fst<A> > aiter(*fst, s); !aiter.Done(); aiter.Next()) {
+        const A& arc = aiter.Value();
+        if (coaccess[arc.nextstate]) {
+          future_coaccess = true;
+          break;
+        }
+      }
+      if (!future_coaccess) {
+        finals.insert(s);
+      }
+    }
+  }
+
+  // Move the final weight. Complexity O(E)
+  vector<A> arcs;
+  for (StateIterator<Fst<A> > siter(*fst); !siter.Done(); siter.Next()) {
+    StateId s = siter.Value();
+    Weight w(fst->Final(s));
+
+    arcs.clear();
+    for (ArcIterator<Fst<A> > aiter(*fst, s); !aiter.Done(); aiter.Next()) {
+      const A& arc = aiter.Value();
+      // is next state in the list of finals
+      if (finals.find(arc.nextstate) != finals.end()) {
+        // sum up all epsilon arcs
+        if (arc.ilabel == 0 && arc.olabel == 0) {
+          w = Plus(Times(fst->Final(arc.nextstate), arc.weight), w);
+        } else {
+          arcs.push_back(arc);
+        }
+      } else {
+        arcs.push_back(arc);
+      }
+    }
+
+    // If some arcs (epsilon arcs) were deleted, delete all
+    // arcs and add back only the non epsilon arcs
+    if (arcs.size() < fst->NumArcs(s)) {
+      fst->DeleteArcs(s);
+      fst->SetFinal(s, w);
+      for (size_t i = 0; i < arcs.size(); ++i) {
+        fst->AddArc(s, arcs[i]);
+      }
+    }
+  }
+
+  Connect(fst);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_RMFINALEPSILON_H__
diff --git a/src/include/fst/script/arcsort.h b/src/include/fst/script/arcsort.h
new file mode 100644
index 0000000..4277332
--- /dev/null
+++ b/src/include/fst/script/arcsort.h
@@ -0,0 +1,49 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_ARCSORT_H_
+#define FST_SCRIPT_ARCSORT_H_
+
+#include <fst/arcsort.h>
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+
+namespace fst {
+namespace script {
+
+enum ArcSortType { ILABEL_COMPARE, OLABEL_COMPARE };
+
+typedef args::Package<MutableFstClass*, const ArcSortType> ArcSortArgs;
+
+template<class Arc>
+void ArcSort(ArcSortArgs *args) {
+  MutableFst<Arc> *fst = args->arg1->GetMutableFst<Arc>();
+
+  if (args->arg2 == ILABEL_COMPARE) {
+    ILabelCompare<Arc> icomp;
+    ArcSort(fst, icomp);
+  } else {       // OLABEL_COMPARE
+    OLabelCompare<Arc> ocomp;
+    ArcSort(fst, ocomp);
+  }
+}
+
+void ArcSort(MutableFstClass *ofst, ArcSortType sort_type);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_ARCSORT_H_
diff --git a/src/include/fst/script/arg-packs.h b/src/include/fst/script/arg-packs.h
new file mode 100644
index 0000000..8ebf8d8
--- /dev/null
+++ b/src/include/fst/script/arg-packs.h
@@ -0,0 +1,240 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+// Convenience templates for defining arg packs for the FstClass operations.
+
+// See operation-templates.h for a discussion about why these are needed; the
+// short story is that all FstClass operations must be implemented by a version
+// that takes one argument, most likely a struct bundling all the
+// logical arguments together. These template structs provide convenient ways
+// to specify these bundles (e.g. by means of appropriate typedefs).
+
+// The ArgPack template is sufficient for bundling together all the args for
+// a particular function. The function is assumed to be void-returning. If
+// you want a space for a return value, use the WithReturnValue template
+// as follows:
+
+// WithReturnValue<bool, ArgPack<...> >
+
+#ifndef FST_SCRIPT_ARG_PACKS_H_
+#define FST_SCRIPT_ARG_PACKS_H_
+
+namespace fst {
+namespace script {
+namespace args {
+
+// Sentinel value that means "no arg here."
+class none_type { };
+
+// Base arg pack template class. Specializations follow that allow
+// fewer numbers of arguments (down to 2). If the maximum number of arguments
+// increases, you will need to change three things:
+//   1) Add more template parameters to this template
+//   2) Add more specializations to allow fewer numbers of parameters than
+//      the new max.
+//   3) Add extra none_types to all existing specializations to fill
+//      the new slots.
+
+
+// 9 args (max)
+template<class T1,
+         class T2 = none_type,
+         class T3 = none_type,
+         class T4 = none_type,
+         class T5 = none_type,
+         class T6 = none_type,
+         class T7 = none_type,
+         class T8 = none_type,
+         class T9 = none_type>
+struct Package {
+  T1 arg1;
+  T2 arg2;
+  T3 arg3;
+  T4 arg4;
+  T5 arg5;
+  T6 arg6;
+  T7 arg7;
+  T8 arg8;
+  T9 arg9;
+
+  Package(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6,
+          T7 arg7, T8 arg8, T9 arg9) :
+      arg1(arg1), arg2(arg2), arg3(arg3), arg4(arg4), arg5(arg5),
+      arg6(arg6), arg7(arg7), arg8(arg8), arg9(arg9) { }
+};
+
+// 8 args
+template<class T1,
+         class T2,
+         class T3,
+         class T4,
+         class T5,
+         class T6,
+         class T7,
+         class T8>
+struct Package<T1, T2, T3, T4, T5, T6, T7, T8, none_type> {
+  T1 arg1;
+  T2 arg2;
+  T3 arg3;
+  T4 arg4;
+  T5 arg5;
+  T6 arg6;
+  T7 arg7;
+  T8 arg8;
+
+  Package(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6,
+          T7 arg7, T8 arg8) :
+      arg1(arg1), arg2(arg2), arg3(arg3), arg4(arg4), arg5(arg5),
+      arg6(arg6), arg7(arg7), arg8(arg8) { }
+};
+
+// 7 args
+template<class T1,
+         class T2,
+         class T3,
+         class T4,
+         class T5,
+         class T6,
+         class T7>
+struct Package<T1, T2, T3, T4, T5, T6, T7,
+               none_type, none_type> {
+  T1 arg1;
+  T2 arg2;
+  T3 arg3;
+  T4 arg4;
+  T5 arg5;
+  T6 arg6;
+  T7 arg7;
+
+  Package(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6,
+          T7 arg7) :
+      arg1(arg1), arg2(arg2), arg3(arg3), arg4(arg4), arg5(arg5),
+      arg6(arg6), arg7(arg7) { }
+};
+
+// 6 args
+template<class T1,
+         class T2,
+         class T3,
+         class T4,
+         class T5,
+         class T6>
+struct Package<T1, T2, T3, T4, T5, T6, none_type,
+               none_type, none_type> {
+  T1 arg1;
+  T2 arg2;
+  T3 arg3;
+  T4 arg4;
+  T5 arg5;
+  T6 arg6;
+
+  Package(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6) :
+      arg1(arg1), arg2(arg2), arg3(arg3), arg4(arg4), arg5(arg5),
+      arg6(arg6) { }
+};
+
+// 5 args
+template<class T1,
+         class T2,
+         class T3,
+         class T4,
+         class T5>
+struct Package<T1, T2, T3, T4, T5, none_type, none_type,
+               none_type, none_type> {
+  T1 arg1;
+  T2 arg2;
+  T3 arg3;
+  T4 arg4;
+  T5 arg5;
+
+  Package(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5) :
+      arg1(arg1), arg2(arg2), arg3(arg3), arg4(arg4), arg5(arg5) { }
+};
+
+// 4 args
+template<class T1,
+         class T2,
+         class T3,
+         class T4>
+struct Package<T1, T2, T3, T4, none_type, none_type,
+               none_type, none_type, none_type> {
+  T1 arg1;
+  T2 arg2;
+  T3 arg3;
+  T4 arg4;
+
+  Package(T1 arg1, T2 arg2, T3 arg3, T4 arg4) :
+      arg1(arg1), arg2(arg2), arg3(arg3), arg4(arg4) { }
+};
+
+// 3 args
+template<class T1,
+         class T2,
+         class T3>
+struct Package<T1, T2, T3, none_type, none_type,
+               none_type, none_type, none_type,
+               none_type> {
+  T1 arg1;
+  T2 arg2;
+  T3 arg3;
+
+  Package(T1 arg1, T2 arg2, T3 arg3) :
+      arg1(arg1), arg2(arg2), arg3(arg3) { }
+};
+
+// 2 args (minimum)
+template<class T1,
+         class T2>
+struct Package<T1, T2, none_type, none_type,
+               none_type, none_type, none_type,
+               none_type, none_type> {
+  T1 arg1;
+  T2 arg2;
+
+  Package(T1 arg1, T2 arg2) :
+      arg1(arg1), arg2(arg2) { }
+};
+
+// Tack this on to an existing arg pack to add a return value.
+// The syntax for accessing the args is then slightly more stilted,
+// as you must do an extra member access (since the args are stored
+// as a member of this class).
+// The alternative is to declare another slew of templates for functions
+// that return a value, analogous to the above.
+
+template<class Retval, class ArgPackage>
+struct WithReturnValue {
+  Retval retval;
+  const ArgPackage &args;
+
+  explicit WithReturnValue(const ArgPackage &args) : args(args) { }
+};
+
+// We don't want to store a reference to a reference, if ArgPackage is
+// already some reference type.
+template<class Retval, class ArgPackage>
+struct WithReturnValue<Retval, ArgPackage&> {
+  Retval retval;
+  const ArgPackage &args;
+
+  explicit WithReturnValue(const ArgPackage &args) : args(args) { }
+};
+
+}  // namespace args
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_ARG_PACKS_H_
diff --git a/src/include/fst/script/closure.h b/src/include/fst/script/closure.h
new file mode 100644
index 0000000..93b5ec3
--- /dev/null
+++ b/src/include/fst/script/closure.h
@@ -0,0 +1,41 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_CLOSURE_H_
+#define FST_SCRIPT_CLOSURE_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/closure.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<MutableFstClass*, const ClosureType> ClosureArgs;
+
+template<class Arc>
+void Closure(ClosureArgs *args) {
+  MutableFst<Arc> *fst = args->arg1->GetMutableFst<Arc>();
+
+  Closure(fst, args->arg2);
+}
+
+void Closure(MutableFstClass *ofst, ClosureType closure_type);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_CLOSURE_H_
diff --git a/src/include/fst/script/compile-impl.h b/src/include/fst/script/compile-impl.h
new file mode 100644
index 0000000..4aab15b
--- /dev/null
+++ b/src/include/fst/script/compile-impl.h
@@ -0,0 +1,215 @@
+// compile.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to to compile a binary Fst from textual input.
+
+#ifndef FST_SCRIPT_COMPILE_IMPL_H_
+#define FST_SCRIPT_COMPILE_IMPL_H_
+
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <sstream>
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <iostream>
+#include <fstream>
+#include <fst/fst.h>
+#include <fst/util.h>
+#include <fst/vector-fst.h>
+
+DECLARE_string(fst_field_separator);
+
+namespace fst {
+
+// Compile a binary Fst from textual input, helper class for fstcompile.cc
+// WARNING: Stand-alone use of this class not recommended, most code should
+// read/write using the binary format which is much more efficient.
+template <class A> class FstCompiler {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+
+  // WARNING: use of 'allow_negative_labels = true' not recommended; may
+  // cause conflicts
+  FstCompiler(istream &istrm, const string &source,
+            const SymbolTable *isyms, const SymbolTable *osyms,
+            const SymbolTable *ssyms, bool accep, bool ikeep,
+              bool okeep, bool nkeep, bool allow_negative_labels = false)
+      : nline_(0), source_(source),
+        isyms_(isyms), osyms_(osyms), ssyms_(ssyms),
+        nstates_(0), keep_state_numbering_(nkeep),
+        allow_negative_labels_(allow_negative_labels) {
+    char line[kLineLen];
+    while (istrm.getline(line, kLineLen)) {
+      ++nline_;
+      vector<char *> col;
+      string separator = FLAGS_fst_field_separator + "\n";
+      SplitToVector(line, separator.c_str(), &col, true);
+      if (col.size() == 0 || col[0][0] == '\0')  // empty line
+        continue;
+      if (col.size() > 5 ||
+          (col.size() > 4 && accep) ||
+          (col.size() == 3 && !accep)) {
+        FSTERROR() << "FstCompiler: Bad number of columns, source = "
+                   << source_
+                   << ", line = " << nline_;
+        fst_.SetProperties(kError, kError);
+        return;
+      }
+      StateId s = StrToStateId(col[0]);
+      while (s >= fst_.NumStates())
+        fst_.AddState();
+      if (nline_ == 1)
+        fst_.SetStart(s);
+
+      Arc arc;
+      StateId d = s;
+      switch (col.size()) {
+      case 1:
+        fst_.SetFinal(s, Weight::One());
+        break;
+      case 2:
+        fst_.SetFinal(s, StrToWeight(col[1], true));
+        break;
+      case 3:
+        arc.nextstate = d = StrToStateId(col[1]);
+        arc.ilabel = StrToILabel(col[2]);
+        arc.olabel = arc.ilabel;
+        arc.weight = Weight::One();
+        fst_.AddArc(s, arc);
+        break;
+      case 4:
+        arc.nextstate = d = StrToStateId(col[1]);
+        arc.ilabel = StrToILabel(col[2]);
+        if (accep) {
+          arc.olabel = arc.ilabel;
+          arc.weight = StrToWeight(col[3], false);
+        } else {
+          arc.olabel = StrToOLabel(col[3]);
+          arc.weight = Weight::One();
+        }
+        fst_.AddArc(s, arc);
+        break;
+      case 5:
+        arc.nextstate = d = StrToStateId(col[1]);
+        arc.ilabel = StrToILabel(col[2]);
+        arc.olabel = StrToOLabel(col[3]);
+        arc.weight = StrToWeight(col[4], false);
+        fst_.AddArc(s, arc);
+      }
+      while (d >= fst_.NumStates())
+        fst_.AddState();
+    }
+    if (ikeep)
+      fst_.SetInputSymbols(isyms);
+    if (okeep)
+      fst_.SetOutputSymbols(osyms);
+  }
+
+  const VectorFst<A> &Fst() const {
+    return fst_;
+  }
+
+ private:
+  // Maximum line length in text file.
+  static const int kLineLen = 8096;
+
+  int64 StrToId(const char *s, const SymbolTable *syms,
+                const char *name, bool allow_negative = false) const {
+    int64 n = 0;
+
+    if (syms) {
+      n = syms->Find(s);
+      if (n == -1 || (!allow_negative && n < 0)) {
+        FSTERROR() << "FstCompiler: Symbol \"" << s
+                   << "\" is not mapped to any integer " << name
+                   << ", symbol table = " << syms->Name()
+                   << ", source = " << source_ << ", line = " << nline_;
+        fst_.SetProperties(kError, kError);
+      }
+    } else {
+      char *p;
+      n = strtoll(s, &p, 10);
+      if (p < s + strlen(s) || (!allow_negative && n < 0)) {
+        FSTERROR() << "FstCompiler: Bad " << name << " integer = \"" << s
+                   << "\", source = " << source_ << ", line = " << nline_;
+        fst_.SetProperties(kError, kError);
+      }
+    }
+    return n;
+  }
+
+  StateId StrToStateId(const char *s) {
+    StateId n = StrToId(s, ssyms_, "state ID");
+
+    if (keep_state_numbering_)
+      return n;
+
+    // remap state IDs to make dense set
+    typename unordered_map<StateId, StateId>::const_iterator it = states_.find(n);
+    if (it == states_.end()) {
+      states_[n] = nstates_;
+      return nstates_++;
+    } else {
+      return it->second;
+    }
+  }
+
+  StateId StrToILabel(const char *s) const {
+    return StrToId(s, isyms_, "arc ilabel", allow_negative_labels_);
+  }
+
+  StateId StrToOLabel(const char *s) const {
+    return StrToId(s, osyms_, "arc olabel", allow_negative_labels_);
+  }
+
+  Weight StrToWeight(const char *s, bool allow_zero) const {
+    Weight w;
+    istringstream strm(s);
+    strm >> w;
+    if (!strm || (!allow_zero && w == Weight::Zero())) {
+      FSTERROR() << "FstCompiler: Bad weight = \"" << s
+                 << "\", source = " << source_ << ", line = " << nline_;
+      fst_.SetProperties(kError, kError);
+      w = Weight::NoWeight();
+    }
+    return w;
+  }
+
+  mutable VectorFst<A> fst_;
+  size_t nline_;
+  string source_;                      // text FST source name
+  const SymbolTable *isyms_;           // ilabel symbol table
+  const SymbolTable *osyms_;           // olabel symbol table
+  const SymbolTable *ssyms_;           // slabel symbol table
+  unordered_map<StateId, StateId> states_;  // state ID map
+  StateId nstates_;                    // number of seen states
+  bool keep_state_numbering_;
+  bool allow_negative_labels_;         // not recommended; may cause conflicts
+
+  DISALLOW_COPY_AND_ASSIGN(FstCompiler);
+};
+
+}  // namespace fst
+
+#endif  // FST_SCRIPT_COMPILE_IMPL_H_
diff --git a/src/include/fst/script/compile.h b/src/include/fst/script/compile.h
new file mode 100644
index 0000000..bb6ea56
--- /dev/null
+++ b/src/include/fst/script/compile.h
@@ -0,0 +1,92 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_COMPILE_H_
+#define FST_SCRIPT_COMPILE_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/compile-impl.h>
+
+namespace fst {
+namespace script {
+
+// Note: it is safe to pass these strings as references because
+// this struct is only used to pass them deeper in the call graph.
+// Be sure you understand why this is so before using this struct
+// for anything else!
+struct FstCompileArgs {
+  fst::istream &istrm;
+  const string &source;
+  const string &dest;
+  const string &fst_type;
+  const fst::SymbolTable *isyms;
+  const fst::SymbolTable *osyms;
+  const fst::SymbolTable *ssyms;
+  const bool accep;
+  const bool ikeep;
+  const bool okeep;
+  const bool nkeep;
+  const bool allow_negative_labels;
+
+  FstCompileArgs(istream &istrm, const string &source, const string &dest,
+                 const string &fst_type, const fst::SymbolTable *isyms,
+                 const fst::SymbolTable *osyms,
+                 const fst::SymbolTable *ssyms,
+                 bool accep, bool ikeep, bool okeep, bool nkeep,
+                 bool allow_negative_labels = false) :
+      istrm(istrm), source(source), dest(dest), fst_type(fst_type),
+      isyms(isyms), osyms(osyms), ssyms(ssyms), accep(accep), ikeep(ikeep),
+      okeep(okeep), nkeep(nkeep),
+      allow_negative_labels(allow_negative_labels) { }
+};
+
+template<class Arc>
+void CompileFst(FstCompileArgs *args) {
+  using fst::FstCompiler;
+  using fst::Convert;
+  using fst::Fst;
+
+  FstCompiler<Arc> fstcompiler(args->istrm, args->source, args->isyms,
+                               args->osyms, args->ssyms,
+                               args->accep, args->ikeep,
+                               args->okeep, args->nkeep,
+                               args->allow_negative_labels);
+
+  const Fst<Arc> *fst = &fstcompiler.Fst();
+  if (args->fst_type != "vector") {
+    fst = Convert<Arc>(*fst, args->fst_type);
+    if (!fst) {
+      FSTERROR() << "Failed to convert FST to desired type: "
+                 << args->fst_type;
+      return;
+    }
+  }
+
+  fst->Write(args->dest);
+}
+
+void CompileFst(istream &istrm, const string &source, const string &dest,
+                const string &fst_type, const string &arc_type,
+                const SymbolTable *isyms,
+                const SymbolTable *osyms, const SymbolTable *ssyms,
+                bool accep, bool ikeep, bool okeep, bool nkeep,
+                bool allow_negative_labels);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_COMPILE_H_
diff --git a/src/include/fst/script/compose.h b/src/include/fst/script/compose.h
new file mode 100644
index 0000000..96375f7
--- /dev/null
+++ b/src/include/fst/script/compose.h
@@ -0,0 +1,63 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_COMPOSE_H_
+#define FST_SCRIPT_COMPOSE_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/compose.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<const FstClass&, const FstClass&,
+                      MutableFstClass*, ComposeFilter> ComposeArgs1;
+
+template<class Arc>
+void Compose(ComposeArgs1 *args) {
+  const Fst<Arc> &ifst1 = *(args->arg1.GetFst<Arc>());
+  const Fst<Arc> &ifst2 = *(args->arg2.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg3->GetMutableFst<Arc>();
+
+  Compose(ifst1, ifst2, ofst, args->arg4);
+}
+
+typedef fst::ComposeOptions ComposeOptions;
+
+typedef args::Package<const FstClass&, const FstClass&,
+                      MutableFstClass*, const ComposeOptions &> ComposeArgs2;
+
+template<class Arc>
+void Compose(ComposeArgs2 *args) {
+  const Fst<Arc> &ifst1 = *(args->arg1.GetFst<Arc>());
+  const Fst<Arc> &ifst2 = *(args->arg2.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg3->GetMutableFst<Arc>();
+
+  Compose(ifst1, ifst2, ofst, args->arg4);
+}
+
+void Compose(const FstClass &ifst1, const FstClass &ifst2,
+             MutableFstClass *ofst,
+             const ComposeOptions &opts = fst::script::ComposeOptions());
+
+void Compose(const FstClass &ifst1, const FstClass &ifst2,
+             MutableFstClass *ofst, ComposeFilter compose_filter);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_COMPOSE_H_
diff --git a/src/include/fst/script/concat.h b/src/include/fst/script/concat.h
new file mode 100644
index 0000000..46c4407
--- /dev/null
+++ b/src/include/fst/script/concat.h
@@ -0,0 +1,54 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_CONCAT_H_
+#define FST_SCRIPT_CONCAT_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/concat.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<MutableFstClass*, const FstClass&> ConcatArgs1;
+typedef args::Package<const FstClass&, MutableFstClass*> ConcatArgs2;
+
+template<class Arc>
+void Concat(ConcatArgs1 *args) {
+  MutableFst<Arc> *ofst = args->arg1->GetMutableFst<Arc>();
+  const Fst<Arc> &ifst = *(args->arg2.GetFst<Arc>());
+
+  Concat(ofst, ifst);
+}
+
+template<class Arc>
+void Concat(ConcatArgs2 *args) {
+  const Fst<Arc> &ifst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+
+  Concat(ifst, ofst);
+}
+
+void Concat(MutableFstClass *ofst, const FstClass &ifst);
+void Concat(const FstClass &ifst, MutableFstClass *ofst);
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_CONCAT_H_
diff --git a/src/include/fst/script/connect.h b/src/include/fst/script/connect.h
new file mode 100644
index 0000000..19c4390
--- /dev/null
+++ b/src/include/fst/script/connect.h
@@ -0,0 +1,45 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_CONNECT_H_
+#define FST_SCRIPT_CONNECT_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/dfs-visit.h>
+#include <fst/connect.h>
+
+namespace fst {
+namespace script {
+
+// This function confuses SWIG, because both versions have the same args
+#ifndef SWIG
+template<class Arc>
+void Connect(MutableFstClass *fst) {
+  MutableFst<Arc> *typed_fst = fst->GetMutableFst<Arc>();
+
+  Connect(typed_fst);
+}
+#endif
+
+void Connect(MutableFstClass *fst);
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_CONNECT_H_
diff --git a/src/include/fst/script/convert.h b/src/include/fst/script/convert.h
new file mode 100644
index 0000000..2c70a70
--- /dev/null
+++ b/src/include/fst/script/convert.h
@@ -0,0 +1,49 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_CONVERT_H_
+#define FST_SCRIPT_CONVERT_H_
+
+#include <string>
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<const FstClass&, const string&> ConvertInnerArgs;
+typedef args::WithReturnValue<FstClass*, ConvertInnerArgs> ConvertArgs;
+
+template<class Arc>
+void Convert(ConvertArgs *args) {
+  const Fst<Arc> &fst = *(args->args.arg1.GetFst<Arc>());
+  const string &new_type = args->args.arg2;
+
+  Fst<Arc> *result = Convert(fst, new_type);
+  args->retval = new FstClass(result);
+  delete result;
+}
+
+#ifdef SWIG
+%newobject Convert;
+#endif
+FstClass *Convert(const FstClass& f, const string &new_type);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_CONVERT_H_
diff --git a/src/include/fst/script/decode.h b/src/include/fst/script/decode.h
new file mode 100644
index 0000000..1064ad5
--- /dev/null
+++ b/src/include/fst/script/decode.h
@@ -0,0 +1,46 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_DECODE_H_
+#define FST_SCRIPT_DECODE_H_
+
+#include <string>
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/encode.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<MutableFstClass*, const string&> DecodeArgs;
+
+template<class Arc>
+void Decode(DecodeArgs *args) {
+  MutableFst<Arc> *ofst = args->arg1->GetMutableFst<Arc>();
+
+  EncodeMapper<Arc> *decoder = EncodeMapper<Arc>::Read(args->arg2, DECODE);
+  Decode(ofst, *decoder);
+
+  delete decoder;
+}
+
+void Decode(MutableFstClass *fst, const string &coder_fname);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_DECODE_H_
diff --git a/src/include/fst/script/determinize.h b/src/include/fst/script/determinize.h
new file mode 100644
index 0000000..38fd7ad
--- /dev/null
+++ b/src/include/fst/script/determinize.h
@@ -0,0 +1,68 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_DETERMINIZE_H_
+#define FST_SCRIPT_DETERMINIZE_H_
+
+#include <fst/determinize.h>
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/weight-class.h>
+
+namespace fst {
+namespace script {
+
+struct DeterminizeOptions {
+  float delta;
+  WeightClass weight_threshold;
+  int64 state_threshold;
+  int64 subsequential_label;
+
+  explicit DeterminizeOptions(float d = fst::kDelta,
+                              WeightClass w =
+                                fst::script::WeightClass::Zero(),
+                              int64 n = fst::kNoStateId, int64 l = 0)
+      : delta(d), weight_threshold(w), state_threshold(n),
+        subsequential_label(l) {}
+};
+
+typedef args::Package<const FstClass&, MutableFstClass*,
+                      const DeterminizeOptions &> DeterminizeArgs;
+
+template<class Arc>
+void Determinize(DeterminizeArgs *args) {
+  const Fst<Arc> &ifst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+  const DeterminizeOptions &opts = args->arg3;
+
+  fst::DeterminizeOptions<Arc> detargs;
+  detargs.delta = opts.delta;
+  detargs.weight_threshold =
+      *(opts.weight_threshold.GetWeight<typename Arc::Weight>());
+  detargs.state_threshold = opts.state_threshold;
+  detargs.subsequential_label = opts.subsequential_label;
+
+  Determinize(ifst, ofst, detargs);
+}
+
+void Determinize(const FstClass &ifst, MutableFstClass *ofst,
+                 const DeterminizeOptions &opts =
+                   fst::script::DeterminizeOptions());
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_DETERMINIZE_H_
diff --git a/src/include/fst/script/difference.h b/src/include/fst/script/difference.h
new file mode 100644
index 0000000..76490d4
--- /dev/null
+++ b/src/include/fst/script/difference.h
@@ -0,0 +1,67 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_DIFFERENCE_H_
+#define FST_SCRIPT_DIFFERENCE_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/compose.h>  // for ComposeFilter
+#include <fst/difference.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<const FstClass&, const FstClass&,
+                      MutableFstClass*, ComposeFilter> DifferenceArgs1;
+
+template<class Arc>
+void Difference(DifferenceArgs1 *args) {
+  const Fst<Arc> &ifst1 = *(args->arg1.GetFst<Arc>());
+  const Fst<Arc> &ifst2 = *(args->arg2.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg3->GetMutableFst<Arc>();
+
+  Difference(ifst1, ifst2, ofst, args->arg4);
+}
+
+typedef args::Package<const FstClass&, const FstClass&,
+                      MutableFstClass*, const ComposeOptions &> DifferenceArgs2;
+
+template<class Arc>
+void Difference(DifferenceArgs2  *args) {
+  const Fst<Arc> &ifst1 = *(args->arg1.GetFst<Arc>());
+  const Fst<Arc> &ifst2 = *(args->arg2.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg3->GetMutableFst<Arc>();
+
+  Difference(ifst1, ifst2, ofst, args->arg4);
+}
+
+
+void Difference(const FstClass &ifst1, const FstClass &ifst2,
+                MutableFstClass *ofst,
+                ComposeFilter compose_filter);
+
+void Difference(const FstClass &ifst1, const FstClass &ifst2,
+                MutableFstClass *ofst,
+                const ComposeOptions &opts = fst::script::ComposeOptions());
+
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_DIFFERENCE_H_
diff --git a/src/include/fst/script/draw-impl.h b/src/include/fst/script/draw-impl.h
new file mode 100644
index 0000000..e346649
--- /dev/null
+++ b/src/include/fst/script/draw-impl.h
@@ -0,0 +1,234 @@
+// draw.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Class to draw a binary FST by producing a text file in dot format,
+// helper class to fstdraw.cc
+
+#ifndef FST_SCRIPT_DRAW_IMPL_H_
+#define FST_SCRIPT_DRAW_IMPL_H_
+
+#include <sstream>
+#include <string>
+
+#include <fst/script/fst-class.h>
+#include <fst/fst.h>
+#include <fst/util.h>
+
+namespace fst {
+
+// Print a binary Fst in the dot textual format, helper class for fstdraw.cc
+// WARNING: Stand-alone use not recommend.
+template <class A> class FstDrawer {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+
+  FstDrawer(const Fst<A> &fst,
+            const SymbolTable *isyms,
+            const SymbolTable *osyms,
+            const SymbolTable *ssyms,
+            bool accep,
+            string title,
+            float width,
+            float height,
+            bool portrait,
+            bool vertical,
+            float ranksep,
+            float nodesep,
+            int fontsize,
+            int precision,
+            bool show_weight_one)
+      : fst_(fst), isyms_(isyms), osyms_(osyms), ssyms_(ssyms),
+        accep_(accep && fst.Properties(kAcceptor, true)), ostrm_(0),
+        title_(title), width_(width), height_(height), portrait_(portrait),
+        vertical_(vertical), ranksep_(ranksep), nodesep_(nodesep),
+        fontsize_(fontsize), precision_(precision),
+        show_weight_one_(show_weight_one) {}
+
+  // Draw Fst to an output buffer (or stdout if buf = 0)
+  void Draw(ostream *strm, const string &dest) {
+    ostrm_ = strm;
+    dest_ = dest;
+    StateId start = fst_.Start();
+    if (start == kNoStateId)
+      return;
+
+    PrintString("digraph FST {\n");
+    if (vertical_)
+      PrintString("rankdir = BT;\n");
+    else
+      PrintString("rankdir = LR;\n");
+    PrintString("size = \"");
+    Print(width_);
+    PrintString(",");
+    Print(height_);
+    PrintString("\";\n");
+    if (!dest_.empty())
+      PrintString("label = \"" + title_ + "\";\n");
+    PrintString("center = 1;\n");
+    if (portrait_)
+      PrintString("orientation = Portrait;\n");
+    else
+      PrintString("orientation = Landscape;\n");
+    PrintString("ranksep = \"");
+    Print(ranksep_);
+    PrintString("\";\n");
+    PrintString("nodesep = \"");
+    Print(nodesep_);
+    PrintString("\";\n");
+    // initial state first
+    DrawState(start);
+    for (StateIterator< Fst<A> > siter(fst_);
+         !siter.Done();
+         siter.Next()) {
+      StateId s = siter.Value();
+      if (s != start)
+        DrawState(s);
+    }
+    PrintString("}\n");
+  }
+
+ private:
+  // Maximum line length in text file.
+  static const int kLineLen = 8096;
+
+  void PrintString(const string &s) const {
+    *ostrm_ << s;
+  }
+
+  // Escapes backslash and double quote if these occur in the string. Dot will
+  // not deal gracefully with these if they are not escaped.
+  inline void EscapeChars(const string &s, string* ns) const {
+    const char* c = s.c_str();
+    while (*c) {
+      if (*c == '\\' || *c == '"') ns->push_back('\\');
+      ns->push_back(*c);
+      ++c;
+    }
+  }
+
+  void PrintId(int64 id, const SymbolTable *syms,
+               const char *name) const {
+    if (syms) {
+      string symbol = syms->Find(id);
+      if (symbol == "") {
+        FSTERROR() << "FstDrawer: Integer " << id
+                   << " is not mapped to any textual symbol"
+                   << ", symbol table = " << syms->Name()
+                   << ", destination = " << dest_;
+        symbol = "?";
+      }
+      string nsymbol;
+      EscapeChars(symbol, &nsymbol);
+      PrintString(nsymbol);
+    } else {
+      ostringstream sid;
+      sid << id;
+      PrintString(sid.str());
+    }
+  }
+
+  void PrintStateId(StateId s) const {
+     PrintId(s, ssyms_, "state ID");
+  }
+
+  void PrintILabel(Label l) const {
+     PrintId(l, isyms_, "arc input label");
+  }
+
+  void PrintOLabel(Label l) const {
+     PrintId(l, osyms_, "arc output label");
+  }
+
+  template <class T>
+  void Print(T t) const {
+    *ostrm_ << t;
+  }
+
+  void DrawState(StateId s) const {
+    Print(s);
+    PrintString(" [label = \"");
+    PrintStateId(s);
+    Weight final = fst_.Final(s);
+    if (final != Weight::Zero()) {
+      if (show_weight_one_ || (final != Weight::One())) {
+        PrintString("/");
+        Print(final);
+      }
+      PrintString("\", shape = doublecircle,");
+    } else {
+      PrintString("\", shape = circle,");
+    }
+    if (s == fst_.Start())
+      PrintString(" style = bold,");
+    else
+      PrintString(" style = solid,");
+    PrintString(" fontsize = ");
+    Print(fontsize_);
+    PrintString("]\n");
+    for (ArcIterator< Fst<A> > aiter(fst_, s);
+         !aiter.Done();
+         aiter.Next()) {
+      Arc arc = aiter.Value();
+      PrintString("\t");
+      Print(s);
+      PrintString(" -> ");
+      Print(arc.nextstate);
+      PrintString(" [label = \"");
+      PrintILabel(arc.ilabel);
+      if (!accep_) {
+        PrintString(":");
+        PrintOLabel(arc.olabel);
+      }
+      if (show_weight_one_ || (arc.weight != Weight::One())) {
+        PrintString("/");
+        Print(arc.weight);
+      }
+      PrintString("\", fontsize = ");
+      Print(fontsize_);
+      PrintString("];\n");
+    }
+  }
+
+  const Fst<A> &fst_;
+  const SymbolTable *isyms_;     // ilabel symbol table
+  const SymbolTable *osyms_;     // olabel symbol table
+  const SymbolTable *ssyms_;     // slabel symbol table
+  bool accep_;                   // print as acceptor when possible
+  ostream *ostrm_;               // drawn FST destination
+  string dest_;                  // drawn FST destination name
+
+  string title_;
+  float width_;
+  float height_;
+  bool portrait_;
+  bool vertical_;
+  float ranksep_;
+  float nodesep_;
+  int fontsize_;
+  int precision_;
+  bool show_weight_one_;
+
+  DISALLOW_COPY_AND_ASSIGN(FstDrawer);
+};
+
+}  // namespace fst
+
+#endif  // FST_SCRIPT_DRAW_IMPL_H_
diff --git a/src/include/fst/script/draw.h b/src/include/fst/script/draw.h
new file mode 100644
index 0000000..1611ad1
--- /dev/null
+++ b/src/include/fst/script/draw.h
@@ -0,0 +1,113 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_DRAW_H_
+#define FST_SCRIPT_DRAW_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/draw-impl.h>
+#include <iostream>
+#include <fstream>
+
+namespace fst {
+namespace script {
+
+// Note: it is safe to pass these strings as references because
+// this struct is only used to pass them deeper in the call graph.
+// Be sure you understand why this is so before using this struct
+// for anything else!
+struct FstDrawerArgs {
+  const FstClass &fst;
+  const SymbolTable *isyms;
+  const SymbolTable *osyms;
+  const SymbolTable *ssyms;
+  const bool accep;
+  const string& title;
+  const float width;
+  const float height;
+  const bool portrait;
+  const bool vertical;
+  const float ranksep;
+  const float nodesep;
+  const int fontsize;
+  const int precision;
+  const bool show_weight_one;
+  ostream *ostrm;
+  const string &dest;
+
+  FstDrawerArgs(const FstClass &fst,
+                const SymbolTable *isyms,
+                const SymbolTable *osyms,
+                const SymbolTable *ssyms,
+                bool accep,
+                const string &title,
+                float width,
+                float height,
+                bool portrait,
+                bool vertical,
+                float ranksep,
+                float nodesep,
+                int fontsize,
+                int precision,
+                bool show_weight_one,
+                ostream *ostrm,
+                const string &dest) :
+      fst(fst), isyms(isyms), osyms(osyms), ssyms(ssyms), accep(accep),
+      title(title), width(width), height(height), portrait(portrait),
+      vertical(vertical), ranksep(ranksep), nodesep(nodesep),
+      fontsize(fontsize), precision(precision),
+      show_weight_one(show_weight_one), ostrm(ostrm), dest(dest) { }
+};
+
+
+template<class Arc>
+void DrawFst(FstDrawerArgs *args) {
+  const Fst<Arc> &fst = *(args->fst.GetFst<Arc>());
+
+  FstDrawer<Arc> fstdrawer(fst, args->isyms, args->osyms, args->ssyms,
+                           args->accep, args->title, args->width,
+                           args->height, args->portrait,
+                           args->vertical, args->ranksep,
+                           args->nodesep, args->fontsize,
+                           args->precision, args->show_weight_one);
+  fstdrawer.Draw(args->ostrm, args->dest);
+}
+
+void DrawFst(const FstClass &fst,
+             const SymbolTable *isyms,
+             const SymbolTable *osyms,
+             const SymbolTable *ssyms,
+             bool accep,
+             const string &title,
+             float width,
+             float height,
+             bool portrait,
+             bool vertical,
+             float ranksep,
+             float nodesep,
+             int fontsize,
+             int precision,
+             bool show_weight_one,
+             ostream *ostrm,
+             const string &dest);
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_DRAW_H_
diff --git a/src/include/fst/script/encode.h b/src/include/fst/script/encode.h
new file mode 100644
index 0000000..dc1a290
--- /dev/null
+++ b/src/include/fst/script/encode.h
@@ -0,0 +1,58 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_ENCODE_H_
+#define FST_SCRIPT_ENCODE_H_
+
+#include <string>
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/encode.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<MutableFstClass*, uint32, bool,
+                      const string &> EncodeArgs;
+
+template<class Arc>
+void Encode(EncodeArgs *args) {
+  MutableFst<Arc> *ofst = args->arg1->GetMutableFst<Arc>();
+  bool reuse_encoder = args->arg3;
+  const string &coder_fname = args->arg4;
+  uint32 flags = args->arg2;
+
+  EncodeMapper<Arc> *encoder = reuse_encoder
+      ? EncodeMapper<Arc>::Read(coder_fname, ENCODE)
+      : new EncodeMapper<Arc>(flags, ENCODE);
+
+  Encode(ofst, encoder);
+  if (!args->arg3)
+    encoder->Write(coder_fname);
+
+  delete encoder;
+}
+
+void Encode(MutableFstClass *fst, uint32 flags, bool reuse_encoder,
+            const string &coder_fname);
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_ENCODE_H_
diff --git a/src/include/fst/script/epsnormalize.h b/src/include/fst/script/epsnormalize.h
new file mode 100644
index 0000000..50b12da
--- /dev/null
+++ b/src/include/fst/script/epsnormalize.h
@@ -0,0 +1,44 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_EPSNORMALIZE_H_
+#define FST_SCRIPT_EPSNORMALIZE_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/epsnormalize.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<const FstClass&, MutableFstClass*,
+                      EpsNormalizeType> EpsNormalizeArgs;
+
+template<class Arc>
+void EpsNormalize(EpsNormalizeArgs  *args) {
+  const Fst<Arc> &ifst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+
+  EpsNormalize(ifst, ofst, args->arg3);
+}
+
+void EpsNormalize(const FstClass &ifst, MutableFstClass *ofst,
+                  EpsNormalizeType norm_type = EPS_NORM_INPUT);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_EPSNORMALIZE_H_
diff --git a/src/include/fst/script/equal.h b/src/include/fst/script/equal.h
new file mode 100644
index 0000000..9fb2d3c
--- /dev/null
+++ b/src/include/fst/script/equal.h
@@ -0,0 +1,45 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_EQUAL_H_
+#define FST_SCRIPT_EQUAL_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/equal.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<const FstClass&, const FstClass&, float> EqualInnerArgs;
+typedef args::WithReturnValue<bool, EqualInnerArgs> EqualArgs;
+
+template<class Arc>
+void Equal(EqualArgs *args) {
+  const Fst<Arc> &fst1 = *(args->args.arg1.GetFst<Arc>());
+  const Fst<Arc> &fst2 = *(args->args.arg2.GetFst<Arc>());
+
+  args->retval = Equal(fst1, fst2, args->args.arg3);
+}
+
+bool Equal(const FstClass &fst1, const FstClass &fst2,
+           float delta = kDelta);
+
+}  // namespace script
+}  // namespace fst
+
+
+#endif  // FST_SCRIPT_EQUAL_H_
diff --git a/src/include/fst/script/equivalent.h b/src/include/fst/script/equivalent.h
new file mode 100644
index 0000000..43460c6
--- /dev/null
+++ b/src/include/fst/script/equivalent.h
@@ -0,0 +1,47 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_EQUIVALENT_H_
+#define FST_SCRIPT_EQUIVALENT_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/equivalent.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<const FstClass &, const FstClass &,
+                      float> EquivalentInnerArgs;
+typedef args::WithReturnValue<bool, EquivalentInnerArgs> EquivalentArgs;
+
+template<class Arc>
+void Equivalent(EquivalentArgs *args) {
+  const Fst<Arc> &fst1 = *(args->args.arg1.GetFst<Arc>());
+  const Fst<Arc> &fst2 = *(args->args.arg2.GetFst<Arc>());
+
+  args->retval = Equivalent(fst1, fst2, args->args.arg3);
+}
+
+bool Equivalent(const FstClass &fst1, const FstClass &fst2,
+                float delta = kDelta);
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_EQUIVALENT_H_
diff --git a/src/include/fst/script/fst-class.h b/src/include/fst/script/fst-class.h
new file mode 100644
index 0000000..3eacab4
--- /dev/null
+++ b/src/include/fst/script/fst-class.h
@@ -0,0 +1,343 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_FST_CLASS_H_
+#define FST_SCRIPT_FST_CLASS_H_
+
+#include <string>
+
+#include <fst/fst.h>
+#include <fst/mutable-fst.h>
+#include <fst/vector-fst.h>
+#include <iostream>
+#include <fstream>
+
+// Classes to support "boxing" all existing types of FST arcs in a single
+// FstClass which hides the arc types. This allows clients to load
+// and work with FSTs without knowing the arc type.
+
+// These classes are only recommended for use in high-level scripting
+// applications. Most users should use the lower-level templated versions
+// corresponding to these classes.
+
+namespace fst {
+namespace script {
+
+//
+// Abstract base class defining the set of functionalities implemented
+// in all impls, and passed through by all bases Below FstClassBase
+// the class hierarchy bifurcates; FstClassImplBase serves as the base
+// class for all implementations (of which FstClassImpl is currently
+// the only one) and FstClass serves as the base class for all
+// interfaces.
+//
+class FstClassBase {
+ public:
+  virtual const string &ArcType() const = 0;
+  virtual const string &FstType() const = 0;
+  virtual const string &WeightType() const = 0;
+  virtual const SymbolTable *InputSymbols() const = 0;
+  virtual const SymbolTable *OutputSymbols() const = 0;
+  virtual void Write(const string& fname) const = 0;
+  virtual uint64 Properties(uint64 mask, bool test) const = 0;
+  virtual ~FstClassBase() { }
+};
+
+class FstClassImplBase : public FstClassBase {
+ public:
+  virtual FstClassImplBase *Copy() = 0;
+  virtual void SetInputSymbols(SymbolTable *is) = 0;
+  virtual void SetOutputSymbols(SymbolTable *is) = 0;
+  virtual ~FstClassImplBase() { }
+};
+
+
+//
+// CONTAINER CLASS
+// Wraps an Fst<Arc>, hiding its arc type. Whether this Fst<Arc>
+// pointer refers to a special kind of FST (e.g. a MutableFst) is
+// known by the type of interface class that owns the pointer to this
+// container.
+//
+
+template<class Arc>
+class FstClassImpl : public FstClassImplBase {
+ public:
+  explicit FstClassImpl(Fst<Arc> *impl,
+                        bool should_own = false) :
+      impl_(should_own ? impl : impl->Copy()) { }
+
+  virtual const string &ArcType() const {
+    return Arc::Type();
+  }
+
+  virtual const string &FstType() const {
+    return impl_->Type();
+  }
+
+  virtual const string &WeightType() const {
+    return Arc::Weight::Type();
+  }
+
+  virtual const SymbolTable *InputSymbols() const {
+    return impl_->InputSymbols();
+  }
+
+  virtual const SymbolTable *OutputSymbols() const {
+    return impl_->OutputSymbols();
+  }
+
+  // Warning: calling this method casts the FST to a mutable FST.
+  virtual void SetInputSymbols(SymbolTable *is) {
+    static_cast<MutableFst<Arc> *>(impl_)->SetInputSymbols(is);
+  }
+
+  // Warning: calling this method casts the FST to a mutable FST.
+  virtual void SetOutputSymbols(SymbolTable *os) {
+    static_cast<MutableFst<Arc> *>(impl_)->SetOutputSymbols(os);
+  }
+
+  virtual void Write(const string &fname) const {
+    impl_->Write(fname);
+  }
+
+  virtual uint64 Properties(uint64 mask, bool test) const {
+    return impl_->Properties(mask, test);
+  }
+
+  virtual ~FstClassImpl() { delete impl_; }
+
+  Fst<Arc> *GetImpl() { return impl_; }
+
+  virtual FstClassImpl *Copy() {
+    return new FstClassImpl<Arc>(impl_);
+  }
+
+ private:
+  Fst<Arc> *impl_;
+};
+
+//
+// BASE CLASS DEFINITIONS
+//
+
+class MutableFstClass;
+
+class FstClass : public FstClassBase {
+ public:
+  template<class Arc>
+  static FstClass *Read(istream &stream,
+                        const FstReadOptions &opts) {
+    if (!opts.header) {
+      FSTERROR() << "FstClass::Read: options header not specified";
+      return 0;
+    }
+    const FstHeader &hdr = *opts.header;
+
+    if (hdr.Properties() & kMutable) {
+      return ReadTypedFst<MutableFstClass, MutableFst<Arc> >(stream, opts);
+    } else {
+      return ReadTypedFst<FstClass, Fst<Arc> >(stream, opts);
+    }
+  }
+
+  template<class Arc>
+  explicit FstClass(Fst<Arc> *fst) : impl_(new FstClassImpl<Arc>(fst)) { }
+
+  explicit FstClass(const FstClass &other) : impl_(other.impl_->Copy()) { }
+
+  static FstClass *Read(const string &fname);
+
+  virtual const string &ArcType() const {
+    return impl_->ArcType();
+  }
+
+  virtual const string& FstType() const {
+    return impl_->FstType();
+  }
+
+  virtual const SymbolTable *InputSymbols() const {
+    return impl_->InputSymbols();
+  }
+
+  virtual const SymbolTable *OutputSymbols() const {
+    return impl_->OutputSymbols();
+  }
+
+  virtual const string& WeightType() const {
+    return impl_->WeightType();
+  }
+
+  virtual void Write(const string &fname) const {
+    impl_->Write(fname);
+  }
+
+  virtual uint64 Properties(uint64 mask, bool test) const {
+    return impl_->Properties(mask, test);
+  }
+
+  template<class Arc>
+  const Fst<Arc> *GetFst() const {
+    if (Arc::Type() != ArcType()) {
+      return NULL;
+    } else {
+      FstClassImpl<Arc> *typed_impl = static_cast<FstClassImpl<Arc> *>(impl_);
+      return typed_impl->GetImpl();
+    }
+  }
+
+  virtual ~FstClass() { delete impl_; }
+
+  // These methods are required by IO registration
+  template<class Arc>
+  static FstClassImplBase *Convert(const FstClass &other) {
+    LOG(ERROR) << "Doesn't make sense to convert any class to type FstClass.";
+    return 0;
+  }
+
+  template<class Arc>
+  static FstClassImplBase *Create() {
+    LOG(ERROR) << "Doesn't make sense to create an FstClass with a "
+               << "particular arc type.";
+    return 0;
+  }
+ protected:
+  explicit FstClass(FstClassImplBase *impl) : impl_(impl) { }
+
+  // Generic template method for reading an arc-templated FST of type
+  // UnderlyingT, and returning it wrapped as FstClassT, with appropriate
+  // error checking. Called from arc-templated Read() static methods.
+  template<class FstClassT, class UnderlyingT>
+  static FstClassT* ReadTypedFst(istream &stream,
+                                     const FstReadOptions &opts) {
+    UnderlyingT *u = UnderlyingT::Read(stream, opts);
+    if (!u) {
+      return 0;
+    } else {
+      FstClassT *r = new FstClassT(u);
+      delete u;
+      return r;
+    }
+  }
+
+  FstClassImplBase *GetImpl() { return impl_; }
+ private:
+  FstClassImplBase *impl_;
+};
+
+//
+// Specific types of FstClass with special properties
+//
+
+class MutableFstClass : public FstClass {
+ public:
+  template<class Arc>
+  explicit MutableFstClass(MutableFst<Arc> *fst) :
+      FstClass(fst) { }
+
+  template<class Arc>
+  MutableFst<Arc> *GetMutableFst() {
+    Fst<Arc> *fst = const_cast<Fst<Arc> *>(this->GetFst<Arc>());
+    MutableFst<Arc> *mfst = static_cast<MutableFst<Arc> *>(fst);
+
+    return mfst;
+  }
+
+  template<class Arc>
+  static MutableFstClass *Read(istream &stream,
+                               const FstReadOptions &opts) {
+    MutableFst<Arc> *mfst = MutableFst<Arc>::Read(stream, opts);
+    if (!mfst) {
+      return 0;
+    } else {
+      MutableFstClass *retval = new MutableFstClass(mfst);
+      delete mfst;
+      return retval;
+    }
+  }
+
+  static MutableFstClass *Read(const string &fname, bool convert = false);
+
+  virtual void SetInputSymbols(SymbolTable *is) {
+    GetImpl()->SetInputSymbols(is);
+  }
+
+  virtual void SetOutputSymbols(SymbolTable *os) {
+    GetImpl()->SetOutputSymbols(os);
+  }
+
+  // These methods are required by IO registration
+  template<class Arc>
+  static FstClassImplBase *Convert(const FstClass &other) {
+    LOG(ERROR) << "Doesn't make sense to convert any class to type "
+               << "MutableFstClass.";
+    return 0;
+  }
+
+  template<class Arc>
+  static FstClassImplBase *Create() {
+    LOG(ERROR) << "Doesn't make sense to create a MutableFstClass with a "
+               << "particular arc type.";
+    return 0;
+  }
+
+ protected:
+  explicit MutableFstClass(FstClassImplBase *impl) : FstClass(impl) { }
+};
+
+
+class VectorFstClass : public MutableFstClass {
+ public:
+  explicit VectorFstClass(const FstClass &other);
+  explicit VectorFstClass(const string &arc_type);
+
+  template<class Arc>
+  explicit VectorFstClass(VectorFst<Arc> *fst) :
+      MutableFstClass(fst) { }
+
+  template<class Arc>
+  static VectorFstClass *Read(istream &stream,
+                              const FstReadOptions &opts) {
+    VectorFst<Arc> *vfst = VectorFst<Arc>::Read(stream, opts);
+    if (!vfst) {
+      return 0;
+    } else {
+      VectorFstClass *retval = new VectorFstClass(vfst);
+      delete vfst;
+      return retval;
+    }
+  }
+
+  static VectorFstClass *Read(const string &fname);
+
+  // Converter / creator for known arc types
+  template<class Arc>
+  static FstClassImplBase *Convert(const FstClass &other) {
+    return new FstClassImpl<Arc>(new VectorFst<Arc>(
+        *other.GetFst<Arc>()), true);
+  }
+
+  template<class Arc>
+  static FstClassImplBase *Create() {
+    return new FstClassImpl<Arc>(new VectorFst<Arc>(), true);
+  }
+};
+
+}  // namespace script
+}  // namespace fst
+
+
+#endif  // FST_SCRIPT_FST_CLASS_H_
diff --git a/src/include/fst/script/fstscript-decl.h b/src/include/fst/script/fstscript-decl.h
new file mode 100644
index 0000000..fee813e
--- /dev/null
+++ b/src/include/fst/script/fstscript-decl.h
@@ -0,0 +1,35 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+// Forward declarations for the FST and FST-script classes.
