Add google-endpoints to third_party/.

third_party/google-endpoints/ply/yacc.py

+# -----------------------------------------------------------------------------
+# ply: yacc.py
+#
+# Copyright (C) 2001-2016
+# David M. Beazley (Dabeaz LLC)
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+# * Redistributions of source code must retain the above copyright notice,
+#   this list of conditions and the following disclaimer.
+# * Redistributions in binary form must reproduce the above copyright notice,
+#   this list of conditions and the following disclaimer in the documentation
+#   and/or other materials provided with the distribution.
+# * Neither the name of the David Beazley or Dabeaz LLC may be used to
+#   endorse or promote products derived from this software without
+#  specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+# -----------------------------------------------------------------------------
+#
+# This implements an LR parser that is constructed from grammar rules defined
+# as Python functions. The grammer is specified by supplying the BNF inside
+# Python documentation strings.  The inspiration for this technique was borrowed
+# from John Aycock's Spark parsing system.  PLY might be viewed as cross between
+# Spark and the GNU bison utility.
+#
+# The current implementation is only somewhat object-oriented. The
+# LR parser itself is defined in terms of an object (which allows multiple
+# parsers to co-exist).  However, most of the variables used during table
+# construction are defined in terms of global variables.  Users shouldn't
+# notice unless they are trying to define multiple parsers at the same
+# time using threads (in which case they should have their head examined).
+#
+# This implementation supports both SLR and LALR(1) parsing.  LALR(1)
+# support was originally implemented by Elias Ioup (ezioup@alumni.uchicago.edu),
+# using the algorithm found in Aho, Sethi, and Ullman "Compilers: Principles,
+# Techniques, and Tools" (The Dragon Book).  LALR(1) has since been replaced
+# by the more efficient DeRemer and Pennello algorithm.
+#
+# :::::::: WARNING :::::::
+#
+# Construction of LR parsing tables is fairly complicated and expensive.
+# To make this module run fast, a *LOT* of work has been put into
+# optimization---often at the expensive of readability and what might
+# consider to be good Python "coding style."   Modify the code at your
+# own risk!
+# ----------------------------------------------------------------------------
+
+import re
+import types
+import sys
+import os.path
+import inspect
+import base64
+import warnings
+
+__version__    = '3.9'
+__tabversion__ = '3.8'
+
+#-----------------------------------------------------------------------------
+#                     === User configurable parameters ===
+#
+# Change these to modify the default behavior of yacc (if you wish)
+#-----------------------------------------------------------------------------
+
+yaccdebug   = True             # Debugging mode.  If set, yacc generates a
+                               # a 'parser.out' file in the current directory
+
+debug_file  = 'parser.out'     # Default name of the debugging file
+tab_module  = 'parsetab'       # Default name of the table module
+default_lr  = 'LALR'           # Default LR table generation method
+
+error_count = 3                # Number of symbols that must be shifted to leave recovery mode
+
+yaccdevel   = False            # Set to True if developing yacc.  This turns off optimized
+                               # implementations of certain functions.
+
+resultlimit = 40               # Size limit of results when running in debug mode.
+
+pickle_protocol = 0            # Protocol to use when writing pickle files
+
+# String type-checking compatibility
+if sys.version_info[0] < 3:
+    string_types = basestring
+else:
+    string_types = str
+
+MAXINT = sys.maxsize
+
+# This object is a stand-in for a logging object created by the
+# logging module.   PLY will use this by default to create things
+# such as the parser.out file.  If a user wants more detailed
+# information, they can create their own logging object and pass
+# it into PLY.
+
+class PlyLogger(object):
+    def __init__(self, f):
+        self.f = f
+
+    def debug(self, msg, *args, **kwargs):
+        self.f.write((msg % args) + '\n')
+
+    info = debug
+
+    def warning(self, msg, *args, **kwargs):
+        self.f.write('WARNING: ' + (msg % args) + '\n')
+
+    def error(self, msg, *args, **kwargs):
+        self.f.write('ERROR: ' + (msg % args) + '\n')
+
+    critical = debug
+
+# Null logger is used when no output is generated. Does nothing.
+class NullLogger(object):
+    def __getattribute__(self, name):
+        return self
+
+    def __call__(self, *args, **kwargs):
+        return self
+
+# Exception raised for yacc-related errors
+class YaccError(Exception):
+    pass
+
+# Format the result message that the parser produces when running in debug mode.
+def format_result(r):
+    repr_str = repr(r)
+    if '\n' in repr_str:
+        repr_str = repr(repr_str)
+    if len(repr_str) > resultlimit:
+        repr_str = repr_str[:resultlimit] + ' ...'
+    result = '<%s @ 0x%x> (%s)' % (type(r).__name__, id(r), repr_str)
+    return result
+
+# Format stack entries when the parser is running in debug mode
+def format_stack_entry(r):
+    repr_str = repr(r)
+    if '\n' in repr_str:
+        repr_str = repr(repr_str)
+    if len(repr_str) < 16:
+        return repr_str
+    else:
+        return '<%s @ 0x%x>' % (type(r).__name__, id(r))
+
+# Panic mode error recovery support.   This feature is being reworked--much of the
+# code here is to offer a deprecation/backwards compatible transition
+
+_errok = None
+_token = None
+_restart = None
+_warnmsg = '''PLY: Don't use global functions errok(), token(), and restart() in p_error().
+Instead, invoke the methods on the associated parser instance:
+
+    def p_error(p):
+        ...
+        # Use parser.errok(), parser.token(), parser.restart()
+        ...
+
+    parser = yacc.yacc()
+'''
+
+def errok():
+    warnings.warn(_warnmsg)
+    return _errok()
+
+def restart():
+    warnings.warn(_warnmsg)
+    return _restart()
+
+def token():
+    warnings.warn(_warnmsg)
+    return _token()
+
+# Utility function to call the p_error() function with some deprecation hacks
+def call_errorfunc(errorfunc, token, parser):
+    global _errok, _token, _restart
+    _errok = parser.errok
+    _token = parser.token
+    _restart = parser.restart
+    r = errorfunc(token)
+    try:
+        del _errok, _token, _restart
+    except NameError:
+        pass
+    return r
+
+#-----------------------------------------------------------------------------
+#                        ===  LR Parsing Engine ===
+#
+# The following classes are used for the LR parser itself.  These are not
+# used during table construction and are independent of the actual LR
+# table generation algorithm
+#-----------------------------------------------------------------------------
+
+# This class is used to hold non-terminal grammar symbols during parsing.
+# It normally has the following attributes set:
+#        .type       = Grammar symbol type
+#        .value      = Symbol value
+#        .lineno     = Starting line number
+#        .endlineno  = Ending line number (optional, set automatically)
+#        .lexpos     = Starting lex position
+#        .endlexpos  = Ending lex position (optional, set automatically)
+
+class YaccSymbol:
+    def __str__(self):
+        return self.type
+
+    def __repr__(self):
+        return str(self)
+
+# This class is a wrapper around the objects actually passed to each
+# grammar rule.   Index lookup and assignment actually assign the
+# .value attribute of the underlying YaccSymbol object.
+# The lineno() method returns the line number of a given
+# item (or 0 if not defined).   The linespan() method returns
+# a tuple of (startline,endline) representing the range of lines
+# for a symbol.  The lexspan() method returns a tuple (lexpos,endlexpos)
+# representing the range of positional information for a symbol.
+
+class YaccProduction:
+    def __init__(self, s, stack=None):
+        self.slice = s
+        self.stack = stack
+        self.lexer = None
+        self.parser = None
+
+    def __getitem__(self, n):
+        if isinstance(n, slice):
+            return [s.value for s in self.slice[n]]
+        elif n >= 0:
+            return self.slice[n].value
+        else:
+            return self.stack[n].value
+
+    def __setitem__(self, n, v):
+        self.slice[n].value = v
+
+    def __getslice__(self, i, j):
+        return [s.value for s in self.slice[i:j]]
+
+    def __len__(self):
+        return len(self.slice)
+
+    def lineno(self, n):
+        return getattr(self.slice[n], 'lineno', 0)
+
+    def set_lineno(self, n, lineno):
+        self.slice[n].lineno = lineno
+
+    def linespan(self, n):
+        startline = getattr(self.slice[n], 'lineno', 0)
+        endline = getattr(self.slice[n], 'endlineno', startline)
+        return startline, endline
+
+    def lexpos(self, n):
+        return getattr(self.slice[n], 'lexpos', 0)
+
+    def lexspan(self, n):
+        startpos = getattr(self.slice[n], 'lexpos', 0)
+        endpos = getattr(self.slice[n], 'endlexpos', startpos)
+        return startpos, endpos
+
+    def error(self):
+        raise SyntaxError
+
+# -----------------------------------------------------------------------------
+#                               == LRParser ==
+#
+# The LR Parsing engine.
+# -----------------------------------------------------------------------------
+
+class LRParser:
+    def __init__(self, lrtab, errorf):
+        self.productions = lrtab.lr_productions
+        self.action = lrtab.lr_action
+        self.goto = lrtab.lr_goto
+        self.errorfunc = errorf
+        self.set_defaulted_states()
+        self.errorok = True
+
+    def errok(self):
+        self.errorok = True
+
+    def restart(self):
+        del self.statestack[:]
+        del self.symstack[:]
+        sym = YaccSymbol()
+        sym.type = '$end'
+        self.symstack.append(sym)
+        self.statestack.append(0)
+
+    # Defaulted state support.
+    # This method identifies parser states where there is only one possible reduction action.
+    # For such states, the parser can make a choose to make a rule reduction without consuming
+    # the next look-ahead token.  This delayed invocation of the tokenizer can be useful in
+    # certain kinds of advanced parsing situations where the lexer and parser interact with
+    # each other or change states (i.e., manipulation of scope, lexer states, etc.).
+    #
+    # See:  http://www.gnu.org/software/bison/manual/html_node/Default-Reductions.html#Default-Reductions
+    def set_defaulted_states(self):
+        self.defaulted_states = {}
+        for state, actions in self.action.items():
+            rules = list(actions.values())
+            if len(rules) == 1 and rules[0] < 0:
+                self.defaulted_states[state] = rules[0]
+
+    def disable_defaulted_states(self):
+        self.defaulted_states = {}
+
+    def parse(self, input=None, lexer=None, debug=False, tracking=False, tokenfunc=None):
+        if debug or yaccdevel:
+            if isinstance(debug, int):
+                debug = PlyLogger(sys.stderr)
+            return self.parsedebug(input, lexer, debug, tracking, tokenfunc)
+        elif tracking:
+            return self.parseopt(input, lexer, debug, tracking, tokenfunc)
+        else:
+            return self.parseopt_notrack(input, lexer, debug, tracking, tokenfunc)
+
+
+    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+    # parsedebug().
