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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
#pragma once
#if !defined(RXCPP_OPERATORS_RX_REDUCE_HPP)
#define RXCPP_OPERATORS_RX_REDUCE_HPP
#include "../rx-includes.hpp"
namespace rxcpp {
namespace operators {
namespace detail {
template<class T, class Seed, class Accumulator>
struct is_accumulate_function_for {
typedef typename std::decay<Accumulator>::type accumulator_type;
typedef typename std::decay<Seed>::type seed_type;
typedef T source_value_type;
struct tag_not_valid {};
template<class CS, class CV, class CRS>
static auto check(int) -> decltype((*(CRS*)nullptr)(*(CS*)nullptr, *(CV*)nullptr));
template<class CS, class CV, class CRS>
static tag_not_valid check(...);
typedef decltype(check<seed_type, source_value_type, accumulator_type>(0)) type;
static const bool value = std::is_same<type, seed_type>::value;
};
template<class Seed, class ResultSelector>
struct is_result_function_for {
typedef typename std::decay<ResultSelector>::type result_selector_type;
typedef typename std::decay<Seed>::type seed_type;
struct tag_not_valid {};
template<class CS, class CRS>
static auto check(int) -> decltype((*(CRS*)nullptr)(*(CS*)nullptr));
template<class CS, class CRS>
static tag_not_valid check(...);
typedef decltype(check<seed_type, result_selector_type>(0)) type;
static const bool value = !std::is_same<type, tag_not_valid>::value;
};
template<class T, class SourceOperator, class Accumulator, class ResultSelector, class Seed>
struct reduce_traits
{
typedef typename std::decay<SourceOperator>::type source_type;
typedef typename std::decay<Accumulator>::type accumulator_type;
typedef typename std::decay<ResultSelector>::type result_selector_type;
typedef typename std::decay<Seed>::type seed_type;
typedef T source_value_type;
static_assert(is_accumulate_function_for<source_value_type, seed_type, accumulator_type>::value, "reduce Accumulator must be a function with the signature Seed(Seed, reduce::source_value_type)");
static_assert(is_result_function_for<seed_type, result_selector_type>::value, "reduce ResultSelector must be a function with the signature reduce::value_type(Seed)");
typedef typename is_result_function_for<seed_type, result_selector_type>::type value_type;
};
template<class T, class SourceOperator, class Accumulator, class ResultSelector, class Seed>
struct reduce : public operator_base<typename reduce_traits<T, SourceOperator, Accumulator, ResultSelector, Seed>::value_type>
{
typedef reduce<T, SourceOperator, Accumulator, ResultSelector, Seed> this_type;
typedef reduce_traits<T, SourceOperator, Accumulator, ResultSelector, Seed> traits;
typedef typename traits::source_type source_type;
typedef typename traits::accumulator_type accumulator_type;
typedef typename traits::result_selector_type result_selector_type;
typedef typename traits::seed_type seed_type;
typedef typename traits::source_value_type source_value_type;
typedef typename traits::value_type value_type;
struct reduce_initial_type
{
~reduce_initial_type()
{
}
reduce_initial_type(source_type o, accumulator_type a, result_selector_type rs, seed_type s)
: source(std::move(o))
, accumulator(std::move(a))
, result_selector(std::move(rs))
, seed(std::move(s))
{
}
source_type source;
accumulator_type accumulator;
result_selector_type result_selector;
seed_type seed;
private:
reduce_initial_type& operator=(reduce_initial_type o) RXCPP_DELETE;
};
reduce_initial_type initial;
~reduce()
{
}
reduce(source_type o, accumulator_type a, result_selector_type rs, seed_type s)
: initial(std::move(o), std::move(a), std::move(rs), std::move(s))
{
}
template<class Subscriber>
void on_subscribe(Subscriber o) const {
struct reduce_state_type
: public reduce_initial_type
, public std::enable_shared_from_this<reduce_state_type>
{
reduce_state_type(reduce_initial_type i, Subscriber scrbr)
: reduce_initial_type(i)
, source(i.source)
, current(reduce_initial_type::seed)
, out(std::move(scrbr))
{
}
observable<T, SourceOperator> source;
seed_type current;
Subscriber out;
private:
reduce_state_type& operator=(reduce_state_type o) RXCPP_DELETE;
};
auto state = std::make_shared<reduce_state_type>(initial, std::move(o));
state->source.subscribe(
state->out,
// on_next
[state](T t) {
auto next = on_exception(
[&](){return state->accumulator(state->current, t);},
state->out);
if (next.empty()) {
return;
}
state->current = next.get();
},
// on_error
[state](std::exception_ptr e) {
state->out.on_error(e);
},
// on_completed
[state]() {
auto result = on_exception(
[&](){return state->result_selector(state->current);},
state->out);
if (result.empty()) {
return;
}
state->out.on_next(result.get());
state->out.on_completed();
}
);
}
private:
reduce& operator=(reduce o) RXCPP_DELETE;
};
template<class Accumulator, class ResultSelector, class Seed>
class reduce_factory
{
typedef typename std::decay<Accumulator>::type accumulator_type;
typedef typename std::decay<ResultSelector>::type result_selector_type;
typedef typename std::decay<Seed>::type seed_type;
accumulator_type accumulator;
result_selector_type result_selector;
seed_type seed;
public:
reduce_factory(accumulator_type a, result_selector_type rs, Seed s)
: accumulator(std::move(a))
, result_selector(std::move(rs))
, seed(std::move(s))
{
}
template<class Observable>
auto operator()(const Observable& source)
-> observable<seed_type, reduce<typename Observable::value_type, typename Observable::source_operator_type, Accumulator, ResultSelector, Seed>> {
return observable<seed_type, reduce<typename Observable::value_type, typename Observable::source_operator_type, Accumulator, ResultSelector, Seed>>(
reduce<typename Observable::value_type, typename Observable::source_operator_type, Accumulator, ResultSelector, Seed>(source.source_operator, accumulator, result_selector, seed));
}
};
template<class T>
struct initialize_seeder {
typedef T seed_type;
seed_type seed() {
return seed_type{};
}
};
template<class T>
struct average {
struct seed_type
{
seed_type()
: value()
, count(0)
{
}
T value;
int count;
rxu::detail::maybe<double> stage;
};
seed_type seed() {
return seed_type{};
}
seed_type operator()(seed_type a, T v) {
if (a.count != 0 &&
(a.count == std::numeric_limits<int>::max() ||
((v > 0) && (a.value > (std::numeric_limits<T>::max() - v))) ||
((v < 0) && (a.value < (std::numeric_limits<T>::min() - v))))) {
// would overflow, calc existing and reset for next batch
// this will add error to the final result, but the alternative
// is to fail on overflow
double avg = a.value / a.count;
a.value = v;
a.count = 1;
if (!a.stage.empty()) {
a.stage.reset((*a.stage + avg) / 2);
} else {
a.stage.reset(avg);
}
} else {
a.value += v;
++a.count;
}
return a;
}
double operator()(seed_type a) {
if (a.count > 0) {
double avg = a.value / a.count;
if (!a.stage.empty()) {
avg = (*a.stage + avg) / 2;
}
return avg;
}
return a.value;
}
};
}
template<class Seed, class Accumulator, class ResultSelector>
auto reduce(Seed s, Accumulator a, ResultSelector rs)
-> detail::reduce_factory<Accumulator, ResultSelector, Seed> {
return detail::reduce_factory<Accumulator, ResultSelector, Seed>(std::move(a), std::move(rs), std::move(s));
}
}
}
#endif
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