+
+#ifndef FST_SCRIPT_FSTSCRIPT_DECL_H_
+#define FST_SCRIPT_FSTSCRIPT_DECL_H_
+
+#include <fst/fst-decl.h>
+
+namespace fst {
+namespace script {
+
+class FstClass;
+class MutableFstClass;
+class VectorFstClass;
+class WeightClass;
+
+}  // namespace script
+}  // namespace fst;
+
+#endif  // FST_SCRIPT_FSTSCRIPT_DECL_H_
diff --git a/src/include/fst/script/fstscript.h b/src/include/fst/script/fstscript.h
new file mode 100644
index 0000000..90e1e75
--- /dev/null
+++ b/src/include/fst/script/fstscript.h
@@ -0,0 +1,154 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+// Convenience file that includes all FstScript functionality
+
+#ifndef FST_SCRIPT_FSTSCRIPT_H_
+#define FST_SCRIPT_FSTSCRIPT_H_
+
+// Major classes
+#include <fst/script/fst-class.h>
+#include <fst/script/weight-class.h>
+#include <fst/script/text-io.h>
+
+// Templates like Operation< >, Apply< >
+#include <fst/script/script-impl.h>
+
+// Operations
+#include <fst/script/arcsort.h>
+#include <fst/script/closure.h>
+#include <fst/script/compile.h>
+#include <fst/script/compose.h>
+#include <fst/script/concat.h>
+#include <fst/script/connect.h>
+#include <fst/script/convert.h>
+#include <fst/script/decode.h>
+#include <fst/script/determinize.h>
+#include <fst/script/difference.h>
+#include <fst/script/draw.h>
+#include <fst/script/encode.h>
+#include <fst/script/epsnormalize.h>
+#include <fst/script/equal.h>
+#include <fst/script/equivalent.h>
+#include <fst/script/info.h>
+#include <fst/script/intersect.h>
+#include <fst/script/invert.h>
+#include <fst/script/map.h>
+#include <fst/script/minimize.h>
+#include <fst/script/print.h>
+#include <fst/script/project.h>
+#include <fst/script/prune.h>
+#include <fst/script/push.h>
+#include <fst/script/randequivalent.h>
+#include <fst/script/randgen.h>
+#include <fst/script/relabel.h>
+#include <fst/script/replace.h>
+#include <fst/script/reverse.h>
+#include <fst/script/reweight.h>
+#include <fst/script/rmepsilon.h>
+#include <fst/script/shortest-distance.h>
+#include <fst/script/shortest-path.h>
+#include <fst/script/symbols.h>
+#include <fst/script/synchronize.h>
+#include <fst/script/topsort.h>
+#include <fst/script/union.h>
+#include <fst/script/verify.h>
+
+//
+// REGISTER OPERATIONS
+//
+
+
+// This class is necessary because registering each of the operations
+// separately overfills the stack, as there's so many of them.
+namespace fst {
+namespace script {
+template<class Arc>
+class AllFstOperationsRegisterer {
+ public:
+  AllFstOperationsRegisterer() {
+    RegisterBatch1();
+    RegisterBatch2();
+  }
+
+ private:
+  void RegisterBatch1() {
+    REGISTER_FST_OPERATION(ArcSort, Arc, ArcSortArgs);
+    REGISTER_FST_OPERATION(Closure, Arc, ClosureArgs);
+    REGISTER_FST_OPERATION(CompileFst, Arc, FstCompileArgs);
+    REGISTER_FST_OPERATION(Compose, Arc, ComposeArgs1);
+    REGISTER_FST_OPERATION(Compose, Arc, ComposeArgs2);
+    REGISTER_FST_OPERATION(Concat, Arc, ConcatArgs1);
+    REGISTER_FST_OPERATION(Concat, Arc, ConcatArgs2);
+    REGISTER_FST_OPERATION(Connect, Arc, MutableFstClass);
+    REGISTER_FST_OPERATION(Convert, Arc, ConvertArgs);
+    REGISTER_FST_OPERATION(Decode, Arc, DecodeArgs);
+    REGISTER_FST_OPERATION(Determinize, Arc, DeterminizeArgs);
+    REGISTER_FST_OPERATION(Difference, Arc, DifferenceArgs1);
+    REGISTER_FST_OPERATION(Difference, Arc, DifferenceArgs2);
+    REGISTER_FST_OPERATION(DrawFst, Arc, FstDrawerArgs);
+    REGISTER_FST_OPERATION(Encode, Arc, EncodeArgs);
+    REGISTER_FST_OPERATION(EpsNormalize, Arc, EpsNormalizeArgs);
+    REGISTER_FST_OPERATION(Equal, Arc, EqualArgs);
+    REGISTER_FST_OPERATION(Equivalent, Arc, EquivalentArgs);
+    REGISTER_FST_OPERATION(PrintFstInfo, Arc, InfoArgs);
+    REGISTER_FST_OPERATION(Intersect, Arc, IntersectArgs1);
+    REGISTER_FST_OPERATION(Intersect, Arc, IntersectArgs2);
+    REGISTER_FST_OPERATION(Invert, Arc, MutableFstClass);
+    REGISTER_FST_OPERATION(Map, Arc, MapArgs);
+    REGISTER_FST_OPERATION(Minimize, Arc, MinimizeArgs);
+  }
+
+  void RegisterBatch2() {
+    REGISTER_FST_OPERATION(PrintFst, Arc, FstPrinterArgs);
+    REGISTER_FST_OPERATION(Project, Arc, ProjectArgs);
+    REGISTER_FST_OPERATION(Prune, Arc, PruneArgs1);
+    REGISTER_FST_OPERATION(Prune, Arc, PruneArgs2);
+    REGISTER_FST_OPERATION(Prune, Arc, PruneArgs3);
+    REGISTER_FST_OPERATION(Prune, Arc, PruneArgs4);
+    REGISTER_FST_OPERATION(Push, Arc, PushArgs1);
+    REGISTER_FST_OPERATION(Push, Arc, PushArgs2);
+    REGISTER_FST_OPERATION(RandEquivalent, Arc, RandEquivalentArgs1);
+    REGISTER_FST_OPERATION(RandEquivalent, Arc, RandEquivalentArgs2);
+    REGISTER_FST_OPERATION(RandGen, Arc, RandGenArgs);
+    REGISTER_FST_OPERATION(Relabel, Arc, RelabelArgs1);
+    REGISTER_FST_OPERATION(Relabel, Arc, RelabelArgs2);
+    REGISTER_FST_OPERATION(Relabel, Arc, RelabelArgs3);
+    REGISTER_FST_OPERATION(Replace, Arc, ReplaceArgs);
+    REGISTER_FST_OPERATION(Reverse, Arc, ReverseArgs);
+    REGISTER_FST_OPERATION(Reweight, Arc, ReweightArgs);
+    REGISTER_FST_OPERATION(RmEpsilon, Arc, RmEpsilonArgs1);
+    REGISTER_FST_OPERATION(RmEpsilon, Arc, RmEpsilonArgs2);
+    REGISTER_FST_OPERATION(RmEpsilon, Arc, RmEpsilonArgs3);
+    REGISTER_FST_OPERATION(ShortestDistance, Arc, ShortestDistanceArgs1);
+    REGISTER_FST_OPERATION(ShortestDistance, Arc, ShortestDistanceArgs2);
+    REGISTER_FST_OPERATION(ShortestDistance, Arc, ShortestDistanceArgs3);
+    REGISTER_FST_OPERATION(ShortestPath, Arc, ShortestPathArgs1);
+    REGISTER_FST_OPERATION(ShortestPath, Arc, ShortestPathArgs2);
+    REGISTER_FST_OPERATION(Synchronize, Arc, SynchronizeArgs);
+    REGISTER_FST_OPERATION(TopSort, Arc, TopSortArgs);
+    REGISTER_FST_OPERATION(Union, Arc, UnionArgs);
+    REGISTER_FST_OPERATION(Verify, Arc, VerifyArgs);
+  }
+};
+}  // namespace script
+}  // namespace fst
+
+
+#define REGISTER_FST_OPERATIONS(Arc) \
+  AllFstOperationsRegisterer<Arc> register_all_fst_operations ## Arc;
+
+#endif  // FST_SCRIPT_FSTSCRIPT_H_
diff --git a/src/include/fst/script/info-impl.h b/src/include/fst/script/info-impl.h
new file mode 100644
index 0000000..408fbcd
--- /dev/null
+++ b/src/include/fst/script/info-impl.h
@@ -0,0 +1,325 @@
+// info.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to compute various information about FSTs, helper class for fstinfo.cc
+
+#ifndef FST_SCRIPT_INFO_IMPL_H_
+#define FST_SCRIPT_INFO_IMPL_H_
+
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/connect.h>
+#include <fst/dfs-visit.h>
+#include <fst/fst.h>
+#include <fst/lookahead-matcher.h>
+#include <fst/matcher.h>
+#include <fst/queue.h>
+#include <fst/test-properties.h>
+#include <fst/verify.h>
+#include <fst/visit.h>
+
+namespace fst {
+
+// Compute various information about FSTs, helper class for fstinfo.cc.
+// WARNING: Stand-alone use of this class is not recommended, most code
+// should call directly the relevant library functions: Fst<A>::NumStates,
+// Fst<A>::NumArcs, TestProperties, ...
+template <class A> class FstInfo {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+
+  // When info_type is "short" (or "auto" and not an ExpandedFst)
+  // then only minimal info is computed and can be requested.
+  FstInfo(const Fst<A> &fst, bool test_properties,
+          const string &arc_filter_type = "any",
+          string info_type = "auto", bool verify = true)
+      : fst_type_(fst.Type()),
+        input_symbols_(fst.InputSymbols() ?
+                       fst.InputSymbols()->Name() : "none"),
+        output_symbols_(fst.OutputSymbols() ?
+                        fst.OutputSymbols()->Name() : "none"),
+        nstates_(0), narcs_(0), start_(kNoStateId), nfinal_(0),
+        nepsilons_(0), niepsilons_(0), noepsilons_(0),
+        naccess_(0), ncoaccess_(0), nconnect_(0), ncc_(0), nscc_(0),
+        input_match_type_(MATCH_NONE), output_match_type_(MATCH_NONE),
+        input_lookahead_(false), output_lookahead_(false),
+        properties_(0), arc_filter_type_(arc_filter_type), long_info_(true) {
+    if (info_type == "long") {
+      long_info_ = true;
+    } else if (info_type == "short") {
+      long_info_ = false;
+    } else if (info_type == "auto") {
+      long_info_ = fst.Properties(kExpanded, false);
+    } else {
+      FSTERROR() << "Bad info type: " << info_type;
+      return;
+    }
+
+    if (!long_info_)
+      return;
+
+    // If the FST is not sane, we return.
+    if (verify && !Verify(fst)) {
+      FSTERROR() << "FstInfo: Verify: FST not well-formed.";
+      return;
+    }
+
+    start_ = fst.Start();
+    properties_ = fst.Properties(kFstProperties, test_properties);
+
+    for (StateIterator< Fst<A> > siter(fst);
+         !siter.Done();
+         siter.Next()) {
+      ++nstates_;
+      StateId s = siter.Value();
+      if (fst.Final(s) != Weight::Zero())
+        ++nfinal_;
+      for (ArcIterator< Fst<A> > aiter(fst, s);
+           !aiter.Done();
+           aiter.Next()) {
+        const A &arc = aiter.Value();
+        ++narcs_;
+        if (arc.ilabel == 0 && arc.olabel == 0)
+          ++nepsilons_;
+        if (arc.ilabel == 0)
+          ++niepsilons_;
+        if (arc.olabel == 0)
+          ++noepsilons_;
+      }
+    }
+
+    {
+      vector<StateId> cc;
+      CcVisitor<Arc> cc_visitor(&cc);
+      FifoQueue<StateId> fifo_queue;
+      if (arc_filter_type == "any") {
+        Visit(fst, &cc_visitor, &fifo_queue);
+      } else if (arc_filter_type == "epsilon") {
+        Visit(fst, &cc_visitor, &fifo_queue, EpsilonArcFilter<Arc>());
+      } else if (arc_filter_type == "iepsilon") {
+        Visit(fst, &cc_visitor, &fifo_queue, InputEpsilonArcFilter<Arc>());
+      } else if (arc_filter_type == "oepsilon") {
+        Visit(fst, &cc_visitor, &fifo_queue, OutputEpsilonArcFilter<Arc>());
+      } else {
+        FSTERROR() << "Bad arc filter type: " << arc_filter_type;
+        return;
+      }
+
+      for (StateId s = 0; s < cc.size(); ++s) {
+        if (cc[s] >= ncc_)
+          ncc_ = cc[s] + 1;
+      }
+    }
+
+    {
+      vector<StateId> scc;
+      vector<bool> access, coaccess;
+      uint64 props = 0;
+      SccVisitor<Arc> scc_visitor(&scc, &access, &coaccess, &props);
+      if (arc_filter_type == "any") {
+        DfsVisit(fst, &scc_visitor);
+      } else if (arc_filter_type == "epsilon") {
+        DfsVisit(fst, &scc_visitor, EpsilonArcFilter<Arc>());
+      } else if (arc_filter_type == "iepsilon") {
+        DfsVisit(fst, &scc_visitor, InputEpsilonArcFilter<Arc>());
+      } else if (arc_filter_type == "oepsilon") {
+        DfsVisit(fst, &scc_visitor, OutputEpsilonArcFilter<Arc>());
+      } else {
+        FSTERROR() << "Bad arc filter type: " << arc_filter_type;
+        return;
+      }
+
+      for (StateId s = 0; s < scc.size(); ++s) {
+        if (access[s])
+          ++naccess_;
+        if (coaccess[s])
+          ++ncoaccess_;
+        if (access[s] && coaccess[s])
+          ++nconnect_;
+        if (scc[s] >= nscc_)
+          nscc_ = scc[s] + 1;
+      }
+    }
+
+    LookAheadMatcher< Fst<A> > imatcher(fst, MATCH_INPUT);
+    input_match_type_ =  imatcher.Type(test_properties);
+    input_lookahead_ =  imatcher.Flags() & kInputLookAheadMatcher;
+
+    LookAheadMatcher< Fst<A> > omatcher(fst, MATCH_OUTPUT);
+    output_match_type_ =  omatcher.Type(test_properties);
+    output_lookahead_ =  omatcher.Flags() & kOutputLookAheadMatcher;
+  }
+
+  // Short info
+  const string& FstType() const { return fst_type_; }
+  const string& ArcType() const { return A::Type(); }
+  const string& InputSymbols() const { return input_symbols_; }
+  const string& OutputSymbols() const { return output_symbols_; }
+  const bool LongInfo() const { return long_info_; }
+  const string& ArcFilterType() const { return arc_filter_type_; }
+
+  // Long info
+  MatchType InputMatchType() const { CheckLong(); return input_match_type_; }
+  MatchType OutputMatchType() const { CheckLong(); return output_match_type_; }
+  bool InputLookAhead() const { CheckLong(); return input_lookahead_; }
+  bool OutputLookAhead() const { CheckLong();  return output_lookahead_; }
+  int64 NumStates() const { CheckLong();  return nstates_; }
+  int64 NumArcs() const { CheckLong();  return narcs_; }
+  int64 Start() const { CheckLong();  return start_; }
+  int64 NumFinal() const { CheckLong();  return nfinal_; }
+  int64 NumEpsilons() const { CheckLong();  return nepsilons_; }
+  int64 NumInputEpsilons() const { CheckLong(); return niepsilons_; }
+  int64 NumOutputEpsilons() const { CheckLong(); return noepsilons_; }
+  int64 NumAccessible() const { CheckLong(); return naccess_; }
+  int64 NumCoAccessible() const { CheckLong(); return ncoaccess_; }
+  int64 NumConnected() const { CheckLong(); return nconnect_; }
+  int64 NumCc() const { CheckLong(); return ncc_; }
+  int64 NumScc() const { CheckLong(); return nscc_; }
+  uint64 Properties() const { CheckLong(); return properties_; }
+
+ private:
+  void CheckLong() const {
+    if (!long_info_)
+      FSTERROR() << "FstInfo: method only available with long info version";
+  }
+
+  string fst_type_;
+  string input_symbols_;
+  string output_symbols_;
+  int64 nstates_;
+  int64 narcs_;
+  int64 start_;
+  int64 nfinal_;
+  int64 nepsilons_;
+  int64 niepsilons_;
+  int64 noepsilons_;
+  int64 naccess_;
+  int64 ncoaccess_;
+  int64 nconnect_;
+  int64 ncc_;
+  int64 nscc_;
+  MatchType input_match_type_;
+  MatchType output_match_type_;
+  bool input_lookahead_;
+  bool output_lookahead_;
+  uint64 properties_;
+  string arc_filter_type_;
+  bool long_info_;
+  DISALLOW_COPY_AND_ASSIGN(FstInfo);
+};
+
+template <class A>
+void PrintFstInfo(const FstInfo<A> &fstinfo, bool pipe = false) {
+  ostream &os = pipe ? cerr : cout;
+
+  ios_base::fmtflags old = os.setf(ios::left);
+  os.width(50);
+  os << "fst type" <<  fstinfo.FstType() << endl;
+  os.width(50);
+  os << "arc type" << fstinfo.ArcType() << endl;
+  os.width(50);
+  os << "input symbol table" << fstinfo.InputSymbols() << endl;
+  os.width(50);
+  os << "output symbol table" << fstinfo.OutputSymbols() << endl;
+
+  if (!fstinfo.LongInfo()) {
+    os.setf(old);
+    return;
+  }
+
+  os.width(50);
+  os << "# of states" << fstinfo.NumStates() << endl;
+  os.width(50);
+  os << "# of arcs" << fstinfo.NumArcs() << endl;
+  os.width(50);
+  os << "initial state" << fstinfo.Start() << endl;
+  os.width(50);
+  os << "# of final states" << fstinfo.NumFinal() << endl;
+  os.width(50);
+  os << "# of input/output epsilons" << fstinfo.NumEpsilons() << endl;
+  os.width(50);
+  os << "# of input epsilons" << fstinfo.NumInputEpsilons() << endl;
+  os.width(50);
+  os << "# of output epsilons" << fstinfo.NumOutputEpsilons() << endl;
+  os.width(50);
+
+  string arc_type = "";
+  if (fstinfo.ArcFilterType() == "epsilon")
+    arc_type = "epsilon ";
+  else if (fstinfo.ArcFilterType() == "iepsilon")
+    arc_type = "input-epsilon ";
+  else if (fstinfo.ArcFilterType() == "oepsilon")
+    arc_type = "output-epsilon ";
+
+  string accessible_label = "# of " +  arc_type + "accessible states";
+  os.width(50);
+  os << accessible_label << fstinfo.NumAccessible() << endl;
+  string coaccessible_label = "# of " +  arc_type + "coaccessible states";
+  os.width(50);
+  os << coaccessible_label << fstinfo.NumCoAccessible() << endl;
+  string connected_label = "# of " +  arc_type + "connected states";
+  os.width(50);
+  os << connected_label << fstinfo.NumConnected() << endl;
+  string numcc_label = "# of " +  arc_type + "connected components";
+  os.width(50);
+  os << numcc_label << fstinfo.NumCc() << endl;
+  string numscc_label = "# of " +  arc_type + "strongly conn components";
+  os.width(50);
+  os << numscc_label << fstinfo.NumScc() << endl;
+
+  os.width(50);
+  os << "input matcher"
+     << (fstinfo.InputMatchType() == MATCH_INPUT ? 'y' :
+         fstinfo.InputMatchType() == MATCH_NONE ? 'n' : '?') << endl;
+  os.width(50);
+  os << "output matcher"
+     << (fstinfo.OutputMatchType() == MATCH_OUTPUT ? 'y' :
+         fstinfo.OutputMatchType() == MATCH_NONE ? 'n' : '?') << endl;
+  os.width(50);
+  os << "input lookahead"
+     << (fstinfo.InputLookAhead() ? 'y' : 'n') << endl;
+  os.width(50);
+  os << "output lookahead"
+     << (fstinfo.OutputLookAhead() ? 'y' : 'n') << endl;
+
+  uint64 prop = 1;
+  for (int i = 0; i < 64; ++i, prop <<= 1) {
+    if (prop & kBinaryProperties) {
+      char value = 'n';
+      if (fstinfo.Properties() & prop) value = 'y';
+      os.width(50);
+      os << PropertyNames[i] << value << endl;
+    } else if (prop & kPosTrinaryProperties) {
+      char value = '?';
+      if (fstinfo.Properties() & prop) value = 'y';
+      else if (fstinfo.Properties() & prop << 1) value = 'n';
+      os.width(50);
+      os << PropertyNames[i] << value << endl;
+    }
+  }
+  os.setf(old);
+}
+
+}  // namespace fst
+
+#endif  // FST_SCRIPT_INFO_IMPL_H_
diff --git a/src/include/fst/script/info.h b/src/include/fst/script/info.h
new file mode 100644
index 0000000..f434bd5
--- /dev/null
+++ b/src/include/fst/script/info.h
@@ -0,0 +1,48 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_INFO_H_
+#define FST_SCRIPT_INFO_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/info-impl.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<const FstClass&, bool, const string&,
+                      const string&, bool, bool> InfoArgs;
+
+template<class Arc>
+void PrintFstInfo(InfoArgs *args) {
+  const Fst<Arc> &fst = *(args->arg1.GetFst<Arc>());
+  FstInfo<Arc> fstinfo(fst, args->arg2, args->arg3,
+                       args->arg4, args->arg5);
+  PrintFstInfo(fstinfo, args->arg6);
+
+  if (args->arg6)
+    fst.Write("");
+}
+
+void PrintFstInfo(const FstClass &f, bool test_properties,
+                  const string &arc_filter, const string &info_type,
+                  bool pipe, bool verify);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_INFO_H_
diff --git a/src/include/fst/script/intersect.h b/src/include/fst/script/intersect.h
new file mode 100644
index 0000000..8011024
--- /dev/null
+++ b/src/include/fst/script/intersect.h
@@ -0,0 +1,65 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_INTERSECT_H_
+#define FST_SCRIPT_INTERSECT_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/intersect.h>
+#include <fst/script/compose.h>  // for ComposeOptions, ComposeFilter
+
+namespace fst {
+namespace script {
+
+typedef args::Package<const FstClass&, const FstClass&,
+                      MutableFstClass*, ComposeFilter> IntersectArgs1;
+
+template<class Arc>
+void Intersect(IntersectArgs1 *args) {
+  const Fst<Arc> &ifst1 = *(args->arg1.GetFst<Arc>());
+  const Fst<Arc> &ifst2 = *(args->arg2.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg3->GetMutableFst<Arc>();
+
+  Intersect(ifst1, ifst2, ofst, args->arg4);
+}
+
+typedef args::Package<const FstClass&, const FstClass&,
+                      MutableFstClass*, const ComposeOptions &> IntersectArgs2;
+
+template<class Arc>
+void Intersect(IntersectArgs2 *args) {
+  const Fst<Arc> &ifst1 = *(args->arg1.GetFst<Arc>());
+  const Fst<Arc> &ifst2 = *(args->arg2.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg3->GetMutableFst<Arc>();
+
+  Intersect(ifst1, ifst2, ofst, args->arg4);
+}
+
+void Intersect(const FstClass &ifst1, const FstClass &ifst2,
+               MutableFstClass *ofst,
+               ComposeFilter compose_filter);
+
+void Intersect(const FstClass &ifst, const FstClass &ifst2,
+               MutableFstClass *ofst,
+               const ComposeOptions &opts = fst::script::ComposeOptions());
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_INTERSECT_H_
diff --git a/src/include/fst/script/invert.h b/src/include/fst/script/invert.h
new file mode 100644
index 0000000..1befd9f
--- /dev/null
+++ b/src/include/fst/script/invert.h
@@ -0,0 +1,43 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_INVERT_H_
+#define FST_SCRIPT_INVERT_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/invert.h>
+
+namespace fst {
+namespace script {
+
+// The following confuses swig, because it has the same arguments
+// as the non-templated version
+#ifndef SWIG
+template<class Arc>
+void Invert(MutableFstClass *fst) {
+  MutableFst<Arc> *typed_fst = fst->GetMutableFst<Arc>();
+
+  Invert(typed_fst);
+}
+#endif
+
+void Invert(MutableFstClass *fst);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_INVERT_H_
diff --git a/src/include/fst/script/map.h b/src/include/fst/script/map.h
new file mode 100644
index 0000000..2332074
--- /dev/null
+++ b/src/include/fst/script/map.h
@@ -0,0 +1,115 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_MAP_H_
+#define FST_SCRIPT_MAP_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/weight-class.h>
+#include <fst/arc-map.h>
+#include <fst/state-map.h>
+
+namespace fst {
+namespace script {
+
+template <class M>
+Fst<typename M::ToArc> *ArcMap(const Fst<typename M::FromArc> &fst,
+                            const M &mapper) {
+  typedef typename M::ToArc ToArc;
+  VectorFst<ToArc> *ofst = new VectorFst<ToArc>;
+  ArcMap(fst, ofst, mapper);
+  return ofst;
+}
+
+template <class M>
+Fst<typename M::ToArc> *StateMap(const Fst<typename M::FromArc> &fst,
+                                 const M &mapper) {
+  typedef typename M::ToArc ToArc;
+  VectorFst<ToArc> *ofst = new VectorFst<ToArc>;
+  StateMap(fst, ofst, mapper);
+  return ofst;
+}
+
+enum MapType { ARC_SUM_MAPPER, IDENTITY_MAPPER, INVERT_MAPPER, PLUS_MAPPER,
+               QUANTIZE_MAPPER, RMWEIGHT_MAPPER, SUPERFINAL_MAPPER,
+               TIMES_MAPPER, TO_LOG_MAPPER, TO_LOG64_MAPPER, TO_STD_MAPPER };
+
+typedef args::Package<const FstClass&, MapType, float,
+                      const WeightClass &> MapInnerArgs;
+typedef args::WithReturnValue<FstClass*, MapInnerArgs> MapArgs;
+
+template <class Arc>
+void Map(MapArgs *args) {
+  const Fst<Arc> &ifst = *(args->args.arg1.GetFst<Arc>());
+  MapType map_type = args->args.arg2;
+  float delta =  args->args.arg3;
+  typename Arc::Weight w = *(args->args.arg4.GetWeight<typename Arc::Weight>());
+
+  if (map_type == ARC_SUM_MAPPER) {
+    args->retval = new FstClass(
+        script::StateMap(ifst, ArcSumMapper<Arc>(ifst)));
+  } else if (map_type == IDENTITY_MAPPER) {
+    args->retval = new FstClass(
+        script::ArcMap(ifst, IdentityArcMapper<Arc>()));
+  } else if (map_type == INVERT_MAPPER) {
+    args->retval = new FstClass(
+        script::ArcMap(ifst, InvertWeightMapper<Arc>()));
+  } else if (map_type == PLUS_MAPPER) {
+    args->retval = new FstClass(
+        script::ArcMap(ifst, PlusMapper<Arc>(w)));
+  } else if (map_type == QUANTIZE_MAPPER) {
+    args->retval = new FstClass(
+        script::ArcMap(ifst, QuantizeMapper<Arc>(delta)));
+  } else if (map_type == RMWEIGHT_MAPPER) {
+    args->retval = new FstClass(
+        script::ArcMap(ifst, RmWeightMapper<Arc>()));
+  } else if (map_type == SUPERFINAL_MAPPER) {
+    args->retval = new FstClass(
+        script::ArcMap(ifst, SuperFinalMapper<Arc>()));
+  } else if (map_type == TIMES_MAPPER) {
+    args->retval = new FstClass(
+        script::ArcMap(ifst, TimesMapper<Arc>(w)));
+  } else if (map_type == TO_LOG_MAPPER) {
+    args->retval = new FstClass(
+        script::ArcMap(ifst, WeightConvertMapper<Arc, LogArc>()));
+  } else if (map_type == TO_LOG64_MAPPER) {
+    args->retval = new FstClass(
+        script::ArcMap(ifst, WeightConvertMapper<Arc, Log64Arc>()));
+  } else if (map_type == TO_STD_MAPPER) {
+    args->retval = new FstClass(
+        script::ArcMap(ifst, WeightConvertMapper<Arc, StdArc>()));
+  } else {
+    FSTERROR() << "Error: unknown/unsupported mapper type: "
+               << map_type;
+    VectorFst<Arc> *ofst = new VectorFst<Arc>;
+    ofst->SetProperties(kError, kError);
+    args->retval = new FstClass(ofst);
+  }
+}
+
+
+#ifdef SWIG
+%newobject Map;
+#endif
+FstClass *Map(const FstClass& f, MapType map_type,
+         float delta = fst::kDelta,
+         const WeightClass &w = fst::script::WeightClass::Zero());
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_MAP_H_
diff --git a/src/include/fst/script/minimize.h b/src/include/fst/script/minimize.h
new file mode 100644
index 0000000..f250d03
--- /dev/null
+++ b/src/include/fst/script/minimize.h
@@ -0,0 +1,45 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_MINIMIZE_H_
+#define FST_SCRIPT_MINIMIZE_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/minimize.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<MutableFstClass*, MutableFstClass*, float> MinimizeArgs;
+
+template<class Arc>
+void Minimize(MinimizeArgs *args) {
+  MutableFst<Arc> *ofst1 = args->arg1->GetMutableFst<Arc>();
+  MutableFst<Arc> *ofst2 = args->arg2 ? args->arg2->GetMutableFst<Arc>() : 0;
+
+  Minimize(ofst1, ofst2, args->arg3);
+}
+
+void Minimize(MutableFstClass *ofst1, MutableFstClass *ofst2 = 0,
+              float delta = kDelta);
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_MINIMIZE_H_
diff --git a/src/include/fst/script/print-impl.h b/src/include/fst/script/print-impl.h
new file mode 100644
index 0000000..1433a29
--- /dev/null
+++ b/src/include/fst/script/print-impl.h
@@ -0,0 +1,149 @@
+// print.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Stand-alone class to print out binary FSTs in the AT&T format,
+// helper class for fstprint.cc
+
+#ifndef FST_SCRIPT_PRINT_IMPL_H_
+#define FST_SCRIPT_PRINT_IMPL_H_
+
+#include <sstream>
+#include <string>
+
+#include <fst/fst.h>
+#include <fst/util.h>
+
+DECLARE_string(fst_field_separator);
+
+namespace fst {
+
+// Print a binary Fst in textual format, helper class for fstprint.cc
+// WARNING: Stand-alone use of this class not recommended, most code should
+// read/write using the binary format which is much more efficient.
+template <class A> class FstPrinter {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+
+  FstPrinter(const Fst<A> &fst,
+             const SymbolTable *isyms,
+             const SymbolTable *osyms,
+             const SymbolTable *ssyms,
+             bool accep,
+             bool show_weight_one)
+      : fst_(fst), isyms_(isyms), osyms_(osyms), ssyms_(ssyms),
+        accep_(accep && fst.Properties(kAcceptor, true)), ostrm_(0),
+        show_weight_one_(show_weight_one) {}
+
+  // Print Fst to an output stream
+  void Print(ostream *ostrm, const string &dest) {
+    ostrm_ = ostrm;
+    dest_ = dest;
+    StateId start = fst_.Start();
+    if (start == kNoStateId)
+      return;
+    // initial state first
+    PrintState(start);
+    for (StateIterator< Fst<A> > siter(fst_);
+         !siter.Done();
+         siter.Next()) {
+      StateId s = siter.Value();
+      if (s != start)
+        PrintState(s);
+    }
+  }
+
+ private:
+  // Maximum line length in text file.
+  static const int kLineLen = 8096;
+
+  void PrintId(int64 id, const SymbolTable *syms,
+               const char *name) const {
+    if (syms) {
+      string symbol = syms->Find(id);
+      if (symbol == "") {
+        FSTERROR() << "FstPrinter: Integer " << id
+                   << " is not mapped to any textual symbol"
+                   << ", symbol table = " << syms->Name()
+                   << ", destination = " << dest_;
+        symbol = "?";
+      }
+      *ostrm_ << symbol;
+    } else {
+      *ostrm_ << id;
+    }
+  }
+
+  void PrintStateId(StateId s) const {
+     PrintId(s, ssyms_, "state ID");
+  }
+
+  void PrintILabel(Label l) const {
+     PrintId(l, isyms_, "arc input label");
+  }
+
+  void PrintOLabel(Label l) const {
+     PrintId(l, osyms_, "arc output label");
+  }
+
+  void PrintState(StateId s) const {
+    bool output = false;
+    for (ArcIterator< Fst<A> > aiter(fst_, s);
+         !aiter.Done();
+         aiter.Next()) {
+      Arc arc = aiter.Value();
+      PrintStateId(s);
+      *ostrm_ << FLAGS_fst_field_separator[0];
+      PrintStateId(arc.nextstate);
+      *ostrm_ << FLAGS_fst_field_separator[0];
+      PrintILabel(arc.ilabel);
+      if (!accep_) {
+        *ostrm_ << FLAGS_fst_field_separator[0];
+        PrintOLabel(arc.olabel);
+      }
+      if (show_weight_one_ || arc.weight != Weight::One())
+        *ostrm_ << FLAGS_fst_field_separator[0] << arc.weight;
+      *ostrm_ << "\n";
+      output = true;
+    }
+    Weight final = fst_.Final(s);
+    if (final != Weight::Zero() || !output) {
+      PrintStateId(s);
+      if (show_weight_one_ || final != Weight::One()) {
+        *ostrm_ << FLAGS_fst_field_separator[0] << final;
+      }
+      *ostrm_ << "\n";
+    }
+  }
+
+  const Fst<A> &fst_;
+  const SymbolTable *isyms_;     // ilabel symbol table
+  const SymbolTable *osyms_;     // olabel symbol table
+  const SymbolTable *ssyms_;     // slabel symbol table
+  bool accep_;                   // print as acceptor when possible
+  ostream *ostrm_;               // text FST destination
+  string dest_;                  // text FST destination name
+  bool show_weight_one_;         // print weights equal to Weight::One()
+  DISALLOW_COPY_AND_ASSIGN(FstPrinter);
+};
+
+}  // namespace fst
+
+#endif  // FST_SCRIPT_PRINT_IMPL_H_
diff --git a/src/include/fst/script/print.h b/src/include/fst/script/print.h
new file mode 100644
index 0000000..f82b19b
--- /dev/null
+++ b/src/include/fst/script/print.h
@@ -0,0 +1,86 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_PRINT_H_
+#define FST_SCRIPT_PRINT_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/print-impl.h>
+
+namespace fst {
+namespace script {
+
+// Note: it is safe to pass these strings as references because
+// this struct is only used to pass them deeper in the call graph.
+// Be sure you understand why this is so before using this struct
+// for anything else!
+struct FstPrinterArgs {
+  const FstClass &fst;
+  const SymbolTable *isyms;
+  const SymbolTable *osyms;
+  const SymbolTable *ssyms;
+  const bool accept;
+  const bool show_weight_one;
+  ostream *ostrm;
+  const string &dest;
+
+  FstPrinterArgs(const FstClass &fst,
+                 const SymbolTable *isyms,
+                 const SymbolTable *osyms,
+                 const SymbolTable *ssyms,
+                 bool accept,
+                 bool show_weight_one,
+                 ostream *ostrm,
+                 const string &dest) :
+      fst(fst), isyms(isyms), osyms(osyms), ssyms(ssyms), accept(accept),
+      show_weight_one(show_weight_one), ostrm(ostrm), dest(dest) { }
+};
+
+template<class Arc>
+void PrintFst(FstPrinterArgs *args) {
+  const Fst<Arc> &fst = *(args->fst.GetFst<Arc>());
+
+  fst::FstPrinter<Arc> fstprinter(fst, args->isyms, args->osyms,
+                                      args->ssyms, args->accept,
+                                      args->show_weight_one);
+  fstprinter.Print(args->ostrm, args->dest);
+}
+
+void PrintFst(const FstClass &fst, ostream &ostrm, const string &dest,
+              const SymbolTable *isyms,
+              const SymbolTable *osyms,
+              const SymbolTable *ssyms,
+              bool accept, bool show_weight_one);
+
+
+// Below are two printing methods with useful defaults for a few of
+// the fst printer arguments.
+template <class Arc>
+void PrintFst(const Fst<Arc> &fst, ostream &os, const string dest = "",
+              const SymbolTable *isyms = NULL,
+              const SymbolTable *osyms = NULL,
+              const SymbolTable *ssyms = NULL) {
+  fst::FstPrinter<Arc> fstprinter(fst, isyms, osyms, ssyms, true, true);
+  fstprinter.Print(&os, dest);
+}
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_PRINT_H_
diff --git a/src/include/fst/script/project.h b/src/include/fst/script/project.h
new file mode 100644
index 0000000..12ee890
--- /dev/null
+++ b/src/include/fst/script/project.h
@@ -0,0 +1,43 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_PROJECT_H_
+#define FST_SCRIPT_PROJECT_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/project.h>  // for ProjectType
+
+namespace fst {
+namespace script {
+
+typedef args::Package<MutableFstClass*, ProjectType> ProjectArgs;
+
+template<class Arc>
+void Project(ProjectArgs *args) {
+  MutableFst<Arc> *ofst = args->arg1->GetMutableFst<Arc>();
+
+  Project(ofst, args->arg2);
+}
+
+void Project(MutableFstClass *ofst, ProjectType project_type);
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_PROJECT_H_
diff --git a/src/include/fst/script/prune.h b/src/include/fst/script/prune.h
new file mode 100644
index 0000000..7118ff1
--- /dev/null
+++ b/src/include/fst/script/prune.h
@@ -0,0 +1,153 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_PRUNE_H_
+#define FST_SCRIPT_PRUNE_H_
+
+#include <vector>
+using std::vector;
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/weight-class.h>
+#include <fst/prune.h>
+#include <fst/arcfilter.h>
+
+namespace fst {
+namespace script {
+
+struct PruneOptions {
+  WeightClass weight_threshold;
+  int64 state_threshold;
+  const vector<WeightClass> *distance;
+  float delta;
+
+  explicit PruneOptions(const WeightClass& w, int64 s,
+                        vector<WeightClass> *d = 0, float e = kDelta)
+      : weight_threshold(w),
+        state_threshold(s),
+        distance(d),
+        delta(e) {}
+ private:
+  PruneOptions();  // disallow
+};
+
+// converts a script::PruneOptions into a fst::PruneOptions.
+// Notes:
+//  If the original opts.distance is not NULL, a new distance will be
+//  created with new; it's the client's responsibility to delete this.
+
+template<class A>
+fst::PruneOptions<A, AnyArcFilter<A> > ConvertPruneOptions(
+    const PruneOptions &opts) {
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  Weight weight_threshold = *(opts.weight_threshold.GetWeight<Weight>());
+  StateId state_threshold = opts.state_threshold;
+  vector<Weight> *distance = 0;
+
+  if (opts.distance) {
+    distance = new vector<Weight>(opts.distance->size());
+    for (unsigned i = 0; i < opts.distance->size(); ++i) {
+      (*distance)[i] = *((*opts.distance)[i].GetWeight<Weight>());
+    }
+  }
+
+  return fst::PruneOptions<A, AnyArcFilter<A> >(
+      weight_threshold, state_threshold, AnyArcFilter<A>(), distance,
+      opts.delta);
+}
+
+// 1
+typedef args::Package<MutableFstClass *, const PruneOptions &> PruneArgs1;
+
+template<class Arc>
+void Prune(PruneArgs1 *args) {
+  MutableFst<Arc> *ofst = args->arg1->GetMutableFst<Arc>();
+
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  fst::PruneOptions<Arc, AnyArcFilter<Arc> > opts =
+      ConvertPruneOptions<Arc>(args->arg2);
+  Prune(ofst, opts);
+  delete opts.distance;
+}
+
+// 2
+typedef args::Package<const FstClass &, MutableFstClass *,
+                      const PruneOptions &> PruneArgs2;
+
+template<class Arc>
+void Prune(PruneArgs2 *args) {
+  const Fst<Arc>& ifst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+
+  fst::PruneOptions<Arc, AnyArcFilter<Arc> > opts =
+      ConvertPruneOptions<Arc>(args->arg3);
+  Prune(ifst, ofst, opts);
+  delete opts.distance;
+}
+
+// 3
+typedef args::Package<const FstClass &,
+                      MutableFstClass *,
+                      const WeightClass &, int64, float> PruneArgs3;
+
+template<class Arc>
+void Prune(PruneArgs3 *args) {
+  const Fst<Arc>& ifst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+  typename Arc::Weight w = *(args->arg3.GetWeight<typename Arc::Weight>());
+
+  Prune(ifst, ofst, w, args->arg4, args->arg5);
+}
+
+// 4
+typedef args::Package<MutableFstClass *, const WeightClass&,
+                      int64, float> PruneArgs4;
+template<class Arc>
+void Prune(PruneArgs4 *args) {
+  MutableFst<Arc> *fst = args->arg1->GetMutableFst<Arc>();
+  typename Arc::Weight w = *(args->arg2.GetWeight<typename Arc::Weight>());
+  Prune(fst, w, args->arg3, args->arg4);
+}
+
+
+// 1
+void Prune(MutableFstClass *fst, const PruneOptions &opts);
+
+// 2
+void Prune(const FstClass &ifst, MutableFstClass *fst,
+           const PruneOptions &opts);
+
+// 3
+void Prune(const FstClass &ifst, MutableFstClass *ofst,
+           const WeightClass &weight_threshold,
+           int64 state_threshold = kNoStateId,
+           float delta = kDelta);
+
+// 4
+void Prune(MutableFstClass *fst, const WeightClass& weight_threshold,
+           int64 state_threshold, float delta);
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_PRUNE_H_
diff --git a/src/include/fst/script/push.h b/src/include/fst/script/push.h
new file mode 100644
index 0000000..cebd655
--- /dev/null
+++ b/src/include/fst/script/push.h
@@ -0,0 +1,70 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_PUSH_H_
+#define FST_SCRIPT_PUSH_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/push.h>
+
+namespace fst {
+namespace script {
+
+// 1
+typedef args::Package<MutableFstClass*, ReweightType, float, bool> PushArgs1;
+
+template<class Arc>
+void Push(PushArgs1 *args) {
+  MutableFst<Arc> *ofst = args->arg1->GetMutableFst<Arc>();
+
+  if (args->arg2 == REWEIGHT_TO_FINAL) {
+    fst::Push(ofst, REWEIGHT_TO_FINAL, args->arg3, args->arg4);
+  } else {
+    fst::Push(ofst, REWEIGHT_TO_INITIAL, args->arg3, args->arg4);
+  }
+}
+
+// 2
+typedef args::Package<const FstClass &, MutableFstClass *, uint32,
+                      ReweightType, float> PushArgs2;
+
+template<class Arc>
+void Push(PushArgs2 *args) {
+  const Fst<Arc> &ifst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+
+  if (args->arg4 == REWEIGHT_TO_FINAL) {
+    fst::Push<Arc, REWEIGHT_TO_FINAL>(ifst, ofst, args->arg3, args->arg5);
+  } else {
+    fst::Push<Arc, REWEIGHT_TO_INITIAL>(ifst, ofst, args->arg3, args->arg5);
+  }
+}
+
+// 1
+void Push(MutableFstClass *ofst, ReweightType type, float delta = kDelta,
+          bool remove_total_weight = false);
+
+// 2
+void Push(const FstClass &ifst, MutableFstClass *ofst, uint32 flags,
+          ReweightType dir, float delta);
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_PUSH_H_
diff --git a/src/include/fst/script/randequivalent.h b/src/include/fst/script/randequivalent.h
new file mode 100644
index 0000000..b929683
--- /dev/null
+++ b/src/include/fst/script/randequivalent.h
@@ -0,0 +1,105 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_RANDEQUIVALENT_H_
+#define FST_SCRIPT_RANDEQUIVALENT_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/randgen.h>  // for RandArcSelection
+#include <fst/randequivalent.h>
+
+namespace fst {
+namespace script {
+
+// 1
+typedef args::Package<const FstClass&, const FstClass&,
+                      int32, float, int, int> RandEquivalentInnerArgs1;
+typedef args::WithReturnValue<bool,
+                              RandEquivalentInnerArgs1> RandEquivalentArgs1;
+
+template<class Arc>
+void RandEquivalent(RandEquivalentArgs1 *args) {
+  const Fst<Arc> &fst1 = *(args->args.arg1.GetFst<Arc>());
+  const Fst<Arc> &fst2 = *(args->args.arg2.GetFst<Arc>());
+
+  args->retval = RandEquivalent(fst1, fst2, args->args.arg3, args->args.arg4,
+                                args->args.arg5, args->args.arg6);
+}
+
+// 2
+typedef args::Package<const FstClass &, const FstClass &, int32,
+                      ssize_t, float,
+                      const RandGenOptions<RandArcSelection> &>
+  RandEquivalentInnerArgs2;
+
+typedef args::WithReturnValue<bool,
+                              RandEquivalentInnerArgs2> RandEquivalentArgs2;
+
+template<class Arc>
+void RandEquivalent(RandEquivalentArgs2 *args) {
+  const Fst<Arc> &fst1 = *(args->args.arg1.GetFst<Arc>());
+  const Fst<Arc> &fst2 = *(args->args.arg2.GetFst<Arc>());
+  const RandGenOptions<RandArcSelection> &opts = args->args.arg6;
+  int32 seed = args->args.arg3;
+
+  if (opts.arc_selector == UNIFORM_ARC_SELECTOR) {
+    UniformArcSelector<Arc> arc_selector(seed);
+    RandGenOptions< UniformArcSelector<Arc> >
+        ropts(arc_selector, opts.max_length, opts.npath);
+
+    args->retval = RandEquivalent(fst1, fst2, args->args.arg4,
+                                  args->args.arg5, ropts);
+  } else if (opts.arc_selector == FAST_LOG_PROB_ARC_SELECTOR) {
+    FastLogProbArcSelector<Arc> arc_selector(seed);
+    RandGenOptions< FastLogProbArcSelector<Arc> >
+        ropts(arc_selector, opts.max_length, opts.npath);
+
+    args->retval = RandEquivalent(fst1, fst2, args->args.arg4,
+                                  args->args.arg5, ropts);
+  } else {
+    LogProbArcSelector<Arc> arc_selector(seed);
+    RandGenOptions< LogProbArcSelector<Arc> >
+        ropts(arc_selector, opts.max_length, opts.npath);
+    args->retval = RandEquivalent(fst1, fst2, args->args.arg4,
+                                  args->args.arg5, ropts);
+  }
+}
+
+
+// 1
+bool RandEquivalent(const FstClass &fst1,
+                    const FstClass &fst2,
+                    int32 seed = time(0),
+                    ssize_t num_paths = 1,
+                    float delta = fst::kDelta,
+                    int path_length = INT_MAX);
+
+// 2
+bool RandEquivalent(const FstClass &fst1,
+                    const FstClass &fst2,
+                    int32 seed,
+                    ssize_t num_paths,
+                    float delta,
+                    const fst::RandGenOptions<
+                      fst::script::RandArcSelection> &opts);
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_RANDEQUIVALENT_H_
diff --git a/src/include/fst/script/randgen.h b/src/include/fst/script/randgen.h
new file mode 100644
index 0000000..817f9c1
--- /dev/null
+++ b/src/include/fst/script/randgen.h
@@ -0,0 +1,76 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_RANDGEN_H_
+#define FST_SCRIPT_RANDGEN_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/randgen.h>
+
+namespace fst {
+namespace script {
+
+enum RandArcSelection {
+  UNIFORM_ARC_SELECTOR,
+  LOG_PROB_ARC_SELECTOR,
+  FAST_LOG_PROB_ARC_SELECTOR
+};
+
+typedef args::Package<const FstClass &, MutableFstClass*, int32,
+                      const RandGenOptions<RandArcSelection> &> RandGenArgs;
+
+template<class Arc>
+void RandGen(RandGenArgs *args) {
+  const Fst<Arc> &ifst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+  int32 seed = args->arg3;
+  const RandGenOptions<RandArcSelection> &opts = args->arg4;
+
+  if (opts.arc_selector == UNIFORM_ARC_SELECTOR) {
+    UniformArcSelector<Arc> arc_selector(seed);
+    RandGenOptions< UniformArcSelector<Arc> >
+        ropts(arc_selector, opts.max_length,
+              opts.npath, opts.weighted);
+    RandGen(ifst, ofst, ropts);
+  } else if (opts.arc_selector == FAST_LOG_PROB_ARC_SELECTOR) {
+    FastLogProbArcSelector<Arc> arc_selector(seed);
+    RandGenOptions< FastLogProbArcSelector<Arc> >
+        ropts(arc_selector, opts.max_length,
+              opts.npath, opts.weighted);
+    RandGen(ifst, ofst, ropts);
+  } else {
+    LogProbArcSelector<Arc> arc_selector(seed);
+    RandGenOptions< LogProbArcSelector<Arc> >
+        ropts(arc_selector, opts.max_length,
+              opts.npath, opts.weighted);
+    RandGen(ifst, ofst, ropts);
+  }
+}
+
+
+// Client-facing prototype
+void RandGen(const FstClass &ifst, MutableFstClass *ofst, int32 seed = time(0),
+             const RandGenOptions<RandArcSelection> &opts =
+             fst::RandGenOptions<fst::script::RandArcSelection>(
+                 fst::script::UNIFORM_ARC_SELECTOR));
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_RANDGEN_H_
diff --git a/src/include/fst/script/register.h b/src/include/fst/script/register.h
new file mode 100644
index 0000000..03e0e36
--- /dev/null
+++ b/src/include/fst/script/register.h
@@ -0,0 +1,120 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_REGISTER_H_
+#define FST_SCRIPT_REGISTER_H_
+
+#include <string>
+
+#include <fst/generic-register.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/weight-class.h>
+
+// Holds methods and classes responsible for maintaining
+// the register for FstClass arc types.
+
+namespace fst {
+namespace script {
+
+//
+// Registers for reading and converting various kinds of FST classes.
+//
+
+// This class definition is to avoid a nested class definition inside
+// the IORegistration struct.