+    #
+    # This is the debugging enabled version of parse().  All changes made to the
+    # parsing engine should be made here.   Optimized versions of this function
+    # are automatically created by the ply/ygen.py script.  This script cuts out
+    # sections enclosed in markers such as this:
+    #
+    #      #--! DEBUG
+    #      statements
+    #      #--! DEBUG
+    #
+    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+    def parsedebug(self, input=None, lexer=None, debug=False, tracking=False, tokenfunc=None):
+        #--! parsedebug-start
+        lookahead = None                         # Current lookahead symbol
+        lookaheadstack = []                      # Stack of lookahead symbols
+        actions = self.action                    # Local reference to action table (to avoid lookup on self.)
+        goto    = self.goto                      # Local reference to goto table (to avoid lookup on self.)
+        prod    = self.productions               # Local reference to production list (to avoid lookup on self.)
+        defaulted_states = self.defaulted_states # Local reference to defaulted states
+        pslice  = YaccProduction(None)           # Production object passed to grammar rules
+        errorcount = 0                           # Used during error recovery
+
+        #--! DEBUG
+        debug.info('PLY: PARSE DEBUG START')
+        #--! DEBUG
+
+        # If no lexer was given, we will try to use the lex module
+        if not lexer:
+            from . import lex
+            lexer = lex.lexer
+
+        # Set up the lexer and parser objects on pslice
+        pslice.lexer = lexer
+        pslice.parser = self
+
+        # If input was supplied, pass to lexer
+        if input is not None:
+            lexer.input(input)
+
+        if tokenfunc is None:
+            # Tokenize function
+            get_token = lexer.token
+        else:
+            get_token = tokenfunc
+
+        # Set the parser() token method (sometimes used in error recovery)
+        self.token = get_token
+
+        # Set up the state and symbol stacks
+
+        statestack = []                # Stack of parsing states
+        self.statestack = statestack
+        symstack   = []                # Stack of grammar symbols
+        self.symstack = symstack
+
+        pslice.stack = symstack         # Put in the production
+        errtoken   = None               # Err token
+
+        # The start state is assumed to be (0,$end)
+
+        statestack.append(0)
+        sym = YaccSymbol()
+        sym.type = '$end'
+        symstack.append(sym)
+        state = 0
+        while True:
+            # Get the next symbol on the input.  If a lookahead symbol
+            # is already set, we just use that. Otherwise, we'll pull
+            # the next token off of the lookaheadstack or from the lexer
+
+            #--! DEBUG
+            debug.debug('')
+            debug.debug('State  : %s', state)
+            #--! DEBUG
+
+            if state not in defaulted_states:
+                if not lookahead:
+                    if not lookaheadstack:
+                        lookahead = get_token()     # Get the next token
+                    else:
+                        lookahead = lookaheadstack.pop()
+                    if not lookahead:
+                        lookahead = YaccSymbol()
+                        lookahead.type = '$end'
+
+                # Check the action table
+                ltype = lookahead.type
+                t = actions[state].get(ltype)
+            else:
+                t = defaulted_states[state]
+                #--! DEBUG
+                debug.debug('Defaulted state %s: Reduce using %d', state, -t)
+                #--! DEBUG
+
+            #--! DEBUG
+            debug.debug('Stack  : %s',
+                        ('%s . %s' % (' '.join([xx.type for xx in symstack][1:]), str(lookahead))).lstrip())
+            #--! DEBUG
+
+            if t is not None:
+                if t > 0:
+                    # shift a symbol on the stack
+                    statestack.append(t)
+                    state = t
+
+                    #--! DEBUG
+                    debug.debug('Action : Shift and goto state %s', t)
+                    #--! DEBUG
+
+                    symstack.append(lookahead)
+                    lookahead = None
+
+                    # Decrease error count on successful shift
+                    if errorcount:
+                        errorcount -= 1
+                    continue
+
+                if t < 0:
+                    # reduce a symbol on the stack, emit a production
+                    p = prod[-t]
+                    pname = p.name
+                    plen  = p.len
+
+                    # Get production function
+                    sym = YaccSymbol()
+                    sym.type = pname       # Production name
+                    sym.value = None
+
+                    #--! DEBUG
+                    if plen:
+                        debug.info('Action : Reduce rule [%s] with %s and goto state %d', p.str,
+                                   '['+','.join([format_stack_entry(_v.value) for _v in symstack[-plen:]])+']',
+                                   goto[statestack[-1-plen]][pname])
+                    else:
+                        debug.info('Action : Reduce rule [%s] with %s and goto state %d', p.str, [],
+                                   goto[statestack[-1]][pname])
+
+                    #--! DEBUG
+
+                    if plen:
+                        targ = symstack[-plen-1:]
+                        targ[0] = sym
+
+                        #--! TRACKING
+                        if tracking:
+                            t1 = targ[1]
+                            sym.lineno = t1.lineno
+                            sym.lexpos = t1.lexpos
+                            t1 = targ[-1]
+                            sym.endlineno = getattr(t1, 'endlineno', t1.lineno)
+                            sym.endlexpos = getattr(t1, 'endlexpos', t1.lexpos)
+                        #--! TRACKING
+
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                        # The code enclosed in this section is duplicated
+                        # below as a performance optimization.  Make sure
+                        # changes get made in both locations.
+
+                        pslice.slice = targ
+
+                        try:
+                            # Call the grammar rule with our special slice object
+                            del symstack[-plen:]
+                            self.state = state
+                            p.callable(pslice)
+                            del statestack[-plen:]
+                            #--! DEBUG
+                            debug.info('Result : %s', format_result(pslice[0]))
+                            #--! DEBUG
+                            symstack.append(sym)
+                            state = goto[statestack[-1]][pname]
+                            statestack.append(state)
+                        except SyntaxError:
+                            # If an error was set. Enter error recovery state
+                            lookaheadstack.append(lookahead)    # Save the current lookahead token
+                            symstack.extend(targ[1:-1])         # Put the production slice back on the stack
+                            statestack.pop()                    # Pop back one state (before the reduce)
+                            state = statestack[-1]
+                            sym.type = 'error'
+                            sym.value = 'error'
+                            lookahead = sym
+                            errorcount = error_count
+                            self.errorok = False
+
+                        continue
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+                    else:
+
+                        #--! TRACKING
+                        if tracking:
+                            sym.lineno = lexer.lineno
+                            sym.lexpos = lexer.lexpos
+                        #--! TRACKING
+
+                        targ = [sym]
+
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                        # The code enclosed in this section is duplicated
+                        # above as a performance optimization.  Make sure
+                        # changes get made in both locations.
+
+                        pslice.slice = targ
+
+                        try:
+                            # Call the grammar rule with our special slice object
+                            self.state = state
+                            p.callable(pslice)
+                            #--! DEBUG
+                            debug.info('Result : %s', format_result(pslice[0]))
+                            #--! DEBUG
+                            symstack.append(sym)
+                            state = goto[statestack[-1]][pname]
+                            statestack.append(state)
+                        except SyntaxError:
+                            # If an error was set. Enter error recovery state
+                            lookaheadstack.append(lookahead)    # Save the current lookahead token
+                            statestack.pop()                    # Pop back one state (before the reduce)
+                            state = statestack[-1]
+                            sym.type = 'error'
+                            sym.value = 'error'
+                            lookahead = sym
+                            errorcount = error_count
+                            self.errorok = False
+
+                        continue
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+                if t == 0:
+                    n = symstack[-1]
+                    result = getattr(n, 'value', None)
+                    #--! DEBUG
+                    debug.info('Done   : Returning %s', format_result(result))
+                    debug.info('PLY: PARSE DEBUG END')
+                    #--! DEBUG
+                    return result
+
+            if t is None:
+
+                #--! DEBUG
+                debug.error('Error  : %s',
+                            ('%s . %s' % (' '.join([xx.type for xx in symstack][1:]), str(lookahead))).lstrip())
+                #--! DEBUG
+
+                # We have some kind of parsing error here.  To handle
+                # this, we are going to push the current token onto
+                # the tokenstack and replace it with an 'error' token.
+                # If there are any synchronization rules, they may
+                # catch it.
+                #
+                # In addition to pushing the error token, we call call
+                # the user defined p_error() function if this is the
+                # first syntax error.  This function is only called if
+                # errorcount == 0.
+                if errorcount == 0 or self.errorok:
+                    errorcount = error_count
+                    self.errorok = False
+                    errtoken = lookahead
+                    if errtoken.type == '$end':
+                        errtoken = None               # End of file!
+                    if self.errorfunc:
+                        if errtoken and not hasattr(errtoken, 'lexer'):
+                            errtoken.lexer = lexer
+                        self.state = state
+                        tok = call_errorfunc(self.errorfunc, errtoken, self)
+                        if self.errorok:
+                            # User must have done some kind of panic
+                            # mode recovery on their own.  The
+                            # returned token is the next lookahead
+                            lookahead = tok
+                            errtoken = None
+                            continue
+                    else:
+                        if errtoken:
+                            if hasattr(errtoken, 'lineno'):
+                                lineno = lookahead.lineno
+                            else:
+                                lineno = 0
+                            if lineno:
+                                sys.stderr.write('yacc: Syntax error at line %d, token=%s\n' % (lineno, errtoken.type))
+                            else:
+                                sys.stderr.write('yacc: Syntax error, token=%s' % errtoken.type)
+                        else:
+                            sys.stderr.write('yacc: Parse error in input. EOF\n')
+                            return
+
+                else:
+                    errorcount = error_count
+
+                # case 1:  the statestack only has 1 entry on it.  If we're in this state, the
+                # entire parse has been rolled back and we're completely hosed.   The token is
+                # discarded and we just keep going.
