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Diffstat (limited to 'lib/python2.7/lib2to3/pgen2/parse.py')
| -rw-r--r-- | lib/python2.7/lib2to3/pgen2/parse.py | 201 |
1 files changed, 0 insertions, 201 deletions
diff --git a/lib/python2.7/lib2to3/pgen2/parse.py b/lib/python2.7/lib2to3/pgen2/parse.py deleted file mode 100644 index 6bebdbb..0000000 --- a/lib/python2.7/lib2to3/pgen2/parse.py +++ /dev/null @@ -1,201 +0,0 @@ -# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved. -# Licensed to PSF under a Contributor Agreement. - -"""Parser engine for the grammar tables generated by pgen. - -The grammar table must be loaded first. - -See Parser/parser.c in the Python distribution for additional info on -how this parsing engine works. - -""" - -# Local imports -from . import token - -class ParseError(Exception): - """Exception to signal the parser is stuck.""" - - def __init__(self, msg, type, value, context): - Exception.__init__(self, "%s: type=%r, value=%r, context=%r" % - (msg, type, value, context)) - self.msg = msg - self.type = type - self.value = value - self.context = context - -class Parser(object): - """Parser engine. - - The proper usage sequence is: - - p = Parser(grammar, [converter]) # create instance - p.setup([start]) # prepare for parsing - <for each input token>: - if p.addtoken(...): # parse a token; may raise ParseError - break - root = p.rootnode # root of abstract syntax tree - - A Parser instance may be reused by calling setup() repeatedly. - - A Parser instance contains state pertaining to the current token - sequence, and should not be used concurrently by different threads - to parse separate token sequences. - - See driver.py for how to get input tokens by tokenizing a file or - string. - - Parsing is complete when addtoken() returns True; the root of the - abstract syntax tree can then be retrieved from the rootnode - instance variable. When a syntax error occurs, addtoken() raises - the ParseError exception. There is no error recovery; the parser - cannot be used after a syntax error was reported (but it can be - reinitialized by calling setup()). - - """ - - def __init__(self, grammar, convert=None): - """Constructor. - - The grammar argument is a grammar.Grammar instance; see the - grammar module for more information. - - The parser is not ready yet for parsing; you must call the - setup() method to get it started. - - The optional convert argument is a function mapping concrete - syntax tree nodes to abstract syntax tree nodes. If not - given, no conversion is done and the syntax tree produced is - the concrete syntax tree. If given, it must be a function of - two arguments, the first being the grammar (a grammar.Grammar - instance), and the second being the concrete syntax tree node - to be converted. The syntax tree is converted from the bottom - up. - - A concrete syntax tree node is a (type, value, context, nodes) - tuple, where type is the node type (a token or symbol number), - value is None for symbols and a string for tokens, context is - None or an opaque value used for error reporting (typically a - (lineno, offset) pair), and nodes is a list of children for - symbols, and None for tokens. - - An abstract syntax tree node may be anything; this is entirely - up to the converter function. - - """ - self.grammar = grammar - self.convert = convert or (lambda grammar, node: node) - - def setup(self, start=None): - """Prepare for parsing. - - This *must* be called before starting to parse. - - The optional argument is an alternative start symbol; it - defaults to the grammar's start symbol. - - You can use a Parser instance to parse any number of programs; - each time you call setup() the parser is reset to an initial - state determined by the (implicit or explicit) start symbol. - - """ - if start is None: - start = self.grammar.start - # Each stack entry is a tuple: (dfa, state, node). - # A node is a tuple: (type, value, context, children), - # where children is a list of nodes or None, and context may be None. - newnode = (start, None, None, []) - stackentry = (self.grammar.dfas[start], 0, newnode) - self.stack = [stackentry] - self.rootnode = None - self.used_names = set() # Aliased to self.rootnode.used_names in pop() - - def addtoken(self, type, value, context): - """Add a token; return True iff this is the end of the program.""" - # Map from token to label - ilabel = self.classify(type, value, context) - # Loop until the token is shifted; may raise exceptions - while True: - dfa, state, node = self.stack[-1] - states, first = dfa - arcs = states[state] - # Look for a state with this label - for i, newstate in arcs: - t, v = self.grammar.labels[i] - if ilabel == i: - # Look it up in the list of labels - assert t < 256 - # Shift a token; we're done with it - self.shift(type, value, newstate, context) - # Pop while we are in an accept-only state - state = newstate - while states[state] == [(0, state)]: - self.pop() - if not self.stack: - # Done parsing! - return True - dfa, state, node = self.stack[-1] - states, first = dfa - # Done with this token - return False - elif t >= 256: - # See if it's a symbol and if we're in its first set - itsdfa = self.grammar.dfas[t] - itsstates, itsfirst = itsdfa - if ilabel in itsfirst: - # Push a symbol - self.push(t, self.grammar.dfas[t], newstate, context) - break # To continue the outer while loop - else: - if (0, state) in arcs: - # An accepting state, pop it and try something else - self.pop() - if not self.stack: - # Done parsing, but another token is input - raise ParseError("too much input", - type, value, context) - else: - # No success finding a transition - raise ParseError("bad input", type, value, context) - - def classify(self, type, value, context): - """Turn a token into a label. (Internal)""" - if type == token.NAME: - # Keep a listing of all used names - self.used_names.add(value) - # Check for reserved words - ilabel = self.grammar.keywords.get(value) - if ilabel is not None: - return ilabel - ilabel = self.grammar.tokens.get(type) - if ilabel is None: - raise ParseError("bad token", type, value, context) - return ilabel - - def shift(self, type, value, newstate, context): - """Shift a token. (Internal)""" - dfa, state, node = self.stack[-1] - newnode = (type, value, context, None) - newnode = self.convert(self.grammar, newnode) - if newnode is not None: - node[-1].append(newnode) - self.stack[-1] = (dfa, newstate, node) - - def push(self, type, newdfa, newstate, context): - """Push a nonterminal. (Internal)""" - dfa, state, node = self.stack[-1] - newnode = (type, None, context, []) - self.stack[-1] = (dfa, newstate, node) - self.stack.append((newdfa, 0, newnode)) - - def pop(self): - """Pop a nonterminal. (Internal)""" - popdfa, popstate, popnode = self.stack.pop() - newnode = self.convert(self.grammar, popnode) - if newnode is not None: - if self.stack: - dfa, state, node = self.stack[-1] - node[-1].append(newnode) - else: - self.rootnode = newnode - self.rootnode.used_names = self.used_names |