+template<class Reader, class Creator, class Converter>
+struct FstClassRegEntry {
+  Reader reader;
+  Creator creator;
+  Converter converter;
+
+  FstClassRegEntry(Reader r, Creator cr, Converter co) :
+      reader(r), creator(cr), converter(co) { }
+  FstClassRegEntry() : reader(0), creator(0), converter(0) { }
+};
+
+template<class Reader, class Creator, class Converter>
+class FstClassIORegister
+    : public GenericRegister<string,
+                             FstClassRegEntry<Reader, Creator, Converter>,
+                             FstClassIORegister<Reader, Creator,
+                                                Converter> > {
+ public:
+  Reader GetReader(const string &arc_type) const {
+    return this->GetEntry(arc_type).reader;
+  }
+
+  Creator GetCreator(const string &arc_type) const {
+    return this->GetEntry(arc_type).creator;
+  }
+
+  Converter GetConverter(const string &arc_type) const {
+    return this->GetEntry(arc_type).converter;
+  }
+
+ protected:
+  virtual string ConvertKeyToSoFilename(
+      const string& key) const {
+    string legal_type(key);
+    ConvertToLegalCSymbol(&legal_type);
+
+    return legal_type + "-arc.so";
+  }
+};
+
+//
+// Struct containing everything needed to register a particular type
+// of FST class (e.g. a plain FstClass, or a MutableFstClass, etc)
+//
+template<class FstClassType>
+struct IORegistration {
+  typedef FstClassType *(*Reader)(istream &stream,
+                                  const FstReadOptions &opts);
+
+  typedef FstClassImplBase *(*Creator)();
+  typedef FstClassImplBase *(*Converter)(const FstClass &other);
+
+  typedef FstClassRegEntry<Reader, Creator, Converter> Entry;
+
+  // FST class Register
+  typedef FstClassIORegister<Reader, Creator, Converter> Register;
+
+  // FST class Register-er
+  typedef GenericRegisterer<FstClassIORegister<Reader, Creator, Converter> >
+    Registerer;
+};
+
+
+//
+// REGISTRATION MACROS
+//
+
+#define REGISTER_FST_CLASS(Class, Arc)                                  \
+  static IORegistration<Class>::Registerer Class ## _ ## Arc ## _registerer( \
+      Arc::Type(),                                                      \
+      IORegistration<Class>::Entry(Class::Read<Arc>,                    \
+                                   Class::Create<Arc>,                  \
+                                   Class::Convert<Arc>))
+
+#define REGISTER_FST_CLASSES(Arc)               \
+  REGISTER_FST_CLASS(FstClass, Arc);            \
+  REGISTER_FST_CLASS(MutableFstClass, Arc);     \
+  REGISTER_FST_CLASS(VectorFstClass, Arc);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_REGISTER_H_
diff --git a/src/include/fst/script/relabel.h b/src/include/fst/script/relabel.h
new file mode 100644
index 0000000..6bbb4c5
--- /dev/null
+++ b/src/include/fst/script/relabel.h
@@ -0,0 +1,102 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_RELABEL_H_
+#define FST_SCRIPT_RELABEL_H_
+
+#include <utility>
+using std::pair; using std::make_pair;
+#include <algorithm>
+#include <vector>
+using std::vector;
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/relabel.h>
+
+namespace fst {
+namespace script {
+
+// 1
+typedef args::Package<MutableFstClass *,
+                      const SymbolTable *, const SymbolTable *, bool,
+                      const SymbolTable *, const SymbolTable *,
+                      bool> RelabelArgs1;
+
+template<class Arc>
+void Relabel(RelabelArgs1 *args) {
+  MutableFst<Arc> *ofst = args->arg1->GetMutableFst<Arc>();
+
+  Relabel(ofst, args->arg2, args->arg3, args->arg4,
+          args->arg5, args->arg6, args->arg7);
+}
+
+// 2
+typedef args::Package<MutableFstClass*,
+                      const vector<pair<int64, int64> > &,
+                      const vector<pair<int64, int64> > > RelabelArgs2;
+
+template<class Arc>
+void Relabel(RelabelArgs2 *args) {
+  MutableFst<Arc> *ofst = args->arg1->GetMutableFst<Arc>();
+
+  // In case int64 is not the same as Arc::Label,
+  // copy the reassignments
+  typedef typename Arc::Label Label;
+
+  vector<pair<Label, Label> > converted_ipairs(args->arg2.size());
+  copy(args->arg2.begin(), args->arg2.end(), converted_ipairs.begin());
+
+  vector<pair<Label, Label> > converted_opairs(args->arg3.size());
+  copy(args->arg3.begin(), args->arg3.end(), converted_opairs.begin());
+
+  Relabel(ofst, converted_ipairs, converted_opairs);
+}
+
+// 3
+typedef args::Package<MutableFstClass*, const SymbolTable*,
+                      const SymbolTable*> RelabelArgs3;
+template<class Arc>
+void Relabel(args::Package<MutableFstClass*, const SymbolTable*,
+             const SymbolTable*> *args) {
+  MutableFst<Arc> *fst = args->arg1->GetMutableFst<Arc>();
+  Relabel(fst, args->arg2, args->arg3);
+}
+
+
+// 1
+void Relabel(MutableFstClass *ofst,
+             const SymbolTable *old_isyms, const SymbolTable *relabel_isyms,
+             bool attach_new_isyms,
+             const SymbolTable *old_osyms, const SymbolTable *relabel_osyms,
+             bool attch_new_osyms);
+
+// 2
+void Relabel(MutableFstClass *ofst,
+             const vector<pair<int64, int64> > &ipairs,
+             const vector<pair<int64, int64> > &opairs);
+
+
+// 3
+void Relabel(MutableFstClass *fst,
+             const SymbolTable *new_isymbols,
+             const SymbolTable *new_osymbols);
+
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_RELABEL_H_
diff --git a/src/include/fst/script/replace.h b/src/include/fst/script/replace.h
new file mode 100644
index 0000000..5eaf5bf
--- /dev/null
+++ b/src/include/fst/script/replace.h
@@ -0,0 +1,62 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_REPLACE_H_
+#define FST_SCRIPT_REPLACE_H_
+
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/replace.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<const vector<pair<int64, const FstClass *> > &,
+                      MutableFstClass *, const int64, bool> ReplaceArgs;
+
+template<class Arc>
+void Replace(ReplaceArgs *args) {
+  // Now that we know the arc type, we construct a vector of
+  // pair<real label, real fst> that the real Replace will use
+  const vector<pair<int64, const FstClass *> >& untyped_tuples =
+      args->arg1;
+
+  vector<pair<typename Arc::Label, const Fst<Arc> *> > fst_tuples(
+      untyped_tuples.size());
+
+  for (unsigned i = 0; i < untyped_tuples.size(); ++i) {
+    fst_tuples[i].first = untyped_tuples[i].first;  // convert label
+    fst_tuples[i].second = untyped_tuples[i].second->GetFst<Arc>();
+  }
+
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+
+  Replace(fst_tuples, ofst, args->arg3, args->arg4);
+}
+
+void Replace(const vector<pair<int64, const FstClass *> > &tuples,
+             MutableFstClass *ofst, const int64 &root,
+             bool epsilon_on_replace = false);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_REPLACE_H_
diff --git a/src/include/fst/script/reverse.h b/src/include/fst/script/reverse.h
new file mode 100644
index 0000000..3930875
--- /dev/null
+++ b/src/include/fst/script/reverse.h
@@ -0,0 +1,42 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_REVERSE_H_
+#define FST_SCRIPT_REVERSE_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/reverse.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<const FstClass &, MutableFstClass *> ReverseArgs;
+
+template<class Arc>
+void Reverse(ReverseArgs *args) {
+  const Fst<Arc> &fst1 = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *fst2 = args->arg2->GetMutableFst<Arc>();
+
+  Reverse(fst1, fst2);
+}
+
+void Reverse(const FstClass &fst1, MutableFstClass *fst2);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_REVERSE_H_
diff --git a/src/include/fst/script/reweight.h b/src/include/fst/script/reweight.h
new file mode 100644
index 0000000..7bce839
--- /dev/null
+++ b/src/include/fst/script/reweight.h
@@ -0,0 +1,53 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_REWEIGHT_H_
+#define FST_SCRIPT_REWEIGHT_H_
+
+#include <vector>
+using std::vector;
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/weight-class.h>
+#include <fst/reweight.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<MutableFstClass *, const vector<WeightClass> &,
+                      ReweightType> ReweightArgs;
+
+template<class Arc>
+void Reweight(ReweightArgs *args) {
+  MutableFst<Arc> *fst = args->arg1->GetMutableFst<Arc>();
+  typedef typename Arc::Weight Weight;
+  vector<Weight> potentials(args->arg2.size());
+
+  for (unsigned i = 0; i < args->arg2.size(); ++i) {
+    potentials[i] = *(args->arg2[i].GetWeight<Weight>());
+  }
+
+  Reweight(fst, potentials, args->arg3);
+}
+
+void Reweight(MutableFstClass *fst, const vector<WeightClass> &potential,
+              ReweightType reweight_type);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_REWEIGHT_H_
diff --git a/src/include/fst/script/rmepsilon.h b/src/include/fst/script/rmepsilon.h
new file mode 100644
index 0000000..62fed03
--- /dev/null
+++ b/src/include/fst/script/rmepsilon.h
@@ -0,0 +1,211 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_RMEPSILON_H_
+#define FST_SCRIPT_RMEPSILON_H_
+
+#include <vector>
+using std::vector;
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/weight-class.h>
+#include <fst/script/shortest-distance.h>  // for ShortestDistanceOptions
+#include <fst/rmepsilon.h>
+#include <fst/queue.h>
+
+// the following is necessary, or SWIG complains mightily about
+// shortestdistanceoptions not being defined before being used as a base.
+#ifdef SWIG
+%include "nlp/fst/script/shortest-distance.h"
+#endif
+
+
+namespace fst {
+namespace script {
+
+//
+// OPTIONS
+//
+
+struct RmEpsilonOptions : public fst::script::ShortestDistanceOptions {
+  bool connect;
+  WeightClass weight_threshold;
+  int64 state_threshold;
+
+  RmEpsilonOptions(QueueType qt = AUTO_QUEUE, float d = kDelta, bool c = true,
+                   WeightClass w = fst::script::WeightClass::Zero(),
+                   int64 n = kNoStateId)
+      : ShortestDistanceOptions(qt, EPSILON_ARC_FILTER,
+                                kNoStateId, d),
+        connect(c), weight_threshold(w), state_threshold(n) { }
+};
+
+
+//
+// TEMPLATES
+//
+
+// this function takes care of transforming a script-land RmEpsilonOptions
+// into a lib-land RmEpsilonOptions
+template<class Arc>
+void RmEpsilonHelper(MutableFst<Arc> *fst,
+                     vector<typename Arc::Weight> *distance,
+                     const RmEpsilonOptions &opts) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+
+  typename Arc::Weight weight_thresh =
+      *(opts.weight_threshold.GetWeight<Weight>());
+
+  switch (opts.queue_type) {
+    case AUTO_QUEUE: {
+      AutoQueue<StateId> queue(*fst, distance, EpsilonArcFilter<Arc>());
+      fst::RmEpsilonOptions<Arc, AutoQueue<StateId> > ropts(
+          &queue, opts.delta, opts.connect, weight_thresh,
+          opts.state_threshold);
+      RmEpsilon(fst, distance, ropts);
+      break;
+    }
+    case FIFO_QUEUE: {
+      FifoQueue<StateId> queue;
+      fst::RmEpsilonOptions<Arc, FifoQueue<StateId> > ropts(
+          &queue, opts.delta, opts.connect, weight_thresh,
+          opts.state_threshold);
+      RmEpsilon(fst, distance, ropts);
+      break;
+    }
+    case LIFO_QUEUE: {
+      LifoQueue<StateId> queue;
+      fst::RmEpsilonOptions<Arc, LifoQueue<StateId> > ropts(
+          &queue, opts.delta, opts.connect, weight_thresh,
+          opts.state_threshold);
+      RmEpsilon(fst, distance, ropts);
+      break;
+    }
+    case SHORTEST_FIRST_QUEUE: {
+      NaturalShortestFirstQueue<StateId, Weight>  queue(*distance);
+      fst::RmEpsilonOptions<Arc, NaturalShortestFirstQueue<StateId,
+                                                               Weight> > ropts(
+          &queue, opts.delta, opts.connect, weight_thresh,
+          opts.state_threshold);
+      RmEpsilon(fst, distance, ropts);
+      break;
+    }
+    case STATE_ORDER_QUEUE: {
+      StateOrderQueue<StateId> queue;
+      fst::RmEpsilonOptions<Arc, StateOrderQueue<StateId> > ropts(
+          &queue, opts.delta, opts.connect, weight_thresh,
+          opts.state_threshold);
+      RmEpsilon(fst, distance, ropts);
+      break;
+    }
+    case TOP_ORDER_QUEUE: {
+      TopOrderQueue<StateId> queue(*fst, EpsilonArcFilter<Arc>());
+      fst::RmEpsilonOptions<Arc, TopOrderQueue<StateId> > ropts(
+          &queue, opts.delta, opts.connect, weight_thresh,
+          opts.state_threshold);
+      RmEpsilon(fst, distance, ropts);
+      break;
+    }
+    default:
+      FSTERROR() << "Unknown or unsupported queue type: " << opts.queue_type;
+      fst->SetProperties(kError, kError);
+  }
+}
+
+// 1
+typedef args::Package<const FstClass &, MutableFstClass *,
+                      bool, const RmEpsilonOptions &> RmEpsilonArgs1;
+
+template<class Arc>
+void RmEpsilon(RmEpsilonArgs1 *args) {
+  const Fst<Arc> &ifst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+  vector<typename Arc::Weight> distance;
+  bool reverse = args->arg3;
+
+  if (reverse) {
+    VectorFst<Arc> rfst;
+    Reverse(ifst, &rfst);
+    RmEpsilonHelper(&rfst, &distance, args->arg4);
+    Reverse(rfst, ofst);
+  } else {
+    *ofst = ifst;
+  }
+  RmEpsilonHelper(ofst, &distance, args->arg4);
+}
+
+// 2
+typedef args::Package<MutableFstClass *, bool,
+                      const WeightClass, int64,
+                      float> RmEpsilonArgs2;
+
+template<class Arc>
+void RmEpsilon(RmEpsilonArgs2 *args) {
+  MutableFst<Arc> *fst = args->arg1->GetMutableFst<Arc>();
+  typename Arc::Weight w = *(args->arg3.GetWeight<typename Arc::Weight>());
+
+  RmEpsilon(fst, args->arg2, w, args->arg4, args->arg5);
+}
+
+// 3
+typedef args::Package<MutableFstClass *, vector<WeightClass> *,
+                      const RmEpsilonOptions &> RmEpsilonArgs3;
+
+template<class Arc>
+void RmEpsilon(RmEpsilonArgs3 *args) {
+  MutableFst<Arc> *fst = args->arg1->GetMutableFst<Arc>();
+  const RmEpsilonOptions &opts = args->arg3;
+
+  vector<typename Arc::Weight> weights;
+
+  RmEpsilonHelper(fst, &weights, opts);
+
+  // Copy the weights back
+  args->arg2->resize(weights.size());
+  for (unsigned i = 0; i < weights.size(); ++i) {
+    (*args->arg2)[i] = WeightClass(weights[i]);
+  }
+}
+
+//
+// PROTOTYPES
+//
+
+// 1
+void RmEpsilon(const FstClass &ifst, MutableFstClass *ofst,
+               bool reverse = false,
+               const RmEpsilonOptions& opts =
+                 fst::script::RmEpsilonOptions());
+
+// 2
+void RmEpsilon(MutableFstClass *arc, bool connect = true,
+               const WeightClass &weight_threshold =
+                 fst::script::WeightClass::Zero(),
+               int64 state_threshold = fst::kNoStateId,
+               float delta = fst::kDelta);
+
+// 3
+void RmEpsilon(MutableFstClass *fst, vector<WeightClass> *distance,
+               const RmEpsilonOptions &opts);
+
+
+}  // namespace script
+}  // namespace fst
+
+
+#endif  // FST_SCRIPT_RMEPSILON_H_
diff --git a/src/include/fst/script/script-impl.h b/src/include/fst/script/script-impl.h
new file mode 100644
index 0000000..452c7c5
--- /dev/null
+++ b/src/include/fst/script/script-impl.h
@@ -0,0 +1,206 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+// This file defines the registration mechanism for new operations.
+// These operations are designed to enable scripts to work with FST classes
+// at a high level.
+
+// If you have a new arc type and want these operations to work with FSTs
+// with that arc type, see below for the registration steps
+// you must take.
+
+// These methods are only recommended for use in high-level scripting
+// applications. Most users should use the lower-level templated versions
+// corresponding to these.
+
+// If you have a new arc type you'd like these operations to work with,
+// use the REGISTER_FST_OPERATIONS macro defined in fstcsript.h
+
+// If you have a custom operation you'd like to define, you need four
+// components. In the following, assume you want to create a new operation
+// with the signature
+//
+//    void Foo(const FstClass &ifst, MutableFstClass *ofst);
+//
+//  You need:
+//
+//  1) A way to bundle the args that your new Foo operation will take, as
+//     a single struct. The template structs in arg-packs.h provide a handy
+//     way to do this. In Foo's case, that might look like this:
+//
+//       typedef args::Package<const FstClass &,
+//                             MutableFstClass *> FooArgs;
+//
+//     Note: this package of args is going to be passed by non-const pointer.
+//
+//  2) A function template that is able to perform Foo, given the args and
+//     arc type. Yours might look like this:
+//
+//       template<class Arc>
+//       void Foo(FooArgs *args) {
+//          // Pull out the actual, arc-templated FSTs
+//          const Fst<Arc> &ifst = args->arg1.GetFst<Arc>();
+//          MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+//
+//          // actually perform foo on ifst and ofst...
+//       }
+//
+//  3) a client-facing function for your operation. This would look like
+//     the following:
+//
+//     void Foo(const FstClass &ifst, MutableFstClass *ofst) {
+//       // Check that the arc types of the FSTs match
+//       if (!ArcTypesMatch(ifst, *ofst, "Foo")) return;
+//       // package the args
+//       FooArgs args(ifst, ofst);
+//       // Finally, call the operation
+//       Apply<Operation<FooArgs> >("Foo", ifst->ArcType(), &args);
+//     }
+//
+//  The Apply<> function template takes care of the link between 2 and 3,
+//  provided you also have:
+//
+//  4) A registration for your new operation, on the arc types you care about.
+//     This can be provided easily by the REGISTER_FST_OPERATION macro in
+//     operations.h:
+//
+//       REGISTER_FST_OPERATION(Foo, StdArc, FooArgs);
+//       REGISTER_FST_OPERATION(Foo, MyArc, FooArgs);
+//       // .. etc
+//
+//
+//  That's it! Now when you call Foo(const FstClass &, MutableFstClass *),
+//  it dispatches (in #3) via the Apply<> function to the correct
+//  instantiation of the template function in #2.
+//
+
+
+#ifndef FST_SCRIPT_SCRIPT_IMPL_H_
+#define FST_SCRIPT_SCRIPT_IMPL_H_
+
+//
+// This file contains general-purpose templates which are used in the
+// implementation of the operations.
+//
+
+#include <utility>
+using std::pair; using std::make_pair;
+#include <string>
+
+#include <fst/script/fst-class.h>
+#include <fst/generic-register.h>
+#include <fst/script/arg-packs.h>
+
+#include <fst/types.h>
+
+namespace fst {
+namespace script {
+
+//
+// A generic register for operations with various kinds of signatures.
+// Needed since every function signature requires a new registration class.
+// The pair<string, string> is understood to be the operation name and arc
+// type; subclasses (or typedefs) need only provide the operation signature.
+//
+
+template<class OperationSignature>
+class GenericOperationRegister
+    : public GenericRegister<pair<string, string>,
+                             OperationSignature,
+                             GenericOperationRegister<OperationSignature> > {
+ public:
+  void RegisterOperation(const string &operation_name,
+                         const string &arc_type,
+                         OperationSignature op) {
+    this->SetEntry(make_pair(operation_name, arc_type), op);
+  }
+
+  OperationSignature GetOperation(
+      const string &operation_name, const string &arc_type) {
+    return this->GetEntry(make_pair(operation_name, arc_type));
+  }
+
+ protected:
+  virtual string ConvertKeyToSoFilename(
+      const pair<string, string>& key) const {
+    // Just use the old-style FST for now.
+    string legal_type(key.second);  // the arc type
+    ConvertToLegalCSymbol(&legal_type);
+
+    return legal_type + "-arc.so";
+  }
+};
+
+
+// Operation package - everything you need to register a new type of operation
+
+// The ArgPack should be the type that's passed into each wrapped function -
+// for instance, it might be a struct containing all the args.
+// It's always passed by pointer, so const members should be used to enforce
+// constness where it's needed. Return values should be implemented as a
+// member of ArgPack as well.
+
+template<class ArgPack>
+struct Operation {
+  typedef ArgPack Args;
+  typedef void (*OpType)(ArgPack *args);
+
+  // The register (hash) type
+  typedef GenericOperationRegister<OpType> Register;
+
+  // The register-er type
+  typedef GenericRegisterer<Register> Registerer;
+};
+
+
+// Macro for registering new types of operations.
+
+#define REGISTER_FST_OPERATION(Op, Arc, ArgPack)                        \
+  static fst::script::Operation<ArgPack>::Registerer                \
+  arc_dispatched_operation_ ## ArgPack ## Op ## Arc ## _registerer(     \
+      make_pair(#Op, Arc::Type()), Op<Arc>)
+
+
+//
+// Template function to apply an operation by name
+//
+
+template<class OpReg>
+void Apply(const string &op_name, const string &arc_type,
+           typename OpReg::Args *args) {
+  typename OpReg::Register *reg = OpReg::Register::GetRegister();
+
+  typename OpReg::OpType op = reg->GetOperation(op_name, arc_type);
+
+  if (op == 0) {
+    FSTERROR() << "No operation found for \"" << op_name << "\" on "
+               << "arc type " << arc_type;
+    return;
+  }
+
+  op(args);
+}
+
+
+// Helper that logs to ERROR if the arc types of a and b don't match.
+// The op_name is also printed.
+bool ArcTypesMatch(const FstClass &a, const FstClass &b,
+                   const string &op_name);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_SCRIPT_IMPL_H_
diff --git a/src/include/fst/script/shortest-distance.h b/src/include/fst/script/shortest-distance.h
new file mode 100644
index 0000000..5fc2976
--- /dev/null
+++ b/src/include/fst/script/shortest-distance.h
@@ -0,0 +1,250 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_SHORTEST_DISTANCE_H_
+#define FST_SCRIPT_SHORTEST_DISTANCE_H_
+
+#include <vector>
+using std::vector;
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/weight-class.h>
+#include <fst/script/prune.h>  // for ArcFilterType
+#include <fst/queue.h>  // for QueueType
+#include <fst/shortest-distance.h>
+
+namespace fst {
+namespace script {
+
+enum ArcFilterType { ANY_ARC_FILTER, EPSILON_ARC_FILTER,
+                     INPUT_EPSILON_ARC_FILTER, OUTPUT_EPSILON_ARC_FILTER };
+
+// See nlp/fst/lib/shortest-distance.h for the template options class
+// that this one shadows
+struct ShortestDistanceOptions {
+  const QueueType queue_type;
+  const ArcFilterType arc_filter_type;
+  const int64 source;
+  const float delta;
+  const bool first_path;
+
+  ShortestDistanceOptions(QueueType qt, ArcFilterType aft, int64 s,
+                          float d)
+      : queue_type(qt), arc_filter_type(aft), source(s), delta(d),
+        first_path(false) { }
+};
+
+
+
+// 1
+typedef args::Package<const FstClass &, vector<WeightClass> *,
+                      const ShortestDistanceOptions &> ShortestDistanceArgs1;
+
+template<class Queue, class Arc, class ArcFilter>
+struct QueueConstructor {
+  //  template<class Arc, class ArcFilter>
+  static Queue *Construct(const Fst<Arc> &,
+                          const vector<typename Arc::Weight> *) {
+    return new Queue();
+  }
+};
+
+// Specializations to deal with AutoQueue, NaturalShortestFirstQueue,
+// and TopOrderQueue's different constructors
+template<class Arc, class ArcFilter>
+struct QueueConstructor<AutoQueue<typename Arc::StateId>, Arc, ArcFilter> {
+  //  template<class Arc, class ArcFilter>
+  static AutoQueue<typename Arc::StateId> *Construct(
+      const Fst<Arc> &fst,
+      const vector<typename Arc::Weight> *distance) {
+    return new AutoQueue<typename Arc::StateId>(fst, distance, ArcFilter());
+  }
+};
+
+template<class Arc, class ArcFilter>
+struct QueueConstructor<NaturalShortestFirstQueue<typename Arc::StateId,
+                                                  typename Arc::Weight>,
+                        Arc, ArcFilter> {
+  //  template<class Arc, class ArcFilter>
+  static NaturalShortestFirstQueue<typename Arc::StateId, typename Arc::Weight>
+  *Construct(const Fst<Arc> &fst,
+            const vector<typename Arc::Weight> *distance) {
+    return new NaturalShortestFirstQueue<typename Arc::StateId,
+                                         typename Arc::Weight>(*distance);
+  }
+};
+
+template<class Arc, class ArcFilter>
+struct QueueConstructor<TopOrderQueue<typename Arc::StateId>, Arc, ArcFilter> {
+  //  template<class Arc, class ArcFilter>
+  static TopOrderQueue<typename Arc::StateId> *Construct(
+      const Fst<Arc> &fst, const vector<typename Arc::Weight> *weights) {
+    return new TopOrderQueue<typename Arc::StateId>(fst, ArcFilter());
+  }
+};
+
+
+template<class Arc, class Queue>
+void ShortestDistanceHelper(ShortestDistanceArgs1 *args) {
+  const Fst<Arc> &fst = *(args->arg1.GetFst<Arc>());
+  const ShortestDistanceOptions &opts = args->arg3;
+
+  vector<typename Arc::Weight> weights;
+
+  switch (opts.arc_filter_type) {
+    case ANY_ARC_FILTER: {
+      Queue *queue =
+          QueueConstructor<Queue, Arc, AnyArcFilter<Arc> >::Construct(
+              fst, &weights);
+      fst::ShortestDistanceOptions<Arc, Queue, AnyArcFilter<Arc> > sdopts(
+          queue, AnyArcFilter<Arc>(), opts.source, opts.delta);
+      ShortestDistance(fst, &weights, sdopts);
+      delete queue;
+      break;
+    }
+    case EPSILON_ARC_FILTER: {
+      Queue *queue =
+          QueueConstructor<Queue, Arc, AnyArcFilter<Arc> >::Construct(
+              fst, &weights);
+      fst::ShortestDistanceOptions<Arc, Queue,
+          EpsilonArcFilter<Arc> > sdopts(
+              queue, EpsilonArcFilter<Arc>(), opts.source, opts.delta);
+      ShortestDistance(fst, &weights, sdopts);
+      delete queue;
+      break;
+    }
+    case INPUT_EPSILON_ARC_FILTER: {
+      Queue *queue =
+          QueueConstructor<Queue, Arc, InputEpsilonArcFilter<Arc> >::Construct(
+              fst, &weights);
+      fst::ShortestDistanceOptions<Arc, Queue,
+          InputEpsilonArcFilter<Arc> > sdopts(
+              queue, InputEpsilonArcFilter<Arc>(), opts.source, opts.delta);
+      ShortestDistance(fst, &weights, sdopts);
+      delete queue;
+      break;
+    }
+    case OUTPUT_EPSILON_ARC_FILTER: {
+      Queue *queue =
+          QueueConstructor<Queue, Arc,
+          OutputEpsilonArcFilter<Arc> >::Construct(
+              fst, &weights);
+      fst::ShortestDistanceOptions<Arc, Queue,
+          OutputEpsilonArcFilter<Arc> > sdopts(
+              queue, OutputEpsilonArcFilter<Arc>(), opts.source, opts.delta);
+      ShortestDistance(fst, &weights, sdopts);
+      delete queue;
+      break;
+    }
+  }
+
+  // Copy the weights back
+  args->arg2->resize(weights.size());
+  for (unsigned i = 0; i < weights.size(); ++i) {
+    (*args->arg2)[i] = WeightClass(weights[i]);
+  }
+}
+
+template<class Arc>
+void ShortestDistance(ShortestDistanceArgs1 *args) {
+  const ShortestDistanceOptions &opts = args->arg3;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+
+  // Must consider (opts.queue_type x opts.filter_type) options
+  switch (opts.queue_type) {
+    default:
+      FSTERROR() << "Unknown queue type." << opts.queue_type;
+
+    case AUTO_QUEUE:
+      ShortestDistanceHelper<Arc, AutoQueue<StateId> >(args);
+      return;
+
+    case FIFO_QUEUE:
+       ShortestDistanceHelper<Arc, FifoQueue<StateId> >(args);
+      return;
+
+    case LIFO_QUEUE:
+       ShortestDistanceHelper<Arc, LifoQueue<StateId> >(args);
+      return;
+
+    case SHORTEST_FIRST_QUEUE:
+      ShortestDistanceHelper<Arc,
+        NaturalShortestFirstQueue<StateId, Weight> >(args);
+      return;
+
+    case STATE_ORDER_QUEUE:
+       ShortestDistanceHelper<Arc, StateOrderQueue<StateId> >(args);
+      return;
+
+    case TOP_ORDER_QUEUE:
+       ShortestDistanceHelper<Arc, TopOrderQueue<StateId> >(args);
+      return;
+  }
+}
+
+// 2
+typedef args::Package<const FstClass&, vector<WeightClass>*,
+                      bool, double> ShortestDistanceArgs2;
+
+template<class Arc>
+void ShortestDistance(ShortestDistanceArgs2 *args) {
+  const Fst<Arc> &fst = *(args->arg1.GetFst<Arc>());
+  vector<typename Arc::Weight> distance;
+
+  ShortestDistance(fst, &distance, args->arg3, args->arg4);
+
+  // convert the typed weights back into weightclass
+  vector<WeightClass> *retval = args->arg2;
+  retval->resize(distance.size());
+
+  for (unsigned i = 0; i < distance.size(); ++i) {
+    (*retval)[i] = WeightClass(distance[i]);
+  }
+}
+
+// 3
+typedef args::WithReturnValue<WeightClass,
+                              const FstClass &> ShortestDistanceArgs3;
+
+template<class Arc>
+void ShortestDistance(ShortestDistanceArgs3 *args) {
+  const Fst<Arc> &fst = *(args->args.GetFst<Arc>());
+
+  args->retval = WeightClass(ShortestDistance(fst));
+}
+
+
+// 1
+void ShortestDistance(const FstClass &fst, vector<WeightClass> *distance,
+                      const ShortestDistanceOptions &opts);
+
+// 2
+void ShortestDistance(const FstClass &ifst, vector<WeightClass> *distance,
+                      bool reverse = false, double delta = fst::kDelta);
+
+#ifndef SWIG
+// 3
+WeightClass ShortestDistance(const FstClass &ifst);
+#endif
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_SHORTEST_DISTANCE_H_
diff --git a/src/include/fst/script/shortest-path.h b/src/include/fst/script/shortest-path.h
new file mode 100644
index 0000000..b3a3eb9
--- /dev/null
+++ b/src/include/fst/script/shortest-path.h
@@ -0,0 +1,190 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_SHORTEST_PATH_H_
+#define FST_SCRIPT_SHORTEST_PATH_H_
+
+#include <vector>
+using std::vector;
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/script/weight-class.h>
+#include <fst/shortest-path.h>
+#include <fst/script/shortest-distance.h>  // for ShortestDistanceOptions
+
+namespace fst {
+namespace script {
+
+struct ShortestPathOptions
+    : public fst::script::ShortestDistanceOptions {
+  const size_t nshortest;
+  const bool unique;
+  const bool has_distance;
+  const bool first_path;
+  const WeightClass weight_threshold;
+  const int64 state_threshold;
+
+  ShortestPathOptions(QueueType qt, size_t n = 1,
+                      bool u = false, bool hasdist = false,
+                      float d = fst::kDelta, bool fp = false,
+                      WeightClass w = fst::script::WeightClass::Zero(),
+                      int64 s = fst::kNoStateId)
+      : ShortestDistanceOptions(qt, ANY_ARC_FILTER, kNoStateId, d),
+        nshortest(n), unique(u), has_distance(hasdist), first_path(fp),
+        weight_threshold(w), state_threshold(s) { }
+};
+
+typedef args::Package<const FstClass &, MutableFstClass *,
+                      vector<WeightClass> *, const ShortestPathOptions &>
+  ShortestPathArgs1;
+
+
+template<class Arc>
+void ShortestPath(ShortestPathArgs1 *args) {
+  const Fst<Arc> &ifst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+  const ShortestPathOptions &opts = args->arg4;
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef AnyArcFilter<Arc> ArcFilter;
+
+  vector<typename Arc::Weight> weights;
+  typename Arc::Weight weight_threshold =
+      *(opts.weight_threshold.GetWeight<Weight>());
+
+  switch (opts.queue_type) {
+    case AUTO_QUEUE: {
+      typedef AutoQueue<StateId> Queue;
+      Queue *queue = QueueConstructor<Queue, Arc,
+          ArcFilter>::Construct(ifst, &weights);
+      fst::ShortestPathOptions<Arc, Queue, ArcFilter> spopts(
+          queue, ArcFilter(), opts.nshortest, opts.unique,
+          opts.has_distance, opts.delta, opts.first_path,
+          weight_threshold, opts.state_threshold);
+      ShortestPath(ifst, ofst, &weights, spopts);
+      delete queue;
+      return;
+    }
+    case FIFO_QUEUE: {
+      typedef FifoQueue<StateId> Queue;
+      Queue *queue = QueueConstructor<Queue, Arc,
+          ArcFilter>::Construct(ifst, &weights);
+      fst::ShortestPathOptions<Arc, Queue, ArcFilter> spopts(
+          queue, ArcFilter(), opts.nshortest, opts.unique,
+          opts.has_distance, opts.delta, opts.first_path,
+          weight_threshold, opts.state_threshold);
+      ShortestPath(ifst, ofst, &weights, spopts);
+      delete queue;
+      return;
+    }
+    case LIFO_QUEUE: {
+      typedef LifoQueue<StateId> Queue;
+      Queue *queue = QueueConstructor<Queue, Arc,
+          ArcFilter >::Construct(ifst, &weights);
+      fst::ShortestPathOptions<Arc, Queue, ArcFilter> spopts(
+          queue, ArcFilter(), opts.nshortest, opts.unique,
+          opts.has_distance, opts.delta, opts.first_path,
+          weight_threshold, opts.state_threshold);
+      ShortestPath(ifst, ofst, &weights, spopts);
+      delete queue;
+      return;
+    }
+    case SHORTEST_FIRST_QUEUE: {
+      typedef NaturalShortestFirstQueue<StateId, Weight> Queue;
+      Queue *queue = QueueConstructor<Queue, Arc,
+          ArcFilter>::Construct(ifst, &weights);
+      fst::ShortestPathOptions<Arc, Queue, ArcFilter> spopts(
+          queue, ArcFilter(), opts.nshortest, opts.unique,
+          opts.has_distance, opts.delta, opts.first_path,
+          weight_threshold, opts.state_threshold);
+      ShortestPath(ifst, ofst, &weights, spopts);
+      delete queue;
+      return;
+    }
+    case STATE_ORDER_QUEUE: {
+      typedef StateOrderQueue<StateId> Queue;
+      Queue *queue = QueueConstructor<Queue, Arc,
+          ArcFilter>::Construct(ifst, &weights);
+      fst::ShortestPathOptions<Arc, Queue, ArcFilter> spopts(
+          queue, ArcFilter(), opts.nshortest, opts.unique,
+          opts.has_distance, opts.delta, opts.first_path,
+          weight_threshold, opts.state_threshold);
+      ShortestPath(ifst, ofst, &weights, spopts);
+      delete queue;
+      return;
+    }
+    case TOP_ORDER_QUEUE: {
+      typedef TopOrderQueue<StateId> Queue;
+      Queue *queue = QueueConstructor<Queue, Arc,
+          ArcFilter>::Construct(ifst, &weights);
+      fst::ShortestPathOptions<Arc, Queue, ArcFilter> spopts(
+          queue, ArcFilter(), opts.nshortest, opts.unique,
+          opts.has_distance, opts.delta, opts.first_path,
+          weight_threshold, opts.state_threshold);
+      ShortestPath(ifst, ofst, &weights, spopts);
+      delete queue;
+      return;
+    }
+    default:
+      FSTERROR() << "Unknown queue type: " << opts.queue_type;
+      ofst->SetProperties(kError, kError);
+  }
+
+  // Copy the weights back
+  args->arg3->resize(weights.size());
+  for (unsigned i = 0; i < weights.size(); ++i) {
+    (*args->arg3)[i] = WeightClass(weights[i]);
+  }
+}
+
+// 2
+typedef args::Package<const FstClass &, MutableFstClass *,
+                      size_t, bool, bool, WeightClass,
+                      int64> ShortestPathArgs2;
+
+template<class Arc>
+void ShortestPath(ShortestPathArgs2 *args) {
+  const Fst<Arc> &ifst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+  typename Arc::Weight weight_threshold =
+      *(args->arg6.GetWeight<typename Arc::Weight>());
+
+  ShortestPath(ifst, ofst, args->arg3, args->arg4, args->arg5,
+               weight_threshold, args->arg7);
+}
+
+
+// 1
+void ShortestPath(const FstClass &ifst, MutableFstClass *ofst,
+                  vector<WeightClass> *distance,
+                  const ShortestPathOptions &opts);
+
+
+// 2
+void ShortestPath(const FstClass &ifst, MutableFstClass *ofst,
+                  size_t n = 1, bool unique = false,
+                  bool first_path = false,
+                  WeightClass weight_threshold =
+                    fst::script::WeightClass::Zero(),
+                  int64 state_threshold = fst::kNoStateId);
+
+}  // namespace script
+}  // namespace fst
+
+
+
+#endif  // FST_SCRIPT_SHORTEST_PATH_H_
diff --git a/src/include/fst/script/symbols.h b/src/include/fst/script/symbols.h
new file mode 100644
index 0000000..927600a
--- /dev/null
+++ b/src/include/fst/script/symbols.h
@@ -0,0 +1,20 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_SYMBOLS_H_
+#define FST_SCRIPT_SYMBOLS_H_
+
+#endif  // FST_SCRIPT_SYMBOLS_H_
diff --git a/src/include/fst/script/synchronize.h b/src/include/fst/script/synchronize.h
new file mode 100644
index 0000000..3c0c905
--- /dev/null
+++ b/src/include/fst/script/synchronize.h
@@ -0,0 +1,42 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_SYNCHRONIZE_H_
+#define FST_SCRIPT_SYNCHRONIZE_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/synchronize.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<const FstClass &, MutableFstClass *> SynchronizeArgs;
+
+template<class Arc>
+void Synchronize(SynchronizeArgs *args) {
+  const Fst<Arc> &ifst = *(args->arg1.GetFst<Arc>());
+  MutableFst<Arc> *ofst = args->arg2->GetMutableFst<Arc>();
+
+  Synchronize(ifst, ofst);
+}
+
+void Synchronize(const FstClass &ifst, MutableFstClass *ofst);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_SYNCHRONIZE_H_
diff --git a/src/include/fst/script/text-io.h b/src/include/fst/script/text-io.h
new file mode 100644
index 0000000..95cc182
--- /dev/null
+++ b/src/include/fst/script/text-io.h
@@ -0,0 +1,50 @@
+// text-io.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+// Modified: jpr@google.com (Jake Ratkiewicz) to work with generic WeightClass
+//
+// \file
+// Utilities for reading and writing textual strings representing
+// states, labels, and weights and files specifying label-label pairs
+// and potentials (state-weight pairs).
+//
+
+#ifndef FST_SCRIPT_TEXT_IO_H__
+#define FST_SCRIPT_TEXT_IO_H__
+
+#include <string>
+#include <vector>
+using std::vector;
+
+
+#include <iostream>
+#include <fstream>
+#include <fst/script/weight-class.h>
+
+namespace fst {
+namespace script {
+
+bool ReadPotentials(const string &weight_type,
+                    const string& filename,
+                    vector<WeightClass>* potential);
+
+bool WritePotentials(const string& filename,
+                     const vector<WeightClass>& potential);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_TEXT_IO_H__
diff --git a/src/include/fst/script/topsort.h b/src/include/fst/script/topsort.h
new file mode 100644
index 0000000..4e27e48
--- /dev/null
+++ b/src/include/fst/script/topsort.h
@@ -0,0 +1,40 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_TOPSORT_H_
+#define FST_SCRIPT_TOPSORT_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/topsort.h>
+
+namespace fst {
+namespace script {
+
+typedef args::WithReturnValue<bool, MutableFstClass*> TopSortArgs;
+
+template<class Arc>
+void TopSort(TopSortArgs *args) {
+  MutableFst<Arc> *fst = args->args->GetMutableFst<Arc>();
+  args->retval = TopSort(fst);
+}
+
+bool TopSort(MutableFstClass *fst);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_TOPSORT_H_
diff --git a/src/include/fst/script/union.h b/src/include/fst/script/union.h
new file mode 100644
index 0000000..780e484
--- /dev/null
+++ b/src/include/fst/script/union.h
@@ -0,0 +1,42 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+#ifndef FST_SCRIPT_UNION_H_
+#define FST_SCRIPT_UNION_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/union.h>
+
+namespace fst {
+namespace script {
+
+typedef args::Package<MutableFstClass *, const FstClass &> UnionArgs;
+
+template<class Arc>
+void Union(UnionArgs *args) {
+  MutableFst<Arc> *fst1 = args->arg1->GetMutableFst<Arc>();
+  const Fst<Arc> &fst2 = *(args->arg2.GetFst<Arc>());
+
+  Union(fst1, fst2);
+}
+
+void Union(MutableFstClass *fst1, const FstClass &fst2);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_UNION_H_
diff --git a/src/include/fst/script/verify.h b/src/include/fst/script/verify.h
new file mode 100644
index 0000000..6904003
--- /dev/null
+++ b/src/include/fst/script/verify.h
@@ -0,0 +1,40 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: sorenj@google.com (Jeffrey Sorensen)
+
+#ifndef FST_SCRIPT_VERIFY_H_
+#define FST_SCRIPT_VERIFY_H_
+
+#include <fst/script/arg-packs.h>
+#include <fst/script/fst-class.h>
+#include <fst/verify.h>
+
+namespace fst {
+namespace script {
+
+typedef args::WithReturnValue<bool, const FstClass *> VerifyArgs;
+
+template<class Arc>
+void Verify(VerifyArgs *args) {
+  const Fst<Arc> *fst = args->args->GetFst<Arc>();
+  args->retval = Verify(*fst);
+}
+
+bool Verify(const FstClass &fst1);
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_VERIFY_H_
diff --git a/src/include/fst/script/weight-class.h b/src/include/fst/script/weight-class.h
new file mode 100644
index 0000000..5a4890f
--- /dev/null
+++ b/src/include/fst/script/weight-class.h
@@ -0,0 +1,216 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: jpr@google.com (Jake Ratkiewicz)
+
+// Represents a generic weight in an FST -- that is, represents a specific
+// type of weight underneath while hiding that type from a client.
+
+
+#ifndef FST_SCRIPT_WEIGHT_CLASS_H_
+#define FST_SCRIPT_WEIGHT_CLASS_H_
+
+#include <string>
+
+#include <fst/generic-register.h>
+#include <fst/util.h>
+
+namespace fst {
+namespace script {
+
+class WeightImplBase {
+ public:
+  virtual WeightImplBase *Copy() const = 0;
+  virtual void Print(ostream *o) const = 0;
+  virtual const string &Type() const = 0;
+  virtual string to_string() const = 0;
+  virtual bool operator == (const WeightImplBase &other) const = 0;
+  virtual ~WeightImplBase() { }
+};
+
+template<class W>
+struct WeightClassImpl : public WeightImplBase {
+  W weight;
+
+  explicit WeightClassImpl(const W& weight) : weight(weight) { }
+
+  virtual WeightClassImpl<W> *Copy() const {
+    return new WeightClassImpl<W>(weight);
+  }
+
+  virtual const string &Type() const { return W::Type(); }
+
+  virtual void Print(ostream *o) const {
+    *o << weight;
+  }
+
+  virtual string to_string() const {
+    ostringstream s;
+    s << weight;
+    return s.str();
+  }
+
+  virtual bool operator == (const WeightImplBase &other) const {
+    if (Type() != other.Type()) {
+      return false;
+    } else {
+      const WeightClassImpl<W> *typed_other =
+          static_cast<const WeightClassImpl<W> *>(&other);
+
+      return typed_other->weight == weight;
+    }
+  }
+};
+
+
+class WeightClass {
+ public:
+  WeightClass() : element_type_(ZERO), impl_(0) { }
+
+  template<class W>
+  explicit WeightClass(const W& weight)
+  : element_type_(OTHER), impl_(new WeightClassImpl<W>(weight)) { }
+
+  WeightClass(const string &weight_type, const string &weight_str);
+
+  WeightClass(const WeightClass &other) :
+      element_type_(other.element_type_),
+      impl_(other.impl_ ? other.impl_->Copy() : 0) { }
+
+  WeightClass &operator = (const WeightClass &other) {
+    if (impl_) delete impl_;
+    impl_ = other.impl_ ? other.impl_->Copy() : 0;
+    element_type_ = other.element_type_;
+    return *this;
+  }
+
+  template<class W>
+  const W* GetWeight() const;
+
+  string to_string() const {
+    switch (element_type_) {
+      case ZERO:
+        return "ZERO";
+      case ONE:
+        return "ONE";
+      default:
+      case OTHER:
+        return impl_->to_string();
+    }
+  }
+
+  bool operator == (const WeightClass &other) const {
+    return element_type_ == other.element_type_ &&
+        ((impl_ && other.impl_ && (*impl_ == *other.impl_)) ||
+         (impl_ == 0 && other.impl_ == 0));
+  }
+
+  static const WeightClass &Zero() {
+    static WeightClass w(ZERO);
+
+    return w;
+  }
+
+  static const WeightClass &One() {
+    static WeightClass w(ONE);
+
+    return w;
+  }
+
+  ~WeightClass() { if (impl_) delete impl_; }
+ private:
+  enum ElementType { ZERO, ONE, OTHER };
+  ElementType element_type_;
+
+  WeightImplBase *impl_;
+
+  explicit WeightClass(ElementType et) : element_type_(et), impl_(0) { }
+
+  friend ostream &operator << (ostream &o, const WeightClass &c);
+};
+
+template<class W>
+const W* WeightClass::GetWeight() const {
+  // We need to store zero and one as statics, because the weight type
+  // W might return them as temporaries. We're returning a pointer,
+  // and it won't do to get the address of a temporary.
+  static const W zero = W::Zero();
+  static const W one = W::One();
+
+  if (element_type_ == ZERO) {
+    return &zero;
+  } else if (element_type_ == ONE) {
+    return &one;
+  } else {
+    if (W::Type() != impl_->Type()) {
+      return NULL;
+    } else {
+      WeightClassImpl<W> *typed_impl =
+          static_cast<WeightClassImpl<W> *>(impl_);
+      return &typed_impl->weight;
+    }
+  }
+}
+
+//
+// Registration for generic weight types.
+//
+
+typedef WeightImplBase* (*StrToWeightImplBaseT)(const string &str,
+                                                const string &src,
+                                                size_t nline);
+
+template<class W>
+WeightImplBase* StrToWeightImplBase(const string &str,
+                                    const string &src, size_t nline) {
+  return new WeightClassImpl<W>(StrToWeight<W>(str, src, nline));
+}
+
+// The following confuses swig, and doesn't need to be wrapped anyway.
+#ifndef SWIG
+ostream& operator << (ostream &o, const WeightClass &c);
+
+class WeightClassRegister : public GenericRegister<string,
+                                                   StrToWeightImplBaseT,
+                                                   WeightClassRegister> {
+ protected:
+  virtual string ConvertKeyToSoFilename(const string &key) const {
+    return key + ".so";
+  }
+};
+
+typedef GenericRegisterer<WeightClassRegister> WeightClassRegisterer;
+#endif
+
+// internal version, needs to be called by wrapper in order for
+// macro args to expand
+#define REGISTER_FST_WEIGHT__(Weight, line)                             \
+  static WeightClassRegisterer weight_registerer ## _ ## line(          \
+      Weight::Type(),                                                   \
+      StrToWeightImplBase<Weight>)
+
+// This layer is where __FILE__ and __LINE__ are expanded
+#define REGISTER_FST_WEIGHT_EXPANDER(Weight, line)      \
+  REGISTER_FST_WEIGHT__(Weight, line)
+
+//
+// Macro for registering new weight types. Clients call this.
+//
+#define REGISTER_FST_WEIGHT(Weight) \
+  REGISTER_FST_WEIGHT_EXPANDER(Weight, __LINE__)
+
+}  // namespace script
+}  // namespace fst
+
+#endif  // FST_SCRIPT_WEIGHT_CLASS_H_
diff --git a/src/include/fst/shortest-distance.h b/src/include/fst/shortest-distance.h
new file mode 100644
index 0000000..5d38409
--- /dev/null
+++ b/src/include/fst/shortest-distance.h
@@ -0,0 +1,347 @@
+// shortest-distance.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Functions and classes to find shortest distance in an FST.
+
+#ifndef FST_LIB_SHORTEST_DISTANCE_H__
+#define FST_LIB_SHORTEST_DISTANCE_H__
+
+#include <deque>
+#include <vector>
+using std::vector;
+
+#include <fst/arcfilter.h>
+#include <fst/cache.h>
+#include <fst/queue.h>
+#include <fst/reverse.h>
+#include <fst/test-properties.h>
+
+
+namespace fst {
+
+template <class Arc, class Queue, class ArcFilter>
+struct ShortestDistanceOptions {
+  typedef typename Arc::StateId StateId;
+
+  Queue *state_queue;    // Queue discipline used; owned by caller
+  ArcFilter arc_filter;  // Arc filter (e.g., limit to only epsilon graph)
+  StateId source;        // If kNoStateId, use the Fst's initial state
+  float delta;           // Determines the degree of convergence required
+  bool first_path;       // For a semiring with the path property (o.w.
+                         // undefined), compute the shortest-distances along
+                         // along the first path to a final state found
+                         // by the algorithm. That path is the shortest-path
+                         // only if the FST has a unique final state (or all
+                         // the final states have the same final weight), the
+                         // queue discipline is shortest-first and all the
+                         // weights in the FST are between One() and Zero()
+                         // according to NaturalLess.
+
+  ShortestDistanceOptions(Queue *q, ArcFilter filt, StateId src = kNoStateId,
+                          float d = kDelta)
+      : state_queue(q), arc_filter(filt), source(src), delta(d),
+        first_path(false) {}
+};
+
+
+// Computation state of the shortest-distance algorithm. Reusable
+// information is maintained across calls to member function
+// ShortestDistance(source) when 'retain' is true for improved
+// efficiency when calling multiple times from different source states
+// (e.g., in epsilon removal). Contrary to usual conventions, 'fst'
+// may not be freed before this class. Vector 'distance' should not be
+// modified by the user between these calls.
+// The Error() method returns true if an error was encountered.
+template<class Arc, class Queue, class ArcFilter>
+class ShortestDistanceState {
+ public:
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+
+  ShortestDistanceState(
+      const Fst<Arc> &fst,
+      vector<Weight> *distance,
+      const ShortestDistanceOptions<Arc, Queue, ArcFilter> &opts,
+      bool retain)
+      : fst_(fst), distance_(distance), state_queue_(opts.state_queue),
+        arc_filter_(opts.arc_filter), delta_(opts.delta),
+        first_path_(opts.first_path), retain_(retain), source_id_(0),
+        error_(false) {
+    distance_->clear();
+  }
+
+  ~ShortestDistanceState() {}
+
+  void ShortestDistance(StateId source);
+
+  bool Error() const { return error_; }
+
+ private:
+  const Fst<Arc> &fst_;
+  vector<Weight> *distance_;
+  Queue *state_queue_;
+  ArcFilter arc_filter_;
+  float delta_;
+  bool first_path_;
+  bool retain_;               // Retain and reuse information across calls
+
+  vector<Weight> rdistance_;  // Relaxation distance.
+  vector<bool> enqueued_;     // Is state enqueued?
+  vector<StateId> sources_;   // Source ID for ith state in 'distance_',
+                              //  'rdistance_', and 'enqueued_' if retained.
+  StateId source_id_;         // Unique ID characterizing each call to SD
+
+  bool error_;
+};
+
+// Compute the shortest distance. If 'source' is kNoStateId, use
+// the initial state of the Fst.