+
+                if len(statestack) <= 1 and lookahead.type != '$end':
+                    lookahead = None
+                    errtoken = None
+                    state = 0
+                    # Nuke the pushback stack
+                    del lookaheadstack[:]
+                    continue
+
+                # case 2: the statestack has a couple of entries on it, but we're
+                # at the end of the file. nuke the top entry and generate an error token
+
+                # Start nuking entries on the stack
+                if lookahead.type == '$end':
+                    # Whoa. We're really hosed here. Bail out
+                    return
+
+                if lookahead.type != 'error':
+                    sym = symstack[-1]
+                    if sym.type == 'error':
+                        # Hmmm. Error is on top of stack, we'll just nuke input
+                        # symbol and continue
+                        #--! TRACKING
+                        if tracking:
+                            sym.endlineno = getattr(lookahead, 'lineno', sym.lineno)
+                            sym.endlexpos = getattr(lookahead, 'lexpos', sym.lexpos)
+                        #--! TRACKING
+                        lookahead = None
+                        continue
+
+                    # Create the error symbol for the first time and make it the new lookahead symbol
+                    t = YaccSymbol()
+                    t.type = 'error'
+
+                    if hasattr(lookahead, 'lineno'):
+                        t.lineno = t.endlineno = lookahead.lineno
+                    if hasattr(lookahead, 'lexpos'):
+                        t.lexpos = t.endlexpos = lookahead.lexpos
+                    t.value = lookahead
+                    lookaheadstack.append(lookahead)
+                    lookahead = t
+                else:
+                    sym = symstack.pop()
+                    #--! TRACKING
+                    if tracking:
+                        lookahead.lineno = sym.lineno
+                        lookahead.lexpos = sym.lexpos
+                    #--! TRACKING
+                    statestack.pop()
+                    state = statestack[-1]
+
+                continue
+
+            # Call an error function here
+            raise RuntimeError('yacc: internal parser error!!!\n')
+
+        #--! parsedebug-end
+
+    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+    # parseopt().
+    #
+    # Optimized version of parse() method.  DO NOT EDIT THIS CODE DIRECTLY!
+    # This code is automatically generated by the ply/ygen.py script. Make
+    # changes to the parsedebug() method instead.
+    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+    def parseopt(self, input=None, lexer=None, debug=False, tracking=False, tokenfunc=None):
+        #--! parseopt-start
+        lookahead = None                         # Current lookahead symbol
+        lookaheadstack = []                      # Stack of lookahead symbols
+        actions = self.action                    # Local reference to action table (to avoid lookup on self.)
+        goto    = self.goto                      # Local reference to goto table (to avoid lookup on self.)
+        prod    = self.productions               # Local reference to production list (to avoid lookup on self.)
+        defaulted_states = self.defaulted_states # Local reference to defaulted states
+        pslice  = YaccProduction(None)           # Production object passed to grammar rules
+        errorcount = 0                           # Used during error recovery
+
+
+        # If no lexer was given, we will try to use the lex module
+        if not lexer:
+            from . import lex
+            lexer = lex.lexer
+
+        # Set up the lexer and parser objects on pslice
+        pslice.lexer = lexer
+        pslice.parser = self
+
+        # If input was supplied, pass to lexer
+        if input is not None:
+            lexer.input(input)
+
+        if tokenfunc is None:
+            # Tokenize function
+            get_token = lexer.token
+        else:
+            get_token = tokenfunc
+
+        # Set the parser() token method (sometimes used in error recovery)
+        self.token = get_token
+
+        # Set up the state and symbol stacks
+
+        statestack = []                # Stack of parsing states
+        self.statestack = statestack
+        symstack   = []                # Stack of grammar symbols
+        self.symstack = symstack
+
+        pslice.stack = symstack         # Put in the production
+        errtoken   = None               # Err token
+
+        # The start state is assumed to be (0,$end)
+
+        statestack.append(0)
+        sym = YaccSymbol()
+        sym.type = '$end'
+        symstack.append(sym)
+        state = 0
+        while True:
+            # Get the next symbol on the input.  If a lookahead symbol
+            # is already set, we just use that. Otherwise, we'll pull
+            # the next token off of the lookaheadstack or from the lexer
+
+
+            if state not in defaulted_states:
+                if not lookahead:
+                    if not lookaheadstack:
+                        lookahead = get_token()     # Get the next token
+                    else:
+                        lookahead = lookaheadstack.pop()
+                    if not lookahead:
+                        lookahead = YaccSymbol()
+                        lookahead.type = '$end'
+
+                # Check the action table
+                ltype = lookahead.type
+                t = actions[state].get(ltype)
+            else:
+                t = defaulted_states[state]
+
+
+            if t is not None:
+                if t > 0:
+                    # shift a symbol on the stack
+                    statestack.append(t)
+                    state = t
+
+
+                    symstack.append(lookahead)
+                    lookahead = None
+
+                    # Decrease error count on successful shift
+                    if errorcount:
+                        errorcount -= 1
+                    continue
+
+                if t < 0:
+                    # reduce a symbol on the stack, emit a production
+                    p = prod[-t]
+                    pname = p.name
+                    plen  = p.len
+
+                    # Get production function
+                    sym = YaccSymbol()
+                    sym.type = pname       # Production name
+                    sym.value = None
+
+
+                    if plen:
+                        targ = symstack[-plen-1:]
+                        targ[0] = sym
+
+                        #--! TRACKING
+                        if tracking:
+                            t1 = targ[1]
+                            sym.lineno = t1.lineno
+                            sym.lexpos = t1.lexpos
+                            t1 = targ[-1]
+                            sym.endlineno = getattr(t1, 'endlineno', t1.lineno)
+                            sym.endlexpos = getattr(t1, 'endlexpos', t1.lexpos)
+                        #--! TRACKING
+
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                        # The code enclosed in this section is duplicated
+                        # below as a performance optimization.  Make sure
+                        # changes get made in both locations.
+
+                        pslice.slice = targ
+
+                        try:
+                            # Call the grammar rule with our special slice object
+                            del symstack[-plen:]
+                            self.state = state
+                            p.callable(pslice)
+                            del statestack[-plen:]
+                            symstack.append(sym)
+                            state = goto[statestack[-1]][pname]
+                            statestack.append(state)
+                        except SyntaxError:
+                            # If an error was set. Enter error recovery state
+                            lookaheadstack.append(lookahead)    # Save the current lookahead token
+                            symstack.extend(targ[1:-1])         # Put the production slice back on the stack
+                            statestack.pop()                    # Pop back one state (before the reduce)
+                            state = statestack[-1]
+                            sym.type = 'error'
+                            sym.value = 'error'
+                            lookahead = sym
+                            errorcount = error_count
+                            self.errorok = False
+
+                        continue
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+                    else:
+
+                        #--! TRACKING
+                        if tracking:
+                            sym.lineno = lexer.lineno
+                            sym.lexpos = lexer.lexpos
+                        #--! TRACKING
+
+                        targ = [sym]
+
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                        # The code enclosed in this section is duplicated
+                        # above as a performance optimization.  Make sure
+                        # changes get made in both locations.
+
+                        pslice.slice = targ
+
+                        try:
+                            # Call the grammar rule with our special slice object
+                            self.state = state
+                            p.callable(pslice)
+                            symstack.append(sym)
+                            state = goto[statestack[-1]][pname]
+                            statestack.append(state)
+                        except SyntaxError:
+                            # If an error was set. Enter error recovery state
+                            lookaheadstack.append(lookahead)    # Save the current lookahead token
+                            statestack.pop()                    # Pop back one state (before the reduce)
+                            state = statestack[-1]
+                            sym.type = 'error'
+                            sym.value = 'error'
+                            lookahead = sym
+                            errorcount = error_count
+                            self.errorok = False
+
+                        continue
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+                if t == 0:
+                    n = symstack[-1]
+                    result = getattr(n, 'value', None)
+                    return result
+
+            if t is None:
+
+
+                # We have some kind of parsing error here.  To handle
+                # this, we are going to push the current token onto
+                # the tokenstack and replace it with an 'error' token.
+                # If there are any synchronization rules, they may
+                # catch it.
+                #
+                # In addition to pushing the error token, we call call
+                # the user defined p_error() function if this is the
+                # first syntax error.  This function is only called if
+                # errorcount == 0.
+                if errorcount == 0 or self.errorok:
+                    errorcount = error_count
+                    self.errorok = False
+                    errtoken = lookahead
+                    if errtoken.type == '$end':
+                        errtoken = None               # End of file!
+                    if self.errorfunc:
+                        if errtoken and not hasattr(errtoken, 'lexer'):
+                            errtoken.lexer = lexer
+                        self.state = state
+                        tok = call_errorfunc(self.errorfunc, errtoken, self)
+                        if self.errorok:
+                            # User must have done some kind of panic
+                            # mode recovery on their own.  The
+                            # returned token is the next lookahead
+                            lookahead = tok
+                            errtoken = None
+                            continue
+                    else:
+                        if errtoken:
+                            if hasattr(errtoken, 'lineno'):
+                                lineno = lookahead.lineno
+                            else:
+                                lineno = 0
+                            if lineno:
+                                sys.stderr.write('yacc: Syntax error at line %d, token=%s\n' % (lineno, errtoken.type))
+                            else:
+                                sys.stderr.write('yacc: Syntax error, token=%s' % errtoken.type)
+                        else:
+                            sys.stderr.write('yacc: Parse error in input. EOF\n')
+                            return
+
+                else:
+                    errorcount = error_count
+
+                # case 1:  the statestack only has 1 entry on it.  If we're in this state, the
+                # entire parse has been rolled back and we're completely hosed.   The token is
+                # discarded and we just keep going.
+
+                if len(statestack) <= 1 and lookahead.type != '$end':
+                    lookahead = None
+                    errtoken = None
+                    state = 0
+                    # Nuke the pushback stack
+                    del lookaheadstack[:]
+                    continue
+
+                # case 2: the statestack has a couple of entries on it, but we're
+                # at the end of the file. nuke the top entry and generate an error token
+
+                # Start nuking entries on the stack
+                if lookahead.type == '$end':
+                    # Whoa. We're really hosed here. Bail out
+                    return
+
+                if lookahead.type != 'error':
+                    sym = symstack[-1]
+                    if sym.type == 'error':
+                        # Hmmm. Error is on top of stack, we'll just nuke input
+                        # symbol and continue
+                        #--! TRACKING
+                        if tracking:
+                            sym.endlineno = getattr(lookahead, 'lineno', sym.lineno)
+                            sym.endlexpos = getattr(lookahead, 'lexpos', sym.lexpos)
+                        #--! TRACKING
+                        lookahead = None
+                        continue
+
+                    # Create the error symbol for the first time and make it the new lookahead symbol
+                    t = YaccSymbol()
+                    t.type = 'error'
+
+                    if hasattr(lookahead, 'lineno'):
+                        t.lineno = t.endlineno = lookahead.lineno
+                    if hasattr(lookahead, 'lexpos'):
+                        t.lexpos = t.endlexpos = lookahead.lexpos
+                    t.value = lookahead
+                    lookaheadstack.append(lookahead)
+                    lookahead = t
+                else:
+                    sym = symstack.pop()
+                    #--! TRACKING
+                    if tracking:
+                        lookahead.lineno = sym.lineno
+                        lookahead.lexpos = sym.lexpos
+                    #--! TRACKING
+                    statestack.pop()
+                    state = statestack[-1]
+
+                continue
+
+            # Call an error function here
+            raise RuntimeError('yacc: internal parser error!!!\n')
+
+        #--! parseopt-end
+
+    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+    # parseopt_notrack().
+    #
+    # Optimized version of parseopt() with line number tracking removed.
+    # DO NOT EDIT THIS CODE DIRECTLY. This code is automatically generated
+    # by the ply/ygen.py script. Make changes to the parsedebug() method instead.
+    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+    def parseopt_notrack(self, input=None, lexer=None, debug=False, tracking=False, tokenfunc=None):
+        #--! parseopt-notrack-start
+        lookahead = None                         # Current lookahead symbol
+        lookaheadstack = []                      # Stack of lookahead symbols
+        actions = self.action                    # Local reference to action table (to avoid lookup on self.)
+        goto    = self.goto                      # Local reference to goto table (to avoid lookup on self.)
+        prod    = self.productions               # Local reference to production list (to avoid lookup on self.)
+        defaulted_states = self.defaulted_states # Local reference to defaulted states
+        pslice  = YaccProduction(None)           # Production object passed to grammar rules
+        errorcount = 0                           # Used during error recovery
+
+
+        # If no lexer was given, we will try to use the lex module
+        if not lexer:
+            from . import lex
+            lexer = lex.lexer
+
+        # Set up the lexer and parser objects on pslice
+        pslice.lexer = lexer
+        pslice.parser = self
+
+        # If input was supplied, pass to lexer
+        if input is not None:
+            lexer.input(input)
+
+        if tokenfunc is None:
+            # Tokenize function
+            get_token = lexer.token
+        else:
+            get_token = tokenfunc
+
+        # Set the parser() token method (sometimes used in error recovery)
+        self.token = get_token
+
+        # Set up the state and symbol stacks
+
+        statestack = []                # Stack of parsing states
+        self.statestack = statestack
+        symstack   = []                # Stack of grammar symbols
+        self.symstack = symstack
+
+        pslice.stack = symstack         # Put in the production
+        errtoken   = None               # Err token
+
+        # The start state is assumed to be (0,$end)
+
+        statestack.append(0)
+        sym = YaccSymbol()
+        sym.type = '$end'
+        symstack.append(sym)
+        state = 0
+        while True:
+            # Get the next symbol on the input.  If a lookahead symbol
+            # is already set, we just use that. Otherwise, we'll pull
+            # the next token off of the lookaheadstack or from the lexer
+
+
+            if state not in defaulted_states:
+                if not lookahead:
+                    if not lookaheadstack:
+                        lookahead = get_token()     # Get the next token
+                    else:
+                        lookahead = lookaheadstack.pop()
+                    if not lookahead:
+                        lookahead = YaccSymbol()
+                        lookahead.type = '$end'
+
+                # Check the action table
+                ltype = lookahead.type
+                t = actions[state].get(ltype)
+            else:
+                t = defaulted_states[state]
+
+
+            if t is not None:
+                if t > 0:
+                    # shift a symbol on the stack
+                    statestack.append(t)
+                    state = t
+
+
+                    symstack.append(lookahead)
+                    lookahead = None
+
+                    # Decrease error count on successful shift
+                    if errorcount:
+                        errorcount -= 1
+                    continue
+
+                if t < 0:
+                    # reduce a symbol on the stack, emit a production
+                    p = prod[-t]
+                    pname = p.name
+                    plen  = p.len
+
+                    # Get production function
+                    sym = YaccSymbol()
+                    sym.type = pname       # Production name
+                    sym.value = None
+
+
+                    if plen:
+                        targ = symstack[-plen-1:]
+                        targ[0] = sym
+
+
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                        # The code enclosed in this section is duplicated
+                        # below as a performance optimization.  Make sure
+                        # changes get made in both locations.
+
+                        pslice.slice = targ
+
+                        try:
+                            # Call the grammar rule with our special slice object
+                            del symstack[-plen:]
+                            self.state = state
+                            p.callable(pslice)
+                            del statestack[-plen:]
+                            symstack.append(sym)
+                            state = goto[statestack[-1]][pname]
+                            statestack.append(state)
+                        except SyntaxError:
+                            # If an error was set. Enter error recovery state
+                            lookaheadstack.append(lookahead)    # Save the current lookahead token
+                            symstack.extend(targ[1:-1])         # Put the production slice back on the stack
+                            statestack.pop()                    # Pop back one state (before the reduce)
+                            state = statestack[-1]
+                            sym.type = 'error'
+                            sym.value = 'error'
+                            lookahead = sym
+                            errorcount = error_count
+                            self.errorok = False
+
+                        continue
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+                    else:
+
+
+                        targ = [sym]
+
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                        # The code enclosed in this section is duplicated
+                        # above as a performance optimization.  Make sure
+                        # changes get made in both locations.
+
+                        pslice.slice = targ
+
+                        try:
+                            # Call the grammar rule with our special slice object
+                            self.state = state
+                            p.callable(pslice)
+                            symstack.append(sym)
+                            state = goto[statestack[-1]][pname]
+                            statestack.append(state)
+                        except SyntaxError:
+                            # If an error was set. Enter error recovery state
+                            lookaheadstack.append(lookahead)    # Save the current lookahead token
+                            statestack.pop()                    # Pop back one state (before the reduce)
+                            state = statestack[-1]
+                            sym.type = 'error'
+                            sym.value = 'error'
+                            lookahead = sym
+                            errorcount = error_count
+                            self.errorok = False
+
+                        continue
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+                if t == 0:
+                    n = symstack[-1]
+                    result = getattr(n, 'value', None)
+                    return result
+
+            if t is None:
+
+
+                # We have some kind of parsing error here.  To handle
+                # this, we are going to push the current token onto
+                # the tokenstack and replace it with an 'error' token.
+                # If there are any synchronization rules, they may
+                # catch it.
+                #
+                # In addition to pushing the error token, we call call
+                # the user defined p_error() function if this is the
+                # first syntax error.  This function is only called if
+                # errorcount == 0.
+                if errorcount == 0 or self.errorok:
+                    errorcount = error_count
+                    self.errorok = False
+                    errtoken = lookahead
+                    if errtoken.type == '$end':
+                        errtoken = None               # End of file!
+                    if self.errorfunc:
+                        if errtoken and not hasattr(errtoken, 'lexer'):
+                            errtoken.lexer = lexer
+                        self.state = state
+                        tok = call_errorfunc(self.errorfunc, errtoken, self)
+                        if self.errorok:
+                            # User must have done some kind of panic
+                            # mode recovery on their own.  The
+                            # returned token is the next lookahead
+                            lookahead = tok
+                            errtoken = None
+                            continue
+                    else:
+                        if errtoken:
+                            if hasattr(errtoken, 'lineno'):
+                                lineno = lookahead.lineno
+                            else:
+                                lineno = 0
+                            if lineno:
+                                sys.stderr.write('yacc: Syntax error at line %d, token=%s\n' % (lineno, errtoken.type))
+                            else:
+                                sys.stderr.write('yacc: Syntax error, token=%s' % errtoken.type)
+                        else:
+                            sys.stderr.write('yacc: Parse error in input. EOF\n')
+                            return
+
+                else:
+                    errorcount = error_count
+
+                # case 1:  the statestack only has 1 entry on it.  If we're in this state, the
+                # entire parse has been rolled back and we're completely hosed.   The token is
+                # discarded and we just keep going.
+
+                if len(statestack) <= 1 and lookahead.type != '$end':
+                    lookahead = None
+                    errtoken = None
+                    state = 0
+                    # Nuke the pushback stack
+                    del lookaheadstack[:]
+                    continue
+
+                # case 2: the statestack has a couple of entries on it, but we're
+                # at the end of the file. nuke the top entry and generate an error token
+
+                # Start nuking entries on the stack
+                if lookahead.type == '$end':
+                    # Whoa. We're really hosed here. Bail out
+                    return
+
+                if lookahead.type != 'error':
+                    sym = symstack[-1]
+                    if sym.type == 'error':
+                        # Hmmm. Error is on top of stack, we'll just nuke input
+                        # symbol and continue
+                        lookahead = None
+                        continue
+
+                    # Create the error symbol for the first time and make it the new lookahead symbol
+                    t = YaccSymbol()
+                    t.type = 'error'
+
+                    if hasattr(lookahead, 'lineno'):
+                        t.lineno = t.endlineno = lookahead.lineno
+                    if hasattr(lookahead, 'lexpos'):
+                        t.lexpos = t.endlexpos = lookahead.lexpos
+                    t.value = lookahead
+                    lookaheadstack.append(lookahead)
+                    lookahead = t
+                else:
+                    sym = symstack.pop()
+                    statestack.pop()
+                    state = statestack[-1]
+
+                continue
+
+            # Call an error function here
+            raise RuntimeError('yacc: internal parser error!!!\n')
+
+        #--! parseopt-notrack-end
+
+# -----------------------------------------------------------------------------
+#                          === Grammar Representation ===
+#
+# The following functions, classes, and variables are used to represent and
+# manipulate the rules that make up a grammar.
+# -----------------------------------------------------------------------------
+
+# regex matching identifiers
+_is_identifier = re.compile(r'^[a-zA-Z0-9_-]+$')
+
+# -----------------------------------------------------------------------------
+# class Production:
+#
+# This class stores the raw information about a single production or grammar rule.
+# A grammar rule refers to a specification such as this:
+#
+#       expr : expr PLUS term
+#
+# Here are the basic attributes defined on all productions
+#
+#       name     - Name of the production.  For example 'expr'
+#       prod     - A list of symbols on the right side ['expr','PLUS','term']
+#       prec     - Production precedence level
+#       number   - Production number.