+template <class Arc, class Queue, class ArcFilter>
+void ShortestDistanceState<Arc, Queue, ArcFilter>::ShortestDistance(
+    StateId source) {
+  if (fst_.Start() == kNoStateId) {
+    if (fst_.Properties(kError, false)) error_ = true;
+    return;
+  }
+
+  if (!(Weight::Properties() & kRightSemiring)) {
+    FSTERROR() << "ShortestDistance: Weight needs to be right distributive: "
+               << Weight::Type();
+    error_ = true;
+    return;
+  }
+
+  if (first_path_ && !(Weight::Properties() & kPath)) {
+    FSTERROR() << "ShortestDistance: first_path option disallowed when "
+               << "Weight does not have the path property: "
+               << Weight::Type();
+    error_ = true;
+    return;
+  }
+
+  state_queue_->Clear();
+
+  if (!retain_) {
+    distance_->clear();
+    rdistance_.clear();
+    enqueued_.clear();
+  }
+
+  if (source == kNoStateId)
+    source = fst_.Start();
+
+  while (distance_->size() <= source) {
+    distance_->push_back(Weight::Zero());
+    rdistance_.push_back(Weight::Zero());
+    enqueued_.push_back(false);
+  }
+  if (retain_) {
+    while (sources_.size() <= source)
+      sources_.push_back(kNoStateId);
+    sources_[source] = source_id_;
+  }
+  (*distance_)[source] = Weight::One();
+  rdistance_[source] = Weight::One();
+  enqueued_[source] = true;
+
+  state_queue_->Enqueue(source);
+
+  while (!state_queue_->Empty()) {
+    StateId s = state_queue_->Head();
+    state_queue_->Dequeue();
+    while (distance_->size() <= s) {
+      distance_->push_back(Weight::Zero());
+      rdistance_.push_back(Weight::Zero());
+      enqueued_.push_back(false);
+    }
+    if (first_path_ && (fst_.Final(s) != Weight::Zero()))
+      break;
+    enqueued_[s] = false;
+    Weight r = rdistance_[s];
+    rdistance_[s] = Weight::Zero();
+    for (ArcIterator< Fst<Arc> > aiter(fst_, s);
+         !aiter.Done();
+         aiter.Next()) {
+      const Arc &arc = aiter.Value();
+      if (!arc_filter_(arc) || arc.weight == Weight::Zero())
+        continue;
+      while (distance_->size() <= arc.nextstate) {
+        distance_->push_back(Weight::Zero());
+        rdistance_.push_back(Weight::Zero());
+        enqueued_.push_back(false);
+      }
+      if (retain_) {
+        while (sources_.size() <= arc.nextstate)
+          sources_.push_back(kNoStateId);
+        if (sources_[arc.nextstate] != source_id_) {
+          (*distance_)[arc.nextstate] = Weight::Zero();
+          rdistance_[arc.nextstate] = Weight::Zero();
+          enqueued_[arc.nextstate] = false;
+          sources_[arc.nextstate] = source_id_;
+        }
+      }
+      Weight &nd = (*distance_)[arc.nextstate];
+      Weight &nr = rdistance_[arc.nextstate];
+      Weight w = Times(r, arc.weight);
+      if (!ApproxEqual(nd, Plus(nd, w), delta_)) {
+        nd = Plus(nd, w);
+        nr = Plus(nr, w);
+        if (!nd.Member() || !nr.Member()) {
+          error_ = true;
+          return;
+        }
+        if (!enqueued_[arc.nextstate]) {
+          state_queue_->Enqueue(arc.nextstate);
+          enqueued_[arc.nextstate] = true;
+        } else {
+          state_queue_->Update(arc.nextstate);
+        }
+      }
+    }
+  }
+  ++source_id_;
+  if (fst_.Properties(kError, false)) error_ = true;
+}
+
+
+// Shortest-distance algorithm: this version allows fine control
+// via the options argument. See below for a simpler interface.
+//
+// This computes the shortest distance from the 'opts.source' state to
+// each visited state S and stores the value in the 'distance' vector.
+// An unvisited state S has distance Zero(), which will be stored in
+// the 'distance' vector if S is less than the maximum visited state.
+// The state queue discipline, arc filter, and convergence delta are
+// taken in the options argument.
+// The 'distance' vector will contain a unique element for which
+// Member() is false if an error was encountered.
+//
+// The weights must must be right distributive and k-closed (i.e., 1 +
+// x + x^2 + ... + x^(k +1) = 1 + x + x^2 + ... + x^k).
+//
+// The algorithm is from Mohri, "Semiring Framweork and Algorithms for
+// Shortest-Distance Problems", Journal of Automata, Languages and
+// Combinatorics 7(3):321-350, 2002. The complexity of algorithm
+// depends on the properties of the semiring and the queue discipline
+// used. Refer to the paper for more details.
+template<class Arc, class Queue, class ArcFilter>
+void ShortestDistance(
+    const Fst<Arc> &fst,
+    vector<typename Arc::Weight> *distance,
+    const ShortestDistanceOptions<Arc, Queue, ArcFilter> &opts) {
+
+  ShortestDistanceState<Arc, Queue, ArcFilter>
+    sd_state(fst, distance, opts, false);
+  sd_state.ShortestDistance(opts.source);
+  if (sd_state.Error()) {
+    distance->clear();
+    distance->resize(1, Arc::Weight::NoWeight());
+  }
+}
+
+// Shortest-distance algorithm: simplified interface. See above for a
+// version that allows finer control.
+//
+// If 'reverse' is false, this computes the shortest distance from the
+// initial state to each state S and stores the value in the
+// 'distance' vector. If 'reverse' is true, this computes the shortest
+// distance from each state to the final states.  An unvisited state S
+// has distance Zero(), which will be stored in the 'distance' vector
+// if S is less than the maximum visited state.  The state queue
+// discipline is automatically-selected.
+// The 'distance' vector will contain a unique element for which
+// Member() is false if an error was encountered.
+//
+// The weights must must be right (left) distributive if reverse is
+// false (true) and k-closed (i.e., 1 + x + x^2 + ... + x^(k +1) = 1 +
+// x + x^2 + ... + x^k).
+//
+// The algorithm is from Mohri, "Semiring Framweork and Algorithms for
+// Shortest-Distance Problems", Journal of Automata, Languages and
+// Combinatorics 7(3):321-350, 2002. The complexity of algorithm
+// depends on the properties of the semiring and the queue discipline
+// used. Refer to the paper for more details.
+template<class Arc>
+void ShortestDistance(const Fst<Arc> &fst,
+                      vector<typename Arc::Weight> *distance,
+                      bool reverse = false,
+                      float delta = kDelta) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+
+  if (!reverse) {
+    AnyArcFilter<Arc> arc_filter;
+    AutoQueue<StateId> state_queue(fst, distance, arc_filter);
+    ShortestDistanceOptions< Arc, AutoQueue<StateId>, AnyArcFilter<Arc> >
+      opts(&state_queue, arc_filter);
+    opts.delta = delta;
+    ShortestDistance(fst, distance, opts);
+  } else {
+    typedef ReverseArc<Arc> ReverseArc;
+    typedef typename ReverseArc::Weight ReverseWeight;
+    AnyArcFilter<ReverseArc> rarc_filter;
+    VectorFst<ReverseArc> rfst;
+    Reverse(fst, &rfst);
+    vector<ReverseWeight> rdistance;
+    AutoQueue<StateId> state_queue(rfst, &rdistance, rarc_filter);
+    ShortestDistanceOptions< ReverseArc, AutoQueue<StateId>,
+      AnyArcFilter<ReverseArc> >
+      ropts(&state_queue, rarc_filter);
+    ropts.delta = delta;
+    ShortestDistance(rfst, &rdistance, ropts);
+    distance->clear();
+    if (rdistance.size() == 1 && !rdistance[0].Member()) {
+      distance->resize(1, Arc::Weight::NoWeight());
+      return;
+    }
+    while (distance->size() < rdistance.size() - 1)
+      distance->push_back(rdistance[distance->size() + 1].Reverse());
+  }
+}
+
+
+// Return the sum of the weight of all successful paths in an FST, i.e.,
+// the shortest-distance from the initial state to the final states.
+// Returns a weight such that Member() is false if an error was encountered.
+template <class Arc>
+typename Arc::Weight ShortestDistance(const Fst<Arc> &fst, float delta = kDelta) {
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+  vector<Weight> distance;
+  if (Weight::Properties() & kRightSemiring) {
+    ShortestDistance(fst, &distance, false, delta);
+    if (distance.size() == 1 && !distance[0].Member())
+      return Arc::Weight::NoWeight();
+    Weight sum = Weight::Zero();
+    for (StateId s = 0; s < distance.size(); ++s)
+      sum = Plus(sum, Times(distance[s], fst.Final(s)));
+    return sum;
+  } else {
+    ShortestDistance(fst, &distance, true, delta);
+    StateId s = fst.Start();
+    if (distance.size() == 1 && !distance[0].Member())
+      return Arc::Weight::NoWeight();
+    return s != kNoStateId && s < distance.size() ?
+        distance[s] : Weight::Zero();
+  }
+}
+
+
+}  // namespace fst
+
+#endif  // FST_LIB_SHORTEST_DISTANCE_H__
diff --git a/src/include/fst/shortest-path.h b/src/include/fst/shortest-path.h
new file mode 100644
index 0000000..f12970c
--- /dev/null
+++ b/src/include/fst/shortest-path.h
@@ -0,0 +1,501 @@
+// shortest-path.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Functions to find shortest paths in an FST.
+
+#ifndef FST_LIB_SHORTEST_PATH_H__
+#define FST_LIB_SHORTEST_PATH_H__
+
+#include <functional>
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+#include <fst/determinize.h>
+#include <fst/queue.h>
+#include <fst/shortest-distance.h>
+#include <fst/test-properties.h>
+
+
+namespace fst {
+
+template <class Arc, class Queue, class ArcFilter>
+struct ShortestPathOptions
+    : public ShortestDistanceOptions<Arc, Queue, ArcFilter> {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  size_t nshortest;   // return n-shortest paths
+  bool unique;        // only return paths with distinct input strings
+  bool has_distance;  // distance vector already contains the
+                      // shortest distance from the initial state
+  bool first_path;    // Single shortest path stops after finding the first
+                      // path to a final state. That path is the shortest path
+                      // only when using the ShortestFirstQueue and
+                      // only when all the weights in the FST are between
+                      // One() and Zero() according to NaturalLess.
+  Weight weight_threshold;   // pruning weight threshold.
+  StateId state_threshold;   // pruning state threshold.
+
+  ShortestPathOptions(Queue *q, ArcFilter filt, size_t n = 1, bool u = false,
+                      bool hasdist = false, float d = kDelta,
+                      bool fp = false, Weight w = Weight::Zero(),
+                      StateId s = kNoStateId)
+      : ShortestDistanceOptions<Arc, Queue, ArcFilter>(q, filt, kNoStateId, d),
+        nshortest(n), unique(u), has_distance(hasdist), first_path(fp),
+        weight_threshold(w), state_threshold(s) {}
+};
+
+
+// Shortest-path algorithm: normally not called directly; prefer
+// 'ShortestPath' below with n=1. 'ofst' contains the shortest path in
+// 'ifst'. 'distance' returns the shortest distances from the source
+// state to each state in 'ifst'. 'opts' is used to specify options
+// such as the queue discipline, the arc filter and delta.
+//
+// The shortest path is the lowest weight path w.r.t. the natural
+// semiring order.
+//
+// The weights need to be right distributive and have the path (kPath)
+// property.
+template<class Arc, class Queue, class ArcFilter>
+void SingleShortestPath(const Fst<Arc> &ifst,
+                  MutableFst<Arc> *ofst,
+                  vector<typename Arc::Weight> *distance,
+                  ShortestPathOptions<Arc, Queue, ArcFilter> &opts) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+
+  ofst->DeleteStates();
+  ofst->SetInputSymbols(ifst.InputSymbols());
+  ofst->SetOutputSymbols(ifst.OutputSymbols());
+
+  if (ifst.Start() == kNoStateId) {
+    if (ifst.Properties(kError, false)) ofst->SetProperties(kError, kError);
+    return;
+  }
+
+  vector<bool> enqueued;
+  vector<StateId> parent;
+  vector<Arc> arc_parent;
+
+  Queue *state_queue = opts.state_queue;
+  StateId source = opts.source == kNoStateId ? ifst.Start() : opts.source;
+  Weight f_distance = Weight::Zero();
+  StateId f_parent = kNoStateId;
+
+  distance->clear();
+  state_queue->Clear();
+  if (opts.nshortest != 1) {
+    FSTERROR() << "SingleShortestPath: for nshortest > 1, use ShortestPath"
+               << " instead";
+    ofst->SetProperties(kError, kError);
+    return;
+  }
+  if (opts.weight_threshold != Weight::Zero() ||
+      opts.state_threshold != kNoStateId) {
+    FSTERROR() <<
+        "SingleShortestPath: weight and state thresholds not applicable";
+    ofst->SetProperties(kError, kError);
+    return;
+  }
+  if ((Weight::Properties() & (kPath | kRightSemiring))
+      != (kPath | kRightSemiring)) {
+    FSTERROR() << "SingleShortestPath: Weight needs to have the path"
+               << " property and be right distributive: " << Weight::Type();
+    ofst->SetProperties(kError, kError);
+    return;
+  }
+  while (distance->size() < source) {
+    distance->push_back(Weight::Zero());
+    enqueued.push_back(false);
+    parent.push_back(kNoStateId);
+    arc_parent.push_back(Arc(kNoLabel, kNoLabel, Weight::Zero(), kNoStateId));
+  }
+  distance->push_back(Weight::One());
+  parent.push_back(kNoStateId);
+  arc_parent.push_back(Arc(kNoLabel, kNoLabel, Weight::Zero(), kNoStateId));
+  state_queue->Enqueue(source);
+  enqueued.push_back(true);
+
+  while (!state_queue->Empty()) {
+    StateId s = state_queue->Head();
+    state_queue->Dequeue();
+    enqueued[s] = false;
+    Weight sd = (*distance)[s];
+    if (ifst.Final(s) != Weight::Zero()) {
+      Weight w = Times(sd, ifst.Final(s));
+      if (f_distance != Plus(f_distance, w)) {
+        f_distance = Plus(f_distance, w);
+        f_parent = s;
+      }
+      if (!f_distance.Member()) {
+        ofst->SetProperties(kError, kError);
+        return;
+      }
+      if (opts.first_path)
+        break;
+    }
+    for (ArcIterator< Fst<Arc> > aiter(ifst, s);
+         !aiter.Done();
+         aiter.Next()) {
+      const Arc &arc = aiter.Value();
+      while (distance->size() <= arc.nextstate) {
+        distance->push_back(Weight::Zero());
+        enqueued.push_back(false);
+        parent.push_back(kNoStateId);
+        arc_parent.push_back(Arc(kNoLabel, kNoLabel, Weight::Zero(),
+                                 kNoStateId));
+      }
+      Weight &nd = (*distance)[arc.nextstate];
+      Weight w = Times(sd, arc.weight);
+      if (nd != Plus(nd, w)) {
+        nd = Plus(nd, w);
+        if (!nd.Member()) {
+          ofst->SetProperties(kError, kError);
+          return;
+        }
+        parent[arc.nextstate] = s;
+        arc_parent[arc.nextstate] = arc;
+        if (!enqueued[arc.nextstate]) {
+          state_queue->Enqueue(arc.nextstate);
+          enqueued[arc.nextstate] = true;
+        } else {
+          state_queue->Update(arc.nextstate);
+        }
+      }
+    }
+  }
+
+  StateId s_p = kNoStateId, d_p = kNoStateId;
+  for (StateId s = f_parent, d = kNoStateId;
+       s != kNoStateId;
+       d = s, s = parent[s]) {
+    d_p = s_p;
+    s_p = ofst->AddState();
+    if (d == kNoStateId) {
+      ofst->SetFinal(s_p, ifst.Final(f_parent));
+    } else {
+      arc_parent[d].nextstate = d_p;
+      ofst->AddArc(s_p, arc_parent[d]);
+    }
+  }
+  ofst->SetStart(s_p);
+  if (ifst.Properties(kError, false)) ofst->SetProperties(kError, kError);
+  ofst->SetProperties(
+      ShortestPathProperties(ofst->Properties(kFstProperties, false)),
+      kFstProperties);
+}
+
+
+template <class S, class W>
+class ShortestPathCompare {
+ public:
+  typedef S StateId;
+  typedef W Weight;
+  typedef pair<StateId, Weight> Pair;
+
+  ShortestPathCompare(const vector<Pair>& pairs,
+                      const vector<Weight>& distance,
+                      StateId sfinal, float d)
+      : pairs_(pairs), distance_(distance), superfinal_(sfinal), delta_(d)  {}
+
+  bool operator()(const StateId x, const StateId y) const {
+    const Pair &px = pairs_[x];
+    const Pair &py = pairs_[y];
+    Weight dx = px.first == superfinal_ ? Weight::One() :
+        px.first < distance_.size() ? distance_[px.first] : Weight::Zero();
+    Weight dy = py.first == superfinal_ ? Weight::One() :
+        py.first < distance_.size() ? distance_[py.first] : Weight::Zero();
+    Weight wx = Times(dx, px.second);
+    Weight wy = Times(dy, py.second);
+    // Penalize complete paths to ensure correct results with inexact weights.
+    // This forms a strict weak order so long as ApproxEqual(a, b) =>
+    // ApproxEqual(a, c) for all c s.t. less_(a, c) && less_(c, b).
+    if (px.first == superfinal_ && py.first != superfinal_) {
+      return less_(wy, wx) || ApproxEqual(wx, wy, delta_);
+    } else if (py.first == superfinal_ && px.first != superfinal_) {
+      return less_(wy, wx) && !ApproxEqual(wx, wy, delta_);
+    } else {
+      return less_(wy, wx);
+    }
+  }
+
+ private:
+  const vector<Pair> &pairs_;
+  const vector<Weight> &distance_;
+  StateId superfinal_;
+  float delta_;
+  NaturalLess<Weight> less_;
+};
+
+
+// N-Shortest-path algorithm: implements the core n-shortest path
+// algorithm. The output is built REVERSED. See below for versions with
+// more options and not reversed.
+//
+// 'ofst' contains the REVERSE of 'n'-shortest paths in 'ifst'.
+// 'distance' must contain the shortest distance from each state to a final
+// state in 'ifst'. 'delta' is the convergence delta.
+//
+// The n-shortest paths are the n-lowest weight paths w.r.t. the
+// natural semiring order. The single path that can be read from the
+// ith of at most n transitions leaving the initial state of 'ofst' is
+// the ith shortest path. Disregarding the initial state and initial
+// transitions, the n-shortest paths, in fact, form a tree rooted at
+// the single final state.
+//
+// The weights need to be left and right distributive (kSemiring) and
+// have the path (kPath) property.
+//
+// The algorithm is from Mohri and Riley, "An Efficient Algorithm for
+// the n-best-strings problem", ICSLP 2002. The algorithm relies on
+// the shortest-distance algorithm. There are some issues with the
+// pseudo-code as written in the paper (viz., line 11).
+//
+// IMPLEMENTATION NOTE: The input fst 'ifst' can be a delayed fst and
+// and at any state in its expansion the values of distance vector need only
+// be defined at that time for the states that are known to exist.
+template<class Arc, class RevArc>
+void NShortestPath(const Fst<RevArc> &ifst,
+                   MutableFst<Arc> *ofst,
+                   const vector<typename Arc::Weight> &distance,
+                   size_t n,
+                   float delta = kDelta,
+                   typename Arc::Weight weight_threshold = Arc::Weight::Zero(),
+                   typename Arc::StateId state_threshold = kNoStateId) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef pair<StateId, Weight> Pair;
+  typedef typename RevArc::Weight RevWeight;
+
+  if (n <= 0) return;
+  if ((Weight::Properties() & (kPath | kSemiring)) != (kPath | kSemiring)) {
+    FSTERROR() << "NShortestPath: Weight needs to have the "
+                 << "path property and be distributive: "
+                 << Weight::Type();
+    ofst->SetProperties(kError, kError);
+    return;
+  }
+  ofst->DeleteStates();
+  ofst->SetInputSymbols(ifst.InputSymbols());
+  ofst->SetOutputSymbols(ifst.OutputSymbols());
+  // Each state in 'ofst' corresponds to a path with weight w from the
+  // initial state of 'ifst' to a state s in 'ifst', that can be
+  // characterized by a pair (s,w).  The vector 'pairs' maps each
+  // state in 'ofst' to the corresponding pair maps states in OFST to
+  // the corresponding pair (s,w).
+  vector<Pair> pairs;
+  // The supefinal state is denoted by -1, 'compare' knows that the
+  // distance from 'superfinal' to the final state is 'Weight::One()',
+  // hence 'distance[superfinal]' is not needed.
+  StateId superfinal = -1;
+  ShortestPathCompare<StateId, Weight>
+    compare(pairs, distance, superfinal, delta);
+  vector<StateId> heap;
+  // 'r[s + 1]', 's' state in 'fst', is the number of states in 'ofst'
+  // which corresponding pair contains 's' ,i.e. , it is number of
+  // paths computed so far to 's'. Valid for 's == -1' (superfinal).
+  vector<int> r;
+  NaturalLess<Weight> less;
+  if (ifst.Start() == kNoStateId ||
+      distance.size() <= ifst.Start() ||
+      distance[ifst.Start()] == Weight::Zero() ||
+      less(weight_threshold, Weight::One()) ||
+      state_threshold == 0) {
+    if (ifst.Properties(kError, false)) ofst->SetProperties(kError, kError);
+    return;
+  }
+  ofst->SetStart(ofst->AddState());
+  StateId final = ofst->AddState();
+  ofst->SetFinal(final, Weight::One());
+  while (pairs.size() <= final)
+    pairs.push_back(Pair(kNoStateId, Weight::Zero()));
+  pairs[final] = Pair(ifst.Start(), Weight::One());
+  heap.push_back(final);
+  Weight limit = Times(distance[ifst.Start()], weight_threshold);
+
+  while (!heap.empty()) {
+    pop_heap(heap.begin(), heap.end(), compare);
+    StateId state = heap.back();
+    Pair p = pairs[state];
+    heap.pop_back();
+    Weight d = p.first == superfinal ? Weight::One() :
+        p.first < distance.size() ? distance[p.first] : Weight::Zero();
+
+    if (less(limit, Times(d, p.second)) ||
+        (state_threshold != kNoStateId &&
+         ofst->NumStates() >= state_threshold))
+      continue;
+
+    while (r.size() <= p.first + 1) r.push_back(0);
+    ++r[p.first + 1];
+    if (p.first == superfinal)
+      ofst->AddArc(ofst->Start(), Arc(0, 0, Weight::One(), state));
+    if ((p.first == superfinal) && (r[p.first + 1] == n)) break;
+    if (r[p.first + 1] > n) continue;
+    if (p.first == superfinal) continue;
+
+    for (ArcIterator< Fst<RevArc> > aiter(ifst, p.first);
+         !aiter.Done();
+         aiter.Next()) {
+      const RevArc &rarc = aiter.Value();
+      Arc arc(rarc.ilabel, rarc.olabel, rarc.weight.Reverse(), rarc.nextstate);
+      Weight w = Times(p.second, arc.weight);
+      StateId next = ofst->AddState();
+      pairs.push_back(Pair(arc.nextstate, w));
+      arc.nextstate = state;
+      ofst->AddArc(next, arc);
+      heap.push_back(next);
+      push_heap(heap.begin(), heap.end(), compare);
+    }
+
+    Weight finalw = ifst.Final(p.first).Reverse();
+    if (finalw != Weight::Zero()) {
+      Weight w = Times(p.second, finalw);
+      StateId next = ofst->AddState();
+      pairs.push_back(Pair(superfinal, w));
+      ofst->AddArc(next, Arc(0, 0, finalw, state));
+      heap.push_back(next);
+      push_heap(heap.begin(), heap.end(), compare);
+    }
+  }
+  Connect(ofst);
+  if (ifst.Properties(kError, false)) ofst->SetProperties(kError, kError);
+  ofst->SetProperties(
+      ShortestPathProperties(ofst->Properties(kFstProperties, false)),
+      kFstProperties);
+}
+
+
+// N-Shortest-path algorithm:  this version allow fine control
+// via the options argument. See below for a simpler interface.
+//
+// 'ofst' contains the n-shortest paths in 'ifst'. 'distance' returns
+// the shortest distances from the source state to each state in
+// 'ifst'. 'opts' is used to specify options such as the number of
+// paths to return, whether they need to have distinct input
+// strings, the queue discipline, the arc filter and the convergence
+// delta.
+//
+// The n-shortest paths are the n-lowest weight paths w.r.t. the
+// natural semiring order. The single path that can be read from the
+// ith of at most n transitions leaving the initial state of 'ofst' is
+// the ith shortest path. Disregarding the initial state and initial
+// transitions, The n-shortest paths, in fact, form a tree rooted at
+// the single final state.
+
+// The weights need to be right distributive and have the path (kPath)
+// property. They need to be left distributive as well for nshortest
+// > 1.
+//
+// The algorithm is from Mohri and Riley, "An Efficient Algorithm for
+// the n-best-strings problem", ICSLP 2002. The algorithm relies on
+// the shortest-distance algorithm. There are some issues with the
+// pseudo-code as written in the paper (viz., line 11).
+template<class Arc, class Queue, class ArcFilter>
+void ShortestPath(const Fst<Arc> &ifst, MutableFst<Arc> *ofst,
+                  vector<typename Arc::Weight> *distance,
+                  ShortestPathOptions<Arc, Queue, ArcFilter> &opts) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef ReverseArc<Arc> ReverseArc;
+
+  size_t n = opts.nshortest;
+  if (n == 1) {
+    SingleShortestPath(ifst, ofst, distance, opts);
+    return;
+  }
+  if (n <= 0) return;
+  if ((Weight::Properties() & (kPath | kSemiring)) != (kPath | kSemiring)) {
+    FSTERROR() << "ShortestPath: n-shortest: Weight needs to have the "
+               << "path property and be distributive: "
+               << Weight::Type();
+    ofst->SetProperties(kError, kError);
+    return;
+  }
+  if (!opts.has_distance) {
+    ShortestDistance(ifst, distance, opts);
+    if (distance->size() == 1 && !(*distance)[0].Member()) {
+      ofst->SetProperties(kError, kError);
+      return;
+    }
+  }
+  // Algorithm works on the reverse of 'fst' : 'rfst', 'distance' is
+  // the distance to the final state in 'rfst', 'ofst' is built as the
+  // reverse of the tree of n-shortest path in 'rfst'.
+  VectorFst<ReverseArc> rfst;
+  Reverse(ifst, &rfst);
+  Weight d = Weight::Zero();
+  for (ArcIterator< VectorFst<ReverseArc> > aiter(rfst, 0);
+       !aiter.Done(); aiter.Next()) {
+    const ReverseArc &arc = aiter.Value();
+    StateId s = arc.nextstate - 1;
+    if (s < distance->size())
+      d = Plus(d, Times(arc.weight.Reverse(), (*distance)[s]));
+  }
+  distance->insert(distance->begin(), d);
+
+  if (!opts.unique) {
+    NShortestPath(rfst, ofst, *distance, n, opts.delta,
+                  opts.weight_threshold, opts.state_threshold);
+  } else {
+    vector<Weight> ddistance;
+    DeterminizeFstOptions<ReverseArc> dopts(opts.delta);
+    DeterminizeFst<ReverseArc> dfst(rfst, *distance, &ddistance, dopts);
+    NShortestPath(dfst, ofst, ddistance, n, opts.delta,
+                  opts.weight_threshold, opts.state_threshold);
+  }
+  distance->erase(distance->begin());
+}
+
+
+// Shortest-path algorithm: simplified interface. See above for a
+// version that allows finer control.
+//
+// 'ofst' contains the 'n'-shortest paths in 'ifst'. The queue
+// discipline is automatically selected. When 'unique' == true, only
+// paths with distinct input labels are returned.
+//
+// The n-shortest paths are the n-lowest weight paths w.r.t. the
+// natural semiring order. The single path that can be read from the
+// ith of at most n transitions leaving the initial state of 'ofst' is
+// the ith best path.
+//
+// The weights need to be right distributive and have the path
+// (kPath) property.
+template<class Arc>
+void ShortestPath(const Fst<Arc> &ifst, MutableFst<Arc> *ofst,
+                  size_t n = 1, bool unique = false,
+                  bool first_path = false,
+                  typename Arc::Weight weight_threshold = Arc::Weight::Zero(),
+                  typename Arc::StateId state_threshold = kNoStateId) {
+  vector<typename Arc::Weight> distance;
+  AnyArcFilter<Arc> arc_filter;
+  AutoQueue<typename Arc::StateId> state_queue(ifst, &distance, arc_filter);
+  ShortestPathOptions< Arc, AutoQueue<typename Arc::StateId>,
+      AnyArcFilter<Arc> > opts(&state_queue, arc_filter, n, unique, false,
+                               kDelta, first_path, weight_threshold,
+                               state_threshold);
+  ShortestPath(ifst, ofst, &distance, opts);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_SHORTEST_PATH_H__
diff --git a/src/include/fst/signed-log-weight.h b/src/include/fst/signed-log-weight.h
new file mode 100644
index 0000000..da96479
--- /dev/null
+++ b/src/include/fst/signed-log-weight.h
@@ -0,0 +1,367 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: krr@google.com (Kasturi Rangan Raghavan)
+// \file
+// LogWeight along with sign information that represents the value X in the
+// linear domain as <sign(X), -ln(|X|)>
+// The sign is a TropicalWeight:
+//  positive, TropicalWeight.Value() > 0.0, recommended value 1.0
+//  negative, TropicalWeight.Value() <= 0.0, recommended value -1.0
+
+#ifndef FST_LIB_SIGNED_LOG_WEIGHT_H_
+#define FST_LIB_SIGNED_LOG_WEIGHT_H_
+
+#include <fst/float-weight.h>
+#include <fst/pair-weight.h>
+
+
+namespace fst {
+template <class T>
+class SignedLogWeightTpl
+    : public PairWeight<TropicalWeight, LogWeightTpl<T> > {
+ public:
+  typedef TropicalWeight X1;
+  typedef LogWeightTpl<T> X2;
+  using PairWeight<X1, X2>::Value1;
+  using PairWeight<X1, X2>::Value2;
+
+  using PairWeight<X1, X2>::Reverse;
+  using PairWeight<X1, X2>::Quantize;
+  using PairWeight<X1, X2>::Member;
+
+  typedef SignedLogWeightTpl<T> ReverseWeight;
+
+  SignedLogWeightTpl() : PairWeight<X1, X2>() {}
+
+  SignedLogWeightTpl(const SignedLogWeightTpl<T>& w)
+      : PairWeight<X1, X2> (w) { }
+
+  SignedLogWeightTpl(const PairWeight<X1, X2>& w)
+      : PairWeight<X1, X2> (w) { }
+
+  SignedLogWeightTpl(const X1& x1, const X2& x2)
+      : PairWeight<X1, X2>(x1, x2) { }
+
+  static const SignedLogWeightTpl<T> &Zero() {
+    static const SignedLogWeightTpl<T> zero(X1(1.0), X2::Zero());
+    return zero;
+  }
+
+  static const SignedLogWeightTpl<T> &One() {
+    static const SignedLogWeightTpl<T> one(X1(1.0), X2::One());
+    return one;
+  }
+
+  static const SignedLogWeightTpl<T> &NoWeight() {
+    static const SignedLogWeightTpl<T> no_weight(X1(1.0), X2::NoWeight());
+    return no_weight;
+  }
+
+  static const string &Type() {
+    static const string type = "signed_log_" + X1::Type() + "_" + X2::Type();
+    return type;
+  }
+
+  ProductWeight<X1, X2> Quantize(float delta = kDelta) const {
+    return PairWeight<X1, X2>::Quantize();
+  }
+
+  ReverseWeight Reverse() const {
+    return PairWeight<X1, X2>::Reverse();
+  }
+
+  bool Member() const {
+    return PairWeight<X1, X2>::Member();
+  }
+
+  static uint64 Properties() {
+    // not idempotent nor path
+    return kLeftSemiring | kRightSemiring | kCommutative;
+  }
+
+  size_t Hash() const {
+    size_t h1;
+    if (Value2() == X2::Zero() || Value1().Value() > 0.0)
+      h1 = TropicalWeight(1.0).Hash();
+    else
+      h1 = TropicalWeight(-1.0).Hash();
+    size_t h2 = Value2().Hash();
+    const int lshift = 5;
+    const int rshift = CHAR_BIT * sizeof(size_t) - 5;
+    return h1 << lshift ^ h1 >> rshift ^ h2;
+  }
+};
+
+template <class T>
+inline SignedLogWeightTpl<T> Plus(const SignedLogWeightTpl<T> &w1,
+                                  const SignedLogWeightTpl<T> &w2) {
+  if (!w1.Member() || !w2.Member())
+    return SignedLogWeightTpl<T>::NoWeight();
+  bool s1 = w1.Value1().Value() > 0.0;
+  bool s2 = w2.Value1().Value() > 0.0;
+  T f1 = w1.Value2().Value();
+  T f2 = w2.Value2().Value();
+  if (f1 == FloatLimits<T>::kPosInfinity)
+    return w2;
+  else if (f2 == FloatLimits<T>::kPosInfinity)
+    return w1;
+  else if (f1 == f2) {
+    if (s1 == s2)
+      return SignedLogWeightTpl<T>(w1.Value1(), (f2 - log(2.0F)));
+    else
+      return SignedLogWeightTpl<T>::Zero();
+  } else if (f1 > f2) {
+    if (s1 == s2) {
+      return SignedLogWeightTpl<T>(
+        w1.Value1(), (f2 - log(1.0F + exp(f2 - f1))));
+    } else {
+      return SignedLogWeightTpl<T>(
+        w2.Value1(), (f2 - log(1.0F - exp(f2 - f1))));
+    }
+  } else {
+    if (s2 == s1) {
+      return SignedLogWeightTpl<T>(
+        w2.Value1(), (f1 - log(1.0F + exp(f1 - f2))));
+    } else {
+      return SignedLogWeightTpl<T>(
+        w1.Value1(), (f1 - log(1.0F - exp(f1 - f2))));
+    }
+  }
+}
+
+template <class T>
+inline SignedLogWeightTpl<T> Minus(const SignedLogWeightTpl<T> &w1,
+                                   const SignedLogWeightTpl<T> &w2) {
+  SignedLogWeightTpl<T> minus_w2(-w2.Value1().Value(), w2.Value2());
+  return Plus(w1, minus_w2);
+}
+
+template <class T>
+inline SignedLogWeightTpl<T> Times(const SignedLogWeightTpl<T> &w1,
+                                   const SignedLogWeightTpl<T> &w2) {
+  if (!w1.Member() || !w2.Member())
+    return SignedLogWeightTpl<T>::NoWeight();
+  bool s1 = w1.Value1().Value() > 0.0;
+  bool s2 = w2.Value1().Value() > 0.0;
+  T f1 = w1.Value2().Value();
+  T f2 = w2.Value2().Value();
+  if (s1 == s2)
+    return SignedLogWeightTpl<T>(TropicalWeight(1.0), (f1 + f2));
+  else
+    return SignedLogWeightTpl<T>(TropicalWeight(-1.0), (f1 + f2));
+}
+
+template <class T>
+inline SignedLogWeightTpl<T> Divide(const SignedLogWeightTpl<T> &w1,
+                                    const SignedLogWeightTpl<T> &w2,
+                                    DivideType typ = DIVIDE_ANY) {
+  if (!w1.Member() || !w2.Member())
+    return SignedLogWeightTpl<T>::NoWeight();
+  bool s1 = w1.Value1().Value() > 0.0;
+  bool s2 = w2.Value1().Value() > 0.0;
+  T f1 = w1.Value2().Value();
+  T f2 = w2.Value2().Value();
+  if (f2 == FloatLimits<T>::kPosInfinity)
+    return SignedLogWeightTpl<T>(TropicalWeight(1.0),
+      FloatLimits<T>::kNumberBad);
+  else if (f1 == FloatLimits<T>::kPosInfinity)
+    return SignedLogWeightTpl<T>(TropicalWeight(1.0),
+      FloatLimits<T>::kPosInfinity);
+  else if (s1 == s2)
+    return SignedLogWeightTpl<T>(TropicalWeight(1.0), (f1 - f2));
+  else
+    return SignedLogWeightTpl<T>(TropicalWeight(-1.0), (f1 - f2));
+}
+
+template <class T>
+inline bool ApproxEqual(const SignedLogWeightTpl<T> &w1,
+                        const SignedLogWeightTpl<T> &w2,
+                        float delta = kDelta) {
+  bool s1 = w1.Value1().Value() > 0.0;
+  bool s2 = w2.Value1().Value() > 0.0;
+  if (s1 == s2) {
+    return ApproxEqual(w1.Value2(), w2.Value2(), delta);
+  } else {
+    return w1.Value2() == LogWeightTpl<T>::Zero()
+        && w2.Value2() == LogWeightTpl<T>::Zero();
+  }
+}
+
+template <class T>
+inline bool operator==(const SignedLogWeightTpl<T> &w1,
+                       const SignedLogWeightTpl<T> &w2) {
+  bool s1 = w1.Value1().Value() > 0.0;
+  bool s2 = w2.Value1().Value() > 0.0;
+  if (s1 == s2)
+    return w1.Value2() == w2.Value2();
+  else
+    return (w1.Value2() == LogWeightTpl<T>::Zero()) &&
+           (w2.Value2() == LogWeightTpl<T>::Zero());
+}
+
+
+// Single-precision signed-log weight
+typedef SignedLogWeightTpl<float> SignedLogWeight;
+// Double-precision signed-log weight
+typedef SignedLogWeightTpl<double> SignedLog64Weight;
+
+//
+// WEIGHT CONVERTER SPECIALIZATIONS.
+//
+
+template <class W1, class W2>
+bool SignedLogConvertCheck(W1 w) {
+  if (w.Value1().Value() < 0.0) {
+    FSTERROR() << "WeightConvert: can't convert weight from \""
+               << W1::Type() << "\" to \"" << W2::Type();
+    return false;
+  }
+  return true;
+}
+
+// Convert to tropical
+template <>
+struct WeightConvert<SignedLogWeight, TropicalWeight> {
+  TropicalWeight operator()(SignedLogWeight w) const {
+    if (!SignedLogConvertCheck<SignedLogWeight, TropicalWeight>(w))
+      return TropicalWeight::NoWeight();
+    return w.Value2().Value();
+  }
+};
+
+template <>
+struct WeightConvert<SignedLog64Weight, TropicalWeight> {
+  TropicalWeight operator()(SignedLog64Weight w) const {
+    if (!SignedLogConvertCheck<SignedLog64Weight, TropicalWeight>(w))
+      return TropicalWeight::NoWeight();
+    return w.Value2().Value();
+  }
+};
+
+// Convert to log
+template <>
+struct WeightConvert<SignedLogWeight, LogWeight> {
+  LogWeight operator()(SignedLogWeight w) const {
+    if (!SignedLogConvertCheck<SignedLogWeight, LogWeight>(w))
+      return LogWeight::NoWeight();
+    return w.Value2().Value();
+  }
+};
+
+template <>
+struct WeightConvert<SignedLog64Weight, LogWeight> {
+  LogWeight operator()(SignedLog64Weight w) const {
+    if (!SignedLogConvertCheck<SignedLog64Weight, LogWeight>(w))
+      return LogWeight::NoWeight();
+    return w.Value2().Value();
+  }
+};
+
+// Convert to log64
+template <>
+struct WeightConvert<SignedLogWeight, Log64Weight> {
+  Log64Weight operator()(SignedLogWeight w) const {
+    if (!SignedLogConvertCheck<SignedLogWeight, Log64Weight>(w))
+      return Log64Weight::NoWeight();
+    return w.Value2().Value();
+  }
+};
+
+template <>
+struct WeightConvert<SignedLog64Weight, Log64Weight> {
+  Log64Weight operator()(SignedLog64Weight w) const {
+    if (!SignedLogConvertCheck<SignedLog64Weight, Log64Weight>(w))
+      return Log64Weight::NoWeight();
+    return w.Value2().Value();
+  }
+};
+
+// Convert to signed log
+template <>
+struct WeightConvert<TropicalWeight, SignedLogWeight> {
+  SignedLogWeight operator()(TropicalWeight w) const {
+    TropicalWeight x1 = 1.0;
+    LogWeight x2 = w.Value();
+    return SignedLogWeight(x1, x2);
+  }
+};
+
+template <>
+struct WeightConvert<LogWeight, SignedLogWeight> {
+  SignedLogWeight operator()(LogWeight w) const {
+    TropicalWeight x1 = 1.0;
+    LogWeight x2 = w.Value();
+    return SignedLogWeight(x1, x2);
+  }
+};
+
+template <>
+struct WeightConvert<Log64Weight, SignedLogWeight> {
+  SignedLogWeight operator()(Log64Weight w) const {
+    TropicalWeight x1 = 1.0;
+    LogWeight x2 = w.Value();
+    return SignedLogWeight(x1, x2);
+  }
+};
+
+template <>
+struct WeightConvert<SignedLog64Weight, SignedLogWeight> {
+  SignedLogWeight operator()(SignedLog64Weight w) const {
+    TropicalWeight x1 = w.Value1();
+    LogWeight x2 = w.Value2().Value();
+    return SignedLogWeight(x1, x2);
+  }
+};
+
+// Convert to signed log64
+template <>
+struct WeightConvert<TropicalWeight, SignedLog64Weight> {
+  SignedLog64Weight operator()(TropicalWeight w) const {
+    TropicalWeight x1 = 1.0;
+    Log64Weight x2 = w.Value();
+    return SignedLog64Weight(x1, x2);
+  }
+};
+
+template <>
+struct WeightConvert<LogWeight, SignedLog64Weight> {
+  SignedLog64Weight operator()(LogWeight w) const {
+    TropicalWeight x1 = 1.0;
+    Log64Weight x2 = w.Value();
+    return SignedLog64Weight(x1, x2);
+  }
+};
+
+template <>
+struct WeightConvert<Log64Weight, SignedLog64Weight> {
+  SignedLog64Weight operator()(Log64Weight w) const {
+    TropicalWeight x1 = 1.0;
+    Log64Weight x2 = w.Value();
+    return SignedLog64Weight(x1, x2);
+  }
+};
+
+template <>
+struct WeightConvert<SignedLogWeight, SignedLog64Weight> {
+  SignedLog64Weight operator()(SignedLogWeight w) const {
+    TropicalWeight x1 = w.Value1();
+    Log64Weight x2 = w.Value2().Value();
+    return SignedLog64Weight(x1, x2);
+  }
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_SIGNED_LOG_WEIGHT_H_
diff --git a/src/include/fst/slist.h b/src/include/fst/slist.h
new file mode 100644
index 0000000..9f94027
--- /dev/null
+++ b/src/include/fst/slist.h
@@ -0,0 +1,61 @@
+// slist.h
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Includes slist definition or defines in terms of STL list as a fallback.
+
+#ifndef FST_LIB_SLIST_H__
+#define FST_LIB_SLIST_H__
+
+#include <fst/config.h>
+
+#if !defined(__ANDROID__) && defined(HAVE___GNU_CXX__SLIST_INT_)
+
+#include <slist>
+
+namespace fst {
+
+using __gnu_cxx::slist;
+
+}
+
+#else
+
+#include <list>
+
+namespace fst {
+
+using std::list;
+
+template <typename T> class slist : public list<T> {
+ public:
+  typedef typename list<T>::iterator iterator;
+  typedef typename list<T>::const_iterator const_iterator;
+
+  using list<T>::erase;
+
+  iterator erase_after(iterator pos) {
+    iterator npos = pos;
+    erase(++npos);
+    return pos;
+  }
+};
+
+}  // namespace fst
+
+#endif  // HAVE___GNU_CXX__SLIST_INT_
+
+#endif  // FST_LIB_SLIST_H__
diff --git a/src/include/fst/sparse-power-weight.h b/src/include/fst/sparse-power-weight.h
new file mode 100644
index 0000000..a1ff56a
--- /dev/null
+++ b/src/include/fst/sparse-power-weight.h
@@ -0,0 +1,225 @@
+// sparse-power-weight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: krr@google.com (Kasturi Rangan Raghavan)
+// Inspiration: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Cartesian power weight semiring operation definitions.
+// Uses SparseTupleWeight as underlying representation.
+
+#ifndef FST_LIB_SPARSE_POWER_WEIGHT_H__
+#define FST_LIB_SPARSE_POWER_WEIGHT_H__
+
+#include<string>
+
+#include <fst/sparse-tuple-weight.h>
+#include <fst/weight.h>
+
+
+namespace fst {
+
+// Below SparseTupleWeight*Mapper are used in conjunction with
+// SparseTupleWeightMap to compute the respective semiring operations
+template<class W, class K>
+struct SparseTupleWeightPlusMapper {
+  W Map(const K& k, const W& v1, const W& v2) const {
+    return Plus(v1, v2);
+  }
+};
+
+template<class W, class K>
+struct SparseTupleWeightTimesMapper {
+  W Map(const K& k, const W& v1, const W& v2) const {
+    return Times(v1, v2);
+  }
+};
+
+template<class W, class K>
+struct SparseTupleWeightDivideMapper {
+  SparseTupleWeightDivideMapper(DivideType divide_type) {
+    divide_type_ = divide_type;
+  }
+  W Map(const K& k, const W& v1, const W& v2) const {
+    return Divide(v1, v2, divide_type_);
+  }
+  DivideType divide_type_;
+};
+
+template<class W, class K>
+struct SparseTupleWeightApproxMapper {
+  SparseTupleWeightApproxMapper(float delta) { delta_ = delta; }
+  W Map(const K& k, const W& v1, const W& v2) const {
+    return ApproxEqual(v1, v2, delta_) ? W::One() : W::Zero();
+  }
+  float delta_;
+};
+
+// Sparse cartesian power semiring: W ^ n
+// Forms:
+//  - a left semimodule when W is a left semiring,
+//  - a right semimodule when W is a right semiring,
+//  - a bisemimodule when W is a semiring,
+//    the free semimodule of rank n over W
+// The Times operation is overloaded to provide the
+// left and right scalar products.
+// K is the key value type. kNoKey(-1) is reserved for internal use
+template <class W, class K = int>
+class SparsePowerWeight : public SparseTupleWeight<W, K> {
+ public:
+  using SparseTupleWeight<W, K>::Zero;
+  using SparseTupleWeight<W, K>::One;
+  using SparseTupleWeight<W, K>::NoWeight;
+  using SparseTupleWeight<W, K>::Quantize;
+  using SparseTupleWeight<W, K>::Reverse;
+
+  typedef SparsePowerWeight<typename W::ReverseWeight, K> ReverseWeight;
+
+  SparsePowerWeight() {}
+
+  SparsePowerWeight(const SparseTupleWeight<W, K> &w) :
+    SparseTupleWeight<W, K>(w) { }
+
+  template <class Iterator>
+  SparsePowerWeight(Iterator begin, Iterator end) :
+    SparseTupleWeight<W, K>(begin, end) { }
+
+  SparsePowerWeight(const K &key, const W &w) :
+    SparseTupleWeight<W, K>(key, w) { }
+
+  static const SparsePowerWeight<W, K> &Zero() {
+    static const SparsePowerWeight<W, K> zero(SparseTupleWeight<W, K>::Zero());
+    return zero;
+  }
+
+  static const SparsePowerWeight<W, K> &One() {
+    static const SparsePowerWeight<W, K> one(SparseTupleWeight<W, K>::One());
+    return one;
+  }
+
+  static const SparsePowerWeight<W, K> &NoWeight() {
+    static const SparsePowerWeight<W, K> no_weight(
+        SparseTupleWeight<W, K>::NoWeight());
+    return no_weight;
+  }
+
+  // Overide this: Overwrite the Type method to reflect the key type
+  // if using non-default key type.
+  static const string &Type() {
+    static string type;
+    if(type.empty()) {
+      type = W::Type() + "_^n";
+      if(sizeof(K) != sizeof(uint32)) {
+        string size;
+        Int64ToStr(8 * sizeof(K), &size);
+        type += "_" + size;
+      }
+    }
+    return type;
+  }
+
+  static uint64 Properties() {
+    uint64 props = W::Properties();
+    return props & (kLeftSemiring | kRightSemiring |
+                    kCommutative | kIdempotent);
+  }
+
+  SparsePowerWeight<W, K> Quantize(float delta = kDelta) const {
+    return SparseTupleWeight<W, K>::Quantize(delta);
+  }
+
+  ReverseWeight Reverse() const {
+    return SparseTupleWeight<W, K>::Reverse();
+  }
+};
+
+// Semimodule plus operation
+template <class W, class K>
+inline SparsePowerWeight<W, K> Plus(const SparsePowerWeight<W, K> &w1,
+                                    const SparsePowerWeight<W, K> &w2) {
+  SparsePowerWeight<W, K> ret;
+  SparseTupleWeightPlusMapper<W, K> operator_mapper;
+  SparseTupleWeightMap(&ret, w1, w2, operator_mapper);
+  return ret;
+}
+
+// Semimodule times operation
+template <class W, class K>
+inline SparsePowerWeight<W, K> Times(const SparsePowerWeight<W, K> &w1,
+                                     const SparsePowerWeight<W, K> &w2) {
+  SparsePowerWeight<W, K> ret;
+  SparseTupleWeightTimesMapper<W, K> operator_mapper;
+  SparseTupleWeightMap(&ret, w1, w2, operator_mapper);
+  return ret;
+}
+
+// Semimodule divide operation
+template <class W, class K>
+inline SparsePowerWeight<W, K> Divide(const SparsePowerWeight<W, K> &w1,
+                                      const SparsePowerWeight<W, K> &w2,
+                                      DivideType type = DIVIDE_ANY) {
+  SparsePowerWeight<W, K> ret;
+  SparseTupleWeightDivideMapper<W, K> operator_mapper(type);
+  SparseTupleWeightMap(&ret, w1, w2, operator_mapper);
+  return ret;
+}
+
+// Semimodule dot product
+template <class W, class K>
+inline const W& DotProduct(const SparsePowerWeight<W, K> &w1,
+                    const SparsePowerWeight<W, K> &w2) {
+  const SparsePowerWeight<W, K>& product = Times(w1, w2);
+  W ret(W::Zero());
+  for (SparseTupleWeightIterator<W, K> it(product); !it.Done(); it.Next()) {
+    ret = Plus(ret, it.Value().second);
+  }
+  return ret;
+}
+
+template <class W, class K>
+inline bool ApproxEqual(const SparsePowerWeight<W, K> &w1,
+                        const SparsePowerWeight<W, K> &w2,
+                        float delta = kDelta) {
+  SparseTupleWeight<W, K> ret;
+  SparseTupleWeightApproxMapper<W, K> operator_mapper(kDelta);
+  SparseTupleWeightMap(&ret, w1, w2, operator_mapper);
+  return ret == SparsePowerWeight<W, K>::One();
+}
+
+template <class W, class K>
+inline SparsePowerWeight<W, K> Times(const W &k,
+                                     const SparsePowerWeight<W, K> &w2) {
+  SparsePowerWeight<W, K> w1(k);
+  return Times(w1, w2);
+}
+
+template <class W, class K>
+inline SparsePowerWeight<W, K> Times(const SparsePowerWeight<W, K> &w1,
+                                     const W &k) {
+  SparsePowerWeight<W, K> w2(k);
+  return Times(w1, w2);
+}
+
+template <class W, class K>
+inline SparsePowerWeight<W, K> Divide(const SparsePowerWeight<W, K> &w1,
+                                      const W &k,
+                                      DivideType divide_type = DIVIDE_ANY) {
+  SparsePowerWeight<W, K> w2(k);
+  return Divide(w1, w2, divide_type);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_SPARSE_POWER_WEIGHT_H__
diff --git a/src/include/fst/sparse-tuple-weight.h b/src/include/fst/sparse-tuple-weight.h
new file mode 100644
index 0000000..d316b17
--- /dev/null
+++ b/src/include/fst/sparse-tuple-weight.h
@@ -0,0 +1,640 @@
+// sparse-tuple-weight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: krr@google.com (Kasturi Rangan Raghavan)
+// Inspiration: allauzen@google.com (Cyril Allauzen)
+// \file
+// Sparse version of tuple-weight, based on tuple-weight.h
+//   Internally stores sparse key, value pairs in linked list
+//   Default value elemnt is the assumed value of unset keys
+//   Internal singleton implementation that stores first key,
+//   value pair as a initialized member variable to avoide
+//   unnecessary allocation on heap.
+// Use SparseTupleWeightIterator to iterate through the key,value pairs
+// Note: this does NOT iterate through the default value.
+//
+// Sparse tuple weight set operation definitions.