+#       func     - Function that executes on reduce
+#       file     - File where production function is defined
+#       lineno   - Line number where production function is defined
+#
+# The following attributes are defined or optional.
+#
+#       len       - Length of the production (number of symbols on right hand side)
+#       usyms     - Set of unique symbols found in the production
+# -----------------------------------------------------------------------------
+
+class Production(object):
+    reduced = 0
+    def __init__(self, number, name, prod, precedence=('right', 0), func=None, file='', line=0):
+        self.name     = name
+        self.prod     = tuple(prod)
+        self.number   = number
+        self.func     = func
+        self.callable = None
+        self.file     = file
+        self.line     = line
+        self.prec     = precedence
+
+        # Internal settings used during table construction
+
+        self.len  = len(self.prod)   # Length of the production
+
+        # Create a list of unique production symbols used in the production
+        self.usyms = []
+        for s in self.prod:
+            if s not in self.usyms:
+                self.usyms.append(s)
+
+        # List of all LR items for the production
+        self.lr_items = []
+        self.lr_next = None
+
+        # Create a string representation
+        if self.prod:
+            self.str = '%s -> %s' % (self.name, ' '.join(self.prod))
+        else:
+            self.str = '%s -> <empty>' % self.name
+
+    def __str__(self):
+        return self.str
+
+    def __repr__(self):
+        return 'Production(' + str(self) + ')'
+
+    def __len__(self):
+        return len(self.prod)
+
+    def __nonzero__(self):
+        return 1
+
+    def __getitem__(self, index):
+        return self.prod[index]
+
+    # Return the nth lr_item from the production (or None if at the end)
+    def lr_item(self, n):
+        if n > len(self.prod):
+            return None
+        p = LRItem(self, n)
+        # Precompute the list of productions immediately following.
+        try:
+            p.lr_after = Prodnames[p.prod[n+1]]
+        except (IndexError, KeyError):
+            p.lr_after = []
+        try:
+            p.lr_before = p.prod[n-1]
+        except IndexError:
+            p.lr_before = None
+        return p
+
+    # Bind the production function name to a callable
+    def bind(self, pdict):
+        if self.func:
+            self.callable = pdict[self.func]
+
+# This class serves as a minimal standin for Production objects when
+# reading table data from files.   It only contains information
+# actually used by the LR parsing engine, plus some additional
+# debugging information.
+class MiniProduction(object):
+    def __init__(self, str, name, len, func, file, line):
+        self.name     = name
+        self.len      = len
+        self.func     = func
+        self.callable = None
+        self.file     = file
+        self.line     = line
+        self.str      = str
+
+    def __str__(self):
+        return self.str
+
+    def __repr__(self):
+        return 'MiniProduction(%s)' % self.str
+
+    # Bind the production function name to a callable
+    def bind(self, pdict):
+        if self.func:
+            self.callable = pdict[self.func]
+
+
+# -----------------------------------------------------------------------------
+# class LRItem
+#
+# This class represents a specific stage of parsing a production rule.  For
+# example:
+#
+#       expr : expr . PLUS term
+#
+# In the above, the "." represents the current location of the parse.  Here
+# basic attributes:
+#
+#       name       - Name of the production.  For example 'expr'
+#       prod       - A list of symbols on the right side ['expr','.', 'PLUS','term']
+#       number     - Production number.
+#
+#       lr_next      Next LR item. Example, if we are ' expr -> expr . PLUS term'
+#                    then lr_next refers to 'expr -> expr PLUS . term'
+#       lr_index   - LR item index (location of the ".") in the prod list.
+#       lookaheads - LALR lookahead symbols for this item
+#       len        - Length of the production (number of symbols on right hand side)
+#       lr_after    - List of all productions that immediately follow
+#       lr_before   - Grammar symbol immediately before
+# -----------------------------------------------------------------------------
+
+class LRItem(object):
+    def __init__(self, p, n):
+        self.name       = p.name
+        self.prod       = list(p.prod)
+        self.number     = p.number
+        self.lr_index   = n
+        self.lookaheads = {}
+        self.prod.insert(n, '.')
+        self.prod       = tuple(self.prod)
+        self.len        = len(self.prod)
+        self.usyms      = p.usyms
+
+    def __str__(self):
+        if self.prod:
+            s = '%s -> %s' % (self.name, ' '.join(self.prod))
+        else:
+            s = '%s -> <empty>' % self.name
+        return s
+
+    def __repr__(self):
+        return 'LRItem(' + str(self) + ')'
+
+# -----------------------------------------------------------------------------
+# rightmost_terminal()
+#
+# Return the rightmost terminal from a list of symbols.  Used in add_production()
+# -----------------------------------------------------------------------------
+def rightmost_terminal(symbols, terminals):
+    i = len(symbols) - 1
+    while i >= 0:
+        if symbols[i] in terminals:
+            return symbols[i]
+        i -= 1
+    return None
+
+# -----------------------------------------------------------------------------
+#                           === GRAMMAR CLASS ===
+#
+# The following class represents the contents of the specified grammar along
+# with various computed properties such as first sets, follow sets, LR items, etc.
+# This data is used for critical parts of the table generation process later.
+# -----------------------------------------------------------------------------
+
+class GrammarError(YaccError):
+    pass
+
+class Grammar(object):
+    def __init__(self, terminals):
+        self.Productions  = [None]  # A list of all of the productions.  The first
+                                    # entry is always reserved for the purpose of
+                                    # building an augmented grammar
+
+        self.Prodnames    = {}      # A dictionary mapping the names of nonterminals to a list of all
+                                    # productions of that nonterminal.
+
+        self.Prodmap      = {}      # A dictionary that is only used to detect duplicate
+                                    # productions.
+
+        self.Terminals    = {}      # A dictionary mapping the names of terminal symbols to a
+                                    # list of the rules where they are used.
+
+        for term in terminals:
+            self.Terminals[term] = []
+
+        self.Terminals['error'] = []
+
+        self.Nonterminals = {}      # A dictionary mapping names of nonterminals to a list
+                                    # of rule numbers where they are used.
+
+        self.First        = {}      # A dictionary of precomputed FIRST(x) symbols
+
+        self.Follow       = {}      # A dictionary of precomputed FOLLOW(x) symbols
+
+        self.Precedence   = {}      # Precedence rules for each terminal. Contains tuples of the
+                                    # form ('right',level) or ('nonassoc', level) or ('left',level)
+
+        self.UsedPrecedence = set() # Precedence rules that were actually used by the grammer.
+                                    # This is only used to provide error checking and to generate
+                                    # a warning about unused precedence rules.
+
+        self.Start = None           # Starting symbol for the grammar
+
+
+    def __len__(self):
+        return len(self.Productions)
+
+    def __getitem__(self, index):
+        return self.Productions[index]
+
+    # -----------------------------------------------------------------------------
+    # set_precedence()
+    #
+    # Sets the precedence for a given terminal. assoc is the associativity such as
+    # 'left','right', or 'nonassoc'.  level is a numeric level.
+    #
+    # -----------------------------------------------------------------------------
+
+    def set_precedence(self, term, assoc, level):
+        assert self.Productions == [None], 'Must call set_precedence() before add_production()'
+        if term in self.Precedence:
+            raise GrammarError('Precedence already specified for terminal %r' % term)
+        if assoc not in ['left', 'right', 'nonassoc']:
+            raise GrammarError("Associativity must be one of 'left','right', or 'nonassoc'")
+        self.Precedence[term] = (assoc, level)
+
+    # -----------------------------------------------------------------------------
+    # add_production()
+    #
+    # Given an action function, this function assembles a production rule and
+    # computes its precedence level.
+    #
+    # The production rule is supplied as a list of symbols.   For example,
+    # a rule such as 'expr : expr PLUS term' has a production name of 'expr' and
+    # symbols ['expr','PLUS','term'].
+    #
+    # Precedence is determined by the precedence of the right-most non-terminal
+    # or the precedence of a terminal specified by %prec.
+    #
+    # A variety of error checks are performed to make sure production symbols
+    # are valid and that %prec is used correctly.
+    # -----------------------------------------------------------------------------
+
+    def add_production(self, prodname, syms, func=None, file='', line=0):
+
+        if prodname in self.Terminals:
+            raise GrammarError('%s:%d: Illegal rule name %r. Already defined as a token' % (file, line, prodname))
+        if prodname == 'error':
+            raise GrammarError('%s:%d: Illegal rule name %r. error is a reserved word' % (file, line, prodname))
+        if not _is_identifier.match(prodname):
+            raise GrammarError('%s:%d: Illegal rule name %r' % (file, line, prodname))
+
+        # Look for literal tokens
+        for n, s in enumerate(syms):
+            if s[0] in "'\"":
+                try:
+                    c = eval(s)
+                    if (len(c) > 1):
+                        raise GrammarError('%s:%d: Literal token %s in rule %r may only be a single character' %
+                                           (file, line, s, prodname))
+                    if c not in self.Terminals:
+                        self.Terminals[c] = []
+                    syms[n] = c
+                    continue
+                except SyntaxError:
+                    pass
+            if not _is_identifier.match(s) and s != '%prec':
+                raise GrammarError('%s:%d: Illegal name %r in rule %r' % (file, line, s, prodname))
+
+        # Determine the precedence level
+        if '%prec' in syms:
+            if syms[-1] == '%prec':
+                raise GrammarError('%s:%d: Syntax error. Nothing follows %%prec' % (file, line))
+            if syms[-2] != '%prec':
+                raise GrammarError('%s:%d: Syntax error. %%prec can only appear at the end of a grammar rule' %
+                                   (file, line))
+            precname = syms[-1]
+            prodprec = self.Precedence.get(precname)
+            if not prodprec:
+                raise GrammarError('%s:%d: Nothing known about the precedence of %r' % (file, line, precname))
+            else:
+                self.UsedPrecedence.add(precname)
+            del syms[-2:]     # Drop %prec from the rule
+        else:
+            # If no %prec, precedence is determined by the rightmost terminal symbol
+            precname = rightmost_terminal(syms, self.Terminals)
+            prodprec = self.Precedence.get(precname, ('right', 0))
+
+        # See if the rule is already in the rulemap
+        map = '%s -> %s' % (prodname, syms)
+        if map in self.Prodmap:
+            m = self.Prodmap[map]
+            raise GrammarError('%s:%d: Duplicate rule %s. ' % (file, line, m) +
+                               'Previous definition at %s:%d' % (m.file, m.line))
+
+        # From this point on, everything is valid.  Create a new Production instance
+        pnumber  = len(self.Productions)
+        if prodname not in self.Nonterminals:
+            self.Nonterminals[prodname] = []
+
+        # Add the production number to Terminals and Nonterminals
+        for t in syms:
+            if t in self.Terminals:
+                self.Terminals[t].append(pnumber)
+            else:
+                if t not in self.Nonterminals:
+                    self.Nonterminals[t] = []
+                self.Nonterminals[t].append(pnumber)
+
+        # Create a production and add it to the list of productions
+        p = Production(pnumber, prodname, syms, prodprec, func, file, line)
+        self.Productions.append(p)
+        self.Prodmap[map] = p
+
+        # Add to the global productions list
+        try:
+            self.Prodnames[prodname].append(p)
+        except KeyError:
+            self.Prodnames[prodname] = [p]
+
+    # -----------------------------------------------------------------------------
+    # set_start()
+    #
+    # Sets the starting symbol and creates the augmented grammar.  Production
+    # rule 0 is S' -> start where start is the start symbol.
+    # -----------------------------------------------------------------------------
+
+    def set_start(self, start=None):
+        if not start:
+            start = self.Productions[1].name
+        if start not in self.Nonterminals:
+            raise GrammarError('start symbol %s undefined' % start)
+        self.Productions[0] = Production(0, "S'", [start])
+        self.Nonterminals[start].append(0)
+        self.Start = start
+
+    # -----------------------------------------------------------------------------
+    # find_unreachable()
+    #
+    # Find all of the nonterminal symbols that can't be reached from the starting
+    # symbol.  Returns a list of nonterminals that can't be reached.
+    # -----------------------------------------------------------------------------
+
+    def find_unreachable(self):
+
+        # Mark all symbols that are reachable from a symbol s
+        def mark_reachable_from(s):
+            if s in reachable:
+                return
+            reachable.add(s)
+            for p in self.Prodnames.get(s, []):
+                for r in p.prod:
+                    mark_reachable_from(r)
+
+        reachable = set()
+        mark_reachable_from(self.Productions[0].prod[0])
+        return [s for s in self.Nonterminals if s not in reachable]
+
+    # -----------------------------------------------------------------------------
+    # infinite_cycles()
+    #
+    # This function looks at the various parsing rules and tries to detect
+    # infinite recursion cycles (grammar rules where there is no possible way
+    # to derive a string of only terminals).
+    # -----------------------------------------------------------------------------
+
+    def infinite_cycles(self):
+        terminates = {}
+
+        # Terminals:
+        for t in self.Terminals:
+            terminates[t] = True
+
+        terminates['$end'] = True
+
+        # Nonterminals:
+
+        # Initialize to false:
+        for n in self.Nonterminals:
+            terminates[n] = False
+
+        # Then propagate termination until no change:
+        while True:
+            some_change = False
+            for (n, pl) in self.Prodnames.items():
+                # Nonterminal n terminates iff any of its productions terminates.
+                for p in pl:
+                    # Production p terminates iff all of its rhs symbols terminate.
+                    for s in p.prod:
+                        if not terminates[s]:
+                            # The symbol s does not terminate,
+                            # so production p does not terminate.
+                            p_terminates = False
+                            break
+                    else:
+                        # didn't break from the loop,
+                        # so every symbol s terminates
+                        # so production p terminates.
+                        p_terminates = True
+
+                    if p_terminates:
+                        # symbol n terminates!
+                        if not terminates[n]:
+                            terminates[n] = True
+                            some_change = True
+                        # Don't need to consider any more productions for this n.
+                        break
+
+            if not some_change:
+                break
+
+        infinite = []
+        for (s, term) in terminates.items():
+            if not term:
+                if s not in self.Prodnames and s not in self.Terminals and s != 'error':
+                    # s is used-but-not-defined, and we've already warned of that,
+                    # so it would be overkill to say that it's also non-terminating.
+                    pass
+                else:
+                    infinite.append(s)
+
+        return infinite
+
+    # -----------------------------------------------------------------------------
+    # undefined_symbols()
+    #
+    # Find all symbols that were used the grammar, but not defined as tokens or
+    # grammar rules.  Returns a list of tuples (sym, prod) where sym in the symbol
+    # and prod is the production where the symbol was used.
+    # -----------------------------------------------------------------------------
+    def undefined_symbols(self):
+        result = []
+        for p in self.Productions:
+            if not p:
+                continue
+
+            for s in p.prod:
+                if s not in self.Prodnames and s not in self.Terminals and s != 'error':
+                    result.append((s, p))
+        return result
+
+    # -----------------------------------------------------------------------------
+    # unused_terminals()
+    #
+    # Find all terminals that were defined, but not used by the grammar.  Returns
+    # a list of all symbols.
+    # -----------------------------------------------------------------------------
+    def unused_terminals(self):
+        unused_tok = []
+        for s, v in self.Terminals.items():
+            if s != 'error' and not v:
+                unused_tok.append(s)
+
+        return unused_tok
+
+    # ------------------------------------------------------------------------------
+    # unused_rules()
+    #
+    # Find all grammar rules that were defined,  but not used (maybe not reachable)
+    # Returns a list of productions.
+    # ------------------------------------------------------------------------------
+
+    def unused_rules(self):
+        unused_prod = []
+        for s, v in self.Nonterminals.items():
+            if not v:
+                p = self.Prodnames[s][0]
+                unused_prod.append(p)
+        return unused_prod
+
+    # -----------------------------------------------------------------------------
+    # unused_precedence()
+    #
+    # Returns a list of tuples (term,precedence) corresponding to precedence
+    # rules that were never used by the grammar.  term is the name of the terminal
+    # on which precedence was applied and precedence is a string such as 'left' or
+    # 'right' corresponding to the type of precedence.
+    # -----------------------------------------------------------------------------
+
+    def unused_precedence(self):
+        unused = []
+        for termname in self.Precedence:
+            if not (termname in self.Terminals or termname in self.UsedPrecedence):
+                unused.append((termname, self.Precedence[termname][0]))
+
+        return unused
+
+    # -------------------------------------------------------------------------
+    # _first()
+    #
+    # Compute the value of FIRST1(beta) where beta is a tuple of symbols.
+    #
+    # During execution of compute_first1, the result may be incomplete.
+    # Afterward (e.g., when called from compute_follow()), it will be complete.
+    # -------------------------------------------------------------------------
+    def _first(self, beta):
+
+        # We are computing First(x1,x2,x3,...,xn)
+        result = []
+        for x in beta:
+            x_produces_empty = False
+
+            # Add all the non-<empty> symbols of First[x] to the result.
+            for f in self.First[x]:
+                if f == '<empty>':
+                    x_produces_empty = True
+                else:
+                    if f not in result:
+                        result.append(f)
+
+            if x_produces_empty:
+                # We have to consider the next x in beta,
+                # i.e. stay in the loop.
+                pass
+            else:
+                # We don't have to consider any further symbols in beta.
+                break
+        else:
+            # There was no 'break' from the loop,
+            # so x_produces_empty was true for all x in beta,
+            # so beta produces empty as well.
+            result.append('<empty>')
+
+        return result
+
+    # -------------------------------------------------------------------------
+    # compute_first()
+    #
+    # Compute the value of FIRST1(X) for all symbols
+    # -------------------------------------------------------------------------
+    def compute_first(self):
+        if self.First:
+            return self.First
+
+        # Terminals:
+        for t in self.Terminals:
+            self.First[t] = [t]
+
+        self.First['$end'] = ['$end']
+
+        # Nonterminals:
+
+        # Initialize to the empty set:
+        for n in self.Nonterminals:
+            self.First[n] = []
+
+        # Then propagate symbols until no change:
+        while True:
+            some_change = False
+            for n in self.Nonterminals:
+                for p in self.Prodnames[n]:
+                    for f in self._first(p.prod):
+                        if f not in self.First[n]:
+                            self.First[n].append(f)
+                            some_change = True
+            if not some_change:
+                break
+
+        return self.First
+
+    # ---------------------------------------------------------------------
+    # compute_follow()
+    #
+    # Computes all of the follow sets for every non-terminal symbol.  The
+    # follow set is the set of all symbols that might follow a given
+    # non-terminal.  See the Dragon book, 2nd Ed. p. 189.
+    # ---------------------------------------------------------------------
+    def compute_follow(self, start=None):
+        # If already computed, return the result
+        if self.Follow:
+            return self.Follow
+
+        # If first sets not computed yet, do that first.
+        if not self.First:
+            self.compute_first()
+
+        # Add '$end' to the follow list of the start symbol
+        for k in self.Nonterminals:
+            self.Follow[k] = []
+
+        if not start:
+            start = self.Productions[1].name
+
+        self.Follow[start] = ['$end']
+
+        while True:
+            didadd = False
+            for p in self.Productions[1:]:
+                # Here is the production set
+                for i, B in enumerate(p.prod):
+                    if B in self.Nonterminals:
+                        # Okay. We got a non-terminal in a production
+                        fst = self._first(p.prod[i+1:])
+                        hasempty = False
+                        for f in fst:
+                            if f != '<empty>' and f not in self.Follow[B]:
+                                self.Follow[B].append(f)
+                                didadd = True
+                            if f == '<empty>':
+                                hasempty = True
+                        if hasempty or i == (len(p.prod)-1):
+                            # Add elements of follow(a) to follow(b)
+                            for f in self.Follow[p.name]:
+                                if f not in self.Follow[B]:
+                                    self.Follow[B].append(f)
+                                    didadd = True
+            if not didadd:
+                break
+        return self.Follow
+
+
+    # -----------------------------------------------------------------------------
+    # build_lritems()
+    #
+    # This function walks the list of productions and builds a complete set of the
+    # LR items.  The LR items are stored in two ways:  First, they are uniquely
+    # numbered and placed in the list _lritems.  Second, a linked list of LR items
+    # is built for each production.  For example:
+    #
+    #   E -> E PLUS E
+    #
+    # Creates the list
+    #
+    #  [E -> . E PLUS E, E -> E . PLUS E, E -> E PLUS . E, E -> E PLUS E . ]
+    # -----------------------------------------------------------------------------
+
+    def build_lritems(self):
+        for p in self.Productions:
+            lastlri = p
+            i = 0
+            lr_items = []
+            while True:
+                if i > len(p):
+                    lri = None
+                else:
+                    lri = LRItem(p, i)
+                    # Precompute the list of productions immediately following
+                    try:
+                        lri.lr_after = self.Prodnames[lri.prod[i+1]]
+                    except (IndexError, KeyError):
+                        lri.lr_after = []
+                    try:
+                        lri.lr_before = lri.prod[i-1]
+                    except IndexError:
+                        lri.lr_before = None
+
+                lastlri.lr_next = lri
+                if not lri:
+                    break
+                lr_items.append(lri)
+                lastlri = lri
+                i += 1
+            p.lr_items = lr_items
+
+# -----------------------------------------------------------------------------
+#                            == Class LRTable ==
+#
+# This basic class represents a basic table of LR parsing information.