+
+#ifndef FST_LIB_SPARSE_TUPLE_WEIGHT_H__
+#define FST_LIB_SPARSE_TUPLE_WEIGHT_H__
+
+#include<string>
+#include<list>
+#include<stack>
+#include<unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+
+#include <fst/weight.h>
+
+
+DECLARE_string(fst_weight_parentheses);
+DECLARE_string(fst_weight_separator);
+
+namespace fst {
+
+template <class W, class K> class SparseTupleWeight;
+
+template<class W, class K>
+class SparseTupleWeightIterator;
+
+template <class W, class K>
+istream &operator>>(istream &strm, SparseTupleWeight<W, K> &w);
+
+// Arbitrary dimension tuple weight, stored as a sorted linked-list
+// W is any weight class,
+// K is the key value type. kNoKey(-1) is reserved for internal use
+template <class W, class K = int>
+class SparseTupleWeight {
+ public:
+  typedef pair<K, W> Pair;
+  typedef SparseTupleWeight<typename W::ReverseWeight, K> ReverseWeight;
+
+  const static K kNoKey = -1;
+  SparseTupleWeight() {
+    Init();
+  }
+
+  template <class Iterator>
+  SparseTupleWeight(Iterator begin, Iterator end) {
+    Init();
+    // Assumes input iterator is sorted
+    for (Iterator it = begin; it != end; ++it)
+      Push(*it);
+  }
+
+
+  SparseTupleWeight(const K& key, const W &w) {
+    Init();
+    Push(key, w);
+  }
+
+  SparseTupleWeight(const W &w) {
+    Init(w);
+  }
+
+  SparseTupleWeight(const SparseTupleWeight<W, K> &w) {
+    Init(w.DefaultValue());
+    SetDefaultValue(w.DefaultValue());
+    for (SparseTupleWeightIterator<W, K> it(w); !it.Done(); it.Next()) {
+      Push(it.Value());
+    }
+  }
+
+  static const SparseTupleWeight<W, K> &Zero() {
+    static SparseTupleWeight<W, K> zero;
+    return zero;
+  }
+
+  static const SparseTupleWeight<W, K> &One() {
+    static SparseTupleWeight<W, K> one(W::One());
+    return one;
+  }
+
+  static const SparseTupleWeight<W, K> &NoWeight() {
+    static SparseTupleWeight<W, K> no_weight(W::NoWeight());
+    return no_weight;
+  }
+
+  istream &Read(istream &strm) {
+    ReadType(strm, &default_);
+    ReadType(strm, &first_);
+    return ReadType(strm, &rest_);
+  }
+
+  ostream &Write(ostream &strm) const {
+    WriteType(strm, default_);
+    WriteType(strm, first_);
+    return WriteType(strm, rest_);
+  }
+
+  SparseTupleWeight<W, K> &operator=(const SparseTupleWeight<W, K> &w) {
+    if (this == &w) return *this; // check for w = w
+    Init(w.DefaultValue());
+    for (SparseTupleWeightIterator<W, K> it(w); !it.Done(); it.Next()) {
+      Push(it.Value());
+    }
+    return *this;
+  }
+
+  bool Member() const {
+    if (!DefaultValue().Member()) return false;
+    for (SparseTupleWeightIterator<W, K> it(*this); !it.Done(); it.Next()) {
+      if (!it.Value().second.Member()) return false;
+    }
+    return true;
+  }
+
+  // Assumes H() function exists for the hash of the key value
+  size_t Hash() const {
+    uint64 h = 0;
+    std::hash<K> H;
+    for (SparseTupleWeightIterator<W, K> it(*this); !it.Done(); it.Next()) {
+      h = 5 * h + H(it.Value().first);
+      h = 13 * h + it.Value().second.Hash();
+    }
+    return size_t(h);
+  }
+
+  SparseTupleWeight<W, K> Quantize(float delta = kDelta) const {
+    SparseTupleWeight<W, K> w;
+    for (SparseTupleWeightIterator<W, K> it(*this); !it.Done(); it.Next()) {
+      w.Push(it.Value().first, it.Value().second.Quantize(delta));
+    }
+    return w;
+  }
+
+  ReverseWeight Reverse() const {
+    SparseTupleWeight<W, K> w;
+    for (SparseTupleWeightIterator<W, K> it(*this); !it.Done(); it.Next()) {
+      w.Push(it.Value().first, it.Value().second.Reverse());
+    }
+    return w;
+  }
+
+  // Common initializer among constructors.
+  void Init() {
+    Init(W::Zero());
+  }
+
+  void Init(const W& default_value) {
+    first_.first = kNoKey;
+    /* initialized to the reserved key value */
+    default_ = default_value;
+    rest_.clear();
+  }
+
+  size_t Size() const {
+    if (first_.first == kNoKey)
+      return 0;
+    else
+      return  rest_.size() + 1;
+  }
+
+  inline void Push(const K &k, const W &w, bool default_value_check = true) {
+    Push(make_pair(k, w), default_value_check);
+  }
+
+  inline void Push(const Pair &p, bool default_value_check = true) {
+    if (default_value_check && p.second == default_) return;
+    if (first_.first == kNoKey) {
+      first_ = p;
+    } else {
+      rest_.push_back(p);
+    }
+  }
+
+  void SetDefaultValue(const W& val) { default_ = val; }
+
+  const W& DefaultValue() const { return default_; }
+
+ protected:
+  static istream& ReadNoParen(
+    istream&, SparseTupleWeight<W, K>&, char separator);
+
+  static istream& ReadWithParen(
+    istream&, SparseTupleWeight<W, K>&,
+    char separator, char open_paren, char close_paren);
+
+ private:
+  // Assumed default value of uninitialized keys, by default W::Zero()
+  W default_;
+
+  // Key values pairs are first stored in first_, then fill rest_
+  // this way we can avoid dynamic allocation in the common case
+  // where the weight is a single key,val pair.
+  Pair first_;
+  list<Pair> rest_;
+
+  friend istream &operator>><W, K>(istream&, SparseTupleWeight<W, K>&);
+  friend class SparseTupleWeightIterator<W, K>;
+};
+
+template<class W, class K>
+class SparseTupleWeightIterator {
+ public:
+  typedef typename SparseTupleWeight<W, K>::Pair Pair;
+  typedef typename list<Pair>::const_iterator const_iterator;
+  typedef typename list<Pair>::iterator iterator;
+
+  explicit SparseTupleWeightIterator(const SparseTupleWeight<W, K>& w)
+    : first_(w.first_), rest_(w.rest_), init_(true),
+      iter_(rest_.begin()) {}
+
+  bool Done() const {
+    if (init_)
+      return first_.first == SparseTupleWeight<W, K>::kNoKey;
+    else
+      return iter_ == rest_.end();
+  }
+
+  const Pair& Value() const { return init_ ? first_ : *iter_; }
+
+  void Next() {
+    if (init_)
+      init_ = false;
+    else
+      ++iter_;
+  }
+
+  void Reset() {
+    init_ = true;
+    iter_ = rest_.begin();
+  }
+
+ private:
+  const Pair &first_;
+  const list<Pair> & rest_;
+  bool init_;  // in the initialized state?
+  typename list<Pair>::const_iterator iter_;
+
+  DISALLOW_COPY_AND_ASSIGN(SparseTupleWeightIterator);
+};
+
+template<class W, class K, class M>
+inline void SparseTupleWeightMap(
+  SparseTupleWeight<W, K>* ret,
+  const SparseTupleWeight<W, K>& w1,
+  const SparseTupleWeight<W, K>& w2,
+  const M& operator_mapper) {
+  SparseTupleWeightIterator<W, K> w1_it(w1);
+  SparseTupleWeightIterator<W, K> w2_it(w2);
+  const W& v1_def = w1.DefaultValue();
+  const W& v2_def = w2.DefaultValue();
+  ret->SetDefaultValue(operator_mapper.Map(0, v1_def, v2_def));
+  while (!w1_it.Done() || !w2_it.Done()) {
+    const K& k1 = (w1_it.Done()) ? w2_it.Value().first : w1_it.Value().first;
+    const K& k2 = (w2_it.Done()) ? w1_it.Value().first : w2_it.Value().first;
+    const W& v1 = (w1_it.Done()) ? v1_def : w1_it.Value().second;
+    const W& v2 = (w2_it.Done()) ? v2_def : w2_it.Value().second;
+    if (k1 == k2) {
+      ret->Push(k1, operator_mapper.Map(k1, v1, v2));
+      if (!w1_it.Done()) w1_it.Next();
+      if (!w2_it.Done()) w2_it.Next();
+    } else if (k1 < k2) {
+      ret->Push(k1, operator_mapper.Map(k1, v1, v2_def));
+      w1_it.Next();
+    } else {
+      ret->Push(k2, operator_mapper.Map(k2, v1_def, v2));
+      w2_it.Next();
+    }
+  }
+}
+
+template <class W, class K>
+inline bool operator==(const SparseTupleWeight<W, K> &w1,
+                       const SparseTupleWeight<W, K> &w2) {
+  const W& v1_def = w1.DefaultValue();
+  const W& v2_def = w2.DefaultValue();
+  if (v1_def != v2_def) return false;
+
+  SparseTupleWeightIterator<W, K> w1_it(w1);
+  SparseTupleWeightIterator<W, K> w2_it(w2);
+  while (!w1_it.Done() || !w2_it.Done()) {
+    const K& k1 = (w1_it.Done()) ? w2_it.Value().first : w1_it.Value().first;
+    const K& k2 = (w2_it.Done()) ? w1_it.Value().first : w2_it.Value().first;
+    const W& v1 = (w1_it.Done()) ? v1_def : w1_it.Value().second;
+    const W& v2 = (w2_it.Done()) ? v2_def : w2_it.Value().second;
+    if (k1 == k2) {
+      if (v1 != v2) return false;
+      if (!w1_it.Done()) w1_it.Next();
+      if (!w2_it.Done()) w2_it.Next();
+    } else if (k1 < k2) {
+      if (v1 != v2_def) return false;
+      w1_it.Next();
+    } else {
+      if (v1_def != v2) return false;
+      w2_it.Next();
+    }
+  }
+  return true;
+}
+
+template <class W, class K>
+inline bool operator!=(const SparseTupleWeight<W, K> &w1,
+                       const SparseTupleWeight<W, K> &w2) {
+  return !(w1 == w2);
+}
+
+template <class W, class K>
+inline ostream &operator<<(ostream &strm, const SparseTupleWeight<W, K> &w) {
+  if(FLAGS_fst_weight_separator.size() != 1) {
+    FSTERROR() << "FLAGS_fst_weight_separator.size() is not equal to 1";
+    strm.clear(std::ios::badbit);
+    return strm;
+  }
+  char separator = FLAGS_fst_weight_separator[0];
+  bool write_parens = false;
+  if (!FLAGS_fst_weight_parentheses.empty()) {
+    if (FLAGS_fst_weight_parentheses.size() != 2) {
+      FSTERROR() << "FLAGS_fst_weight_parentheses.size() is not equal to 2";
+      strm.clear(std::ios::badbit);
+      return strm;
+    }
+    write_parens = true;
+  }
+
+  if (write_parens)
+    strm << FLAGS_fst_weight_parentheses[0];
+
+  strm << w.DefaultValue();
+  strm << separator;
+
+  size_t n = w.Size();
+  strm << n;
+  strm << separator;
+
+  for (SparseTupleWeightIterator<W, K> it(w); !it.Done(); it.Next()) {
+      strm << it.Value().first;
+      strm << separator;
+      strm << it.Value().second;
+      strm << separator;
+  }
+
+  if (write_parens)
+    strm << FLAGS_fst_weight_parentheses[1];
+
+  return strm;
+}
+
+template <class W, class K>
+inline istream &operator>>(istream &strm, SparseTupleWeight<W, K> &w) {
+  if(FLAGS_fst_weight_separator.size() != 1) {
+    FSTERROR() << "FLAGS_fst_weight_separator.size() is not equal to 1";
+    strm.clear(std::ios::badbit);
+    return strm;
+  }
+  char separator = FLAGS_fst_weight_separator[0];
+
+  if (!FLAGS_fst_weight_parentheses.empty()) {
+    if (FLAGS_fst_weight_parentheses.size() != 2) {
+      FSTERROR() << "FLAGS_fst_weight_parentheses.size() is not equal to 2";
+      strm.clear(std::ios::badbit);
+      return strm;
+    }
+    return SparseTupleWeight<W, K>::ReadWithParen(
+        strm, w, separator, FLAGS_fst_weight_parentheses[0],
+        FLAGS_fst_weight_parentheses[1]);
+  } else {
+    return SparseTupleWeight<W, K>::ReadNoParen(strm, w, separator);
+  }
+}
+
+// Reads SparseTupleWeight when there are no parentheses around tuple terms
+template <class W, class K>
+inline istream& SparseTupleWeight<W, K>::ReadNoParen(
+    istream &strm,
+    SparseTupleWeight<W, K> &w,
+    char separator) {
+  int c;
+  size_t n;
+
+  do {
+    c = strm.get();
+  } while (isspace(c));
+
+
+  { // Read default weight
+    W default_value;
+    string s;
+    while (c != separator) {
+      if (c == EOF) {
+        strm.clear(std::ios::badbit);
+        return strm;
+      }
+      s += c;
+      c = strm.get();
+    }
+    istringstream sstrm(s);
+    sstrm >> default_value;
+    w.SetDefaultValue(default_value);
+  }
+
+  c = strm.get();
+
+  { // Read n
+    string s;
+    while (c != separator) {
+      if (c == EOF) {
+        strm.clear(std::ios::badbit);
+        return strm;
+      }
+      s += c;
+      c = strm.get();
+    }
+    istringstream sstrm(s);
+    sstrm >> n;
+  }
+
+  // Read n elements
+  for (size_t i = 0; i < n; ++i) {
+    // discard separator
+    c = strm.get();
+    K p;
+    W r;
+
+    { // read key
+      string s;
+      while (c != separator) {
+        if (c == EOF) {
+          strm.clear(std::ios::badbit);
+          return strm;
+        }
+        s += c;
+        c = strm.get();
+      }
+      istringstream sstrm(s);
+      sstrm >> p;
+    }
+
+    c = strm.get();
+
+    { // read weight
+      string s;
+      while (c != separator) {
+        if (c == EOF) {
+          strm.clear(std::ios::badbit);
+          return strm;
+        }
+        s += c;
+        c = strm.get();
+      }
+      istringstream sstrm(s);
+      sstrm >> r;
+    }
+
+    w.Push(p, r);
+  }
+
+  c = strm.get();
+  if (c != separator) {
+    strm.clear(std::ios::badbit);
+  }
+
+  return strm;
+}
+
+// Reads SparseTupleWeight when there are parentheses around tuple terms
+template <class W, class K>
+inline istream& SparseTupleWeight<W, K>::ReadWithParen(
+    istream &strm,
+    SparseTupleWeight<W, K> &w,
+    char separator,
+    char open_paren,
+    char close_paren) {
+  int c;
+  size_t n;
+
+  do {
+    c = strm.get();
+  } while (isspace(c));
+
+  if (c != open_paren) {
+    FSTERROR() << "is fst_weight_parentheses flag set correcty? ";
+    strm.clear(std::ios::badbit);
+    return strm;
+  }
+
+  c = strm.get();
+
+  { // Read weight
+    W default_value;
+    stack<int> parens;
+    string s;
+    while (c != separator || !parens.empty()) {
+      if (c == EOF) {
+        strm.clear(std::ios::badbit);
+        return strm;
+      }
+      s += c;
+      // If parens encountered before separator, they must be matched
+      if (c == open_paren) {
+        parens.push(1);
+      } else if (c == close_paren) {
+        // Fail for mismatched parens
+        if (parens.empty()) {
+          strm.clear(std::ios::failbit);
+          return strm;
+        }
+        parens.pop();
+      }
+      c = strm.get();
+    }
+    istringstream sstrm(s);
+    sstrm >> default_value;
+    w.SetDefaultValue(default_value);
+  }
+
+  c = strm.get();
+
+  { // Read n
+    string s;
+    while (c != separator) {
+      if (c == EOF) {
+        strm.clear(std::ios::badbit);
+        return strm;
+      }
+      s += c;
+      c = strm.get();
+    }
+    istringstream sstrm(s);
+    sstrm >> n;
+  }
+
+  // Read n elements
+  for (size_t i = 0; i < n; ++i) {
+    // discard separator
+    c = strm.get();
+    K p;
+    W r;
+
+    { // Read key
+      stack<int> parens;
+      string s;
+      while (c != separator || !parens.empty()) {
+        if (c == EOF) {
+          strm.clear(std::ios::badbit);
+          return strm;
+        }
+        s += c;
+        // If parens encountered before separator, they must be matched
+        if (c == open_paren) {
+          parens.push(1);
+        } else if (c == close_paren) {
+          // Fail for mismatched parens
+          if (parens.empty()) {
+            strm.clear(std::ios::failbit);
+            return strm;
+          }
+          parens.pop();
+        }
+        c = strm.get();
+      }
+      istringstream sstrm(s);
+      sstrm >> p;
+    }
+
+    c = strm.get();
+
+    { // Read weight
+      stack<int> parens;
+      string s;
+      while (c != separator || !parens.empty()) {
+        if (c == EOF) {
+          strm.clear(std::ios::badbit);
+          return strm;
+        }
+        s += c;
+        // If parens encountered before separator, they must be matched
+        if (c == open_paren) {
+          parens.push(1);
+        } else if (c == close_paren) {
+          // Fail for mismatched parens
+          if (parens.empty()) {
+            strm.clear(std::ios::failbit);
+            return strm;
+          }
+          parens.pop();
+        }
+        c = strm.get();
+      }
+      istringstream sstrm(s);
+      sstrm >> r;
+    }
+
+    w.Push(p, r);
+  }
+
+  if (c != separator) {
+    FSTERROR() << " separator expected, not found! ";
+    strm.clear(std::ios::badbit);
+    return strm;
+  }
+
+  c = strm.get();
+  if (c != close_paren) {
+    FSTERROR() << " is fst_weight_parentheses flag set correcty? ";
+    strm.clear(std::ios::badbit);
+    return strm;
+  }
+
+  return strm;
+}
+
+
+
+}  // namespace fst
+
+#endif  // FST_LIB_SPARSE_TUPLE_WEIGHT_H__
diff --git a/src/include/fst/state-map.h b/src/include/fst/state-map.h
new file mode 100644
index 0000000..ace4a3c
--- /dev/null
+++ b/src/include/fst/state-map.h
@@ -0,0 +1,601 @@
+// map.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to map over/transform states e.g., sort transitions
+// Consider using when operation does not change the number of states.
+
+#ifndef FST_LIB_STATE_MAP_H__
+#define FST_LIB_STATE_MAP_H__
+
+#include <algorithm>
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <string>
+#include <utility>
+using std::pair; using std::make_pair;
+
+#include <fst/cache.h>
+#include <fst/arc-map.h>
+#include <fst/mutable-fst.h>
+
+
+namespace fst {
+
+// StateMapper Interface - class determinies how states are mapped.
+// Useful for implementing operations that do not change the number of states.
+//
+// class StateMapper {
+//  public:
+//   typedef A FromArc;
+//   typedef B ToArc;
+//
+//   // Typical constructor
+//   StateMapper(const Fst<A> &fst);
+//   // Required copy constructor that allows updating Fst argument;
+//   // pass only if relevant and changed.
+//   StateMapper(const StateMapper &mapper, const Fst<A> *fst = 0);
+//
+//   // Specifies initial state of result
+//   B::StateId Start() const;
+//   // Specifies state's final weight in result
+//   B::Weight Final(B::StateId s) const;
+//
+//   // These methods iterate through a state's arcs in result
+//   // Specifies state to iterate over
+//   void SetState(B::StateId s);
+//   // End of arcs?
+//   bool Done() const;
+//   // Current arc
+
+//   const B &Value() const;
+//   // Advance to next arc (when !Done)
+//   void Next();
+//
+//   // Specifies input symbol table action the mapper requires (see above).
+//   MapSymbolsAction InputSymbolsAction() const;
+//   // Specifies output symbol table action the mapper requires (see above).
+//   MapSymbolsAction OutputSymbolsAction() const;
+//   // This specifies the known properties of an Fst mapped by this
+//   // mapper. It takes as argument the input Fst's known properties.
+//   uint64 Properties(uint64 props) const;
+// };
+//
+// We include a various state map versions below. One dimension of
+// variation is whether the mapping mutates its input, writes to a
+// new result Fst, or is an on-the-fly Fst. Another dimension is how
+// we pass the mapper. We allow passing the mapper by pointer
+// for cases that we need to change the state of the user's mapper.
+// We also include map versions that pass the mapper
+// by value or const reference when this suffices.
+
+// Maps an arc type A using a mapper function object C, passed
+// by pointer.  This version modifies its Fst input.
+template<class A, class C>
+void StateMap(MutableFst<A> *fst, C* mapper) {
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  if (mapper->InputSymbolsAction() == MAP_CLEAR_SYMBOLS)
+    fst->SetInputSymbols(0);
+
+  if (mapper->OutputSymbolsAction() == MAP_CLEAR_SYMBOLS)
+    fst->SetOutputSymbols(0);
+
+  if (fst->Start() == kNoStateId)
+    return;
+
+  uint64 props = fst->Properties(kFstProperties, false);
+
+  fst->SetStart(mapper->Start());
+
+  for (StateId s = 0; s < fst->NumStates(); ++s) {
+    mapper->SetState(s);
+    fst->DeleteArcs(s);
+    for (; !mapper->Done(); mapper->Next())
+      fst->AddArc(s, mapper->Value());
+    fst->SetFinal(s, mapper->Final(s));
+  }
+
+  fst->SetProperties(mapper->Properties(props), kFstProperties);
+}
+
+// Maps an arc type A using a mapper function object C, passed
+// by value.  This version modifies its Fst input.
+template<class A, class C>
+void StateMap(MutableFst<A> *fst, C mapper) {
+  StateMap(fst, &mapper);
+}
+
+
+// Maps an arc type A to an arc type B using mapper function
+// object C, passed by pointer. This version writes the mapped
+// input Fst to an output MutableFst.
+template<class A, class B, class C>
+void StateMap(const Fst<A> &ifst, MutableFst<B> *ofst, C* mapper) {
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  ofst->DeleteStates();
+
+  if (mapper->InputSymbolsAction() == MAP_COPY_SYMBOLS)
+    ofst->SetInputSymbols(ifst.InputSymbols());
+  else if (mapper->InputSymbolsAction() == MAP_CLEAR_SYMBOLS)
+    ofst->SetInputSymbols(0);
+
+  if (mapper->OutputSymbolsAction() == MAP_COPY_SYMBOLS)
+    ofst->SetOutputSymbols(ifst.OutputSymbols());
+  else if (mapper->OutputSymbolsAction() == MAP_CLEAR_SYMBOLS)
+    ofst->SetOutputSymbols(0);
+
+  uint64 iprops = ifst.Properties(kCopyProperties, false);
+
+  if (ifst.Start() == kNoStateId) {
+    if (iprops & kError) ofst->SetProperties(kError, kError);
+    return;
+  }
+
+  // Add all states.
+  if (ifst.Properties(kExpanded, false))
+    ofst->ReserveStates(CountStates(ifst));
+  for (StateIterator< Fst<A> > siter(ifst); !siter.Done(); siter.Next())
+    ofst->AddState();
+
+  ofst->SetStart(mapper->Start());
+
+  for (StateIterator< Fst<A> > siter(ifst); !siter.Done(); siter.Next()) {
+    StateId s = siter.Value();
+    mapper->SetState(s);
+    for (; !mapper->Done(); mapper->Next())
+      ofst->AddArc(s, mapper->Value());
+    ofst->SetFinal(s, mapper->Final(s));
+  }
+
+  uint64 oprops = ofst->Properties(kFstProperties, false);
+  ofst->SetProperties(mapper->Properties(iprops) | oprops, kFstProperties);
+}
+
+// Maps an arc type A to an arc type B using mapper function
+// object C, passed by value. This version writes the mapped input
+// Fst to an output MutableFst.
+template<class A, class B, class C>
+void StateMap(const Fst<A> &ifst, MutableFst<B> *ofst, C mapper) {
+  StateMap(ifst, ofst, &mapper);
+}
+
+typedef CacheOptions StateMapFstOptions;
+
+template <class A, class B, class C> class StateMapFst;
+
+// Implementation of delayed StateMapFst.
+template <class A, class B, class C>
+class StateMapFstImpl : public CacheImpl<B> {
+ public:
+  using FstImpl<B>::SetType;
+  using FstImpl<B>::SetProperties;
+  using FstImpl<B>::SetInputSymbols;
+  using FstImpl<B>::SetOutputSymbols;
+
+  using VectorFstBaseImpl<typename CacheImpl<B>::State>::NumStates;
+
+  using CacheImpl<B>::PushArc;
+  using CacheImpl<B>::HasArcs;
+  using CacheImpl<B>::HasFinal;
+  using CacheImpl<B>::HasStart;
+  using CacheImpl<B>::SetArcs;
+  using CacheImpl<B>::SetFinal;
+  using CacheImpl<B>::SetStart;
+
+  friend class StateIterator< StateMapFst<A, B, C> >;
+
+  typedef B Arc;
+  typedef typename B::Weight Weight;
+  typedef typename B::StateId StateId;
+
+  StateMapFstImpl(const Fst<A> &fst, const C &mapper,
+                 const StateMapFstOptions& opts)
+      : CacheImpl<B>(opts),
+        fst_(fst.Copy()),
+        mapper_(new C(mapper, fst_)),
+        own_mapper_(true) {
+    Init();
+  }
+
+  StateMapFstImpl(const Fst<A> &fst, C *mapper,
+                 const StateMapFstOptions& opts)
+      : CacheImpl<B>(opts),
+        fst_(fst.Copy()),
+        mapper_(mapper),
+        own_mapper_(false) {
+    Init();
+  }
+
+  StateMapFstImpl(const StateMapFstImpl<A, B, C> &impl)
+      : CacheImpl<B>(impl),
+        fst_(impl.fst_->Copy(true)),
+        mapper_(new C(*impl.mapper_, fst_)),
+        own_mapper_(true) {
+    Init();
+  }
+
+  ~StateMapFstImpl() {
+    delete fst_;
+    if (own_mapper_) delete mapper_;
+  }
+
+  StateId Start() {
+    if (!HasStart())
+      SetStart(mapper_->Start());
+    return CacheImpl<B>::Start();
+  }
+
+  Weight Final(StateId s) {
+    if (!HasFinal(s))
+      SetFinal(s, mapper_->Final(s));
+    return CacheImpl<B>::Final(s);
+  }
+
+  size_t NumArcs(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<B>::NumArcs(s);
+  }
+
+  size_t NumInputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<B>::NumInputEpsilons(s);
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<B>::NumOutputEpsilons(s);
+  }
+
+  void InitStateIterator(StateIteratorData<A> *data) const {
+    fst_->InitStateIterator(data);
+  }
+
+  void InitArcIterator(StateId s, ArcIteratorData<B> *data) {
+    if (!HasArcs(s))
+      Expand(s);
+    CacheImpl<B>::InitArcIterator(s, data);
+  }
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if ((mask & kError) && (fst_->Properties(kError, false) ||
+                            (mapper_->Properties(0) & kError)))
+      SetProperties(kError, kError);
+    return FstImpl<Arc>::Properties(mask);
+  }
+
+  void Expand(StateId s) {
+    // Add exiting arcs.
+    for (mapper_->SetState(s); !mapper_->Done(); mapper_->Next())
+      PushArc(s, mapper_->Value());
+    SetArcs(s);
+  }
+
+ private:
+  void Init() {
+    SetType("statemap");
+
+    if (mapper_->InputSymbolsAction() == MAP_COPY_SYMBOLS)
+      SetInputSymbols(fst_->InputSymbols());
+    else if (mapper_->InputSymbolsAction() == MAP_CLEAR_SYMBOLS)
+      SetInputSymbols(0);
+
+    if (mapper_->OutputSymbolsAction() == MAP_COPY_SYMBOLS)
+      SetOutputSymbols(fst_->OutputSymbols());
+    else if (mapper_->OutputSymbolsAction() == MAP_CLEAR_SYMBOLS)
+      SetOutputSymbols(0);
+
+    uint64 props = fst_->Properties(kCopyProperties, false);
+    SetProperties(mapper_->Properties(props));
+  }
+
+  const Fst<A> *fst_;
+  C*  mapper_;
+  bool own_mapper_;
+
+  void operator=(const StateMapFstImpl<A, B, C> &);  // disallow
+};
+
+
+// Maps an arc type A to an arc type B using Mapper function object
+// C. This version is a delayed Fst.
+template <class A, class B, class C>
+class StateMapFst : public ImplToFst< StateMapFstImpl<A, B, C> > {
+ public:
+  friend class ArcIterator< StateMapFst<A, B, C> >;
+
+  typedef B Arc;
+  typedef typename B::Weight Weight;
+  typedef typename B::StateId StateId;
+  typedef CacheState<B> State;
+  typedef StateMapFstImpl<A, B, C> Impl;
+
+  StateMapFst(const Fst<A> &fst, const C &mapper,
+              const StateMapFstOptions& opts)
+      : ImplToFst<Impl>(new Impl(fst, mapper, opts)) {}
+
+  StateMapFst(const Fst<A> &fst, C* mapper, const StateMapFstOptions& opts)
+      : ImplToFst<Impl>(new Impl(fst, mapper, opts)) {}
+
+  StateMapFst(const Fst<A> &fst, const C &mapper)
+      : ImplToFst<Impl>(new Impl(fst, mapper, StateMapFstOptions())) {}
+
+  StateMapFst(const Fst<A> &fst, C* mapper)
+      : ImplToFst<Impl>(new Impl(fst, mapper, StateMapFstOptions())) {}
+
+  // See Fst<>::Copy() for doc.
+  StateMapFst(const StateMapFst<A, B, C> &fst, bool safe = false)
+    : ImplToFst<Impl>(fst, safe) {}
+
+  // Get a copy of this StateMapFst. See Fst<>::Copy() for further doc.
+  virtual StateMapFst<A, B, C> *Copy(bool safe = false) const {
+    return new StateMapFst<A, B, C>(*this, safe);
+  }
+
+  virtual void InitStateIterator(StateIteratorData<A> *data) const {
+    GetImpl()->InitStateIterator(data);
+  }
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<B> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+ private:
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const StateMapFst<A, B, C> &fst);  // disallow
+};
+
+
+// Specialization for StateMapFst.
+template <class A, class B, class C>
+class ArcIterator< StateMapFst<A, B, C> >
+    : public CacheArcIterator< StateMapFst<A, B, C> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const StateMapFst<A, B, C> &fst, StateId s)
+      : CacheArcIterator< StateMapFst<A, B, C> >(fst.GetImpl(), s) {
+    if (!fst.GetImpl()->HasArcs(s))
+      fst.GetImpl()->Expand(s);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+//
+// Utility Mappers
+//
+
+// Mapper that returns its input.
+template <class A>
+class IdentityStateMapper {
+ public:
+  typedef A FromArc;
+  typedef A ToArc;
+
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  explicit IdentityStateMapper(const Fst<A> &fst) : fst_(fst), aiter_(0) {}
+
+  // Allows updating Fst argument; pass only if changed.
+  IdentityStateMapper(const IdentityStateMapper<A> &mapper,
+                      const Fst<A> *fst = 0)
+      : fst_(fst ? *fst : mapper.fst_), aiter_(0) {}
+
+  ~IdentityStateMapper() { delete aiter_; }
+
+  StateId Start() const { return fst_.Start(); }
+
+  Weight Final(StateId s) const { return fst_.Final(s); }
+
+  void SetState(StateId s) {
+    if (aiter_) delete aiter_;
+    aiter_ = new ArcIterator< Fst<A> >(fst_, s);
+  }
+
+  bool Done() const { return aiter_->Done(); }
+  const A &Value() const { return aiter_->Value(); }
+  void Next() { aiter_->Next(); }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS;}
+
+  uint64 Properties(uint64 props) const { return props; }
+
+ private:
+  const Fst<A> &fst_;
+  ArcIterator< Fst<A> > *aiter_;
+};
+
+template <class A>
+class ArcSumMapper {
+ public:
+  typedef A FromArc;
+  typedef A ToArc;
+
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  explicit ArcSumMapper(const Fst<A> &fst) : fst_(fst), i_(0) {}
+
+  // Allows updating Fst argument; pass only if changed.
+  ArcSumMapper(const ArcSumMapper<A> &mapper,
+               const Fst<A> *fst = 0)
+      : fst_(fst ? *fst : mapper.fst_), i_(0) {}
+
+  StateId Start() const { return fst_.Start(); }
+  Weight Final(StateId s) const { return fst_.Final(s); }
+
+  void SetState(StateId s) {
+    i_ = 0;
+    arcs_.clear();
+    arcs_.reserve(fst_.NumArcs(s));
+    for (ArcIterator<Fst<A> > aiter(fst_, s); !aiter.Done(); aiter.Next())
+      arcs_.push_back(aiter.Value());
+
+    // First sorts the exiting arcs by input label, output label
+    // and destination state and then sums weights of arcs with
+    // the same input label, output label, and destination state.
+    sort(arcs_.begin(), arcs_.end(), comp_);
+    size_t narcs = 0;
+    for (size_t i = 0; i < arcs_.size(); ++i) {
+      if (narcs > 0 && equal_(arcs_[i], arcs_[narcs - 1])) {
+        arcs_[narcs - 1].weight = Plus(arcs_[narcs - 1].weight,
+                                       arcs_[i].weight);
+      } else {
+        arcs_[narcs++] = arcs_[i];
+      }
+    }
+    arcs_.resize(narcs);
+  }
+
+  bool Done() const { return i_ >= arcs_.size(); }
+  const A &Value() const { return arcs_[i_]; }
+  void Next() { ++i_; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  uint64 Properties(uint64 props) const {
+    return props & kArcSortProperties &
+        kDeleteArcsProperties & kWeightInvariantProperties;
+  }
+
+ private:
+  struct Compare {
+    bool operator()(const A& x, const A& y) {
+      if (x.ilabel < y.ilabel) return true;
+      if (x.ilabel > y.ilabel) return false;
+      if (x.olabel < y.olabel) return true;
+      if (x.olabel > y.olabel) return false;
+      if (x.nextstate < y.nextstate) return true;
+      if (x.nextstate > y.nextstate) return false;
+      return false;
+    }
+  };
+
+  struct Equal {
+    bool operator()(const A& x, const A& y) {
+      return (x.ilabel == y.ilabel &&
+              x.olabel == y.olabel &&
+              x.nextstate == y.nextstate);
+    }
+  };
+
+  const Fst<A> &fst_;
+  Compare comp_;
+  Equal equal_;
+  vector<A> arcs_;
+  ssize_t i_;               // current arc position
+
+  void operator=(const ArcSumMapper<A> &);  // disallow
+};
+
+template <class A>
+class ArcUniqueMapper {
+ public:
+  typedef A FromArc;
+  typedef A ToArc;
+
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  explicit ArcUniqueMapper(const Fst<A> &fst) : fst_(fst), i_(0) {}
+
+  // Allows updating Fst argument; pass only if changed.
+  ArcUniqueMapper(const ArcSumMapper<A> &mapper,
+                  const Fst<A> *fst = 0)
+      : fst_(fst ? *fst : mapper.fst_), i_(0) {}
+
+  StateId Start() const { return fst_.Start(); }
+  Weight Final(StateId s) const { return fst_.Final(s); }
+
+  void SetState(StateId s) {
+    i_ = 0;
+    arcs_.clear();
+    arcs_.reserve(fst_.NumArcs(s));
+    for (ArcIterator<Fst<A> > aiter(fst_, s); !aiter.Done(); aiter.Next())
+      arcs_.push_back(aiter.Value());
+
+    // First sorts the exiting arcs by input label, output label
+    // and destination state and then uniques identical arcs
+    sort(arcs_.begin(), arcs_.end(), comp_);
+    typename vector<A>::iterator unique_end =
+        unique(arcs_.begin(), arcs_.end(), equal_);
+    arcs_.resize(unique_end - arcs_.begin());
+  }
+
+  bool Done() const { return i_ >= arcs_.size(); }
+  const A &Value() const { return arcs_[i_]; }
+  void Next() { ++i_; }
+
+  MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+  MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
+
+  uint64 Properties(uint64 props) const {
+    return props & kArcSortProperties & kDeleteArcsProperties;
+  }
+
+ private:
+  struct Compare {
+    bool operator()(const A& x, const A& y) {
+      if (x.ilabel < y.ilabel) return true;
+      if (x.ilabel > y.ilabel) return false;
+      if (x.olabel < y.olabel) return true;
+      if (x.olabel > y.olabel) return false;
+      if (x.nextstate < y.nextstate) return true;
+      if (x.nextstate > y.nextstate) return false;
+      return false;
+    }
+  };
+
+  struct Equal {
+    bool operator()(const A& x, const A& y) {
+      return (x.ilabel == y.ilabel &&
+              x.olabel == y.olabel &&
+              x.nextstate == y.nextstate &&
+              x.weight == y.weight);
+    }
+  };
+
+  const Fst<A> &fst_;
+  Compare comp_;
+  Equal equal_;
+  vector<A> arcs_;
+  ssize_t i_;               // current arc position
+
+  void operator=(const ArcUniqueMapper<A> &);  // disallow
+};
+
+
+}  // namespace fst
+
+#endif  // FST_LIB_STATE_MAP_H__
diff --git a/src/include/fst/state-reachable.h b/src/include/fst/state-reachable.h
new file mode 100644
index 0000000..6d0c971
--- /dev/null
+++ b/src/include/fst/state-reachable.h
@@ -0,0 +1,198 @@
+// state-reachable.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Class to determine whether a given (final) state can be reached from some
+// other given state.
+
+#ifndef FST_LIB_STATE_REACHABLE_H__
+#define FST_LIB_STATE_REACHABLE_H__
+
+#include <vector>
+using std::vector;
+
+#include <fst/dfs-visit.h>
+#include <fst/fst.h>
+#include <fst/interval-set.h>
+
+
+namespace fst {
+
+// Computes the (final) states reachable from a given state in an FST.
+// After this visitor has been called, a final state f can be reached
+// from a state s iff (*isets)[s].Member(state2index[f]) is true, where
+// (*isets[s]) is a set of half-open inteval of final state indices
+// and state2index[f] maps from a final state to its index.
+//
+// If state2index is empty, it is filled-in with suitable indices.
+// If it is non-empty, those indices are used; in this case, the
+// final states must have out-degree 0.
+template <class A, typename I = typename A::StateId>
+class IntervalReachVisitor {
+ public:
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename IntervalSet<I>::Interval Interval;
+
+  IntervalReachVisitor(const Fst<A> &fst,
+                       vector< IntervalSet<I> > *isets,
+                       vector<I> *state2index)
+      : fst_(fst),
+        isets_(isets),
+        state2index_(state2index),
+        index_(state2index->empty() ? 1 : -1),
+        error_(false) {
+    isets_->clear();
+  }
+
+  void InitVisit(const Fst<A> &fst) { error_ = false; }
+
+  bool InitState(StateId s, StateId r) {
+    while (isets_->size() <= s)
+      isets_->push_back(IntervalSet<Label>());
+    while (state2index_->size() <= s)
+      state2index_->push_back(-1);
+
+    if (fst_.Final(s) != Weight::Zero()) {
+      // Create tree interval
+      vector<Interval> *intervals = (*isets_)[s].Intervals();
+      if (index_ < 0) {  // Use state2index_ map to set index
+        if (fst_.NumArcs(s) > 0) {
+          FSTERROR() << "IntervalReachVisitor: state2index map must be empty "
+                     << "for this FST";
+          error_ = true;
+          return false;
+        }
+        I index = (*state2index_)[s];
+        if (index < 0) {
+          FSTERROR() << "IntervalReachVisitor: state2index map incomplete";
+          error_ = true;
+          return false;
+        }
+        intervals->push_back(Interval(index, index + 1));
+      } else {           // Use pre-order index
+        intervals->push_back(Interval(index_, index_ + 1));
+        (*state2index_)[s] = index_++;
+      }
+    }
+    return true;
+  }
+
+  bool TreeArc(StateId s, const A &arc) {
+    return true;
+  }
+
+  bool BackArc(StateId s, const A &arc) {
+    FSTERROR() << "IntervalReachVisitor: cyclic input";
+    error_ = true;
+    return false;
+  }
+
+  bool ForwardOrCrossArc(StateId s, const A &arc) {
+    // Non-tree interval
+    (*isets_)[s].Union((*isets_)[arc.nextstate]);
+    return true;
+  }
+
+  void FinishState(StateId s, StateId p, const A *arc) {
+    if (index_ >= 0 && fst_.Final(s) != Weight::Zero()) {
+      vector<Interval> *intervals = (*isets_)[s].Intervals();
+      (*intervals)[0].end = index_;      // Update tree interval end
+    }
+    (*isets_)[s].Normalize();
+    if (p != kNoStateId)
+      (*isets_)[p].Union((*isets_)[s]);  // Propagate intervals to parent
+  }
+
+  void FinishVisit() {}
+
+  bool Error() const { return error_; }
+
+ private:
+  const Fst<A> &fst_;
+  vector< IntervalSet<I> > *isets_;
+  vector<I> *state2index_;
+  I index_;
+  bool error_;
+};
+
+
+// Tests reachability of final states from a given state. To test for
+// reachability from a state s, first do SetState(s). Then a final
+// state f can be reached from state s of FST iff Reach(f) is true.
+template <class A, typename I = typename A::StateId>
+class StateReachable {
+ public:
+  typedef A Arc;
+  typedef I Index;
+  typedef typename A::StateId StateId;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename IntervalSet<I>::Interval Interval;
+
+  StateReachable(const Fst<A> &fst)
+      : error_(false) {
+    IntervalReachVisitor<Arc> reach_visitor(fst, &isets_, &state2index_);
+    DfsVisit(fst, &reach_visitor);
+    if (reach_visitor.Error()) error_ = true;
+  }
+
+  StateReachable(const StateReachable<A> &reachable) {
+    FSTERROR() << "Copy constructor for state reachable class "
+               << "not yet implemented.";
+    error_ = true;
+  }
+
+  // Set current state.
+  void SetState(StateId s) { s_ = s; }
+
+  // Can reach this label from current state?
+  bool Reach(StateId s) {
+    if (s >= state2index_.size())
+      return false;
+
+    I i =  state2index_[s];
+    if (i < 0) {
+      FSTERROR() << "StateReachable: state non-final: " << s;
+      error_ = true;
+      return false;
+    }
+    return isets_[s_].Member(i);
+  }
+
+  // Access to the state-to-index mapping. Unassigned states have index -1.
+  vector<I> &State2Index() { return state2index_; }
+
+  // Access to the interval sets. These specify the reachability
+  // to the final states as intervals of the final state indices.
+  const vector< IntervalSet<I> > &IntervalSets() { return isets_; }
+
+  bool Error() const { return error_; }
+
+ private:
+  StateId s_;                                 // Current state
+  vector< IntervalSet<I> > isets_;            // Interval sets per state
+  vector<I> state2index_;                     // Finds index for a final state
+  bool error_;
+
+  void operator=(const StateReachable<A> &);  // Disallow
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_STATE_REACHABLE_H__
diff --git a/src/include/fst/state-table.h b/src/include/fst/state-table.h
new file mode 100644
index 0000000..7d863a0
--- /dev/null
+++ b/src/include/fst/state-table.h
@@ -0,0 +1,469 @@
+// state-table.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Classes for representing the mapping between state tuples and state Ids.
+
+#ifndef FST_LIB_STATE_TABLE_H__
+#define FST_LIB_STATE_TABLE_H__
+
+#include <deque>
+#include <vector>
+using std::vector;
+
+#include <fst/bi-table.h>
+#include <fst/expanded-fst.h>
+
+
+namespace fst {
+
+// STATE TABLES - these determine the bijective mapping between state
+// tuples (e.g. in composition triples of two FST states and a
+// composition filter state) and their corresponding state IDs.
+// They are classes, templated on state tuples, of the form:
+//
+// template <class T>
+// class StateTable {
+//  public:
+//   typedef typename T StateTuple;
+//
+//   // Required constructors.
+//   StateTable();
+//
+//   // Lookup state ID by tuple. If it doesn't exist, then add it.
+//   StateId FindState(const StateTuple &);
+//   // Lookup state tuple by state ID.
+//   const StateTuple<StateId> &Tuple(StateId) const;
+//   // # of stored tuples.
+//   StateId Size() const;
+// };
+//
+// A state tuple has the form:
+//
+// template <class S>
+// struct StateTuple {
+//   typedef typename S StateId;
+//
+//   // Required constructor.
+//   StateTuple();
+// };
+
+
+// An implementation using a hash map for the tuple to state ID mapping.
+// The state tuple T must have == defined and the default constructor
+// must produce a tuple that will never be seen. H is the hash function.
+template <class T, class H>
+class HashStateTable : public HashBiTable<typename T::StateId, T, H> {
+ public:
+  typedef T StateTuple;
+  typedef typename StateTuple::StateId StateId;
+  using HashBiTable<StateId, T, H>::FindId;
+  using HashBiTable<StateId, T, H>::FindEntry;
+  using HashBiTable<StateId, T, H>::Size;
+
+  HashStateTable() : HashBiTable<StateId, T, H>() {}
+  StateId FindState(const StateTuple &tuple) { return FindId(tuple); }
+  const StateTuple &Tuple(StateId s) const { return FindEntry(s); }
+};
+
+
+// An implementation using a hash set for the tuple to state ID
+// mapping. The state tuple T must have == defined and the default
+// constructor must produce a tuple that will never be seen. H is the
+// hash function.
+template <class T, class H>
+class CompactHashStateTable
+    : public CompactHashBiTable<typename T::StateId, T, H> {
+ public:
+  typedef T StateTuple;
+  typedef typename StateTuple::StateId StateId;
+  using CompactHashBiTable<StateId, T, H>::FindId;
+  using CompactHashBiTable<StateId, T, H>::FindEntry;
+  using CompactHashBiTable<StateId, T, H>::Size;
+
+  CompactHashStateTable() : CompactHashBiTable<StateId, T, H>() {}
+
+  // Reserves space for table_size elements.
+  explicit CompactHashStateTable(size_t table_size)
+      : CompactHashBiTable<StateId, T, H>(table_size) {}
+
+  StateId FindState(const StateTuple &tuple) { return FindId(tuple); }
+  const StateTuple &Tuple(StateId s) const { return FindEntry(s); }
+};
+
+// An implementation using a vector for the tuple to state mapping.
+// It is passed a function object FP that should fingerprint tuples
+// uniquely to an integer that can used as a vector index. Normally,
+// VectorStateTable constructs the FP object.  The user can instead
+// pass in this object; in that case, VectorStateTable takes its
+// ownership.
+template <class T, class FP>
+class VectorStateTable
+    : public VectorBiTable<typename T::StateId, T, FP> {
+ public:
+  typedef T StateTuple;
+  typedef typename StateTuple::StateId StateId;
+  using VectorBiTable<StateId, T, FP>::FindId;
+  using VectorBiTable<StateId, T, FP>::FindEntry;
+  using VectorBiTable<StateId, T, FP>::Size;
+  using VectorBiTable<StateId, T, FP>::Fingerprint;
+
+  explicit VectorStateTable(FP *fp = 0) : VectorBiTable<StateId, T, FP>(fp) {}
+  StateId FindState(const StateTuple &tuple) { return FindId(tuple); }
+  const StateTuple &Tuple(StateId s) const { return FindEntry(s); }
+};
+
+
+// An implementation using a vector and a compact hash table. The
+// selecting functor S returns true for tuples to be hashed in the
+// vector.  The fingerprinting functor FP returns a unique fingerprint
+// for each tuple to be hashed in the vector (these need to be
+// suitable for indexing in a vector).  The hash functor H is used when
+// hashing tuple into the compact hash table.
+template <class T, class S, class FP, class H>
+class VectorHashStateTable
+    : public VectorHashBiTable<typename T::StateId, T, S, FP, H> {
+ public:
+  typedef T StateTuple;
+  typedef typename StateTuple::StateId StateId;
+  using VectorHashBiTable<StateId, T, S, FP, H>::FindId;
+  using VectorHashBiTable<StateId, T, S, FP, H>::FindEntry;
+  using VectorHashBiTable<StateId, T, S, FP, H>::Size;
+  using VectorHashBiTable<StateId, T, S, FP, H>::Selector;
+  using VectorHashBiTable<StateId, T, S, FP, H>::Fingerprint;
+  using VectorHashBiTable<StateId, T, S, FP, H>::Hash;
+
+  VectorHashStateTable(S *s, FP *fp, H *h,
+                       size_t vector_size = 0,
+                       size_t tuple_size = 0)
+      : VectorHashBiTable<StateId, T, S, FP, H>(
+          s, fp, h, vector_size, tuple_size) {}
+
+  StateId FindState(const StateTuple &tuple) { return FindId(tuple); }
+  const StateTuple &Tuple(StateId s) const { return FindEntry(s); }
+};
+
+
+// An implementation using a hash map for the tuple to state ID
+// mapping. This version permits erasing of states.  The state tuple T
+// must have == defined and its default constructor must produce a
+// tuple that will never be seen. F is the hash function.
+template <class T, class F>
+class ErasableStateTable : public ErasableBiTable<typename T::StateId, T, F> {
+ public:
+  typedef T StateTuple;
+  typedef typename StateTuple::StateId StateId;
+  using ErasableBiTable<StateId, T, F>::FindId;
+  using ErasableBiTable<StateId, T, F>::FindEntry;
+  using ErasableBiTable<StateId, T, F>::Size;
+  using ErasableBiTable<StateId, T, F>::Erase;
+
+  ErasableStateTable() : ErasableBiTable<StateId, T, F>() {}
+  StateId FindState(const StateTuple &tuple) { return FindId(tuple); }
+  const StateTuple &Tuple(StateId s) const { return FindEntry(s); }
+};
+
+//
+// COMPOSITION STATE TUPLES AND TABLES
+//
+// The composition state table has the form:
+//
+// template <class A, class F>
+// class ComposeStateTable {
+//  public:
+//   typedef A Arc;
+//   typedef F FilterState;
+//   typedef typename A::StateId StateId;
+//   typedef ComposeStateTuple<StateId> StateTuple;
+//
+//   // Required constructors. Copy constructor does not copy state.
+//   ComposeStateTable(const Fst<Arc> &fst1, const Fst<Arc> &fst2);
+//   ComposeStateTable(const ComposeStateTable<A, F> &table);
+//   // Lookup state ID by tuple. If it doesn't exist, then add it.
+//   StateId FindState(const StateTuple &);
+//   // Lookup state tuple by state ID.
+//   const StateTuple<StateId> &Tuple(StateId) const;
+//   // # of stored tuples.
+//   StateId Size() const;
+//   // Return true if error encountered
+//   bool Error() const;
+// };
+
+// Represents the composition state.
+template <typename S, typename F>
+struct ComposeStateTuple {
+  typedef S StateId;
+  typedef F FilterState;
+
+  ComposeStateTuple()
+      : state_id1(kNoStateId), state_id2(kNoStateId),
+        filter_state(FilterState::NoState()) {}
+
+  ComposeStateTuple(StateId s1, StateId s2, const FilterState &f)
+      : state_id1(s1), state_id2(s2), filter_state(f) {}
+
+  StateId state_id1;         // State Id on fst1
+  StateId state_id2;         // State Id on fst2
+  FilterState filter_state;  // State of composition filter
+};
+
+// Equality of composition state tuples.
+template <typename S, typename F>
+inline bool operator==(const ComposeStateTuple<S, F>& x,
+                       const ComposeStateTuple<S, F>& y) {
+  if (&x == &y)
+    return true;
+  return x.state_id1 == y.state_id1 &&
+      x.state_id2 == y.state_id2 &&
+      x.filter_state == y.filter_state;
+}
+
+
+// Hashing of composition state tuples.
+template <typename S, typename F>
+class ComposeHash {
+ public:
+  size_t operator()(const ComposeStateTuple<S, F>& t) const {
+    return t.state_id1 + t.state_id2 * kPrime0 +
+        t.filter_state.Hash() * kPrime1;
+  }
+ private:
+  static const size_t kPrime0;
+  static const size_t kPrime1;
+};
+
+template <typename S, typename F>
+const size_t ComposeHash<S, F>::kPrime0 = 7853;
+
+template <typename S, typename F>
+const size_t ComposeHash<S, F>::kPrime1 = 7867;
+
+
+// A HashStateTable over composition tuples.
+template <typename A,
+          typename F,
+          typename H =
+          CompactHashStateTable<ComposeStateTuple<typename A::StateId, F>,
+                                ComposeHash<typename A::StateId, F> > >
+class GenericComposeStateTable : public H {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef F FilterState;
+  typedef ComposeStateTuple<StateId, F> StateTuple;
+
+  GenericComposeStateTable(const Fst<A> &fst1, const Fst<A> &fst2) {}
+
+  GenericComposeStateTable(const GenericComposeStateTable<A, F> &table) {}
+
+  bool Error() const { return false; }
+
+ private:
+  void operator=(const GenericComposeStateTable<A, F> &table);  // disallow
+};
+
+
+//  Fingerprint for general composition tuples.