+# Methods for generating the tables are not defined here.  They are defined
+# in the derived class LRGeneratedTable.
+# -----------------------------------------------------------------------------
+
+class VersionError(YaccError):
+    pass
+
+class LRTable(object):
+    def __init__(self):
+        self.lr_action = None
+        self.lr_goto = None
+        self.lr_productions = None
+        self.lr_method = None
+
+    def read_table(self, module):
+        if isinstance(module, types.ModuleType):
+            parsetab = module
+        else:
+            exec('import %s' % module)
+            parsetab = sys.modules[module]
+
+        if parsetab._tabversion != __tabversion__:
+            raise VersionError('yacc table file version is out of date')
+
+        self.lr_action = parsetab._lr_action
+        self.lr_goto = parsetab._lr_goto
+
+        self.lr_productions = []
+        for p in parsetab._lr_productions:
+            self.lr_productions.append(MiniProduction(*p))
+
+        self.lr_method = parsetab._lr_method
+        return parsetab._lr_signature
+
+    def read_pickle(self, filename):
+        try:
+            import cPickle as pickle
+        except ImportError:
+            import pickle
+
+        if not os.path.exists(filename):
+          raise ImportError
+
+        in_f = open(filename, 'rb')
+
+        tabversion = pickle.load(in_f)
+        if tabversion != __tabversion__:
+            raise VersionError('yacc table file version is out of date')
+        self.lr_method = pickle.load(in_f)
+        signature      = pickle.load(in_f)
+        self.lr_action = pickle.load(in_f)
+        self.lr_goto   = pickle.load(in_f)
+        productions    = pickle.load(in_f)
+
+        self.lr_productions = []
+        for p in productions:
+            self.lr_productions.append(MiniProduction(*p))
+
+        in_f.close()
+        return signature
+
+    # Bind all production function names to callable objects in pdict
+    def bind_callables(self, pdict):
+        for p in self.lr_productions:
+            p.bind(pdict)
+
+
+# -----------------------------------------------------------------------------
+#                           === LR Generator ===
+#
+# The following classes and functions are used to generate LR parsing tables on
+# a grammar.
+# -----------------------------------------------------------------------------
+
+# -----------------------------------------------------------------------------
+# digraph()
+# traverse()
+#
+# The following two functions are used to compute set valued functions
+# of the form:
+#
+#     F(x) = F'(x) U U{F(y) | x R y}
+#
+# This is used to compute the values of Read() sets as well as FOLLOW sets
+# in LALR(1) generation.
+#
+# Inputs:  X    - An input set
+#          R    - A relation
+#          FP   - Set-valued function
+# ------------------------------------------------------------------------------
+
+def digraph(X, R, FP):
+    N = {}
+    for x in X:
+        N[x] = 0
+    stack = []
+    F = {}
+    for x in X:
+        if N[x] == 0:
+            traverse(x, N, stack, F, X, R, FP)
+    return F
+
+def traverse(x, N, stack, F, X, R, FP):
+    stack.append(x)
+    d = len(stack)
+    N[x] = d
+    F[x] = FP(x)             # F(X) <- F'(x)
+
+    rel = R(x)               # Get y's related to x
+    for y in rel:
+        if N[y] == 0:
+            traverse(y, N, stack, F, X, R, FP)
+        N[x] = min(N[x], N[y])
+        for a in F.get(y, []):
+            if a not in F[x]:
+                F[x].append(a)
+    if N[x] == d:
+        N[stack[-1]] = MAXINT
+        F[stack[-1]] = F[x]
+        element = stack.pop()
+        while element != x:
+            N[stack[-1]] = MAXINT
+            F[stack[-1]] = F[x]
+            element = stack.pop()
+
+class LALRError(YaccError):
+    pass
+
+# -----------------------------------------------------------------------------
+#                             == LRGeneratedTable ==
+#
+# This class implements the LR table generation algorithm.  There are no
+# public methods except for write()
+# -----------------------------------------------------------------------------
+
+class LRGeneratedTable(LRTable):
+    def __init__(self, grammar, method='LALR', log=None):
+        if method not in ['SLR', 'LALR']:
+            raise LALRError('Unsupported method %s' % method)
+
+        self.grammar = grammar
+        self.lr_method = method
+
+        # Set up the logger
+        if not log:
+            log = NullLogger()
+        self.log = log
+
+        # Internal attributes
+        self.lr_action     = {}        # Action table
+        self.lr_goto       = {}        # Goto table
+        self.lr_productions  = grammar.Productions    # Copy of grammar Production array
+        self.lr_goto_cache = {}        # Cache of computed gotos
+        self.lr0_cidhash   = {}        # Cache of closures
+
+        self._add_count    = 0         # Internal counter used to detect cycles
+
+        # Diagonistic information filled in by the table generator
+        self.sr_conflict   = 0
+        self.rr_conflict   = 0
+        self.conflicts     = []        # List of conflicts
+
+        self.sr_conflicts  = []
+        self.rr_conflicts  = []
+
+        # Build the tables
+        self.grammar.build_lritems()
+        self.grammar.compute_first()
+        self.grammar.compute_follow()
+        self.lr_parse_table()
+
+    # Compute the LR(0) closure operation on I, where I is a set of LR(0) items.
+
+    def lr0_closure(self, I):
+        self._add_count += 1
+
+        # Add everything in I to J
+        J = I[:]
+        didadd = True
+        while didadd:
+            didadd = False
+            for j in J:
+                for x in j.lr_after:
+                    if getattr(x, 'lr0_added', 0) == self._add_count:
+                        continue
+                    # Add B --> .G to J
+                    J.append(x.lr_next)
+                    x.lr0_added = self._add_count
+                    didadd = True
+
+        return J
+
+    # Compute the LR(0) goto function goto(I,X) where I is a set
+    # of LR(0) items and X is a grammar symbol.   This function is written
+    # in a way that guarantees uniqueness of the generated goto sets
+    # (i.e. the same goto set will never be returned as two different Python
+    # objects).  With uniqueness, we can later do fast set comparisons using
+    # id(obj) instead of element-wise comparison.
+
+    def lr0_goto(self, I, x):
+        # First we look for a previously cached entry
+        g = self.lr_goto_cache.get((id(I), x))
+        if g:
+            return g
+
+        # Now we generate the goto set in a way that guarantees uniqueness
+        # of the result
+
+        s = self.lr_goto_cache.get(x)
+        if not s:
+            s = {}
+            self.lr_goto_cache[x] = s
+
+        gs = []
+        for p in I:
+            n = p.lr_next
+            if n and n.lr_before == x:
+                s1 = s.get(id(n))
+                if not s1:
+                    s1 = {}
+                    s[id(n)] = s1
+                gs.append(n)
+                s = s1
+        g = s.get('$end')
+        if not g:
+            if gs:
+                g = self.lr0_closure(gs)
+                s['$end'] = g
+            else:
+                s['$end'] = gs
+        self.lr_goto_cache[(id(I), x)] = g
+        return g
+
+    # Compute the LR(0) sets of item function
+    def lr0_items(self):
+        C = [self.lr0_closure([self.grammar.Productions[0].lr_next])]
+        i = 0
+        for I in C:
+            self.lr0_cidhash[id(I)] = i
+            i += 1
+
+        # Loop over the items in C and each grammar symbols
+        i = 0
+        while i < len(C):
+            I = C[i]
+            i += 1
+
+            # Collect all of the symbols that could possibly be in the goto(I,X) sets
+            asyms = {}
+            for ii in I:
+                for s in ii.usyms:
+                    asyms[s] = None
+
+            for x in asyms:
+                g = self.lr0_goto(I, x)
+                if not g or id(g) in self.lr0_cidhash:
+                    continue
+                self.lr0_cidhash[id(g)] = len(C)
+                C.append(g)
+
+        return C
+
+    # -----------------------------------------------------------------------------
+    #                       ==== LALR(1) Parsing ====
+    #
+    # LALR(1) parsing is almost exactly the same as SLR except that instead of
+    # relying upon Follow() sets when performing reductions, a more selective
+    # lookahead set that incorporates the state of the LR(0) machine is utilized.
+    # Thus, we mainly just have to focus on calculating the lookahead sets.
+    #
+    # The method used here is due to DeRemer and Pennelo (1982).
+    #
+    # DeRemer, F. L., and T. J. Pennelo: "Efficient Computation of LALR(1)
+    #     Lookahead Sets", ACM Transactions on Programming Languages and Systems,
+    #     Vol. 4, No. 4, Oct. 1982, pp. 615-649
+    #
+    # Further details can also be found in:
+    #
+    #  J. Tremblay and P. Sorenson, "The Theory and Practice of Compiler Writing",
+    #      McGraw-Hill Book Company, (1985).
+    #
+    # -----------------------------------------------------------------------------
+
+    # -----------------------------------------------------------------------------
+    # compute_nullable_nonterminals()
+    #
+    # Creates a dictionary containing all of the non-terminals that might produce
+    # an empty production.
+    # -----------------------------------------------------------------------------
+
+    def compute_nullable_nonterminals(self):
+        nullable = set()
+        num_nullable = 0
+        while True:
+            for p in self.grammar.Productions[1:]:
+                if p.len == 0:
+                    nullable.add(p.name)
+                    continue
+                for t in p.prod:
+                    if t not in nullable:
+                        break
+                else:
+                    nullable.add(p.name)
+            if len(nullable) == num_nullable:
+                break
+            num_nullable = len(nullable)
+        return nullable
+
+    # -----------------------------------------------------------------------------
+    # find_nonterminal_trans(C)
+    #
+    # Given a set of LR(0) items, this functions finds all of the non-terminal
+    # transitions.    These are transitions in which a dot appears immediately before
+    # a non-terminal.   Returns a list of tuples of the form (state,N) where state
+    # is the state number and N is the nonterminal symbol.