+template  <typename S, typename F>
+class ComposeFingerprint {
+ public:
+  typedef S StateId;
+  typedef F FilterState;
+  typedef ComposeStateTuple<S, F> StateTuple;
+
+  // Required but suboptimal constructor.
+  ComposeFingerprint() : mult1_(8192), mult2_(8192) {
+    LOG(WARNING) << "TupleFingerprint: # of FST states should be provided.";
+  }
+
+  // Constructor is provided the sizes of the input FSTs
+  ComposeFingerprint(StateId nstates1, StateId nstates2)
+      : mult1_(nstates1), mult2_(nstates1 * nstates2) { }
+
+  size_t operator()(const StateTuple &tuple) {
+    return tuple.state_id1 + tuple.state_id2 * mult1_ +
+        tuple.filter_state.Hash() * mult2_;
+  }
+
+ private:
+  ssize_t mult1_;
+  ssize_t mult2_;
+};
+
+
+// Useful when the first composition state determines the tuple.
+template  <typename S, typename F>
+class ComposeState1Fingerprint {
+ public:
+  typedef S StateId;
+  typedef F FilterState;
+  typedef ComposeStateTuple<S, F> StateTuple;
+
+  size_t operator()(const StateTuple &tuple) { return tuple.state_id1; }
+};
+
+
+// Useful when the second composition state determines the tuple.
+template  <typename S, typename F>
+class ComposeState2Fingerprint {
+ public:
+  typedef S StateId;
+  typedef F FilterState;
+  typedef ComposeStateTuple<S, F> StateTuple;
+
+  size_t operator()(const StateTuple &tuple) { return tuple.state_id2; }
+};
+
+
+// A VectorStateTable over composition tuples.  This can be used when
+// the product of number of states in FST1 and FST2 (and the
+// composition filter state hash) is manageable. If the FSTs are not
+// expanded Fsts, they will first have their states counted.
+template  <typename A, typename F>
+class ProductComposeStateTable : public
+VectorStateTable<ComposeStateTuple<typename A::StateId, F>,
+                 ComposeFingerprint<typename A::StateId, F> > {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef F FilterState;
+  typedef ComposeStateTuple<StateId, F> StateTuple;
+
+  ProductComposeStateTable(const Fst<A> &fst1, const Fst<A> &fst2)
+      : VectorStateTable<ComposeStateTuple<StateId, F>,
+                         ComposeFingerprint<StateId, F> >
+  (new ComposeFingerprint<StateId, F>(CountStates(fst1),
+                                      CountStates(fst2))) { }
+
+  ProductComposeStateTable(const ProductComposeStateTable<A, F> &table)
+      : VectorStateTable<ComposeStateTuple<StateId, F>,
+                         ComposeFingerprint<StateId, F> >
+        (new ComposeFingerprint<StateId, F>(table.Fingerprint())) {}
+
+  bool Error() const { return false; }
+
+ private:
+  void operator=(const ProductComposeStateTable<A, F> &table);  // disallow
+};
+
+// A VectorStateTable over composition tuples.  This can be used when
+// FST1 is a string (satisfies kStringProperties) and FST2 is
+// epsilon-free and deterministic. It should be used with a
+// composition filter that creates at most one filter state per tuple
+// under these conditions (e.g. SequenceComposeFilter or
+// MatchComposeFilter).
+template <typename A, typename F>
+class StringDetComposeStateTable : public
+VectorStateTable<ComposeStateTuple<typename A::StateId, F>,
+                 ComposeState1Fingerprint<typename A::StateId, F> > {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef F FilterState;
+  typedef ComposeStateTuple<StateId, F> StateTuple;
+
+  StringDetComposeStateTable(const Fst<A> &fst1, const Fst<A> &fst2)
+      : error_(false) {
+    uint64 props1 = kString;
+    uint64 props2 = kIDeterministic | kNoIEpsilons;
+    if (fst1.Properties(props1, true) != props1 ||
+        fst2.Properties(props2, true) != props2) {
+      FSTERROR() << "StringDetComposeStateTable: fst1 not a string or"
+                 << " fst2 not input deterministic and epsilon-free";
+      error_ = true;
+    }
+  }
+
+  StringDetComposeStateTable(const StringDetComposeStateTable<A, F> &table)
+   : error_(table.error_) {}
+
+  bool Error() const { return error_; }
+
+ private:
+  bool error_;
+
+  void operator=(const StringDetComposeStateTable<A, F> &table);  // disallow
+};
+
+
+// A VectorStateTable over composition tuples.  This can be used when
+// FST2 is a string (satisfies kStringProperties) and FST1 is
+// epsilon-free and deterministic. It should be used with a
+// composition filter that creates at most one filter state per tuple
+// under these conditions (e.g. SequenceComposeFilter or
+// MatchComposeFilter).
+template <typename A, typename F>
+class DetStringComposeStateTable : public
+VectorStateTable<ComposeStateTuple<typename A::StateId, F>,
+                 ComposeState1Fingerprint<typename A::StateId, F> > {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef F FilterState;
+  typedef ComposeStateTuple<StateId, F> StateTuple;
+
+  DetStringComposeStateTable(const Fst<A> &fst1, const Fst<A> &fst2)
+      :error_(false) {
+    uint64 props1 = kODeterministic | kNoOEpsilons;
+    uint64 props2 = kString;
+    if (fst1.Properties(props1, true) != props1 ||
+        fst2.Properties(props2, true) != props2) {
+      FSTERROR() << "StringDetComposeStateTable: fst2 not a string or"
+                 << " fst1 not output deterministic and epsilon-free";
+      error_ = true;
+    }
+  }
+
+  DetStringComposeStateTable(const DetStringComposeStateTable<A, F> &table)
+      : error_(table.error_) {}
+
+  bool Error() const { return error_; }
+
+ private:
+  bool error_;
+
+  void operator=(const DetStringComposeStateTable<A, F> &table);  // disallow
+};
+
+
+// An ErasableStateTable over composition tuples. The Erase(StateId) method
+// can be called if the user either is sure that composition will never return
+// to that tuple or doesn't care that if it does, it is assigned a new
+// state ID.
+template <typename A, typename F>
+class ErasableComposeStateTable : public
+ErasableStateTable<ComposeStateTuple<typename A::StateId, F>,
+                   ComposeHash<typename A::StateId, F> > {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef F FilterState;
+  typedef ComposeStateTuple<StateId, F> StateTuple;
+
+  ErasableComposeStateTable(const Fst<A> &fst1, const Fst<A> &fst2) {}
+
+  ErasableComposeStateTable(const ErasableComposeStateTable<A, F> &table) {}
+
+  bool Error() const { return false; }
+
+ private:
+  void operator=(const ErasableComposeStateTable<A, F> &table);  // disallow
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_STATE_TABLE_H__
diff --git a/src/include/fst/statesort.h b/src/include/fst/statesort.h
new file mode 100644
index 0000000..6f827f4
--- /dev/null
+++ b/src/include/fst/statesort.h
@@ -0,0 +1,97 @@
+// statesort.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Function to sort states of an Fst.
+
+#ifndef FST_LIB_STATESORT_H__
+#define FST_LIB_STATESORT_H__
+
+#include <vector>
+using std::vector;
+#include <algorithm>
+
+#include <fst/mutable-fst.h>
+
+
+namespace fst {
+
+// Sorts the input states of an FST, modifying it. ORDER[i] gives the
+// the state Id after sorting that corresponds to state Id i before
+// sorting.  ORDER must be a permutation of FST's states ID sequence:
+// (0, 1, 2, ..., fst->NumStates() - 1).
+template <class Arc>
+void StateSort(MutableFst<Arc> *fst,
+               const vector<typename Arc::StateId> &order) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+
+  if (order.size() != fst->NumStates()) {
+    FSTERROR() << "StateSort: bad order vector size: " << order.size();
+    fst->SetProperties(kError, kError);
+    return;
+  }
+
+  if (fst->Start() == kNoStateId)
+    return;
+
+  uint64 props = fst->Properties(kStateSortProperties, false);
+
+  vector<bool> done(order.size(), false);
+  vector<Arc> arcsa, arcsb;
+  vector<Arc> *arcs1 = &arcsa, *arcs2 = &arcsb;
+
+  fst->SetStart(order[fst->Start()]);
+
+  for (StateIterator< MutableFst<Arc> > siter(*fst);
+       !siter.Done();
+       siter.Next()) {
+    StateId s1 = siter.Value(), s2;
+    if (done[s1])
+      continue;
+    Weight final1 = fst->Final(s1), final2 = Weight::Zero();
+    arcs1->clear();
+    for (ArcIterator< MutableFst<Arc> > aiter(*fst, s1);
+         !aiter.Done();
+         aiter.Next())
+      arcs1->push_back(aiter.Value());
+    for (; !done[s1]; s1 = s2, final1 = final2, swap(arcs1, arcs2)) {
+      s2 = order[s1];
+      if (!done[s2]) {
+        final2 = fst->Final(s2);
+        arcs2->clear();
+        for (ArcIterator< MutableFst<Arc> > aiter(*fst, s2);
+             !aiter.Done();
+             aiter.Next())
+          arcs2->push_back(aiter.Value());
+      }
+      fst->SetFinal(s2, final1);
+      fst->DeleteArcs(s2);
+      for (size_t i = 0; i < arcs1->size(); ++i) {
+        Arc arc = (*arcs1)[i];
+        arc.nextstate = order[arc.nextstate];
+        fst->AddArc(s2, arc);
+      }
+      done[s1] = true;
+    }
+  }
+  fst->SetProperties(props, kFstProperties);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_STATESORT_H__
diff --git a/src/include/fst/string-weight.h b/src/include/fst/string-weight.h
new file mode 100644
index 0000000..1beeb33
--- /dev/null
+++ b/src/include/fst/string-weight.h
@@ -0,0 +1,560 @@
+// string-weight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// String weight set and associated semiring operation definitions.
+
+#ifndef FST_LIB_STRING_WEIGHT_H__
+#define FST_LIB_STRING_WEIGHT_H__
+
+#include <list>
+#include <string>
+
+#include <fst/product-weight.h>
+#include <fst/weight.h>
+
+namespace fst {
+
+const int kStringInfinity = -1;      // Label for the infinite string
+const int kStringBad = -2;           // Label for a non-string
+const char kStringSeparator = '_';   // Label separator in strings
+
+// Determines whether to use left or right string semiring.  Includes
+// restricted versions that signal an error if proper prefixes
+// (suffixes) would otherwise be returned by Plus, useful with various
+// algorithms that require functional transducer input with the
+// string semirings.
+enum StringType { STRING_LEFT = 0, STRING_RIGHT = 1 ,
+                  STRING_LEFT_RESTRICT = 2, STRING_RIGHT_RESTRICT };
+
+#define REVERSE_STRING_TYPE(S)                                  \
+   ((S) == STRING_LEFT ? STRING_RIGHT :                         \
+    ((S) == STRING_RIGHT ? STRING_LEFT :                        \
+     ((S) == STRING_LEFT_RESTRICT ? STRING_RIGHT_RESTRICT :     \
+      STRING_LEFT_RESTRICT)))
+
+template <typename L, StringType S = STRING_LEFT>
+class StringWeight;
+
+template <typename L, StringType S = STRING_LEFT>
+class StringWeightIterator;
+
+template <typename L, StringType S = STRING_LEFT>
+class StringWeightReverseIterator;
+
+template <typename L, StringType S>
+bool operator==(const StringWeight<L, S> &,  const StringWeight<L, S> &);
+
+
+// String semiring: (longest_common_prefix/suffix, ., Infinity, Epsilon)
+template <typename L, StringType S>
+class StringWeight {
+ public:
+  typedef L Label;
+  typedef StringWeight<L, REVERSE_STRING_TYPE(S)> ReverseWeight;
+
+  friend class StringWeightIterator<L, S>;
+  friend class StringWeightReverseIterator<L, S>;
+  friend bool operator==<>(const StringWeight<L, S> &,
+                           const StringWeight<L, S> &);
+
+  StringWeight() { Init(); }
+
+  template <typename Iter>
+  StringWeight(const Iter &begin, const Iter &end) {
+    Init();
+    for (Iter iter = begin; iter != end; ++iter)
+      PushBack(*iter);
+  }
+
+  explicit StringWeight(L l) { Init(); PushBack(l); }
+
+  static const StringWeight<L, S> &Zero() {
+    static const StringWeight<L, S> zero(kStringInfinity);
+    return zero;
+  }
+
+  static const StringWeight<L, S> &One() {
+    static const StringWeight<L, S> one;
+    return one;
+  }
+
+  static const StringWeight<L, S> &NoWeight() {
+    static const StringWeight<L, S> no_weight(kStringBad);
+    return no_weight;
+  }
+
+  static const string &Type() {
+    static const string type =
+        S == STRING_LEFT ? "string" :
+        (S == STRING_RIGHT ? "right_string" :
+         (S == STRING_LEFT_RESTRICT ? "restricted_string" :
+          "right_restricted_string"));
+    return type;
+  }
+
+  bool Member() const;
+
+  istream &Read(istream &strm);
+
+  ostream &Write(ostream &strm) const;
+
+  size_t Hash() const;
+
+  StringWeight<L, S> Quantize(float delta = kDelta) const {
+    return *this;
+  }
+
+  ReverseWeight Reverse() const;
+
+  static uint64 Properties() {
+    return (S == STRING_LEFT || S == STRING_LEFT_RESTRICT ?
+            kLeftSemiring : kRightSemiring) | kIdempotent;
+  }
+
+  // NB: This needs to be uncommented only if default fails for this impl.
+  // StringWeight<L, S> &operator=(const StringWeight<L, S> &w);
+
+  // These operations combined with the StringWeightIterator and
+  // StringWeightReverseIterator provide the access and mutation of
+  // the string internal elements.
+
+  // Common initializer among constructors.
+  void Init() { first_ = 0; }
+
+  // Clear existing StringWeight.
+  void Clear() { first_ = 0; rest_.clear(); }
+
+  size_t Size() const { return first_ ? rest_.size() + 1 : 0; }
+
+  void PushFront(L l) {
+    if (first_)
+      rest_.push_front(first_);
+    first_ = l;
+  }
+
+  void PushBack(L l) {
+    if (!first_)
+      first_ = l;
+    else
+      rest_.push_back(l);
+  }
+
+ private:
+  L first_;         // first label in string (0 if empty)
+  list<L> rest_;    // remaining labels in string
+};
+
+
+// Traverses string in forward direction.
+template <typename L, StringType S>
+class StringWeightIterator {
+ public:
+  explicit StringWeightIterator(const StringWeight<L, S>& w)
+      : first_(w.first_), rest_(w.rest_), init_(true),
+        iter_(rest_.begin()) {}
+
+  bool Done() const {
+    if (init_) return first_ == 0;
+    else return iter_ == rest_.end();
+  }
+
+  const L& Value() const { return init_ ? first_ : *iter_; }
+
+  void Next() {
+    if (init_) init_ = false;
+    else  ++iter_;
+  }
+
+  void Reset() {
+    init_ = true;
+    iter_ = rest_.begin();
+  }
+
+ private:
+  const L &first_;
+  const list<L> &rest_;
+  bool init_;   // in the initialized state?
+  typename list<L>::const_iterator iter_;
+
+  DISALLOW_COPY_AND_ASSIGN(StringWeightIterator);
+};
+
+
+// Traverses string in backward direction.
+template <typename L, StringType S>
+class StringWeightReverseIterator {
+ public:
+  explicit StringWeightReverseIterator(const StringWeight<L, S>& w)
+      : first_(w.first_), rest_(w.rest_), fin_(first_ == 0),
+        iter_(rest_.rbegin()) {}
+
+  bool Done() const { return fin_; }
+
+  const L& Value() const { return iter_ == rest_.rend() ? first_ : *iter_; }
+
+  void Next() {
+    if (iter_ == rest_.rend()) fin_ = true;
+    else  ++iter_;
+  }
+
+  void Reset() {
+    fin_ = false;
+    iter_ = rest_.rbegin();
+  }
+
+ private:
+  const L &first_;
+  const list<L> &rest_;
+  bool fin_;   // in the final state?
+  typename list<L>::const_reverse_iterator iter_;
+
+  DISALLOW_COPY_AND_ASSIGN(StringWeightReverseIterator);
+};
+
+
+// StringWeight member functions follow that require
+// StringWeightIterator or StringWeightReverseIterator.
+
+template <typename L, StringType S>
+inline istream &StringWeight<L, S>::Read(istream &strm) {
+  Clear();
+  int32 size;
+  ReadType(strm, &size);
+  for (int i = 0; i < size; ++i) {
+    L label;
+    ReadType(strm, &label);
+    PushBack(label);
+  }
+  return strm;
+}
+
+template <typename L, StringType S>
+inline ostream &StringWeight<L, S>::Write(ostream &strm) const {
+  int32 size =  Size();
+  WriteType(strm, size);
+  for (StringWeightIterator<L, S> iter(*this); !iter.Done(); iter.Next()) {
+    L label = iter.Value();
+    WriteType(strm, label);
+  }
+  return strm;
+}
+
+template <typename L, StringType S>
+inline bool StringWeight<L, S>::Member() const {
+  if (Size() != 1)
+    return true;
+  StringWeightIterator<L, S> iter(*this);
+  return iter.Value() != kStringBad;
+}
+
+template <typename L, StringType S>
+inline typename StringWeight<L, S>::ReverseWeight
+StringWeight<L, S>::Reverse() const {
+  ReverseWeight rw;
+  for (StringWeightIterator<L, S> iter(*this); !iter.Done(); iter.Next())
+    rw.PushFront(iter.Value());
+  return rw;
+}
+
+template <typename L, StringType S>
+inline size_t StringWeight<L, S>::Hash() const {
+  size_t h = 0;
+  for (StringWeightIterator<L, S> iter(*this); !iter.Done(); iter.Next())
+    h ^= h<<1 ^ iter.Value();
+  return h;
+}
+
+// NB: This needs to be uncommented only if default fails for this the impl.
+//
+// template <typename L, StringType S>
+// inline StringWeight<L, S>
+// &StringWeight<L, S>::operator=(const StringWeight<L, S> &w) {
+//   if (this != &w) {
+//     Clear();
+//     for (StringWeightIterator<L, S> iter(w); !iter.Done(); iter.Next())
+//       PushBack(iter.Value());
+//   }
+//   return *this;
+// }
+
+template <typename L, StringType S>
+inline bool operator==(const StringWeight<L, S> &w1,
+                       const StringWeight<L, S> &w2) {
+  if (w1.Size() != w2.Size())
+    return false;
+
+  StringWeightIterator<L, S> iter1(w1);
+  StringWeightIterator<L, S> iter2(w2);
+
+  for (; !iter1.Done() ; iter1.Next(), iter2.Next())
+    if (iter1.Value() != iter2.Value())
+      return false;
+
+  return true;
+}
+
+template <typename L, StringType S>
+inline bool operator!=(const StringWeight<L, S> &w1,
+                       const StringWeight<L, S> &w2) {
+  return !(w1 == w2);
+}
+
+template <typename L, StringType S>
+inline bool ApproxEqual(const StringWeight<L, S> &w1,
+                        const StringWeight<L, S> &w2,
+                        float delta = kDelta) {
+  return w1 == w2;
+}
+
+template <typename L, StringType S>
+inline ostream &operator<<(ostream &strm, const StringWeight<L, S> &w) {
+  StringWeightIterator<L, S> iter(w);
+  if (iter.Done())
+    return strm << "Epsilon";
+  else if (iter.Value() == kStringInfinity)
+    return strm << "Infinity";
+  else if (iter.Value() == kStringBad)
+    return strm << "BadString";
+  else
+    for (size_t i = 0; !iter.Done(); ++i, iter.Next()) {
+      if (i > 0)
+        strm << kStringSeparator;
+      strm << iter.Value();
+    }
+  return strm;
+}
+
+template <typename L, StringType S>
+inline istream &operator>>(istream &strm, StringWeight<L, S> &w) {
+  string s;
+  strm >> s;
+  if (s == "Infinity") {
+    w = StringWeight<L, S>::Zero();
+  } else if (s == "Epsilon") {
+    w = StringWeight<L, S>::One();
+  } else {
+    w.Clear();
+    char *p = 0;
+    for (const char *cs = s.c_str(); !p || *p != '\0'; cs = p + 1) {
+      int l = strtoll(cs, &p, 10);
+      if (p == cs || (*p != 0 && *p != kStringSeparator)) {
+        strm.clear(std::ios::badbit);
+        break;
+      }
+      w.PushBack(l);
+    }
+  }
+  return strm;
+}
+
+
+// Default is for the restricted left and right semirings.  String
+// equality is required (for non-Zero() input. This restriction
+// is used in e.g. Determinize to ensure functional input.
+template <typename L, StringType S>  inline StringWeight<L, S>
+Plus(const StringWeight<L, S> &w1,
+     const StringWeight<L, S> &w2) {
+  if (!w1.Member() || !w2.Member())
+    return StringWeight<L, S>::NoWeight();
+  if (w1 == StringWeight<L, S>::Zero())
+    return w2;
+  if (w2 == StringWeight<L, S>::Zero())
+    return w1;
+
+  if (w1 != w2) {
+    FSTERROR() << "StringWeight::Plus: unequal arguments "
+               << "(non-functional FST?)"
+               << " w1 = " << w1
+               << " w2 = " << w2;
+    return StringWeight<L, S>::NoWeight();
+  }
+
+  return w1;
+}
+
+
+// Longest common prefix for left string semiring.
+template <typename L>  inline StringWeight<L, STRING_LEFT>
+Plus(const StringWeight<L, STRING_LEFT> &w1,
+     const StringWeight<L, STRING_LEFT> &w2) {
+  if (!w1.Member() || !w2.Member())
+    return StringWeight<L, STRING_LEFT>::NoWeight();
+  if (w1 == StringWeight<L, STRING_LEFT>::Zero())
+    return w2;
+  if (w2 == StringWeight<L, STRING_LEFT>::Zero())
+    return w1;
+
+  StringWeight<L, STRING_LEFT> sum;
+  StringWeightIterator<L, STRING_LEFT> iter1(w1);
+  StringWeightIterator<L, STRING_LEFT> iter2(w2);
+  for (; !iter1.Done() && !iter2.Done() && iter1.Value() == iter2.Value();
+       iter1.Next(), iter2.Next())
+    sum.PushBack(iter1.Value());
+  return sum;
+}
+
+
+// Longest common suffix for right string semiring.
+template <typename L>  inline StringWeight<L, STRING_RIGHT>
+Plus(const StringWeight<L, STRING_RIGHT> &w1,
+     const StringWeight<L, STRING_RIGHT> &w2) {
+  if (!w1.Member() || !w2.Member())
+    return StringWeight<L, STRING_RIGHT>::NoWeight();
+  if (w1 == StringWeight<L, STRING_RIGHT>::Zero())
+    return w2;
+  if (w2 == StringWeight<L, STRING_RIGHT>::Zero())
+    return w1;
+
+  StringWeight<L, STRING_RIGHT> sum;
+  StringWeightReverseIterator<L, STRING_RIGHT> iter1(w1);
+  StringWeightReverseIterator<L, STRING_RIGHT> iter2(w2);
+  for (; !iter1.Done() && !iter2.Done() && iter1.Value() == iter2.Value();
+       iter1.Next(), iter2.Next())
+    sum.PushFront(iter1.Value());
+  return sum;
+}
+
+
+template <typename L, StringType S>
+inline StringWeight<L, S> Times(const StringWeight<L, S> &w1,
+                             const StringWeight<L, S> &w2) {
+  if (!w1.Member() || !w2.Member())
+    return StringWeight<L, S>::NoWeight();
+  if (w1 == StringWeight<L, S>::Zero() || w2 == StringWeight<L, S>::Zero())
+    return StringWeight<L, S>::Zero();
+
+  StringWeight<L, S> prod(w1);
+  for (StringWeightIterator<L, S> iter(w2); !iter.Done(); iter.Next())
+    prod.PushBack(iter.Value());
+
+  return prod;
+}
+
+
+// Default is for left division in the left string and the
+// left restricted string semirings.
+template <typename L, StringType S> inline StringWeight<L, S>
+Divide(const StringWeight<L, S> &w1,
+       const StringWeight<L, S> &w2,
+       DivideType typ) {
+
+  if (typ != DIVIDE_LEFT) {
+    FSTERROR() << "StringWeight::Divide: only left division is defined "
+               << "for the " << StringWeight<L, S>::Type() << " semiring";
+    return StringWeight<L, S>::NoWeight();
+  }
+
+  if (!w1.Member() || !w2.Member())
+    return StringWeight<L, S>::NoWeight();
+
+  if (w2 == StringWeight<L, S>::Zero())
+    return StringWeight<L, S>(kStringBad);
+  else if (w1 == StringWeight<L, S>::Zero())
+    return StringWeight<L, S>::Zero();
+
+  StringWeight<L, S> div;
+  StringWeightIterator<L, S> iter(w1);
+  for (int i = 0; !iter.Done(); iter.Next(), ++i) {
+    if (i >= w2.Size())
+      div.PushBack(iter.Value());
+  }
+  return div;
+}
+
+
+// Right division in the right string semiring.
+template <typename L> inline StringWeight<L, STRING_RIGHT>
+Divide(const StringWeight<L, STRING_RIGHT> &w1,
+       const StringWeight<L, STRING_RIGHT> &w2,
+       DivideType typ) {
+
+  if (typ != DIVIDE_RIGHT) {
+    FSTERROR() << "StringWeight::Divide: only right division is defined "
+               << "for the right string semiring";
+    return StringWeight<L, STRING_RIGHT>::NoWeight();
+  }
+
+  if (!w1.Member() || !w2.Member())
+    return StringWeight<L, STRING_RIGHT>::NoWeight();
+
+  if (w2 == StringWeight<L, STRING_RIGHT>::Zero())
+    return StringWeight<L, STRING_RIGHT>(kStringBad);
+  else if (w1 == StringWeight<L, STRING_RIGHT>::Zero())
+    return StringWeight<L, STRING_RIGHT>::Zero();
+
+  StringWeight<L, STRING_RIGHT> div;
+  StringWeightReverseIterator<L, STRING_RIGHT> iter(w1);
+  for (int i = 0; !iter.Done(); iter.Next(), ++i) {
+    if (i >= w2.Size())
+      div.PushFront(iter.Value());
+  }
+  return div;
+}
+
+
+// Right division in the right restricted string semiring.
+template <typename L> inline StringWeight<L, STRING_RIGHT_RESTRICT>
+Divide(const StringWeight<L, STRING_RIGHT_RESTRICT> &w1,
+       const StringWeight<L, STRING_RIGHT_RESTRICT> &w2,
+       DivideType typ) {
+
+  if (typ != DIVIDE_RIGHT) {
+    FSTERROR() << "StringWeight::Divide: only right division is defined "
+               << "for the right restricted string semiring";
+    return StringWeight<L, STRING_RIGHT_RESTRICT>::NoWeight();
+  }
+
+  if (!w1.Member() || !w2.Member())
+    return StringWeight<L, STRING_RIGHT_RESTRICT>::NoWeight();
+
+  if (w2 == StringWeight<L, STRING_RIGHT_RESTRICT>::Zero())
+    return StringWeight<L, STRING_RIGHT_RESTRICT>(kStringBad);
+  else if (w1 == StringWeight<L, STRING_RIGHT_RESTRICT>::Zero())
+    return StringWeight<L, STRING_RIGHT_RESTRICT>::Zero();
+
+  StringWeight<L, STRING_RIGHT_RESTRICT> div;
+  StringWeightReverseIterator<L, STRING_RIGHT_RESTRICT> iter(w1);
+  for (int i = 0; !iter.Done(); iter.Next(), ++i) {
+    if (i >= w2.Size())
+      div.PushFront(iter.Value());
+  }
+  return div;
+}
+
+
+// Product of string weight and an arbitray weight.
+template <class L, class W, StringType S = STRING_LEFT>
+struct GallicWeight : public ProductWeight<StringWeight<L, S>, W> {
+  typedef GallicWeight<L, typename W::ReverseWeight, REVERSE_STRING_TYPE(S)>
+  ReverseWeight;
+
+  GallicWeight() {}
+
+  GallicWeight(StringWeight<L, S> w1, W w2)
+      : ProductWeight<StringWeight<L, S>, W>(w1, w2) {}
+
+  explicit GallicWeight(const string &s, int *nread = 0)
+      : ProductWeight<StringWeight<L, S>, W>(s, nread) {}
+
+  GallicWeight(const ProductWeight<StringWeight<L, S>, W> &w)
+      : ProductWeight<StringWeight<L, S>, W>(w) {}
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_STRING_WEIGHT_H__
diff --git a/src/include/fst/string.h b/src/include/fst/string.h
new file mode 100644
index 0000000..3099b87
--- /dev/null
+++ b/src/include/fst/string.h
@@ -0,0 +1,247 @@
+
+// string.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Utilities to convert strings into FSTs.
+//
+
+#ifndef FST_LIB_STRING_H_
+#define FST_LIB_STRING_H_
+
+#include <fst/compact-fst.h>
+#include <fst/mutable-fst.h>
+
+DECLARE_string(fst_field_separator);
+
+namespace fst {
+
+// Functor compiling a string in an FST
+template <class A>
+class StringCompiler {
+ public:
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+
+  enum TokenType { SYMBOL = 1, BYTE = 2, UTF8 = 3 };
+
+  StringCompiler(TokenType type, const SymbolTable *syms = 0,
+                 Label unknown_label = kNoLabel,
+                 bool allow_negative = false)
+      : token_type_(type), syms_(syms), unknown_label_(unknown_label),
+        allow_negative_(allow_negative) {}
+
+  // Compile string 's' into FST 'fst'.
+  template <class F>
+  bool operator()(const string &s, F *fst) {
+    vector<Label> labels;
+    if (!ConvertStringToLabels(s, &labels))
+      return false;
+    Compile(labels, fst);
+    return true;
+  }
+
+ private:
+  bool ConvertStringToLabels(const string &str, vector<Label> *labels) const {
+    labels->clear();
+    if (token_type_ == BYTE) {
+      for (size_t i = 0; i < str.size(); ++i)
+        labels->push_back(static_cast<unsigned char>(str[i]));
+    } else if (token_type_ == UTF8) {
+      return UTF8StringToLabels(str, labels);
+    } else {
+      char *c_str = new char[str.size() + 1];
+      str.copy(c_str, str.size());
+      c_str[str.size()] = 0;
+      vector<char *> vec;
+      string separator = "\n" + FLAGS_fst_field_separator;
+      SplitToVector(c_str, separator.c_str(), &vec, true);
+      for (size_t i = 0; i < vec.size(); ++i) {
+        Label label;
+        if (!ConvertSymbolToLabel(vec[i], &label))
+          return false;
+        labels->push_back(label);
+      }
+      delete[] c_str;
+    }
+    return true;
+  }
+
+  void Compile(const vector<Label> &labels, MutableFst<A> *fst) const {
+    fst->DeleteStates();
+    while (fst->NumStates() <= labels.size())
+      fst->AddState();
+    for (size_t i = 0; i < labels.size(); ++i)
+      fst->AddArc(i, Arc(labels[i], labels[i], Weight::One(), i + 1));
+    fst->SetStart(0);
+    fst->SetFinal(labels.size(), Weight::One());
+  }
+
+  template <class Unsigned>
+  void Compile(const vector<Label> &labels, CompactFst<A, StringCompactor<A>,
+               Unsigned> *fst) const {
+    fst->SetCompactElements(labels.begin(), labels.end());
+  }
+
+  bool ConvertSymbolToLabel(const char *s, Label* output) const {
+    int64 n;
+    if (syms_) {
+      n = syms_->Find(s);
+      if ((n == -1) && (unknown_label_ != kNoLabel))
+        n = unknown_label_;
+      if (n == -1 || (!allow_negative_ && n < 0)) {
+        VLOG(1) << "StringCompiler::ConvertSymbolToLabel: Symbol \"" << s
+                << "\" is not mapped to any integer label, symbol table = "
+                 << syms_->Name();
+        return false;
+      }
+    } else {
+      char *p;
+      n = strtoll(s, &p, 10);
+      if (p < s + strlen(s) || (!allow_negative_ && n < 0)) {
+        VLOG(1) << "StringCompiler::ConvertSymbolToLabel: Bad label integer "
+                << "= \"" << s << "\"";
+        return false;
+      }
+    }
+    *output = n;
+    return true;
+  }
+
+  TokenType token_type_;     // Token type: symbol, byte or utf8 encoded
+  const SymbolTable *syms_;  // Symbol table used when token type is symbol
+  Label unknown_label_;      // Label for token missing from symbol table
+  bool allow_negative_;      // Negative labels allowed?
+
+  DISALLOW_COPY_AND_ASSIGN(StringCompiler);
+};
+
+// Functor to print a string FST as a string.
+template <class A>
+class StringPrinter {
+ public:
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  enum TokenType { SYMBOL = 1, BYTE = 2, UTF8 = 3 };
+
+  StringPrinter(TokenType token_type,
+                const SymbolTable *syms = 0)
+      : token_type_(token_type), syms_(syms) {}
+
+  // Convert the FST 'fst' into the string 'output'
+  bool operator()(const Fst<A> &fst, string *output) {
+    bool is_a_string = FstToLabels(fst);
+    if (!is_a_string) {
+      VLOG(1) << "StringPrinter::operator(): Fst is not a string.";
+      return false;
+    }
+
+    output->clear();
+
+    if (token_type_ == SYMBOL) {
+      stringstream sstrm;
+      for (size_t i = 0; i < labels_.size(); ++i) {
+        if (i)
+          sstrm << *(FLAGS_fst_field_separator.rbegin());
+        if (!PrintLabel(labels_[i], sstrm))
+          return false;
+      }
+      *output = sstrm.str();
+    } else if (token_type_ == BYTE) {
+      for (size_t i = 0; i < labels_.size(); ++i) {
+        output->push_back(labels_[i]);
+      }
+    } else if (token_type_ == UTF8) {
+      return LabelsToUTF8String(labels_, output);
+    } else {
+      VLOG(1) << "StringPrinter::operator(): Unknown token type: "
+              << token_type_;
+      return false;
+    }
+    return true;
+  }
+
+ private:
+  bool FstToLabels(const Fst<A> &fst) {
+    labels_.clear();
+
+    StateId s = fst.Start();
+    if (s == kNoStateId) {
+      VLOG(2) << "StringPrinter::FstToLabels: Invalid starting state for "
+              << "string fst.";
+      return false;
+    }
+
+    while (fst.Final(s) == Weight::Zero()) {
+      ArcIterator<Fst<A> > aiter(fst, s);
+      if (aiter.Done()) {
+        VLOG(2) << "StringPrinter::FstToLabels: String fst traversal does "
+                << "not reach final state.";
+        return false;
+      }
+
+      const A& arc = aiter.Value();
+      labels_.push_back(arc.olabel);
+
+      s = arc.nextstate;
+      if (s == kNoStateId) {
+        VLOG(2) << "StringPrinter::FstToLabels: Transition to invalid "
+                << "state.";
+        return false;
+      }
+
+      aiter.Next();
+      if (!aiter.Done()) {
+        VLOG(2) << "StringPrinter::FstToLabels: State with multiple "
+                << "outgoing arcs found.";
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  bool PrintLabel(Label lab, ostream& ostrm) {
+    if (syms_) {
+      string symbol = syms_->Find(lab);
+      if (symbol == "") {
+        VLOG(2) << "StringPrinter::PrintLabel: Integer " << lab << " is not "
+                << "mapped to any textual symbol, symbol table = "
+                 << syms_->Name();
+        return false;
+      }
+      ostrm << symbol;
+    } else {
+      ostrm << lab;
+    }
+    return true;
+  }
+
+  TokenType token_type_;     // Token type: symbol, byte or utf8 encoded
+  const SymbolTable *syms_;  // Symbol table used when token type is symbol
+  vector<Label> labels_;     // Input FST labels.
+
+  DISALLOW_COPY_AND_ASSIGN(StringPrinter);
+};
+
+}  // namespace fst
+
+#endif // FST_LIB_STRING_H_
diff --git a/src/include/fst/symbol-table-ops.h b/src/include/fst/symbol-table-ops.h
new file mode 100644
index 0000000..e46c4c2
--- /dev/null
+++ b/src/include/fst/symbol-table-ops.h
@@ -0,0 +1,91 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: sorenj@google.com (Jeffrey Sorensen)
+
+#ifndef FST_LIB_SYMBOL_TABLE_OPS_H_
+#define FST_LIB_SYMBOL_TABLE_OPS_H_
+
+#include <vector>
+using std::vector;
+#include <string>
+#include <unordered_set>
+using std::tr1::unordered_set;
+using std::tr1::unordered_multiset;
+
+
+#include <fst/fst.h>
+#include <fst/symbol-table.h>
+
+
+namespace fst {
+
+// Returns a minimal symbol table containing only symbols referenced by the
+// passed fst.  Symbols preserve their original numbering, so fst does not
+// require relabeling.
+template<class Arc>
+SymbolTable *PruneSymbolTable(const Fst<Arc> &fst, const SymbolTable &syms,
+                              bool input) {
+  unordered_set<typename Arc::Label> seen;
+  seen.insert(0);  // Always keep epslion
+  StateIterator<Fst<Arc> > siter(fst);
+  for (; !siter.Done(); siter.Next()) {
+    ArcIterator<Fst<Arc> > aiter(fst, siter.Value());
+    for (; !aiter.Done(); aiter.Next()) {
+      typename Arc::Label sym = (input) ? aiter.Value().ilabel :
+                                          aiter.Value().olabel;
+      seen.insert(sym);
+    }
+  }
+  SymbolTable *pruned = new SymbolTable(syms.Name() + "_pruned");
+  for (SymbolTableIterator stiter(syms); !stiter.Done(); stiter.Next()) {
+    typename Arc::Label label = stiter.Value();
+    if (seen.find(label) != seen.end()) {
+      pruned->AddSymbol(stiter.Symbol(), stiter.Value());
+    }
+  }
+  return pruned;
+}
+
+// Relabels a symbol table to make it a contiguous mapping.
+SymbolTable *CompactSymbolTable(const SymbolTable &syms);
+
+// Merges two SymbolTables, all symbols from left will be merged into right
+// with the same ids.  Symbols in right that have conflicting ids with those
+// in left will be assigned to value assigned from the left SymbolTable.
+// The returned symbol table will never modify symbol assignments from the left
+// side, but may do so on the right.  If right_relabel_output is non-NULL, it
+// will be assigned true if the symbols from the right table needed to be
+// reassigned.
+// A potential use case is to Compose two Fst's that have different symbol
+// tables.  You can reconcile them in the following way:
+//   Fst<Arc> a, b;
+//   bool relabel;
+//   SymbolTable *bnew = MergeSymbolTable(a.OutputSymbols(),
+//                                        b.InputSymbols(), &relabel);
+//   if (relabel) {
+//     Relabel(b, bnew, NULL);
+//   }
+//   b.SetInputSymbols(bnew);
+//   delete bnew;
+SymbolTable *MergeSymbolTable(const SymbolTable &left, const SymbolTable &right,
+                              bool *right_relabel_output = 0);
+
+// Read the symbol table from any Fst::Read()able file, without loading the
+// corresponding Fst.  Returns NULL if the Fst does not contain a symbol table
+// or the symbol table cannot be read.
+SymbolTable *FstReadSymbols(const string &filename, bool input);
+
+}  // namespace fst
+#endif  // FST_LIB_SYMBOL_TABLE_OPS_H_
diff --git a/src/include/fst/symbol-table.h b/src/include/fst/symbol-table.h
new file mode 100644
index 0000000..93ebe76
--- /dev/null
+++ b/src/include/fst/symbol-table.h
@@ -0,0 +1,507 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// All Rights Reserved.
+//
+// Author : Johan Schalkwyk
+//
+// \file
+// Classes to provide symbol-to-integer and integer-to-symbol mappings.
+
+#ifndef FST_LIB_SYMBOL_TABLE_H__
+#define FST_LIB_SYMBOL_TABLE_H__
+
+#include <cstring>
+#include <string>
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+
+#include <fst/compat.h>
+#include <iostream>
+#include <fstream>
+
+
+#include <map>
+
+DECLARE_bool(fst_compat_symbols);
+
+namespace fst {
+
+// WARNING: Reading via symbol table read options should
+//          not be used. This is a temporary work around for
+//          reading symbol ranges of previously stored symbol sets.
+struct SymbolTableReadOptions {
+  SymbolTableReadOptions() { }
+
+  SymbolTableReadOptions(vector<pair<int64, int64> > string_hash_ranges_,
+                         const string& source_)
+      : string_hash_ranges(string_hash_ranges_),
+        source(source_) { }
+
+  vector<pair<int64, int64> > string_hash_ranges;
+  string source;
+};
+
+class SymbolTableImpl {
+ public:
+  SymbolTableImpl(const string &name)
+      : name_(name),
+        available_key_(0),
+        dense_key_limit_(0),
+        check_sum_finalized_(false) {}
+
+  explicit SymbolTableImpl(const SymbolTableImpl& impl)
+      : name_(impl.name_),
+        available_key_(0),
+        dense_key_limit_(0),
+        check_sum_finalized_(false) {
+    for (size_t i = 0; i < impl.symbols_.size(); ++i) {
+      AddSymbol(impl.symbols_[i], impl.Find(impl.symbols_[i]));
+    }
+  }
+
+  ~SymbolTableImpl() {
+    for (size_t i = 0; i < symbols_.size(); ++i)
+      delete[] symbols_[i];
+  }
+
+  // TODO(johans): Add flag to specify whether the symbol
+  //               should be indexed as string or int or both.
+  int64 AddSymbol(const string& symbol, int64 key);
+
+  int64 AddSymbol(const string& symbol) {
+    int64 key = Find(symbol);
+    return (key == -1) ? AddSymbol(symbol, available_key_++) : key;
+  }
+
+  static SymbolTableImpl* ReadText(istream &strm,
+                                   const string &name,
+                                   bool allow_negative = false);
+
+  static SymbolTableImpl* Read(istream &strm,
+                               const SymbolTableReadOptions& opts);
+
+  bool Write(ostream &strm) const;
+
+  //
+  // Return the string associated with the key. If the key is out of
+  // range (<0, >max), return an empty string.
+  string Find(int64 key) const {
+    if (key >=0 && key < dense_key_limit_)
+      return string(symbols_[key]);
+
+    map<int64, const char*>::const_iterator it =
+        key_map_.find(key);
+    if (it == key_map_.end()) {
+      return "";
+    }
+    return string(it->second);
+  }
+
+  //
+  // Return the key associated with the symbol. If the symbol
+  // does not exists, return SymbolTable::kNoSymbol.
+  int64 Find(const string& symbol) const {
+    return Find(symbol.c_str());
+  }
+
+  //
+  // Return the key associated with the symbol. If the symbol
+  // does not exists, return SymbolTable::kNoSymbol.
+  int64 Find(const char* symbol) const {
+    map<const char *, int64, StrCmp>::const_iterator it =
+        symbol_map_.find(symbol);
+    if (it == symbol_map_.end()) {
+      return -1;
+    }
+    return it->second;
+  }
+
+  int64 GetNthKey(ssize_t pos) const {
+    if ((pos < 0) || (pos >= symbols_.size())) return -1;
+    else return Find(symbols_[pos]);
+  }
+
+  const string& Name() const { return name_; }
+
+  int IncrRefCount() const {
+    return ref_count_.Incr();
+  }
+  int DecrRefCount() const {
+    return ref_count_.Decr();
+  }
+  int RefCount() const {
+    return ref_count_.count();
+  }
+
+  string CheckSum() const {
+    MutexLock check_sum_lock(&check_sum_mutex_);
+    MaybeRecomputeCheckSum();
+    return check_sum_string_;
+  }
+
+  string LabeledCheckSum() const {
+    MutexLock check_sum_lock(&check_sum_mutex_);
+    MaybeRecomputeCheckSum();
+    return labeled_check_sum_string_;
+  }
+
+  int64 AvailableKey() const {
+    return available_key_;
+  }
+
+  size_t NumSymbols() const {
+    return symbols_.size();
+  }
+
+ private:
+  // Recomputes the checksums (both of them) if we've had changes since the last
+  // computation (i.e., if check_sum_finalized_ is false).
+  void MaybeRecomputeCheckSum() const;
+
+  struct StrCmp {
+    bool operator()(const char *s1, const char *s2) const {
+      return strcmp(s1, s2) < 0;
+    }
+  };
+
+  string name_;
+  int64 available_key_;
+  int64 dense_key_limit_;
+  vector<const char *> symbols_;
+  map<int64, const char*> key_map_;
+  map<const char *, int64, StrCmp> symbol_map_;
+
+  mutable RefCounter ref_count_;
+  mutable bool check_sum_finalized_;
+  mutable CheckSummer check_sum_;
+  mutable CheckSummer labeled_check_sum_;
+  mutable string check_sum_string_;
+  mutable string labeled_check_sum_string_;
+  mutable Mutex check_sum_mutex_;
+};
+
+//
+// \class SymbolTable
+// \brief Symbol (string) to int and reverse mapping
+//
+// The SymbolTable implements the mappings of labels to strings and reverse.
+// SymbolTables are used to describe the alphabet of the input and output
+// labels for arcs in a Finite State Transducer.
+//
+// SymbolTables are reference counted and can therefore be shared across
+// multiple machines. For example a language model grammar G, with a
+// SymbolTable for the words in the language model can share this symbol
+// table with the lexical representation L o G.
+//
+class SymbolTable {
+ public:
+  static const int64 kNoSymbol = -1;
+
+  // Construct symbol table with a unique name.
+  SymbolTable(const string& name) : impl_(new SymbolTableImpl(name)) {}
+
+  // Create a reference counted copy.
+  SymbolTable(const SymbolTable& table) : impl_(table.impl_) {
+    impl_->IncrRefCount();
+  }
+
+  // Derefence implentation object. When reference count hits 0, delete
+  // implementation.
+  virtual ~SymbolTable() {
+    if (!impl_->DecrRefCount()) delete impl_;
+  }
+
+  // Read an ascii representation of the symbol table from an istream. Pass a
+  // name to give the resulting SymbolTable.
+  static SymbolTable* ReadText(istream &strm,
+                               const string& name,
+                               bool allow_negative = false) {
+    SymbolTableImpl* impl = SymbolTableImpl::ReadText(strm,
+                                                      name,
+                                                      allow_negative);
+    if (!impl)
+      return 0;
+    else
+      return new SymbolTable(impl);
+  }
+
+  // read an ascii representation of the symbol table
+  static SymbolTable* ReadText(const string& filename,
+                               bool allow_negative = false) {
+    ifstream strm(filename.c_str(), ifstream::in);
+    if (!strm) {
+      LOG(ERROR) << "SymbolTable::ReadText: Can't open file " << filename;
+      return 0;
+    }
+    return ReadText(strm, filename, allow_negative);
+  }
+
+
+  // WARNING: Reading via symbol table read options should
+  //          not be used. This is a temporary work around.
+  static SymbolTable* Read(istream &strm,
+                           const SymbolTableReadOptions& opts) {
+    SymbolTableImpl* impl = SymbolTableImpl::Read(strm, opts);
+    if (!impl)
+      return 0;
+    else
+      return new SymbolTable(impl);
+  }
+
+  // read a binary dump of the symbol table from a stream
+  static SymbolTable* Read(istream &strm, const string& source) {
+    SymbolTableReadOptions opts;
+    opts.source = source;
+    return Read(strm, opts);
+  }
+
+  // read a binary dump of the symbol table
+  static SymbolTable* Read(const string& filename) {
+    ifstream strm(filename.c_str(), ifstream::in | ifstream::binary);
+    if (!strm) {
+      LOG(ERROR) << "SymbolTable::Read: Can't open file " << filename;
+      return 0;
+    }
+    return Read(strm, filename);
+  }
+
+  //--------------------------------------------------------
+  // Derivable Interface (final)
+  //--------------------------------------------------------
+  // create a reference counted copy
+  virtual SymbolTable* Copy() const {
+    return new SymbolTable(*this);
+  }
+
+  // Add a symbol with given key to table. A symbol table also
+  // keeps track of the last available key (highest key value in
+  // the symbol table).
+  virtual int64 AddSymbol(const string& symbol, int64 key) {
+    MutateCheck();
+    return impl_->AddSymbol(symbol, key);
+  }
+
+  // Add a symbol to the table. The associated value key is automatically
+  // assigned by the symbol table.
+  virtual int64 AddSymbol(const string& symbol) {
+    MutateCheck();
+    return impl_->AddSymbol(symbol);
+  }
+
+  // Add another symbol table to this table. All key values will be offset
+  // by the current available key (highest key value in the symbol table).
+  // Note string symbols with the same key value with still have the same
+  // key value after the symbol table has been merged, but a different
+  // value. Adding symbol tables do not result in changes in the base table.
+  virtual void AddTable(const SymbolTable& table);
+
+  // return the name of the symbol table
+  virtual const string& Name() const {
+    return impl_->Name();
+  }
+
+  // Return the label-agnostic MD5 check-sum for this table.  All new symbols
+  // added to the table will result in an updated checksum.
+  // DEPRECATED.
+  virtual string CheckSum() const {
+    return impl_->CheckSum();
+  }
+
+  // Same as CheckSum(), but this returns an label-dependent version.
+  virtual string LabeledCheckSum() const {
+    return impl_->LabeledCheckSum();
+  }
+
+  virtual bool Write(ostream &strm) const {
+    return impl_->Write(strm);
+  }
+
+  bool Write(const string& filename) const {
+    ofstream strm(filename.c_str(), ofstream::out | ofstream::binary);
+    if (!strm) {
+      LOG(ERROR) << "SymbolTable::Write: Can't open file " << filename;
+      return false;
+    }
+    return Write(strm);
+  }
+
+  // Dump an ascii text representation of the symbol table via a stream
+  virtual bool WriteText(ostream &strm) const;
+
+  // Dump an ascii text representation of the symbol table
+  bool WriteText(const string& filename) const {
+    ofstream strm(filename.c_str());
+    if (!strm) {
+      LOG(ERROR) << "SymbolTable::WriteText: Can't open file " << filename;
+      return false;
+    }
+    return WriteText(strm);
+  }
+
+  // Return the string associated with the key. If the key is out of
+  // range (<0, >max), log error and return an empty string.
+  virtual string Find(int64 key) const {
+    return impl_->Find(key);
+  }
+
+  // Return the key associated with the symbol. If the symbol
+  // does not exists, log error and  return SymbolTable::kNoSymbol
+  virtual int64 Find(const string& symbol) const {
+    return impl_->Find(symbol);
+  }
+
+  // Return the key associated with the symbol. If the symbol
+  // does not exists, log error and  return SymbolTable::kNoSymbol
+  virtual int64 Find(const char* symbol) const {
+    return impl_->Find(symbol);
+  }
+
+  // Return the current available key (i.e highest key number+1) in
+  // the symbol table
+  virtual int64 AvailableKey(void) const {
+    return impl_->AvailableKey();
+  }
+
+  // Return the current number of symbols in table (not necessarily
+  // equal to AvailableKey())
+  virtual size_t NumSymbols(void) const {
+    return impl_->NumSymbols();
+  }
+
+  virtual int64 GetNthKey(ssize_t pos) const {
+    return impl_->GetNthKey(pos);
+  }
+
+ private:
+  explicit SymbolTable(SymbolTableImpl* impl) : impl_(impl) {}
+
+  void MutateCheck() {
+    // Copy on write
+    if (impl_->RefCount() > 1) {
+      impl_->DecrRefCount();
+      impl_ = new SymbolTableImpl(*impl_);
+    }
+  }
+
+  const SymbolTableImpl* Impl() const {
+    return impl_;
+  }
+
+ private:
+  SymbolTableImpl* impl_;
+
+  void operator=(const SymbolTable &table);  // disallow
+};
+
+
+//
+// \class SymbolTableIterator
+// \brief Iterator class for symbols in a symbol table
+class SymbolTableIterator {
+ public:
+  SymbolTableIterator(const SymbolTable& table)
+      : table_(table),
+        pos_(0),
+        nsymbols_(table.NumSymbols()),
+        key_(table.GetNthKey(0)) { }
+
+  ~SymbolTableIterator() { }
+
+  // is iterator done
+  bool Done(void) {
+    return (pos_ == nsymbols_);
+  }
+
+  // return the Value() of the current symbol (int64 key)
+  int64 Value(void) {
+    return key_;
+  }
+
+  // return the string of the current symbol
+  string Symbol(void) {
+    return table_.Find(key_);
+  }
+
+  // advance iterator forward
+  void Next(void) {
+    ++pos_;
+    if (pos_ < nsymbols_) key_ = table_.GetNthKey(pos_);
+  }
+
+  // reset iterator
+  void Reset(void) {
+    pos_ = 0;
+    key_ = table_.GetNthKey(0);
+  }
+
+ private:
+  const SymbolTable& table_;
+  ssize_t pos_;
+  size_t nsymbols_;
+  int64 key_;
+};
+
+
+// Tests compatibilty between two sets of symbol tables
+inline bool CompatSymbols(const SymbolTable *syms1, const SymbolTable *syms2,
+                          bool warning = true) {
+  if (!FLAGS_fst_compat_symbols) {
+    return true;
+  } else if (!syms1 && !syms2) {
+    return true;
+  } else if (syms1 && !syms2) {
+    if (warning)
+      LOG(WARNING) <<
+          "CompatSymbols: first symbol table present but second missing";
+    return false;
+  } else if (!syms1 && syms2) {
+    if (warning)
+      LOG(WARNING) <<
+          "CompatSymbols: second symbol table present but first missing";
+    return false;
+  } else if (syms1->LabeledCheckSum() != syms2->LabeledCheckSum()) {
+    if (warning)
+      LOG(WARNING) << "CompatSymbols: Symbol table check sums do not match";
+    return false;
+  } else {
+    return true;
+  }
+}
+
+
+// Relabels a symbol table as specified by the input vector of pairs
+// (old label, new label). The new symbol table only retains symbols
+// for which a relabeling is *explicitely* specified.
+// TODO(allauzen): consider adding options to allow for some form
+// of implicit identity relabeling.
+template <class Label>
+SymbolTable *RelabelSymbolTable(const SymbolTable *table,
+                                const vector<pair<Label, Label> > &pairs) {
+  SymbolTable *new_table = new SymbolTable(
+      table->Name().empty() ? string() :
+      (string("relabeled_") + table->Name()));
+
+  for (size_t i = 0; i < pairs.size(); ++i)
+    new_table->AddSymbol(table->Find(pairs[i].first), pairs[i].second);
+
+  return new_table;
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_SYMBOL_TABLE_H__
diff --git a/src/include/fst/synchronize.h b/src/include/fst/synchronize.h
new file mode 100644
index 0000000..28d1262
--- /dev/null
+++ b/src/include/fst/synchronize.h
@@ -0,0 +1,457 @@
+// synchronize.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Synchronize an FST with bounded delay.
+
+#ifndef FST_LIB_SYNCHRONIZE_H__
+#define FST_LIB_SYNCHRONIZE_H__
+
+#include <algorithm>
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <unordered_set>
+using std::tr1::unordered_set;
+using std::tr1::unordered_multiset;
+#include <string>
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+#include <fst/test-properties.h>
+
+
+namespace fst {
+
+typedef CacheOptions SynchronizeFstOptions;
+
+
+// Implementation class for SynchronizeFst
+template <class A>
+class SynchronizeFstImpl
+    : public CacheImpl<A> {
+ public:
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+
+  using CacheBaseImpl< CacheState<A> >::PushArc;
+  using CacheBaseImpl< CacheState<A> >::HasArcs;
+  using CacheBaseImpl< CacheState<A> >::HasFinal;
+  using CacheBaseImpl< CacheState<A> >::HasStart;
+  using CacheBaseImpl< CacheState<A> >::SetArcs;
+  using CacheBaseImpl< CacheState<A> >::SetFinal;
+  using CacheBaseImpl< CacheState<A> >::SetStart;
+
+  typedef A Arc;
+  typedef typename A::Label Label;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  typedef basic_string<Label> String;
+
+  struct Element {
+    Element() {}
+
+    Element(StateId s, const String *i, const String *o)
+        : state(s), istring(i), ostring(o) {}
+
+    StateId state;     // Input state Id
+    const String *istring;     // Residual input labels
+    const String *ostring;     // Residual output labels
+    // Residual strings are represented by const pointers to
+    // basic_string<Label> and are stored in a hash_set. The pointed
+    // memory is owned by the hash_set string_set_.
+  };
+
+  SynchronizeFstImpl(const Fst<A> &fst, const SynchronizeFstOptions &opts)
+      : CacheImpl<A>(opts), fst_(fst.Copy()) {
+    SetType("synchronize");
+    uint64 props = fst.Properties(kFstProperties, false);
+    SetProperties(SynchronizeProperties(props), kCopyProperties);
+
+    SetInputSymbols(fst.InputSymbols());
+    SetOutputSymbols(fst.OutputSymbols());
+  }
+
+  SynchronizeFstImpl(const SynchronizeFstImpl &impl)
+      : CacheImpl<A>(impl),
+        fst_(impl.fst_->Copy(true)) {
+    SetType("synchronize");
+    SetProperties(impl.Properties(), kCopyProperties);
+    SetInputSymbols(impl.InputSymbols());
+    SetOutputSymbols(impl.OutputSymbols());
+  }
+
+  ~SynchronizeFstImpl() {
+    delete fst_;
+    // Extract pointers from the hash set
+    vector<const String*> strings;
+    typename StringSet::iterator it = string_set_.begin();
+    for (; it != string_set_.end(); ++it)
+      strings.push_back(*it);
+    // Free the extracted pointers
+    for (size_t i = 0; i < strings.size(); ++i)
+      delete strings[i];
+  }
+
+  StateId Start() {
+    if (!HasStart()) {
+      StateId s = fst_->Start();
+      if (s == kNoStateId)
+        return kNoStateId;
+      const String *empty = FindString(new String());
+      StateId start = FindState(Element(fst_->Start(), empty, empty));
+      SetStart(start);
+    }
+    return CacheImpl<A>::Start();
+  }
+
+  Weight Final(StateId s) {
+    if (!HasFinal(s)) {
+      const Element &e = elements_[s];
+      Weight w = e.state == kNoStateId ? Weight::One() : fst_->Final(e.state);
+      if ((w != Weight::Zero()) && (e.istring)->empty() && (e.ostring)->empty())
+        SetFinal(s, w);
+      else
+        SetFinal(s, Weight::Zero());
+    }
+    return CacheImpl<A>::Final(s);
+  }
+
+  size_t NumArcs(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumArcs(s);
+  }
+
+  size_t NumInputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumInputEpsilons(s);
+  }
+
+  size_t NumOutputEpsilons(StateId s) {
+    if (!HasArcs(s))
+      Expand(s);
+    return CacheImpl<A>::NumOutputEpsilons(s);
+  }
+
+  uint64 Properties() const { return Properties(kFstProperties); }
+
+  // Set error if found; return FST impl properties.
+  uint64 Properties(uint64 mask) const {
+    if ((mask & kError) && fst_->Properties(kError, false))
+      SetProperties(kError, kError);
+    return FstImpl<Arc>::Properties(mask);
+  }
+
+  void InitArcIterator(StateId s, ArcIteratorData<A> *data) {
+    if (!HasArcs(s))
+      Expand(s);
+    CacheImpl<A>::InitArcIterator(s, data);
+  }
+
+  // Returns the first character of the string obtained by
+  // concatenating s and l.
+  Label Car(const String *s, Label l = 0) const {
+    if (!s->empty())
+      return (*s)[0];
+    else
+      return l;
+  }
+
+  // Computes the residual string obtained by removing the first
+  // character in the concatenation of s and l.
+  const String *Cdr(const String *s, Label l = 0) {
+    String *r = new String();
+    for (int i = 1; i < s->size(); ++i)
+      r->push_back((*s)[i]);
+    if (l && !(s->empty())) r->push_back(l);
+    return FindString(r);
+  }
+
+  // Computes the concatenation of s and l.
+  const String *Concat(const String *s, Label l = 0) {
+    String *r = new String();
+    for (int i = 0; i < s->size(); ++i)
+      r->push_back((*s)[i]);
+    if (l) r->push_back(l);
+    return FindString(r);
+  }
+
+  // Tests if the concatenation of s and l is empty
+  bool Empty(const String *s, Label l = 0) const {
+    if (s->empty())
+      return l == 0;
+    else
+      return false;
+  }
+
+  // Finds the string pointed by s in the hash set. Transfers the
+  // pointer ownership to the hash set.
+  const String *FindString(const String *s) {
+    typename StringSet::iterator it = string_set_.find(s);
+    if (it != string_set_.end()) {
+      delete s;
+      return (*it);
+    } else {
+      string_set_.insert(s);
+      return s;
+    }
+  }
+
+  // Finds state corresponding to an element. Creates new state
+  // if element not found.
+  StateId FindState(const Element &e) {
+    typename ElementMap::iterator eit = element_map_.find(e);
+    if (eit != element_map_.end()) {
+      return (*eit).second;
+    } else {
+      StateId s = elements_.size();
+      elements_.push_back(e);
+      element_map_.insert(pair<const Element, StateId>(e, s));
+      return s;
+    }
+  }
+
+
+  // Computes the outgoing transitions from a state, creating new destination
+  // states as needed.
+  void Expand(StateId s) {
+    Element e = elements_[s];
+
+    if (e.state != kNoStateId)
+      for (ArcIterator< Fst<A> > ait(*fst_, e.state);
+           !ait.Done();
+           ait.Next()) {
+        const A &arc = ait.Value();
+        if (!Empty(e.istring, arc.ilabel)  && !Empty(e.ostring, arc.olabel)) {
+          const String *istring = Cdr(e.istring, arc.ilabel);
+          const String *ostring = Cdr(e.ostring, arc.olabel);
+          StateId d = FindState(Element(arc.nextstate, istring, ostring));
+          PushArc(s, Arc(Car(e.istring, arc.ilabel),
+                        Car(e.ostring, arc.olabel), arc.weight, d));
+        } else {
+          const String *istring = Concat(e.istring, arc.ilabel);
+          const String *ostring = Concat(e.ostring, arc.olabel);
+          StateId d = FindState(Element(arc.nextstate, istring, ostring));
+          PushArc(s, Arc(0 , 0, arc.weight, d));
+        }
+      }
+
+    Weight w = e.state == kNoStateId ? Weight::One() : fst_->Final(e.state);
+    if ((w != Weight::Zero()) &&
+        ((e.istring)->size() + (e.ostring)->size() > 0)) {
+      const String *istring = Cdr(e.istring);
+      const String *ostring = Cdr(e.ostring);
+      StateId d = FindState(Element(kNoStateId, istring, ostring));
+      PushArc(s, Arc(Car(e.istring), Car(e.ostring), w, d));
+    }
+    SetArcs(s);
+  }
+
+ private:
+  // Equality function for Elements, assume strings have been hashed.
+  class ElementEqual {
+   public:
+    bool operator()(const Element &x, const Element &y) const {
+      return x.state == y.state &&
+              x.istring == y.istring &&
+              x.ostring == y.ostring;
+    }
+  };
+
+  // Hash function for Elements to Fst states.
+  class ElementKey {
+   public:
+    size_t operator()(const Element &x) const {
+      size_t key = x.state;
+      key = (key << 1) ^ (x.istring)->size();
+      for (size_t i = 0; i < (x.istring)->size(); ++i)
+        key = (key << 1) ^ (*x.istring)[i];
+      key = (key << 1) ^ (x.ostring)->size();
+      for (size_t i = 0; i < (x.ostring)->size(); ++i)
+        key = (key << 1) ^ (*x.ostring)[i];
+      return key;
+    }
+  };
+
+  // Equality function for strings
+  class StringEqual {
+   public:
+    bool operator()(const String * const &x, const String * const &y) const {
+      if (x->size() != y->size()) return false;
+      for (size_t i = 0; i < x->size(); ++i)
+        if ((*x)[i] != (*y)[i]) return false;
+      return true;
+    }
+  };
+
+  // Hash function for set of strings
+  class StringKey{
+   public:
+    size_t operator()(const String * const & x) const {
+      size_t key = x->size();
+      for (size_t i = 0; i < x->size(); ++i)
+        key = (key << 1) ^ (*x)[i];
+      return key;
+    }
+  };
+
+
+  typedef unordered_map<Element, StateId, ElementKey, ElementEqual> ElementMap;
+  typedef unordered_set<const String*, StringKey, StringEqual> StringSet;
+
+  const Fst<A> *fst_;
+  vector<Element> elements_;  // mapping Fst state to Elements
+  ElementMap element_map_;    // mapping Elements to Fst state
+  StringSet string_set_;
+
+  void operator=(const SynchronizeFstImpl<A> &);  // disallow
+};
+
+
+// Synchronizes a transducer. This version is a delayed Fst.  The
+// result will be an equivalent FST that has the property that during
+// the traversal of a path, the delay is either zero or strictly
+// increasing, where the delay is the difference between the number of
+// non-epsilon output labels and input labels along the path.
+//
+// For the algorithm to terminate, the input transducer must have
+// bounded delay, i.e., the delay of every cycle must be zero.
+//
+// Complexity:
+// - A has bounded delay: exponential
+// - A does not have bounded delay: does not terminate
+//
+// References:
+// - Mehryar Mohri. Edit-Distance of Weighted Automata: General
+//   Definitions and Algorithms, International Journal of Computer
+//   Science, 14(6): 957-982 (2003).
+//
+// This class attaches interface to implementation and handles
+// reference counting, delegating most methods to ImplToFst.
+template <class A>
+class SynchronizeFst : public ImplToFst< SynchronizeFstImpl<A> > {
+ public:
+  friend class ArcIterator< SynchronizeFst<A> >;
+  friend class StateIterator< SynchronizeFst<A> >;
+
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+  typedef CacheState<A> State;
+  typedef SynchronizeFstImpl<A> Impl;
+
+  SynchronizeFst(const Fst<A> &fst)
+      : ImplToFst<Impl>(new Impl(fst, SynchronizeFstOptions())) {}
+
+  SynchronizeFst(const Fst<A> &fst,  const SynchronizeFstOptions &opts)
+      : ImplToFst<Impl>(new Impl(fst, opts)) {}
+
+  // See Fst<>::Copy() for doc.
+  SynchronizeFst(const SynchronizeFst<A> &fst, bool safe = false)
+      : ImplToFst<Impl>(fst, safe) {}
+
+  // Get a copy of this SynchronizeFst. See Fst<>::Copy() for further doc.
+  virtual SynchronizeFst<A> *Copy(bool safe = false) const {
+    return new SynchronizeFst<A>(*this, safe);
+  }
+
+  virtual inline void InitStateIterator(StateIteratorData<A> *data) const;
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<A> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+ private:
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
+
+  void operator=(const SynchronizeFst<A> &fst);  // Disallow
+};
+
+
+// Specialization for SynchronizeFst.
+template<class A>
+class StateIterator< SynchronizeFst<A> >
+    : public CacheStateIterator< SynchronizeFst<A> > {
+ public:
+  explicit StateIterator(const SynchronizeFst<A> &fst)
+      : CacheStateIterator< SynchronizeFst<A> >(fst, fst.GetImpl()) {}
+};
+
+
+// Specialization for SynchronizeFst.
+template <class A>
+class ArcIterator< SynchronizeFst<A> >
+    : public CacheArcIterator< SynchronizeFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const SynchronizeFst<A> &fst, StateId s)
+      : CacheArcIterator< SynchronizeFst<A> >(fst.GetImpl(), s) {
+    if (!fst.GetImpl()->HasArcs(s))
+      fst.GetImpl()->Expand(s);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+
+template <class A> inline
+void SynchronizeFst<A>::InitStateIterator(StateIteratorData<A> *data) const
+{
+  data->base = new StateIterator< SynchronizeFst<A> >(*this);
+}
+
+
+
+// Synchronizes a transducer. This version writes the synchronized
+// result to a MutableFst.  The result will be an equivalent FST that
+// has the property that during the traversal of a path, the delay is
+// either zero or strictly increasing, where the delay is the
+// difference between the number of non-epsilon output labels and
+// input labels along the path.
+//
+// For the algorithm to terminate, the input transducer must have
+// bounded delay, i.e., the delay of every cycle must be zero.
+//
+// Complexity:
+// - A has bounded delay: exponential
+// - A does not have bounded delay: does not terminate
+//
+// References:
+// - Mehryar Mohri. Edit-Distance of Weighted Automata: General
+//   Definitions and Algorithms, International Journal of Computer
+//   Science, 14(6): 957-982 (2003).
+template<class Arc>
+void Synchronize(const Fst<Arc> &ifst, MutableFst<Arc> *ofst) {
+  SynchronizeFstOptions opts;
+  opts.gc_limit = 0;  // Cache only the last state for fastest copy.
+  *ofst = SynchronizeFst<Arc>(ifst, opts);
+}
+
+}  // namespace fst
+
+#endif // FST_LIB_SYNCHRONIZE_H__
diff --git a/src/include/fst/test-properties.h b/src/include/fst/test-properties.h
new file mode 100644
index 0000000..db1ddcc
--- /dev/null
+++ b/src/include/fst/test-properties.h
@@ -0,0 +1,246 @@
+// test-properties.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Functions to manipulate and test property bits
+
+#ifndef FST_LIB_TEST_PROPERTIES_H__
+#define FST_LIB_TEST_PROPERTIES_H__
+
+#include <unordered_set>
+using std::tr1::unordered_set;
+using std::tr1::unordered_multiset;
+
+#include <fst/dfs-visit.h>
+#include <fst/connect.h>
+
+
+DECLARE_bool(fst_verify_properties);
+
+namespace fst {
+
+// For a binary property, the bit is always returned set.
+// For a trinary (i.e. two-bit) property, both bits are
+// returned set iff either corresponding input bit is set.
+inline uint64 KnownProperties(uint64 props) {
+  return kBinaryProperties | (props & kTrinaryProperties) |
+    ((props & kPosTrinaryProperties) << 1) |
+    ((props & kNegTrinaryProperties) >> 1);
+}
+
+// Tests compatibility between two sets of properties
+inline bool CompatProperties(uint64 props1, uint64 props2) {
+  uint64 known_props1 = KnownProperties(props1);
+  uint64 known_props2 = KnownProperties(props2);
+  uint64 known_props = known_props1 & known_props2;
+  uint64 incompat_props = (props1 & known_props) ^ (props2 & known_props);
+  if (incompat_props) {
+    uint64 prop = 1;
+    for (int i = 0; i < 64; ++i, prop <<= 1)
+      if (prop & incompat_props)
+        LOG(ERROR) << "CompatProperties: mismatch: " << PropertyNames[i]
+                   << ": props1 = " << (props1 & prop ? "true" : "false")
+                   << ", props2 = " << (props2 & prop ? "true" : "false");
+    return false;
+  } else {
+    return true;
+  }
+}
+
+// Computes FST property values defined in properties.h.  The value of
+// each property indicated in the mask will be determined and returned
+// (these will never be unknown here). In the course of determining
+// the properties specifically requested in the mask, certain other
+// properties may be determined (those with little additional expense)
+// and their values will be returned as well. The complete set of
+// known properties (whether true or false) determined by this
+// operation will be assigned to the the value pointed to by KNOWN.
+// If 'use_stored' is true, pre-computed FST properties may be used
+// when possible. This routine is seldom called directly; instead it
+// is used to implement fst.Properties(mask, true).
+template<class Arc>
+uint64 ComputeProperties(const Fst<Arc> &fst, uint64 mask, uint64 *known,
+                         bool use_stored) {
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  uint64 fst_props = fst.Properties(kFstProperties, false);  // Fst-stored
+
+  // Check stored FST properties first if allowed.
+  if (use_stored) {
+    uint64 known_props = KnownProperties(fst_props);
+    // If FST contains required info, return it.
+    if ((known_props & mask) == mask) {
+      *known = known_props;
+      return fst_props;
+    }
+  }
+
+  // Compute (trinary) properties explicitly.
+
+  // Initialize with binary properties (already known).
+  uint64 comp_props = fst_props & kBinaryProperties;
+
+  // Compute these trinary properties with a DFS. We compute only those
+  // that need a DFS here, since we otherwise would like to avoid a DFS
+  // since its stack could grow large.
+  uint64 dfs_props = kCyclic | kAcyclic | kInitialCyclic | kInitialAcyclic |
+                     kAccessible | kNotAccessible |
+                     kCoAccessible | kNotCoAccessible;
+  if (mask & dfs_props) {
+    SccVisitor<Arc> scc_visitor(&comp_props);
+    DfsVisit(fst, &scc_visitor);
+  }
+
+  // Compute any remaining trinary properties via a state and arcs iterations
+  if (mask & ~(kBinaryProperties | dfs_props)) {
+    comp_props |= kAcceptor | kNoEpsilons | kNoIEpsilons | kNoOEpsilons |
+        kILabelSorted | kOLabelSorted | kUnweighted | kTopSorted | kString;
+    if (mask & (kIDeterministic | kNonIDeterministic))
+      comp_props |= kIDeterministic;
+    if (mask & (kODeterministic | kNonODeterministic))
+      comp_props |= kODeterministic;
+
+    unordered_set<Label> *ilabels = 0;
+    unordered_set<Label> *olabels = 0;
+
+    StateId nfinal = 0;
+    for (StateIterator< Fst<Arc> > siter(fst);
+         !siter.Done();
+         siter.Next()) {
+      StateId s = siter.Value();
+
+      Arc prev_arc(kNoLabel, kNoLabel, Weight::One(), 0);
+      // Create these only if we need to
+      if (mask & (kIDeterministic | kNonIDeterministic))
+        ilabels = new unordered_set<Label>;
+      if (mask & (kODeterministic | kNonODeterministic))
+        olabels = new unordered_set<Label>;
+
+      for (ArcIterator< Fst<Arc> > aiter(fst, s);
+           !aiter.Done();
+           aiter.Next()) {
+        const Arc &arc =aiter.Value();
+
+        if (ilabels && ilabels->find(arc.ilabel) != ilabels->end()) {
+          comp_props |= kNonIDeterministic;
+          comp_props &= ~kIDeterministic;
+        }
+        if (olabels && olabels->find(arc.olabel) != olabels->end()) {
+          comp_props |= kNonODeterministic;
+          comp_props &= ~kODeterministic;
+        }
+        if (arc.ilabel != arc.olabel) {
+          comp_props |= kNotAcceptor;
+          comp_props &= ~kAcceptor;
+        }
+        if (arc.ilabel == 0 && arc.olabel == 0) {
+          comp_props |= kEpsilons;
+          comp_props &= ~kNoEpsilons;
+        }
+        if (arc.ilabel == 0) {
+          comp_props |= kIEpsilons;
+          comp_props &= ~kNoIEpsilons;
+        }
+        if (arc.olabel == 0) {
+          comp_props |= kOEpsilons;
+          comp_props &= ~kNoOEpsilons;
+        }
+        if (prev_arc.ilabel != kNoLabel && arc.ilabel < prev_arc.ilabel) {
+          comp_props |= kNotILabelSorted;
+          comp_props &= ~kILabelSorted;
+        }
+        if (prev_arc.olabel != kNoLabel && arc.olabel < prev_arc.olabel) {
+          comp_props |= kNotOLabelSorted;
+          comp_props &= ~kOLabelSorted;
+        }
+        if (arc.weight != Weight::One() && arc.weight != Weight::Zero()) {
+          comp_props |= kWeighted;
+          comp_props &= ~kUnweighted;
+        }
+        if (arc.nextstate <= s) {
+          comp_props |= kNotTopSorted;
+          comp_props &= ~kTopSorted;
+        }
+        if (arc.nextstate != s + 1) {
+          comp_props |= kNotString;
+          comp_props &= ~kString;
+        }
+        prev_arc = arc;
+        if (ilabels)
+          ilabels->insert(arc.ilabel);
+        if (olabels)
+          olabels->insert(arc.olabel);
+      }
+
+      if (nfinal > 0) {             // final state not last
+        comp_props |= kNotString;
+        comp_props &= ~kString;
+      }
+
+      Weight final = fst.Final(s);
+
+      if (final != Weight::Zero()) {  // final state
+        if (final != Weight::One()) {
+          comp_props |= kWeighted;
+          comp_props &= ~kUnweighted;
+        }
+        ++nfinal;
+      } else {                        // non-final state
+        if (fst.NumArcs(s) != 1) {
+          comp_props |= kNotString;
+          comp_props &= ~kString;
+        }
+      }
+
+      delete ilabels;
+      delete olabels;
+    }
+
+    if (fst.Start() != kNoStateId && fst.Start() != 0) {
+      comp_props |= kNotString;
+      comp_props &= ~kString;
+    }
+  }
+
+  *known = KnownProperties(comp_props);
+  return comp_props;
+}
+
+// This is a wrapper around ComputeProperties that will cause a fatal
+// error if the stored properties and the computed properties are
+// incompatible when 'FLAGS_fst_verify_properties' is true.  This
+// routine is seldom called directly; instead it is used to implement
+// fst.Properties(mask, true).
+template<class Arc>
+uint64 TestProperties(const Fst<Arc> &fst, uint64 mask, uint64 *known) {
+  if (FLAGS_fst_verify_properties) {
+    uint64 stored_props = fst.Properties(kFstProperties, false);
+    uint64 computed_props = ComputeProperties(fst, mask, known, false);
+    if (!CompatProperties(stored_props, computed_props))
+      LOG(FATAL) << "TestProperties: stored Fst properties incorrect"
+                 << " (stored: props1, computed: props2)";
+    return computed_props;
+  } else {
+    return ComputeProperties(fst, mask, known, true);
+  }
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_TEST_PROPERTIES_H__
diff --git a/src/include/fst/topsort.h b/src/include/fst/topsort.h
new file mode 100644
index 0000000..53735e5
--- /dev/null
+++ b/src/include/fst/topsort.h
@@ -0,0 +1,112 @@
+// topsort.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Topological sort of FSTs
+
+#ifndef FST_LIB_TOPSORT_H__
+#define FST_LIB_TOPSORT_H__
+
+#include <algorithm>
+#include <vector>
+using std::vector;
+
+
+#include <fst/dfs-visit.h>
+#include <fst/fst.h>
+#include <fst/statesort.h>
+
+
+namespace fst {
+
+// DFS visitor class to return topological ordering.
+template <class A>
+class TopOrderVisitor {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+
+  // If acyclic, ORDER[i] gives the topological position of state Id i;
+  // otherwise unchanged. ACYCLIC will be true iff the FST has
+  // no cycles.
+  TopOrderVisitor(vector<StateId> *order, bool *acyclic)
+      : order_(order), acyclic_(acyclic) {}
+
+  void InitVisit(const Fst<A> &fst) {
+    finish_ = new vector<StateId>;
+    *acyclic_ = true;
+  }
+
+  bool InitState(StateId s, StateId r) { return true; }
+
+  bool TreeArc(StateId s, const A &arc) { return true; }
+
+  bool BackArc(StateId s, const A &arc) { return (*acyclic_ = false); }
+
+  bool ForwardOrCrossArc(StateId s, const A &arc) { return true; }
+
+  void FinishState(StateId s, StateId p, const A *) { finish_->push_back(s); }
+
+  void FinishVisit() {
+    if (*acyclic_) {
+      order_->clear();
+      for (StateId s = 0; s < finish_->size(); ++s)
+        order_->push_back(kNoStateId);
+      for (StateId s = 0; s < finish_->size(); ++s)
+        (*order_)[(*finish_)[finish_->size() - s - 1]] = s;
+    }
+    delete finish_;
+  }
+
+ private:
+  vector<StateId> *order_;
+  bool *acyclic_;
+  vector<StateId> *finish_;  // states in finishing-time order
+};
+
+
+// Topologically sorts its input if acyclic, modifying it.  Otherwise,
+// the input is unchanged.  When sorted, all transitions are from
+// lower to higher state IDs.
+//
+// Complexity:
+// - Time:  O(V + E)
+// - Space: O(V + E)
+// where V = # of states and E = # of arcs.
+template <class Arc>
+bool TopSort(MutableFst<Arc> *fst) {
+  typedef typename Arc::StateId StateId;
+
+  vector<StateId> order;
+  bool acyclic;
+
+  TopOrderVisitor<Arc> top_order_visitor(&order, &acyclic);
+  DfsVisit(*fst, &top_order_visitor);
+
+  if (acyclic) {
+    StateSort(fst, order);
+    fst->SetProperties(kAcyclic | kInitialAcyclic | kTopSorted,
+                       kAcyclic | kInitialAcyclic | kTopSorted);
+  } else {
+    fst->SetProperties(kCyclic | kNotTopSorted, kCyclic | kNotTopSorted);
+  }
+  return acyclic;
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_TOPSORT_H__
diff --git a/src/include/fst/tuple-weight.h b/src/include/fst/tuple-weight.h
new file mode 100644
index 0000000..184026c
--- /dev/null
+++ b/src/include/fst/tuple-weight.h
@@ -0,0 +1,332 @@
+// tuple-weight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google (Cyril Allauzen)
+//
+// \file
+// Tuple weight set operation definitions.
+
+#ifndef FST_LIB_TUPLE_WEIGHT_H__
+#define FST_LIB_TUPLE_WEIGHT_H__
+
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/weight.h>
+
+
+DECLARE_string(fst_weight_parentheses);
+DECLARE_string(fst_weight_separator);
+
+namespace fst {
+
+template<class W, unsigned int n> class TupleWeight;
+template <class W, unsigned int n>
+istream &operator>>(istream &strm, TupleWeight<W, n> &w);
+
+// n-tuple weight, element of the n-th catersian power of W
+template <class W, unsigned int n>
+class TupleWeight {
+ public:
+  typedef TupleWeight<typename W::ReverseWeight, n> ReverseWeight;
+
+  TupleWeight() {}
+
+  TupleWeight(const TupleWeight &w) {
+    for (size_t i = 0; i < n; ++i)
+      values_[i] = w.values_[i];
+  }
+
+  template <class Iterator>
+  TupleWeight(Iterator begin, Iterator end) {
+    for (Iterator iter = begin; iter != end; ++iter)
+      values_[iter - begin] = *iter;
+  }
+
+  TupleWeight(const W &w) {
+    for (size_t i = 0; i < n; ++i)
+      values_[i] = w;
+  }
+
+  static const TupleWeight<W, n> &Zero() {
+    static const TupleWeight<W, n> zero(W::Zero());
+    return zero;
+  }
+
+  static const TupleWeight<W, n> &One() {
+    static const TupleWeight<W, n> one(W::One());
+    return one;
+  }
+
+  static const TupleWeight<W, n> &NoWeight() {
+    static const TupleWeight<W, n> no_weight(W::NoWeight());
+    return no_weight;
+  }
+
+  static unsigned int Length() {
+    return n;
+  }
+
+  istream &Read(istream &strm) {
+    for (size_t i = 0; i < n; ++i)
+      values_[i].Read(strm);
+    return strm;
+  }
+
+  ostream &Write(ostream &strm) const {
+    for (size_t i = 0; i < n; ++i)
+      values_[i].Write(strm);
+    return strm;
+  }
+
+  TupleWeight<W, n> &operator=(const TupleWeight<W, n> &w) {
+    for (size_t i = 0; i < n; ++i)
+      values_[i] = w.values_[i];
+    return *this;
+  }
+
+  bool Member() const {
+    bool member = true;
+    for (size_t i = 0; i < n; ++i)
+      member = member && values_[i].Member();
+    return member;
+  }
+
+  size_t Hash() const {
+    uint64 hash = 0;
+    for (size_t i = 0; i < n; ++i)
+      hash = 5 * hash + values_[i].Hash();
+    return size_t(hash);
+  }
+
+  TupleWeight<W, n> Quantize(float delta = kDelta) const {
+    TupleWeight<W, n> w;
+    for (size_t i = 0; i < n; ++i)
+      w.values_[i] = values_[i].Quantize(delta);
+    return w;
+  }
+
+  ReverseWeight Reverse() const {
+    TupleWeight<W, n> w;
+    for (size_t i = 0; i < n; ++i)
+      w.values_[i] = values_[i].Reverse();
+    return w;
+  }
+
+  const W& Value(size_t i) const { return values_[i]; }
+
+  void SetValue(size_t i, const W &w) { values_[i] = w; }
+
+ protected:
+  // Reads TupleWeight when there are no parentheses around tuple terms
+  inline static istream &ReadNoParen(istream &strm,
+                                     TupleWeight<W, n> &w,
+                                     char separator) {
+    int c;
+    do {
+      c = strm.get();
+    } while (isspace(c));
+
+    for (size_t i = 0; i < n - 1; ++i) {
+      string s;
+      if (i)
+        c = strm.get();
+      while (c != separator) {
+        if (c == EOF) {
+          strm.clear(std::ios::badbit);
+          return strm;
+        }
+        s += c;
+        c = strm.get();
+      }
+      // read (i+1)-th element
+      istringstream sstrm(s);
+      W r = W::Zero();
+      sstrm >> r;
+      w.SetValue(i, r);
+    }
+
+    // read n-th element
+    W r = W::Zero();
+    strm >> r;
+    w.SetValue(n - 1, r);
+
+    return strm;
+  }
+
+  // Reads TupleWeight when there are parentheses around tuple terms
+  inline static istream &ReadWithParen(istream &strm,
+                                       TupleWeight<W, n> &w,
+                                       char separator,
+                                       char open_paren,
+                                       char close_paren) {
+    int c;
+    do {
+      c = strm.get();
+    } while (isspace(c));
+
+    if (c != open_paren) {
+      FSTERROR() << " is fst_weight_parentheses flag set correcty? ";
+      strm.clear(std::ios::badbit);
+      return strm;
+    }
+
+    for (size_t i = 0; i < n - 1; ++i) {
+      // read (i+1)-th element
+      stack<int> parens;
+      string s;
+      c = strm.get();
+      while (c != separator || !parens.empty()) {
+        if (c == EOF) {
+          strm.clear(std::ios::badbit);
+          return strm;
+        }
+        s += c;
+        // if parens encountered before separator, they must be matched
+        if (c == open_paren) {
+          parens.push(1);
+        } else if (c == close_paren) {
+          // Fail for mismatched parens
+          if (parens.empty()) {
+            strm.clear(std::ios::failbit);
+            return strm;
+          }
+          parens.pop();
+        }
+        c = strm.get();
+      }
+      istringstream sstrm(s);
+      W r = W::Zero();
+      sstrm >> r;
+      w.SetValue(i, r);
+    }
+
+    // read n-th element
+    string s;
+    c = strm.get();
+    while (c != EOF) {
+      s += c;
+      c = strm.get();
+    }
+    if (s.empty() || *s.rbegin() != close_paren) {
+      FSTERROR() << " is fst_weight_parentheses flag set correcty? ";
+      strm.clear(std::ios::failbit);
+      return strm;
+    }
+    s.erase(s.size() - 1, 1);
+    istringstream sstrm(s);
+    W r = W::Zero();
+    sstrm >> r;
+    w.SetValue(n - 1, r);
+
+    return strm;
+  }
+
+
+ private:
+  W values_[n];
+
+  friend istream &operator>><W, n>(istream&, TupleWeight<W, n>&);
+};
+
+template <class W, unsigned int n>
+inline bool operator==(const TupleWeight<W, n> &w1,
+                       const TupleWeight<W, n> &w2) {
+  bool equal = true;
+  for (size_t i = 0; i < n; ++i)
+    equal = equal && (w1.Value(i) == w2.Value(i));
+  return equal;
+}
+
+template <class W, unsigned int n>
+inline bool operator!=(const TupleWeight<W, n> &w1,
+                       const TupleWeight<W, n> &w2) {
+  bool not_equal = false;
+  for (size_t i = 0; (i < n) && !not_equal; ++i)
+    not_equal = not_equal || (w1.Value(i) != w2.Value(i));
+  return not_equal;
+}
+
+template <class W, unsigned int n>
+inline bool ApproxEqual(const TupleWeight<W, n> &w1,
+                        const TupleWeight<W, n> &w2,
+                        float delta = kDelta) {
+  bool approx_equal = true;
+  for (size_t i = 0; i < n; ++i)
+    approx_equal = approx_equal &&
+        ApproxEqual(w1.Value(i), w2.Value(i), delta);
+  return approx_equal;
+}
+
+template <class W, unsigned int n>
+inline ostream &operator<<(ostream &strm, const TupleWeight<W, n> &w) {
+  if(FLAGS_fst_weight_separator.size() != 1) {
+    FSTERROR() << "FLAGS_fst_weight_separator.size() is not equal to 1";
+    strm.clear(std::ios::badbit);
+    return strm;
+  }
+  char separator = FLAGS_fst_weight_separator[0];
+  bool write_parens = false;
+  if (!FLAGS_fst_weight_parentheses.empty()) {
+    if (FLAGS_fst_weight_parentheses.size() != 2) {
+      FSTERROR() << "FLAGS_fst_weight_parentheses.size() is not equal to 2";
+      strm.clear(std::ios::badbit);
+      return strm;
+    }
+    write_parens = true;
+  }
+
+  if (write_parens)
+    strm << FLAGS_fst_weight_parentheses[0];
+  for (size_t i  = 0; i < n; ++i) {
+    if(i)
+      strm << separator;
+    strm << w.Value(i);
+  }
+  if (write_parens)
+    strm << FLAGS_fst_weight_parentheses[1];
+
+  return strm;
+}
+
+template <class W, unsigned int n>
+inline istream &operator>>(istream &strm, TupleWeight<W, n> &w) {
+  if(FLAGS_fst_weight_separator.size() != 1) {
+    FSTERROR() << "FLAGS_fst_weight_separator.size() is not equal to 1";
+    strm.clear(std::ios::badbit);
+    return strm;
+  }
+  char separator = FLAGS_fst_weight_separator[0];
+
+  if (!FLAGS_fst_weight_parentheses.empty()) {
+    if (FLAGS_fst_weight_parentheses.size() != 2) {
+      FSTERROR() << "FLAGS_fst_weight_parentheses.size() is not equal to 2";
+      strm.clear(std::ios::badbit);
+      return strm;
+    }
+    return TupleWeight<W, n>::ReadWithParen(
+        strm, w, separator, FLAGS_fst_weight_parentheses[0],
+        FLAGS_fst_weight_parentheses[1]);
+  } else {
+    return TupleWeight<W, n>::ReadNoParen(strm, w, separator);
+  }
+}
+
+
+
+}  // namespace fst
+
+#endif  // FST_LIB_TUPLE_WEIGHT_H__
diff --git a/src/include/fst/types.h b/src/include/fst/types.h
new file mode 100644
index 0000000..8c4367a
--- /dev/null
+++ b/src/include/fst/types.h
@@ -0,0 +1,38 @@
+// types.h
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Various type definitions (mostly for Google compatibility).
+
+#include <cstdlib>       // for ssize_t
+#include <stdint.h>      // *int*_t
+
+#include <fst/compat.h>  // for DISALLOW_COPY_AND_ASSIGN
+
+#ifndef FST_LIB_TYPES_H__
+#define FST_LIB_TYPES_H__
+
+typedef int8_t int8;
+typedef int16_t int16;
+typedef int32_t int32;
+typedef int64_t int64;
+
+typedef uint8_t uint8;
+typedef uint16_t uint16;
+typedef uint32_t uint32;
+typedef uint64_t uint64;
+
+#endif  // FST_LIB_TYPES_H__
diff --git a/src/include/fst/union-find.h b/src/include/fst/union-find.h
new file mode 100644
index 0000000..c8633e0
--- /dev/null
+++ b/src/include/fst/union-find.h
@@ -0,0 +1,110 @@
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: wojciech@google.com (Wojciech Skut)
+//
+// \file Union-Find algorithm for dense sets of non-negative
+// integers. Implemented using disjoint tree forests with rank
+// heuristics and path compression.
+
+#ifndef __fst_union_find_inl_h__
+#define __fst_union_find_inl_h__
+
+#include <stack>
+#include <vector>
+using std::vector;
+#include <fst/types.h>
+
+namespace fst {
+
+// Union-Find algorithm for dense sets of non-negative integers
+// (exact type: T).
+template <class T>
+class UnionFind {
+ public:
+  // Ctor: creates a disjoint set forest for the range [0;max).
+  // 'fail' is a value indicating that an element hasn't been
+  // initialized using MakeSet(...). The upper bound of the range
+  // can be reset (increased) using MakeSet(...).
+  UnionFind(T max, T fail)
+      : parent_(max, fail), rank_(max), fail_(fail) { }
+
+  // Finds the representative of the set 'item' belongs to.
+  // Performs path compression if needed.
+  T FindSet(T item) {
+    if (item >= parent_.size()
+        || item == fail_
+        || parent_[item] == fail_) return fail_;
+
+    T *p = &parent_[item];
+    for (; *p != item; item = *p, p = &parent_[item]) {
+      exec_stack_.push(p);
+    }
+    for (; ! exec_stack_.empty(); exec_stack_.pop()) {
+      *exec_stack_.top() = *p;
+    }
+    return *p;
+  }
+
+  // Creates the (destructive) union of the sets x and y belong to.
+  void Union(T x, T y) {
+    Link(FindSet(x), FindSet(y));
+  }
+
+  // Initialization of an element: creates a singleton set containing
+  // 'item'. The range [0;max) is reset if item >= max.
+  T MakeSet(T item) {
+    if (item >= parent_.size()) {
+      // New value in parent_ should be initialized to fail_
+      size_t nitem = item > 0 ? 2 * item : 2;
+      parent_.resize(nitem, fail_);
+      rank_.resize(nitem);
+    }
+    parent_[item] = item;
+    return item;
+  }
+
+  // Initialization of all elements starting from 0 to max - 1 to distinct sets
+  void MakeAllSet(T max) {
+    parent_.resize(max);
+    for (T item = 0; item < max; ++item) {
+      parent_[item] = item;
+    }
+  }
+
+ private:
+  vector<T> parent_;      // Parent nodes.
+  vector<int> rank_;      // Rank of an element = min. depth in tree.
+  T fail_;                // Value indicating lookup failure.
+  stack<T*> exec_stack_;  // Used for path compression.
+
+  // Links trees rooted in 'x' and 'y'.
+  void Link(T x, T y) {
+    if (x == y) return;
+
+    if (rank_[x] > rank_[y]) {
+      parent_[y] = x;
+    } else {
+      parent_[x] = y;
+      if (rank_[x] == rank_[y]) {
+        ++rank_[y];
+      }
+    }
+  }
+  DISALLOW_COPY_AND_ASSIGN(UnionFind);
+};
+
+}  // namespace fst
+
+#endif  // __fst_union_find_inl_h__
diff --git a/src/include/fst/union.h b/src/include/fst/union.h
new file mode 100644
index 0000000..a2f97fb
--- /dev/null
+++ b/src/include/fst/union.h
@@ -0,0 +1,185 @@
+// union.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Functions and classes to compute the union of two FSTs.
+
+#ifndef FST_LIB_UNION_H__
+#define FST_LIB_UNION_H__
+
+#include <vector>
+using std::vector;
+#include <algorithm>
+
+#include <fst/mutable-fst.h>
+#include <fst/rational.h>
+
+
+namespace fst {
+
+// Computes the union (sum) of two FSTs.  This version writes the
+// union to an output MurableFst. If A transduces string x to y with
+// weight a and B transduces string w to v with weight b, then their
+// union transduces x to y with weight a and w to v with weight b.
+//
+// Complexity:
+// - Time: (V2 + E2)
+// - Space: O(V2 + E2)
+// where Vi = # of states and Ei = # of arcs of the ith FST.
+template <class Arc>
+void Union(MutableFst<Arc> *fst1, const Fst<Arc> &fst2) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+
+  // TODO(riley): restore when voice actions issues fixed
+  // Check that the symbol table are compatible
+  if (!CompatSymbols(fst1->InputSymbols(), fst2.InputSymbols()) ||
+      !CompatSymbols(fst1->OutputSymbols(), fst2.OutputSymbols())) {
+    LOG(ERROR) << "Union: input/output symbol tables of 1st argument "
+               << "do not match input/output symbol tables of 2nd argument";
+    // fst1->SetProperties(kError, kError);
+    // return;
+  }
+
+  StateId numstates1 = fst1->NumStates();
+  bool initial_acyclic1 = fst1->Properties(kInitialAcyclic, true);
+  uint64 props1 = fst1->Properties(kFstProperties, false);
+  uint64 props2 = fst2.Properties(kFstProperties, false);
+
+  StateId start2 = fst2.Start();
+  if (start2 == kNoStateId) {
+    if (props2 & kError) fst1->SetProperties(kError, kError);
+    return;
+  }
+
+  if (fst2.Properties(kExpanded, false)) {
+    fst1->ReserveStates(
+        numstates1 + CountStates(fst2) + (initial_acyclic1 ? 0 : 1));
+  }
+
+  for (StateIterator< Fst<Arc> > siter(fst2);
+       !siter.Done();
+       siter.Next()) {
+    StateId s1 = fst1->AddState();
+    StateId s2 = siter.Value();
+    fst1->SetFinal(s1, fst2.Final(s2));
+    fst1->ReserveArcs(s1, fst2.NumArcs(s2));
+    for (ArcIterator< Fst<Arc> > aiter(fst2, s2);
+         !aiter.Done();
+         aiter.Next()) {
+      Arc arc = aiter.Value();
+      arc.nextstate += numstates1;
+      fst1->AddArc(s1, arc);
+    }
+  }
+  StateId start1 = fst1->Start();
+  if (start1 == kNoStateId) {
+    fst1->SetStart(start2);
+    fst1->SetProperties(props2, kCopyProperties);
+    return;
+  }
+
+  if (initial_acyclic1) {
+    fst1->AddArc(start1,  Arc(0, 0, Weight::One(), start2 + numstates1));
+  } else {
+    StateId nstart1 = fst1->AddState();
+    fst1->SetStart(nstart1);
+    fst1->AddArc(nstart1,  Arc(0, 0, Weight::One(), start1));
+    fst1->AddArc(nstart1,  Arc(0, 0, Weight::One(), start2 + numstates1));
+  }
+  fst1->SetProperties(UnionProperties(props1, props2), kFstProperties);
+}
+
+
+// Computes the union of two FSTs; this version modifies its
+// RationalFst argument.
+template<class Arc>
+void Union(RationalFst<Arc> *fst1, const Fst<Arc> &fst2) {
+  fst1->GetImpl()->AddUnion(fst2);
+}
+
+
+typedef RationalFstOptions UnionFstOptions;
+
+
+// Computes the union (sum) of two FSTs. This version is a delayed
+// Fst. If A transduces string x to y with weight a and B transduces
+// string w to v with weight b, then their union transduces x to y
+// with weight a and w to v with weight b.
+//
+// Complexity:
+// - Time: O(v1 + e1 + v2 + e2)
+// - Sapce: O(v1 + v2)
+// where vi = # of states visited and ei = # of arcs visited of the
+// ith FST. Constant time and space to visit an input state or arc
+// is assumed and exclusive of caching.
+template <class A>
+class UnionFst : public RationalFst<A> {
+ public:
+  using ImplToFst< RationalFstImpl<A> >::GetImpl;
+
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  UnionFst(const Fst<A> &fst1, const Fst<A> &fst2) {
+    GetImpl()->InitUnion(fst1, fst2);
+  }
+
+  UnionFst(const Fst<A> &fst1, const Fst<A> &fst2, const UnionFstOptions &opts)
+      : RationalFst<A>(opts) {
+    GetImpl()->InitUnion(fst1, fst2);
+  }
+
+  // See Fst<>::Copy() for doc.
+  UnionFst(const UnionFst<A> &fst, bool safe = false)
+      : RationalFst<A>(fst, safe) {}
+
+  // Get a copy of this UnionFst. See Fst<>::Copy() for further doc.
+  virtual UnionFst<A> *Copy(bool safe = false) const {
+    return new UnionFst<A>(*this, safe);
+  }
+};
+
+
+// Specialization for UnionFst.
+template <class A>
+class StateIterator< UnionFst<A> > : public StateIterator< RationalFst<A> > {
+ public:
+  explicit StateIterator(const UnionFst<A> &fst)
+      : StateIterator< RationalFst<A> >(fst) {}
+};
+
+
+// Specialization for UnionFst.
+template <class A>
+class ArcIterator< UnionFst<A> > : public ArcIterator< RationalFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const UnionFst<A> &fst, StateId s)
+      : ArcIterator< RationalFst<A> >(fst, s) {}
+};
+
+
+// Useful alias when using StdArc.
+typedef UnionFst<StdArc> StdUnionFst;
+
+}  // namespace fst
+
+#endif  // FST_LIB_UNION_H__
diff --git a/src/include/fst/util.h b/src/include/fst/util.h
new file mode 100644
index 0000000..87231e1
--- /dev/null
+++ b/src/include/fst/util.h
@@ -0,0 +1,409 @@
+// util.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// FST utility inline definitions.
+
+#ifndef FST_LIB_UTIL_H__
+#define FST_LIB_UTIL_H__
+
+#include <unordered_map>
+using std::tr1::unordered_map;
+using std::tr1::unordered_multimap;
+#include <unordered_set>
+using std::tr1::unordered_set;
+using std::tr1::unordered_multiset;
+#include <list>
+#include <map>
+#include <set>
+#include <sstream>
+#include <string>
+#include <vector>
+using std::vector;
+
+
+#include <fst/compat.h>
+#include <fst/types.h>
+
+#include <iostream>
+#include <fstream>
+
+//
+// UTILITY FOR ERROR HANDLING
+//
+
+DECLARE_bool(fst_error_fatal);
+
+#define FSTERROR() (FLAGS_fst_error_fatal ? LOG(FATAL) : LOG(ERROR))
+
+namespace fst {
+
+//
+// UTILITIES FOR TYPE I/O
+//
+
+// Read some types from an input stream.
+
+// Generic case.
+template <typename T>
+inline istream &ReadType(istream &strm, T *t) {
+  return t->Read(strm);
+}
+
+// Fixed size, contiguous memory read.
+#define READ_POD_TYPE(T)                                    \
+inline istream &ReadType(istream &strm, T *t) {             \
+  return strm.read(reinterpret_cast<char *>(t), sizeof(T)); \
+}
+
+READ_POD_TYPE(bool);
+READ_POD_TYPE(char);
+READ_POD_TYPE(signed char);
+READ_POD_TYPE(unsigned char);
+READ_POD_TYPE(short);
+READ_POD_TYPE(unsigned short);
+READ_POD_TYPE(int);
+READ_POD_TYPE(unsigned int);
+READ_POD_TYPE(long);
+READ_POD_TYPE(unsigned long);
+READ_POD_TYPE(long long);
+READ_POD_TYPE(unsigned long long);
+READ_POD_TYPE(float);
+READ_POD_TYPE(double);
+
+// String case.
+inline istream &ReadType(istream &strm, string *s) {
+  s->clear();
+  int32 ns = 0;
+  strm.read(reinterpret_cast<char *>(&ns), sizeof(ns));
+  for (int i = 0; i < ns; ++i) {
+    char c;
+    strm.read(&c, 1);
+    *s += c;
+  }
+  return strm;
+}
+
+// Pair case.
+template <typename S, typename T>
+inline istream &ReadType(istream &strm, pair<S, T> *p) {
+  ReadType(strm, &p->first);
+  ReadType(strm, &p->second);
+  return strm;
+}
+
+template <typename S, typename T>
+inline istream &ReadType(istream &strm, pair<const S, T> *p) {
+  ReadType(strm, const_cast<S *>(&p->first));
+  ReadType(strm, &p->second);
+  return strm;
+}
+
+// General case - no-op.
+template <typename C>
+void StlReserve(C *c, int64 n) {}
+
+// Specialization for vectors.
+template <typename S, typename T>
+void StlReserve(vector<S, T> *c, int64 n) {
+  c->reserve(n);
+}
+
+// STL sequence container.
+#define READ_STL_SEQ_TYPE(C)                             \
+template <typename S, typename T>                        \
+inline istream &ReadType(istream &strm, C<S, T> *c) {    \
+  c->clear();                                            \
+  int64 n = 0;                                           \
+  strm.read(reinterpret_cast<char *>(&n), sizeof(n));    \
+  StlReserve(c, n);                                      \
+  for (ssize_t i = 0; i < n; ++i) {                      \
+    typename C<S, T>::value_type value;                  \
+    ReadType(strm, &value);                              \
+    c->insert(c->end(), value);                          \
+  }                                                      \
+  return strm;                                           \
+}
+
+READ_STL_SEQ_TYPE(vector);
+READ_STL_SEQ_TYPE(list);
+
+// STL associative container.
+#define READ_STL_ASSOC_TYPE(C)                           \
+template <typename S, typename T, typename U>            \
+inline istream &ReadType(istream &strm, C<S, T, U> *c) { \
+  c->clear();                                            \
+  int64 n = 0;                                           \
+  strm.read(reinterpret_cast<char *>(&n), sizeof(n));    \
+  for (ssize_t i = 0; i < n; ++i) {                      \
+    typename C<S, T, U>::value_type value;               \
+    ReadType(strm, &value);                              \
+    c->insert(value);                                    \
+  }                                                      \
+  return strm;                                           \
+}
+
+READ_STL_ASSOC_TYPE(set);
+READ_STL_ASSOC_TYPE(unordered_set);
+READ_STL_ASSOC_TYPE(map);
+READ_STL_ASSOC_TYPE(unordered_map);
+
+// Write some types to an output stream.
+
+// Generic case.
+template <typename T>
+inline ostream &WriteType(ostream &strm, const T t) {
+  t.Write(strm);
+  return strm;
+}
+
+// Fixed size, contiguous memory write.
+#define WRITE_POD_TYPE(T)                                           \
+inline ostream &WriteType(ostream &strm, const T t) {               \
+  return strm.write(reinterpret_cast<const char *>(&t), sizeof(T)); \
+}
+
+WRITE_POD_TYPE(bool);
+WRITE_POD_TYPE(char);
+WRITE_POD_TYPE(signed char);
+WRITE_POD_TYPE(unsigned char);
+WRITE_POD_TYPE(short);
+WRITE_POD_TYPE(unsigned short);
+WRITE_POD_TYPE(int);
+WRITE_POD_TYPE(unsigned int);
+WRITE_POD_TYPE(long);
+WRITE_POD_TYPE(unsigned long);
+WRITE_POD_TYPE(long long);
+WRITE_POD_TYPE(unsigned long long);
+WRITE_POD_TYPE(float);
+WRITE_POD_TYPE(double);
+
+// String case.
+inline ostream &WriteType(ostream &strm, const string &s) {
+  int32 ns = s.size();
+  strm.write(reinterpret_cast<const char *>(&ns), sizeof(ns));
+  return strm.write(s.data(), ns);
+}
+
+// Pair case.
+template <typename S, typename T>
+inline ostream &WriteType(ostream &strm, const pair<S, T> &p) {
+  WriteType(strm, p.first);
+  WriteType(strm, p.second);
+  return strm;
+}
+
+// STL sequence container.
+#define WRITE_STL_SEQ_TYPE(C)                                                \
+template <typename S, typename T>                                            \
+inline ostream &WriteType(ostream &strm, const C<S, T> &c) {                 \
+  int64 n = c.size();                                                        \
+  strm.write(reinterpret_cast<char *>(&n), sizeof(n));                       \
+  for (typename C<S, T>::const_iterator it = c.begin();                      \
+       it != c.end(); ++it)                                                  \
+     WriteType(strm, *it);                                                   \
+  return strm;                                                               \
+}
+
+WRITE_STL_SEQ_TYPE(vector);
+WRITE_STL_SEQ_TYPE(list);
+
+// STL associative container.
+#define WRITE_STL_ASSOC_TYPE(C)                                              \
+template <typename S, typename T, typename U>                                \
+inline ostream &WriteType(ostream &strm, const C<S, T, U> &c) {              \
+  int64 n = c.size();                                                        \
+  strm.write(reinterpret_cast<char *>(&n), sizeof(n));                       \
+  for (typename C<S, T, U>::const_iterator it = c.begin();                   \
+       it != c.end(); ++it)                                                  \
+     WriteType(strm, *it);                                                   \
+  return strm;                                                               \
+}
+
+WRITE_STL_ASSOC_TYPE(set);
+WRITE_STL_ASSOC_TYPE(unordered_set);
+WRITE_STL_ASSOC_TYPE(map);
+WRITE_STL_ASSOC_TYPE(unordered_map);
+
+// Utilities for converting between int64 or Weight and string.
+
+int64 StrToInt64(const string &s, const string &src, size_t nline,
+                 bool allow_negative, bool *error = 0);
+
+template <typename Weight>
+Weight StrToWeight(const string &s, const string &src, size_t nline) {
+  Weight w;
+  istringstream strm(s);
+  strm >> w;
+  if (!strm) {
+    FSTERROR() << "StrToWeight: Bad weight = \"" << s
+               << "\", source = " << src << ", line = " << nline;
+    return Weight::NoWeight();
+  }
+  return w;
+}
+
+void Int64ToStr(int64 n, string *s);
+
+template <typename Weight>
+void WeightToStr(Weight w, string *s) {
+  ostringstream strm;
+  strm.precision(9);
+  strm << w;
+  *s += strm.str();
+}
+
+// Utilities for reading/writing label pairs
+
+// Returns true on success
+template <typename Label>
+bool ReadLabelPairs(const string& filename,
+                    vector<pair<Label, Label> >* pairs,
+                    bool allow_negative = false) {
+  ifstream strm(filename.c_str());
+
+  if (!strm) {
+    LOG(ERROR) << "ReadLabelPairs: Can't open file: " << filename;
+    return false;
+  }
+
+  const int kLineLen = 8096;
+  char line[kLineLen];
+  size_t nline = 0;
+
+  pairs->clear();
+  while (strm.getline(line, kLineLen)) {
+    ++nline;
+    vector<char *> col;
+    SplitToVector(line, "\n\t ", &col, true);
+    if (col.size() == 0 || col[0][0] == '\0')  // empty line
+      continue;
+    if (col.size() != 2) {
+      LOG(ERROR) << "ReadLabelPairs: Bad number of columns, "
+                 << "file = " << filename << ", line = " << nline;
+      return false;
+    }
+
+    bool err;
+    Label frmlabel = StrToInt64(col[0], filename, nline, allow_negative, &err);
+    if (err) return false;
+    Label tolabel = StrToInt64(col[1], filename, nline, allow_negative, &err);
+    if (err) return false;
+    pairs->push_back(make_pair(frmlabel, tolabel));
+  }
+  return true;
+}
+
+// Returns true on success
+template <typename Label>
+bool WriteLabelPairs(const string& filename,
+                     const vector<pair<Label, Label> >& pairs) {
+  ostream *strm = &std::cout;
+  if (!filename.empty()) {
+    strm = new ofstream(filename.c_str());
+    if (!*strm) {
+      LOG(ERROR) << "WriteLabelPairs: Can't open file: " << filename;
+      return false;
+    }
+  }
+
+  for (ssize_t n = 0; n < pairs.size(); ++n)
+    *strm << pairs[n].first << "\t" << pairs[n].second << "\n";
+
+  if (!*strm) {
+    LOG(ERROR) << "WriteLabelPairs: Write failed: "
+               << (filename.empty() ? "standard output" : filename);
+    return false;
+  }
+  if (strm != &std::cout)
+    delete strm;
+  return true;
+}
+
+// Utilities for converting a type name to a legal C symbol.
+
+void ConvertToLegalCSymbol(string *s);
+
+
+//
+// UTILITIES FOR STREAM I/O
+//
+
+bool AlignInput(istream &strm, int align);
+bool AlignOutput(ostream &strm, int align);
+
+//
+// UTILITIES FOR PROTOCOL BUFFER I/O
+//
+
+
+// An associative container for which testing membership is
+// faster than an STL set if members are restricted to an interval
+// that excludes most non-members. A 'Key' must have ==, !=, and < defined.
+// Element 'NoKey' should be a key that marks an uninitialized key and
+// is otherwise unused. 'Find()' returns an STL const_iterator to the match
+// found, otherwise it equals 'End()'.
+template <class Key, Key NoKey>
+class CompactSet {
+public:
+  typedef typename set<Key>::const_iterator const_iterator;
+
+  CompactSet()
+    : min_key_(NoKey),
+      max_key_(NoKey) { }
+
+  CompactSet(const CompactSet<Key, NoKey> &compact_set)
+    : set_(compact_set.set_),
+      min_key_(compact_set.min_key_),
+      max_key_(compact_set.max_key_) { }
+
+  void Insert(Key key) {
+    set_.insert(key);
+    if (min_key_ == NoKey || key < min_key_)
+      min_key_ = key;
+    if (max_key_ == NoKey || max_key_ < key)
+        max_key_ = key;
+  }
+
+  void Clear() {
+    set_.clear();
+    min_key_ = max_key_ = NoKey;
+  }
+
+  const_iterator Find(Key key) const {
+    if (min_key_ == NoKey ||
+        key < min_key_ || max_key_ < key)
+      return set_.end();
+    else
+      return set_.find(key);
+  }
+
+  const_iterator Begin() const { return set_.begin(); }
+
+  const_iterator End() const { return set_.end(); }
+
+private:
+  set<Key> set_;
+  Key min_key_;
+  Key max_key_;
+
+  void operator=(const CompactSet<Key, NoKey> &);  //disallow
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_UTIL_H__
diff --git a/src/include/fst/vector-fst.h b/src/include/fst/vector-fst.h
new file mode 100644
index 0000000..f6d8a6d
--- /dev/null
+++ b/src/include/fst/vector-fst.h
@@ -0,0 +1,727 @@
+// vector-fst.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Simple concrete, mutable FST whose states and arcs are stored in STL
+// vectors.
+
+#ifndef FST_LIB_VECTOR_FST_H__
+#define FST_LIB_VECTOR_FST_H__
+
+#include <string>
+#include <vector>
+using std::vector;
+
+#include <fst/mutable-fst.h>
+#include <fst/test-properties.h>
+
+
+namespace fst {
+
+template <class A> class VectorFst;
+template <class F, class G> void Cast(const F &, G *);
+
+
+// States and arcs implemented by STL vectors, templated on the
+// State definition. This does not manage the Fst properties.
+template <class State>
+class VectorFstBaseImpl : public FstImpl<typename State::Arc> {
+ public:
+  typedef typename State::Arc Arc;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  VectorFstBaseImpl() : start_(kNoStateId) {}
+
+  ~VectorFstBaseImpl() {
+    for (StateId s = 0; s < states_.size(); ++s)
+      delete states_[s];
+  }
+
+  StateId Start() const { return start_; }
+
+  Weight Final(StateId s) const { return states_[s]->final; }
+
+  StateId NumStates() const { return states_.size(); }
+
+  size_t NumArcs(StateId s) const { return states_[s]->arcs.size(); }
+
+  void SetStart(StateId s) { start_ = s; }
+
+  void SetFinal(StateId s, Weight w) { states_[s]->final = w; }
+
+  StateId AddState() {
+    states_.push_back(new State);
+    return states_.size() - 1;
+  }
+
+  StateId AddState(State *state) {
+    states_.push_back(state);
+    return states_.size() - 1;
+  }
+
+  void AddArc(StateId s, const Arc &arc) {
+    states_[s]->arcs.push_back(arc);
+  }
+
+  void DeleteStates(const vector<StateId>& dstates) {
+    vector<StateId> newid(states_.size(), 0);
+    for (size_t i = 0; i < dstates.size(); ++i)
+      newid[dstates[i]] = kNoStateId;
+    StateId nstates = 0;
+    for (StateId s = 0; s < states_.size(); ++s) {
+      if (newid[s] != kNoStateId) {
+        newid[s] = nstates;
+        if (s != nstates)
+          states_[nstates] = states_[s];
+        ++nstates;
+      } else {
+        delete states_[s];
+      }
+    }
+    states_.resize(nstates);
+    for (StateId s = 0; s < states_.size(); ++s) {
+      vector<Arc> &arcs = states_[s]->arcs;
+      size_t narcs = 0;
+      for (size_t i = 0; i < arcs.size(); ++i) {
+        StateId t = newid[arcs[i].nextstate];
+        if (t != kNoStateId) {
+          arcs[i].nextstate = t;
+          if (i != narcs)
+            arcs[narcs] = arcs[i];
+          ++narcs;
+        } else {
+          if (arcs[i].ilabel == 0)
+            --states_[s]->niepsilons;
+          if (arcs[i].olabel == 0)
+            --states_[s]->noepsilons;
+        }
+      }
+      arcs.resize(narcs);
+    }
+    if (Start() != kNoStateId)
+      SetStart(newid[Start()]);
+  }
+
+  void DeleteStates() {
+    for (StateId s = 0; s < states_.size(); ++s)
+      delete states_[s];
+    states_.clear();
+    SetStart(kNoStateId);
+  }
+
+  void DeleteArcs(StateId s, size_t n) {
+    states_[s]->arcs.resize(states_[s]->arcs.size() - n);
+  }
+
+  void DeleteArcs(StateId s) { states_[s]->arcs.clear(); }
+
+  State *GetState(StateId s) { return states_[s]; }
+
+  const State *GetState(StateId s) const { return states_[s]; }
+
+  void SetState(StateId s, State *state) { states_[s] = state; }
+
+  void ReserveStates(StateId n) { states_.reserve(n); }
+
+  void ReserveArcs(StateId s, size_t n) { states_[s]->arcs.reserve(n); }
+
+  // Provide information needed for generic state iterator
+  void InitStateIterator(StateIteratorData<Arc> *data) const {
+    data->base = 0;
+    data->nstates = states_.size();
+  }
+
+  // Provide information needed for generic arc iterator
+  void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) const {
+    data->base = 0;
+    data->narcs = states_[s]->arcs.size();
+    data->arcs = data->narcs > 0 ? &states_[s]->arcs[0] : 0;
+    data->ref_count = 0;
+  }
+
+ private:
+  vector<State *> states_;      // States represenation.
+  StateId start_;               // initial state
+
+  DISALLOW_COPY_AND_ASSIGN(VectorFstBaseImpl);
+};
+
+// Arcs implemented by an STL vector per state.
+template <class A>
+struct VectorState {
+  typedef A Arc;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  VectorState() : final(Weight::Zero()), niepsilons(0), noepsilons(0) {}
+
+  Weight final;              // Final weight
+  vector<A> arcs;            // Arcs represenation
+  size_t niepsilons;         // # of input epsilons
+  size_t noepsilons;         // # of output epsilons
+};
+
+// This is a VectorFstBaseImpl container that holds VectorState's.  It
+// manages Fst properties and the # of input and output epsilons.
+template <class A>
+class VectorFstImpl : public VectorFstBaseImpl< VectorState<A> > {
+ public:
+  using FstImpl<A>::SetInputSymbols;
+  using FstImpl<A>::SetOutputSymbols;
+  using FstImpl<A>::SetType;
+  using FstImpl<A>::SetProperties;
+  using FstImpl<A>::Properties;
+
+  using VectorFstBaseImpl<VectorState<A> >::Start;
+  using VectorFstBaseImpl<VectorState<A> >::NumStates;
+  using VectorFstBaseImpl<VectorState<A> >::GetState;
+  using VectorFstBaseImpl<VectorState<A> >::ReserveArcs;
+
+  friend class MutableArcIterator< VectorFst<A> >;
+
+  typedef VectorFstBaseImpl< VectorState<A> > BaseImpl;
+  typedef typename A::Weight Weight;
+  typedef typename A::StateId StateId;
+
+  VectorFstImpl() {
+    SetType("vector");
+    SetProperties(kNullProperties | kStaticProperties);
+  }
+  explicit VectorFstImpl(const Fst<A> &fst);
+
+  static VectorFstImpl<A> *Read(istream &strm, const FstReadOptions &opts);
+
+  size_t NumInputEpsilons(StateId s) const { return GetState(s)->niepsilons; }
+
+  size_t NumOutputEpsilons(StateId s) const { return GetState(s)->noepsilons; }
+
+  void SetStart(StateId s) {
+    BaseImpl::SetStart(s);
+    SetProperties(SetStartProperties(Properties()));
+  }
+
+  void SetFinal(StateId s, Weight w) {
+    Weight ow = BaseImpl::Final(s);
+    BaseImpl::SetFinal(s, w);
+    SetProperties(SetFinalProperties(Properties(), ow, w));
+  }
+
+  StateId AddState() {
+    StateId s = BaseImpl::AddState();
+    SetProperties(AddStateProperties(Properties()));
+    return s;
+  }
+
+  void AddArc(StateId s, const A &arc) {
+    VectorState<A> *state = GetState(s);
+    if (arc.ilabel == 0) {
+      ++state->niepsilons;
+    }
+    if (arc.olabel == 0) {
+      ++state->noepsilons;
+    }
+
+    const A *parc = state->arcs.empty() ? 0 : &(state->arcs.back());
+    SetProperties(AddArcProperties(Properties(), s, arc, parc));
+
+    BaseImpl::AddArc(s, arc);
+  }
+
+  void DeleteStates(const vector<StateId> &dstates) {
+    BaseImpl::DeleteStates(dstates);
+    SetProperties(DeleteStatesProperties(Properties()));
+  }
+
+  void DeleteStates() {
+    BaseImpl::DeleteStates();
+    SetProperties(DeleteAllStatesProperties(Properties(),
+                                            kStaticProperties));
+  }
+
+  void DeleteArcs(StateId s, size_t n) {
+    const vector<A> &arcs = GetState(s)->arcs;
+    for (size_t i = 0; i < n; ++i) {
+      size_t j = arcs.size() - i - 1;
+      if (arcs[j].ilabel == 0)
+        --GetState(s)->niepsilons;
+      if (arcs[j].olabel == 0)
+        --GetState(s)->noepsilons;
+    }
+    BaseImpl::DeleteArcs(s, n);
+    SetProperties(DeleteArcsProperties(Properties()));
+  }
+
+  void DeleteArcs(StateId s) {
+    GetState(s)->niepsilons = 0;
+    GetState(s)->noepsilons = 0;
+    BaseImpl::DeleteArcs(s);
+    SetProperties(DeleteArcsProperties(Properties()));
+  }
+
+ private:
+  // Properties always true of this Fst class
+  static const uint64 kStaticProperties = kExpanded | kMutable;
+  // Current file format version
+  static const int kFileVersion = 2;
+  // Minimum file format version supported
+  static const int kMinFileVersion = 1;
+
+  DISALLOW_COPY_AND_ASSIGN(VectorFstImpl);
+};
+
+template <class A> const uint64 VectorFstImpl<A>::kStaticProperties;
+template <class A> const int VectorFstImpl<A>::kFileVersion;
+template <class A> const int VectorFstImpl<A>::kMinFileVersion;
+
+
+template <class A>
+VectorFstImpl<A>::VectorFstImpl(const Fst<A> &fst) {
+  SetType("vector");
+  SetInputSymbols(fst.InputSymbols());
+  SetOutputSymbols(fst.OutputSymbols());
+  BaseImpl::SetStart(fst.Start());
+  if (fst.Properties(kExpanded, false))
+    BaseImpl::ReserveStates(CountStates(fst));
+
+  for (StateIterator< Fst<A> > siter(fst);
+       !siter.Done();
+       siter.Next()) {
+    StateId s = siter.Value();
+    BaseImpl::AddState();
+    BaseImpl::SetFinal(s, fst.Final(s));
+    ReserveArcs(s, fst.NumArcs(s));
+    for (ArcIterator< Fst<A> > aiter(fst, s);
+         !aiter.Done();
+         aiter.Next()) {
+      const A &arc = aiter.Value();
+      BaseImpl::AddArc(s, arc);
+      if (arc.ilabel == 0)
+        ++GetState(s)->niepsilons;
+      if (arc.olabel == 0)
+        ++GetState(s)->noepsilons;
+    }
+  }
+  SetProperties(fst.Properties(kCopyProperties, false) | kStaticProperties);
+}
+
+template <class A>
+VectorFstImpl<A> *VectorFstImpl<A>::Read(istream &strm,
+                                         const FstReadOptions &opts) {
+  VectorFstImpl<A> *impl = new VectorFstImpl;
+  FstHeader hdr;
+  if (!impl->ReadHeader(strm, opts, kMinFileVersion, &hdr)) {
+    delete impl;
+    return 0;
+  }
+  impl->BaseImpl::SetStart(hdr.Start());
+  if (hdr.NumStates() != kNoStateId) {
+    impl->ReserveStates(hdr.NumStates());
+  }
+
+  StateId s = 0;
+  for (;hdr.NumStates() == kNoStateId || s < hdr.NumStates(); ++s) {
+    typename A::Weight final;
+    if (!final.Read(strm)) break;
+    impl->BaseImpl::AddState();
+    VectorState<A> *state = impl->GetState(s);
+    state->final = final;
+    int64 narcs;
+    ReadType(strm, &narcs);
+    if (!strm) {
+      LOG(ERROR) << "VectorFst::Read: read failed: " << opts.source;
+      delete impl;
+      return 0;
+    }
+    impl->ReserveArcs(s, narcs);
+    for (size_t j = 0; j < narcs; ++j) {
+      A arc;
+      ReadType(strm, &arc.ilabel);
+      ReadType(strm, &arc.olabel);
+      arc.weight.Read(strm);
+       ReadType(strm, &arc.nextstate);
+       if (!strm) {
+        LOG(ERROR) << "VectorFst::Read: read failed: " << opts.source;
+        delete impl;
+        return 0;
+      }
+      impl->BaseImpl::AddArc(s, arc);
+      if (arc.ilabel == 0)
+        ++state->niepsilons;
+      if (arc.olabel == 0)
+        ++state->noepsilons;
+    }
+  }
+  if (hdr.NumStates() != kNoStateId && s != hdr.NumStates()) {
+    LOG(ERROR) << "VectorFst::Read: unexpected end of file: " << opts.source;
+    delete impl;
+    return 0;
+  }
+  return impl;
+}
+
+// Converts a string into a weight.
+template <class W> class WeightFromString {
+ public:
+  W operator()(const string &s);
+};
+
+// Generic case fails.
+template <class W> inline
+W WeightFromString<W>::operator()(const string &s) {
+  FSTERROR() << "VectorFst::Read: Obsolete file format";
+  return W::NoWeight();
+}
+
+// TropicalWeight version.
+template <> inline
+TropicalWeight WeightFromString<TropicalWeight>::operator()(const string &s) {
+  float f;
+  memcpy(&f, s.data(), sizeof(f));
+  return TropicalWeight(f);
+}
+
+// LogWeight version.
+template <> inline
+LogWeight WeightFromString<LogWeight>::operator()(const string &s) {
+  float f;
+  memcpy(&f, s.data(), sizeof(f));
+  return LogWeight(f);
+}
+
+// Simple concrete, mutable FST. This class attaches interface to
+// implementation and handles reference counting, delegating most
+// methods to ImplToMutableFst. Supports additional operations:
+// ReserveStates and ReserveArcs (cf. STL vectors).
+template <class A>
+class VectorFst : public ImplToMutableFst< VectorFstImpl<A> > {
+ public:
+  friend class StateIterator< VectorFst<A> >;
+  friend class ArcIterator< VectorFst<A> >;
+  friend class MutableArcIterator< VectorFst<A> >;
+  template <class F, class G> friend void Cast(const F &, G *);
+
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+  typedef VectorFstImpl<A> Impl;
+
+  VectorFst() : ImplToMutableFst<Impl>(new Impl) {}
+
+  explicit VectorFst(const Fst<A> &fst)
+      : ImplToMutableFst<Impl>(new Impl(fst)) {}
+
+  VectorFst(const VectorFst<A> &fst) : ImplToMutableFst<Impl>(fst) {}
+
+  // Get a copy of this VectorFst. See Fst<>::Copy() for further doc.
+  virtual VectorFst<A> *Copy(bool safe = false) const {
+    return new VectorFst<A>(*this);
+  }
+
+  VectorFst<A> &operator=(const VectorFst<A> &fst) {
+    SetImpl(fst.GetImpl(), false);
+    return *this;
+  }
+
+  virtual VectorFst<A> &operator=(const Fst<A> &fst) {
+    if (this != &fst) SetImpl(new Impl(fst));
+    return *this;
+  }
+
+  // Read a VectorFst from an input stream; return NULL on error
+  static VectorFst<A> *Read(istream &strm, const FstReadOptions &opts) {
+    Impl* impl = Impl::Read(strm, opts);
+    return impl ? new VectorFst<A>(impl) : 0;
+  }
+
+  // Read a VectorFst from a file; return NULL on error
+  // Empty filename reads from standard input
+  static VectorFst<A> *Read(const string &filename) {
+    Impl* impl = ImplToExpandedFst<Impl, MutableFst<A> >::Read(filename);
+    return impl ? new VectorFst<A>(impl) : 0;
+  }
+
+  virtual bool Write(ostream &strm, const FstWriteOptions &opts) const {
+    return WriteFst(*this, strm, opts);
+  }
+
+  virtual bool Write(const string &filename) const {
+    return Fst<A>::WriteFile(filename);
+  }
+
+  template <class F>
+  static bool WriteFst(const F &fst, ostream &strm,
+                       const FstWriteOptions &opts);
+
+  void ReserveStates(StateId n) {
+    MutateCheck();
+    GetImpl()->ReserveStates(n);
+  }
+
+  void ReserveArcs(StateId s, size_t n) {
+    MutateCheck();
+    GetImpl()->ReserveArcs(s, n);
+  }
+
+  virtual void InitStateIterator(StateIteratorData<Arc> *data) const {
+    GetImpl()->InitStateIterator(data);
+  }
+
+  virtual void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) const {
+    GetImpl()->InitArcIterator(s, data);
+  }
+
+  virtual inline
+  void InitMutableArcIterator(StateId s, MutableArcIteratorData<A> *);
+
+ private:
+  explicit VectorFst(Impl *impl) : ImplToMutableFst<Impl>(impl) {}
+
+  // Makes visible to friends.
+  Impl *GetImpl() const { return ImplToFst< Impl, MutableFst<A> >::GetImpl(); }
+
+  void SetImpl(Impl *impl, bool own_impl = true) {
+    ImplToFst< Impl, MutableFst<A> >::SetImpl(impl, own_impl);
+  }
+
+  void MutateCheck() { return ImplToMutableFst<Impl>::MutateCheck(); }
+};
+
+// Specialization for VectorFst; see generic version in fst.h
+// for sample usage (but use the VectorFst type!). This version
+// should inline.
+template <class A>
+class StateIterator< VectorFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  explicit StateIterator(const VectorFst<A> &fst)
+      : nstates_(fst.GetImpl()->NumStates()), s_(0) {}
+
+  bool Done() const { return s_ >= nstates_; }
+
+  StateId Value() const { return s_; }
+
+  void Next() { ++s_; }
+
+  void Reset() { s_ = 0; }
+
+ private:
+  StateId nstates_;
+  StateId s_;
+
+  DISALLOW_COPY_AND_ASSIGN(StateIterator);
+};
+
+// Writes Fst to file, will call CountStates so may involve two passes if
+// called from an Fst that is not derived from Expanded.
+template <class A>
+template <class F>
+bool VectorFst<A>::WriteFst(const F &fst, ostream &strm,
+                            const FstWriteOptions &opts) {
+  static const int kFileVersion = 2;
+  bool update_header = true;
+  FstHeader hdr;
+  hdr.SetStart(fst.Start());
+  hdr.SetNumStates(kNoStateId);
+  size_t start_offset = 0;
+  if (fst.Properties(kExpanded, false) || (start_offset = strm.tellp()) != -1) {
+    hdr.SetNumStates(CountStates(fst));
+    update_header = false;
+  }
+  FstImpl<A>::WriteFstHeader(fst, strm, opts, kFileVersion, "vector", &hdr);
+  StateId num_states = 0;
+  for (StateIterator<F> siter(fst); !siter.Done(); siter.Next()) {
+    typename A::StateId s = siter.Value();
+    fst.Final(s).Write(strm);
+    int64 narcs = fst.NumArcs(s);
+    WriteType(strm, narcs);
+    for (ArcIterator<F> aiter(fst, s); !aiter.Done(); aiter.Next()) {
+      const A &arc = aiter.Value();
+      WriteType(strm, arc.ilabel);
+      WriteType(strm, arc.olabel);
+      arc.weight.Write(strm);
+      WriteType(strm, arc.nextstate);
+    }
+    num_states++;
+  }
+  strm.flush();
+  if (!strm) {
+    LOG(ERROR) << "VectorFst::Write: write failed: " << opts.source;
+    return false;
+  }
+  if (update_header) {
+    hdr.SetNumStates(num_states);
+    return FstImpl<A>::UpdateFstHeader(fst, strm, opts, kFileVersion, "vector",
+                                       &hdr, start_offset);
+  } else {
+    if (num_states != hdr.NumStates()) {
+      LOG(ERROR) << "Inconsistent number of states observed during write";
+      return false;
+    }
+  }
+  return true;
+}
+
+// Specialization for VectorFst; see generic version in fst.h
+// for sample usage (but use the VectorFst type!). This version
+// should inline.
+template <class A>
+class ArcIterator< VectorFst<A> > {
+ public:
+  typedef typename A::StateId StateId;
+
+  ArcIterator(const VectorFst<A> &fst, StateId s)
+      : arcs_(fst.GetImpl()->GetState(s)->arcs), i_(0) {}
+
+  bool Done() const { return i_ >= arcs_.size(); }
+
+  const A& Value() const { return arcs_[i_]; }
+
+  void Next() { ++i_; }
+
+  void Reset() { i_ = 0; }
+
+  void Seek(size_t a) { i_ = a; }
+
+  size_t Position() const { return i_; }
+
+  uint32 Flags() const {
+    return kArcValueFlags;
+  }
+
+  void SetFlags(uint32 f, uint32 m) {}
+
+ private:
+  const vector<A>& arcs_;
+  size_t i_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArcIterator);
+};
+
+// Specialization for VectorFst; see generic version in fst.h
+// for sample usage (but use the VectorFst type!). This version
+// should inline.
+template <class A>
+class MutableArcIterator< VectorFst<A> >
+  : public MutableArcIteratorBase<A> {
+ public:
+  typedef typename A::StateId StateId;
+  typedef typename A::Weight Weight;
+
+  MutableArcIterator(VectorFst<A> *fst, StateId s) : i_(0) {
+    fst->MutateCheck();
+    state_ = fst->GetImpl()->GetState(s);
+    properties_ = &fst->GetImpl()->properties_;
+  }
+
+  bool Done() const { return i_ >= state_->arcs.size(); }
+
+  const A& Value() const { return state_->arcs[i_]; }
+
+  void Next() { ++i_; }
+
+  size_t Position() const { return i_; }
+
+  void Reset() { i_ = 0; }
+
+  void Seek(size_t a) { i_ = a; }
+
+  void SetValue(const A &arc) {
+    A& oarc = state_->arcs[i_];
+    if (oarc.ilabel != oarc.olabel)
+      *properties_ &= ~kNotAcceptor;
+    if (oarc.ilabel == 0) {
+      --state_->niepsilons;
+      *properties_ &= ~kIEpsilons;
+      if (oarc.olabel == 0)
+        *properties_ &= ~kEpsilons;
+    }
+    if (oarc.olabel == 0) {
+      --state_->noepsilons;
+      *properties_ &= ~kOEpsilons;
+    }
+    if (oarc.weight != Weight::Zero() && oarc.weight != Weight::One())
+      *properties_ &= ~kWeighted;
+    oarc = arc;
+    if (arc.ilabel != arc.olabel) {
+      *properties_ |= kNotAcceptor;
+      *properties_ &= ~kAcceptor;
+    }
+    if (arc.ilabel == 0) {
+      ++state_->niepsilons;
+      *properties_ |= kIEpsilons;
+      *properties_ &= ~kNoIEpsilons;
+      if (arc.olabel == 0) {
+        *properties_ |= kEpsilons;
+        *properties_ &= ~kNoEpsilons;
+      }
+    }
+    if (arc.olabel == 0) {
+      ++state_->noepsilons;
+      *properties_ |= kOEpsilons;
+      *properties_ &= ~kNoOEpsilons;
+    }
+    if (arc.weight != Weight::Zero() && arc.weight != Weight::One()) {
+      *properties_ |= kWeighted;
+      *properties_ &= ~kUnweighted;
+    }
+    *properties_ &= kSetArcProperties | kAcceptor | kNotAcceptor |
+        kEpsilons | kNoEpsilons | kIEpsilons | kNoIEpsilons |
+        kOEpsilons | kNoOEpsilons | kWeighted | kUnweighted;
+  }
+
+  uint32 Flags() const {
+    return kArcValueFlags;
+  }
+
+  void SetFlags(uint32 f, uint32 m) {}
+
+
+ private:
+  // This allows base-class virtual access to non-virtual derived-
+  // class members of the same name. It makes the derived class more
+  // efficient to use but unsafe to further derive.
+  virtual bool Done_() const { return Done(); }
+  virtual const A& Value_() const { return Value(); }
+  virtual void Next_() { Next(); }
+  virtual size_t Position_() const { return Position(); }
+  virtual void Reset_() { Reset(); }
+  virtual void Seek_(size_t a) { Seek(a); }
+  virtual void SetValue_(const A &a) { SetValue(a); }
+  uint32 Flags_() const { return Flags(); }
+  void SetFlags_(uint32 f, uint32 m) { SetFlags(f, m); }
+
+  struct VectorState<A> *state_;
+  uint64 *properties_;
+  size_t i_;
+
+  DISALLOW_COPY_AND_ASSIGN(MutableArcIterator);
+};
+
+// Provide information needed for the generic mutable arc iterator
+template <class A> inline
+void VectorFst<A>::InitMutableArcIterator(
+    StateId s, MutableArcIteratorData<A> *data) {
+  data->base = new MutableArcIterator< VectorFst<A> >(this, s);
+}
+
+// A useful alias when using StdArc.
+typedef VectorFst<StdArc> StdVectorFst;
+
+}  // namespace fst
+
+#endif  // FST_LIB_VECTOR_FST_H__
diff --git a/src/include/fst/verify.h b/src/include/fst/verify.h
new file mode 100644
index 0000000..576cfca
--- /dev/null
+++ b/src/include/fst/verify.h
@@ -0,0 +1,126 @@
+// verify.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Function to verify an Fst's contents
+
+#ifndef FST_LIB_VERIFY_H__
+#define FST_LIB_VERIFY_H__
+
+#include <fst/fst.h>
+#include <fst/test-properties.h>
+
+
+namespace fst {
+
+// Verifies that an Fst's contents are sane.
+template<class Arc>
+bool Verify(const Fst<Arc> &fst, bool allow_negative_labels = false) {
+  typedef typename Arc::Label Label;
+  typedef typename Arc::Weight Weight;
+  typedef typename Arc::StateId StateId;
+
+  StateId start = fst.Start();
+  const SymbolTable *isyms = fst.InputSymbols();
+  const SymbolTable *osyms = fst.OutputSymbols();
+
+  // Count states
+  StateId ns = 0;
+  for (StateIterator< Fst<Arc> > siter(fst);
+       !siter.Done();
+       siter.Next())
+    ++ns;
+
+  if (start == kNoStateId && ns > 0) {
+    LOG(ERROR) << "Verify: Fst start state ID unset";
+    return false;
+  } else if (start >= ns) {
+    LOG(ERROR) << "Verify: Fst start state ID exceeds number of states";
+    return false;
+  }
+
+  for (StateIterator< Fst<Arc> > siter(fst);
+       !siter.Done();
+       siter.Next()) {
+    StateId s = siter.Value();
+    size_t na = 0;
+    for (ArcIterator< Fst<Arc> > aiter(fst, s);
+         !aiter.Done();
+         aiter.Next()) {
+      const Arc &arc =aiter.Value();
+      if (!allow_negative_labels && arc.ilabel < 0) {
+        LOG(ERROR) << "Verify: Fst input label ID of arc at position "
+                   << na << " of state " << s << " is negative";
+        return false;
+      } else if (isyms && isyms->Find(arc.ilabel) == "") {
+        LOG(ERROR) << "Verify: Fst input label ID " << arc.ilabel
+                   << " of arc at position " << na << " of state " <<  s
+                   << " is missing from input symbol table \""
+                   << isyms->Name() << "\"";
+        return false;
+      } else if (!allow_negative_labels && arc.olabel < 0) {
+        LOG(ERROR) << "Verify: Fst output label ID of arc at position "
+                   << na << " of state " << s << " is negative";
+        return false;
+      } else if (osyms && osyms->Find(arc.olabel) == "") {
+        LOG(ERROR) << "Verify: Fst output label ID " << arc.olabel
+                   << " of arc at position " << na << " of state " <<  s
+                   << " is missing from output symbol table \""
+                   << osyms->Name() << "\"";
+        return false;
+      } else if (!arc.weight.Member() || arc.weight == Weight::Zero()) {
+        LOG(ERROR) << "Verify: Fst weight of arc at position "
+                   << na << " of state " << s << " is invalid";
+        return false;
+      } else if (arc.nextstate < 0) {
+        LOG(ERROR) << "Verify: Fst destination state ID of arc at position "
+                   << na << " of state " << s << " is negative";
+        return false;
+      } else if (arc.nextstate >= ns) {
+        LOG(ERROR) << "Verify: Fst destination state ID of arc at position "
+                   << na << " of state " << s
+                   << " exceeds number of states";
+        return false;
+      }
+      ++na;
+    }
+    if (!fst.Final(s).Member()) {
+      LOG(ERROR) << "Verify: Fst final weight of state " << s << " is invalid";
+      return false;
+    }
+  }
+  uint64 fst_props = fst.Properties(kFstProperties, false);
+  if (fst_props & kError) {
+    LOG(ERROR) << "Verify: Fst error property is set";
+    return false;
+  }
+
+  uint64 known_props;
+  uint64 test_props = ComputeProperties(fst, kFstProperties, &known_props,
+                                        false);
+  if (!CompatProperties(fst_props, test_props)) {
+    LOG(ERROR) << "Verify: stored Fst properties incorrect "
+               << "(props1 = stored props, props2 = tested)";
+    return false;
+  } else {
+    return true;
+  }
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_VERIFY_H__
diff --git a/src/include/fst/visit.h b/src/include/fst/visit.h
new file mode 100644
index 0000000..31a00a8
--- /dev/null
+++ b/src/include/fst/visit.h
@@ -0,0 +1,270 @@
+// visit.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Queue-dependent visitation of finite-state transducers. See also
+// dfs-visit.h.
+
+#ifndef FST_LIB_VISIT_H__
+#define FST_LIB_VISIT_H__
+
+
+#include <fst/arcfilter.h>
+#include <fst/mutable-fst.h>
+
+
+namespace fst {
+
+// Visitor Interface - class determines actions taken during a visit.
+// If any of the boolean member functions return false, the visit is
+// aborted by first calling FinishState() on all unfinished (grey)
+// states and then calling FinishVisit().
+//
+// Note this is more general than the visitor interface in
+// dfs-visit.h but lacks some DFS-specific behavior.
+//
+// template <class Arc>
+// class Visitor {
+//  public:
+//   typedef typename Arc::StateId StateId;
+//
+//   Visitor(T *return_data);
+//   // Invoked before visit
+//   void InitVisit(const Fst<Arc> &fst);
+//   // Invoked when state discovered (2nd arg is visitation root)
+//   bool InitState(StateId s, StateId root);
+//   // Invoked when arc to white/undiscovered state examined
+//   bool WhiteArc(StateId s, const Arc &a);
+//   // Invoked when arc to grey/unfinished state examined
+//   bool GreyArc(StateId s, const Arc &a);
+//   // Invoked when arc to black/finished state examined
+//   bool BlackArc(StateId s, const Arc &a);
+//   // Invoked when state finished.
+//   void FinishState(StateId s);
+//   // Invoked after visit
+//   void FinishVisit();
+// };
+
+// Performs queue-dependent visitation. Visitor class argument
+// determines actions and contains any return data. ArcFilter
+// determines arcs that are considered.
+//
+// Note this is more general than DfsVisit() in dfs-visit.h but lacks
+// some DFS-specific Visitor behavior.
+template <class Arc, class V, class Q, class ArcFilter>
+void Visit(const Fst<Arc> &fst, V *visitor, Q *queue, ArcFilter filter) {
+
+  typedef typename Arc::StateId StateId;
+  typedef ArcIterator< Fst<Arc> > AIterator;
+
+  visitor->InitVisit(fst);
+
+  StateId start = fst.Start();
+  if (start == kNoStateId) {
+    visitor->FinishVisit();
+    return;
+  }
+
+  // An Fst state's visit color
+  const unsigned kWhiteState =  0x01;    // Undiscovered
+  const unsigned kGreyState =   0x02;    // Discovered & unfinished
+  const unsigned kBlackState =  0x04;    // Finished
+
+  // We destroy an iterator as soon as possible and mark it so
+  const unsigned kArcIterDone = 0x08;      // Arc iterator done and destroyed
+
+  vector<unsigned char> state_status;
+  vector<AIterator *> arc_iterator;
+
+  StateId nstates = start + 1;             // # of known states in general case
+  bool expanded = false;
+  if (fst.Properties(kExpanded, false)) {  // tests if expanded case, then
+    nstates = CountStates(fst);            // uses ExpandedFst::NumStates().
+    expanded = true;
+  }
+
+  state_status.resize(nstates, kWhiteState);
+  arc_iterator.resize(nstates);
+  StateIterator< Fst<Arc> > siter(fst);
+
+  // Continues visit while true
+  bool visit = true;
+
+  // Iterates over trees in visit forest.
+  for (StateId root = start; visit && root < nstates;) {
+    visit = visitor->InitState(root, root);
+    state_status[root] = kGreyState;
+    queue->Enqueue(root);
+    while (!queue->Empty()) {
+      StateId s = queue->Head();
+      if (s >= state_status.size()) {
+        nstates = s + 1;
+        state_status.resize(nstates, kWhiteState);
+        arc_iterator.resize(nstates);
+      }
+      // Creates arc iterator if needed.
+      if (arc_iterator[s] == 0 && !(state_status[s] & kArcIterDone) && visit)
+        arc_iterator[s] = new AIterator(fst, s);
+      // Deletes arc iterator if done.
+      AIterator *aiter = arc_iterator[s];
+      if ((aiter && aiter->Done()) || !visit) {
+        delete aiter;
+        arc_iterator[s] = 0;
+        state_status[s] |= kArcIterDone;
+      }
+      // Dequeues state and marks black if done
+      if (state_status[s] & kArcIterDone) {
+        queue->Dequeue();
+        visitor->FinishState(s);
+        state_status[s] = kBlackState;
+        continue;
+      }
+
+      const Arc &arc = aiter->Value();
+      if (arc.nextstate >= state_status.size()) {
+        nstates = arc.nextstate + 1;
+        state_status.resize(nstates, kWhiteState);
+        arc_iterator.resize(nstates);
+      }
+      // Visits respective arc types
+      if (filter(arc)) {
+        // Enqueues destination state and marks grey if white
+        if (state_status[arc.nextstate] == kWhiteState) {
+          visit = visitor->WhiteArc(s, arc);
+          if (!visit) continue;
+          visit = visitor->InitState(arc.nextstate, root);
+          state_status[arc.nextstate] = kGreyState;
+          queue->Enqueue(arc.nextstate);
+        } else if (state_status[arc.nextstate] == kBlackState) {
+          visit = visitor->BlackArc(s, arc);
+        } else {
+          visit = visitor->GreyArc(s, arc);
+        }
+      }
+      aiter->Next();
+      // Destroys an iterator ASAP for efficiency.
+      if (aiter->Done()) {
+        delete aiter;
+        arc_iterator[s] = 0;
+        state_status[s] |= kArcIterDone;
+      }
+    }
+    // Finds next tree root
+    for (root = root == start ? 0 : root + 1;
+         root < nstates && state_status[root] != kWhiteState;
+         ++root);
+
+    // Check for a state beyond the largest known state
+    if (!expanded && root == nstates) {
+      for (; !siter.Done(); siter.Next()) {
+        if (siter.Value() == nstates) {
+          ++nstates;
+          state_status.push_back(kWhiteState);
+          arc_iterator.push_back(0);
+          break;
+        }
+      }
+    }
+  }
+  visitor->FinishVisit();
+}
+
+
+template <class Arc, class V, class Q>
+inline void Visit(const Fst<Arc> &fst, V *visitor, Q* queue) {
+  Visit(fst, visitor, queue, AnyArcFilter<Arc>());
+}
+
+// Copies input FST to mutable FST following queue order.
+template <class A>
+class CopyVisitor {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+
+  CopyVisitor(MutableFst<Arc> *ofst) : ifst_(0), ofst_(ofst) {}
+
+  void InitVisit(const Fst<A> &ifst) {
+    ifst_ = &ifst;
+    ofst_->DeleteStates();
+    ofst_->SetStart(ifst_->Start());
+  }
+
+  bool InitState(StateId s, StateId) {
+    while (ofst_->NumStates() <= s)
+      ofst_->AddState();
+    return true;
+  }
+
+  bool WhiteArc(StateId s, const Arc &arc) {
+    ofst_->AddArc(s, arc);
+    return true;
+  }
+
+  bool GreyArc(StateId s, const Arc &arc) {
+    ofst_->AddArc(s, arc);
+    return true;
+  }
+
+  bool BlackArc(StateId s, const Arc &arc) {
+    ofst_->AddArc(s, arc);
+    return true;
+  }
+
+  void FinishState(StateId s) {
+    ofst_->SetFinal(s, ifst_->Final(s));
+  }
+
+  void FinishVisit() {}
+
+ private:
+  const Fst<Arc> *ifst_;
+  MutableFst<Arc> *ofst_;
+};
+
+
+// Visits input FST up to a state limit following queue order.
+template <class A>
+class PartialVisitor {
+ public:
+  typedef A Arc;
+  typedef typename A::StateId StateId;
+
+  explicit PartialVisitor(StateId maxvisit) : maxvisit_(maxvisit) {}
+
+  void InitVisit(const Fst<A> &ifst) { nvisit_ = 0; }
+
+  bool InitState(StateId s, StateId) {
+    ++nvisit_;
+    return nvisit_ <= maxvisit_;
+  }
+
+  bool WhiteArc(StateId s, const Arc &arc) { return true; }
+  bool GreyArc(StateId s, const Arc &arc) { return true; }
+  bool BlackArc(StateId s, const Arc &arc) { return true; }
+  void FinishState(StateId s) {}
+  void FinishVisit() {}
+
+ private:
+  StateId maxvisit_;
+  StateId nvisit_;
+};
+
+
+}  // namespace fst
+
+#endif  // FST_LIB_VISIT_H__
diff --git a/src/include/fst/weight.h b/src/include/fst/weight.h
new file mode 100644
index 0000000..72f5a22
--- /dev/null
+++ b/src/include/fst/weight.h
@@ -0,0 +1,179 @@
+// weight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// General weight set and associated semiring operation definitions.
+//
+// A semiring is specified by two binary operations Plus and Times and
+// two designated elements Zero and One with the following properties:
+//   Plus: associative, commutative, and has Zero as its identity.
+//   Times: associative and has identity One, distributes w.r.t. Plus, and
+//     has Zero as an annihilator:
+//          Times(Zero(), a) == Times(a, Zero()) = Zero().
+//
+//  A left semiring distributes on the left; a right semiring is
+//  similarly defined.
+//
+// A Weight class is required to be (at least) a left or right semiring.
+//
+// In addition, the following should be defined for a Weight:
+//   Member: predicate on set membership.
+//   NoWeight: returns an element that is not a member, should only be
+//     used to signal an error.
+//   >>: reads weight.
+//   <<: prints weight.
+//   Read(istream &strm): reads from an input stream.
+//   Write(ostream &strm): writes to an output stream.
+//   Hash: maps weight to size_t.
+//   ApproxEqual: approximate equality (for inexact weights)
+//   Quantize: quantizes wrt delta (for inexact weights)
+//   Divide: for all a,b,c s.t. Times(a, b) == c
+//     --> b' = Divide(c, a, DIVIDE_LEFT) if a left semiring, b'.Member()
+//      and Times(a, b') == c
+//     --> a' = Divide(c, b, DIVIDE_RIGHT) if a right semiring, a'.Member()
+//      and Times(a', b) == c
+//     --> b' = Divide(c, a)
+//            = Divide(c, a, DIVIDE_ANY)
+//            = Divide(c, a, DIVIDE_LEFT)
+//            = Divide(c, a, DIVIDE_RIGHT) if a commutative semiring,
+//      b'.Member() and Times(a, b') == Times(b', a) == c
+//   ReverseWeight: the type of the corresponding reverse weight.
+//     Typically the same type as Weight for a (both left and right) semiring.
+//     For the left string semiring, it is the right string semiring.
+//   Reverse: a mapping from Weight to ReverseWeight s.t.
+//     --> Reverse(Reverse(a)) = a
+//     --> Reverse(Plus(a, b)) = Plus(Reverse(a), Reverse(b))
+//     --> Reverse(Times(a, b)) = Times(Reverse(b), Reverse(a))
+//     Typically the identity mapping in a (both left and right) semiring.
+//     In the left string semiring, it maps to the reverse string
+//     in the right string semiring.
+//   Properties: specifies additional properties that hold:
+//      LeftSemiring: indicates weights form a left semiring.
+//      RightSemiring: indicates weights form a right semiring.
+//      Commutative: for all a,b: Times(a,b) == Times(b,a)
+//      Idempotent: for all a: Plus(a, a) == a.
+//      Path Property: for all a, b: Plus(a, b) == a or Plus(a, b) == b.
+
+
+#ifndef FST_LIB_WEIGHT_H__
+#define FST_LIB_WEIGHT_H__
+
+#include <cmath>
+#include <cctype>
+#include <iostream>
+#include <sstream>
+
+#include <fst/compat.h>
+
+#include <fst/util.h>
+
+
+namespace fst {
+
+//
+// CONSTANT DEFINITIONS
+//
+
+// A representable float near .001
+const float kDelta =                   1.0F/1024.0F;
+
+// For all a,b,c: Times(c, Plus(a,b)) = Plus(Times(c,a), Times(c, b))
+const uint64 kLeftSemiring =           0x0000000000000001ULL;
+
+// For all a,b,c: Times(Plus(a,b), c) = Plus(Times(a,c), Times(b, c))
+const uint64 kRightSemiring =          0x0000000000000002ULL;
+
+const uint64 kSemiring = kLeftSemiring | kRightSemiring;
+
+// For all a,b: Times(a,b) = Times(b,a)
+const uint64 kCommutative =       0x0000000000000004ULL;
+
+// For all a: Plus(a, a) = a
+const uint64 kIdempotent =             0x0000000000000008ULL;
+
+// For all a,b: Plus(a,b) = a or Plus(a,b) = b
+const uint64 kPath =                   0x0000000000000010ULL;
+
+
+// Determines direction of division.
+enum DivideType { DIVIDE_LEFT,   // left division
+                  DIVIDE_RIGHT,  // right division
+                  DIVIDE_ANY };  // division in a commutative semiring
+
+// NATURAL ORDER
+//
+// By definition:
+//                 a <= b iff a + b = a
+// The natural order is a negative partial order iff the semiring is
+// idempotent. It is trivially monotonic for plus. It is left
+// (resp. right) monotonic for times iff the semiring is left
+// (resp. right) distributive. It is a total order iff the semiring
+// has the path property. See Mohri, "Semiring Framework and
+// Algorithms for Shortest-Distance Problems", Journal of Automata,
+// Languages and Combinatorics 7(3):321-350, 2002. We define the
+// strict version of this order below.
+
+template <class W>
+class NaturalLess {
+ public:
+  typedef W Weight;
+
+  NaturalLess() {
+    if (!(W::Properties() & kIdempotent)) {
+      FSTERROR() << "NaturalLess: Weight type is not idempotent: "
+                 << W::Type();
+    }
+  }
+
+  bool operator()(const W &w1, const W &w2) const {
+    return (Plus(w1, w2) == w1) && w1 != w2;
+  }
+};
+
+
+// Power is the iterated product for arbitrary semirings such that
+// Power(w, 0) is One() for the semiring, and
+// Power(w, n) = Times(Power(w, n-1), w)
+
+template <class W>
+W Power(W w, size_t n) {
+  W result = W::One();
+  for (size_t i = 0; i < n; ++i) {
+    result = Times(result, w);
+  }
+  return result;
+}
+
+// General weight converter - raises error.
+template <class W1, class W2>
+struct WeightConvert {
+  W2 operator()(W1 w1) const {
+    FSTERROR() << "WeightConvert: can't convert weight from \""
+               << W1::Type() << "\" to \"" << W2::Type();
+    return W2::NoWeight();
+  }
+};
+
+// Specialized weight converter to self.
+template <class W>
+struct WeightConvert<W, W> {
+  W operator()(W w) const { return w; }
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_WEIGHT_H__