+    #
+    # The input C is the set of LR(0) items.
+    # -----------------------------------------------------------------------------
+
+    def find_nonterminal_transitions(self, C):
+        trans = []
+        for stateno, state in enumerate(C):
+            for p in state:
+                if p.lr_index < p.len - 1:
+                    t = (stateno, p.prod[p.lr_index+1])
+                    if t[1] in self.grammar.Nonterminals:
+                        if t not in trans:
+                            trans.append(t)
+        return trans
+
+    # -----------------------------------------------------------------------------
+    # dr_relation()
+    #
+    # Computes the DR(p,A) relationships for non-terminal transitions.  The input
+    # is a tuple (state,N) where state is a number and N is a nonterminal symbol.
+    #
+    # Returns a list of terminals.
+    # -----------------------------------------------------------------------------
+
+    def dr_relation(self, C, trans, nullable):
+        dr_set = {}
+        state, N = trans
+        terms = []
+
+        g = self.lr0_goto(C[state], N)
+        for p in g:
+            if p.lr_index < p.len - 1:
+                a = p.prod[p.lr_index+1]
+                if a in self.grammar.Terminals:
+                    if a not in terms:
+                        terms.append(a)
+
+        # This extra bit is to handle the start state
+        if state == 0 and N == self.grammar.Productions[0].prod[0]:
+            terms.append('$end')
+
+        return terms
+
+    # -----------------------------------------------------------------------------
+    # reads_relation()
+    #
+    # Computes the READS() relation (p,A) READS (t,C).
+    # -----------------------------------------------------------------------------
+
+    def reads_relation(self, C, trans, empty):
+        # Look for empty transitions
+        rel = []
+        state, N = trans
+
+        g = self.lr0_goto(C[state], N)
+        j = self.lr0_cidhash.get(id(g), -1)
+        for p in g:
+            if p.lr_index < p.len - 1:
+                a = p.prod[p.lr_index + 1]
+                if a in empty:
+                    rel.append((j, a))
+
+        return rel
+
+    # -----------------------------------------------------------------------------
+    # compute_lookback_includes()
+    #
+    # Determines the lookback and includes relations
+    #
+    # LOOKBACK:
+    #
+    # This relation is determined by running the LR(0) state machine forward.
+    # For example, starting with a production "N : . A B C", we run it forward
+    # to obtain "N : A B C ."   We then build a relationship between this final
+    # state and the starting state.   These relationships are stored in a dictionary
+    # lookdict.
+    #
+    # INCLUDES:
+    #
+    # Computes the INCLUDE() relation (p,A) INCLUDES (p',B).
+    #
+    # This relation is used to determine non-terminal transitions that occur
+    # inside of other non-terminal transition states.   (p,A) INCLUDES (p', B)
+    # if the following holds:
+    #
+    #       B -> LAT, where T -> epsilon and p' -L-> p
+    #
+    # L is essentially a prefix (which may be empty), T is a suffix that must be
+    # able to derive an empty string.  State p' must lead to state p with the string L.
+    #
+    # -----------------------------------------------------------------------------
+
+    def compute_lookback_includes(self, C, trans, nullable):
+        lookdict = {}          # Dictionary of lookback relations
+        includedict = {}       # Dictionary of include relations
+
+        # Make a dictionary of non-terminal transitions
+        dtrans = {}
+        for t in trans:
+            dtrans[t] = 1
+
+        # Loop over all transitions and compute lookbacks and includes
+        for state, N in trans:
+            lookb = []
+            includes = []
+            for p in C[state]:
+                if p.name != N:
+                    continue
+
+                # Okay, we have a name match.  We now follow the production all the way
+                # through the state machine until we get the . on the right hand side
+
+                lr_index = p.lr_index
+                j = state
+                while lr_index < p.len - 1:
+                    lr_index = lr_index + 1
+                    t = p.prod[lr_index]
+
+                    # Check to see if this symbol and state are a non-terminal transition
+                    if (j, t) in dtrans:
+                        # Yes.  Okay, there is some chance that this is an includes relation
+                        # the only way to know for certain is whether the rest of the
+                        # production derives empty
+
+                        li = lr_index + 1
+                        while li < p.len:
+                            if p.prod[li] in self.grammar.Terminals:
+                                break      # No forget it
+                            if p.prod[li] not in nullable:
+                                break
+                            li = li + 1
+                        else:
+                            # Appears to be a relation between (j,t) and (state,N)
+                            includes.append((j, t))
+
+                    g = self.lr0_goto(C[j], t)               # Go to next set
+                    j = self.lr0_cidhash.get(id(g), -1)      # Go to next state
+
+                # When we get here, j is the final state, now we have to locate the production
+                for r in C[j]:
+                    if r.name != p.name:
+                        continue
+                    if r.len != p.len:
+                        continue
+                    i = 0
+                    # This look is comparing a production ". A B C" with "A B C ."
+                    while i < r.lr_index:
+                        if r.prod[i] != p.prod[i+1]:
+                            break
+                        i = i + 1
+                    else:
+                        lookb.append((j, r))
+            for i in includes:
+                if i not in includedict:
+                    includedict[i] = []
+                includedict[i].append((state, N))
+            lookdict[(state, N)] = lookb
+
+        return lookdict, includedict
+
+    # -----------------------------------------------------------------------------
+    # compute_read_sets()
+    #
+    # Given a set of LR(0) items, this function computes the read sets.
+    #
+    # Inputs:  C        =  Set of LR(0) items
+    #          ntrans   = Set of nonterminal transitions
+    #          nullable = Set of empty transitions
+    #
+    # Returns a set containing the read sets
+    # -----------------------------------------------------------------------------
+
+    def compute_read_sets(self, C, ntrans, nullable):
+        FP = lambda x: self.dr_relation(C, x, nullable)
+        R =  lambda x: self.reads_relation(C, x, nullable)
+        F = digraph(ntrans, R, FP)
+        return F
+
+    # -----------------------------------------------------------------------------
+    # compute_follow_sets()
+    #
+    # Given a set of LR(0) items, a set of non-terminal transitions, a readset,
+    # and an include set, this function computes the follow sets
+    #
+    # Follow(p,A) = Read(p,A) U U {Follow(p',B) | (p,A) INCLUDES (p',B)}
+    #
+    # Inputs:
+    #            ntrans     = Set of nonterminal transitions
+    #            readsets   = Readset (previously computed)
+    #            inclsets   = Include sets (previously computed)
+    #
+    # Returns a set containing the follow sets
+    # -----------------------------------------------------------------------------
+
+    def compute_follow_sets(self, ntrans, readsets, inclsets):
+        FP = lambda x: readsets[x]
+        R  = lambda x: inclsets.get(x, [])
+        F = digraph(ntrans, R, FP)
+        return F
+
+    # -----------------------------------------------------------------------------
+    # add_lookaheads()
+    #
+    # Attaches the lookahead symbols to grammar rules.
+    #
+    # Inputs:    lookbacks         -  Set of lookback relations
+    #            followset         -  Computed follow set
+    #
+    # This function directly attaches the lookaheads to productions contained
+    # in the lookbacks set
+    # -----------------------------------------------------------------------------
+
+    def add_lookaheads(self, lookbacks, followset):
+        for trans, lb in lookbacks.items():
+            # Loop over productions in lookback
+            for state, p in lb:
+                if state not in p.lookaheads:
+                    p.lookaheads[state] = []
+                f = followset.get(trans, [])
+                for a in f:
+                    if a not in p.lookaheads[state]:
+                        p.lookaheads[state].append(a)
+
+    # -----------------------------------------------------------------------------
+    # add_lalr_lookaheads()
+    #
+    # This function does all of the work of adding lookahead information for use
+    # with LALR parsing
+    # -----------------------------------------------------------------------------
+
+    def add_lalr_lookaheads(self, C):
+        # Determine all of the nullable nonterminals
+        nullable = self.compute_nullable_nonterminals()
+
+        # Find all non-terminal transitions
+        trans = self.find_nonterminal_transitions(C)
+
+        # Compute read sets
+        readsets = self.compute_read_sets(C, trans, nullable)
+
+        # Compute lookback/includes relations
+        lookd, included = self.compute_lookback_includes(C, trans, nullable)
+
+        # Compute LALR FOLLOW sets
+        followsets = self.compute_follow_sets(trans, readsets, included)
+
+        # Add all of the lookaheads
+        self.add_lookaheads(lookd, followsets)
+
+    # -----------------------------------------------------------------------------
+    # lr_parse_table()
+    #
+    # This function constructs the parse tables for SLR or LALR
+    # -----------------------------------------------------------------------------
+    def lr_parse_table(self):
+        Productions = self.grammar.Productions
+        Precedence  = self.grammar.Precedence
+        goto   = self.lr_goto         # Goto array
+        action = self.lr_action       # Action array
+        log    = self.log             # Logger for output
+
+        actionp = {}                  # Action production array (temporary)
+
+        log.info('Parsing method: %s', self.lr_method)
+
+        # Step 1: Construct C = { I0, I1, ... IN}, collection of LR(0) items
+        # This determines the number of states
+
+        C = self.lr0_items()
+
+        if self.lr_method == 'LALR':
+            self.add_lalr_lookaheads(C)
+
+        # Build the parser table, state by state
+        st = 0
+        for I in C:
+            # Loop over each production in I
+            actlist = []              # List of actions
+            st_action  = {}
+            st_actionp = {}
+            st_goto    = {}
+            log.info('')
+            log.info('state %d', st)
+            log.info('')
+            for p in I:
+                log.info('    (%d) %s', p.number, p)
+            log.info('')
+
+            for p in I:
+                    if p.len == p.lr_index + 1:
+                        if p.name == "S'":
+                            # Start symbol. Accept!
+                            st_action['$end'] = 0
+                            st_actionp['$end'] = p
+                        else:
+                            # We are at the end of a production.  Reduce!
+                            if self.lr_method == 'LALR':
+                                laheads = p.lookaheads[st]
+                            else:
+                                laheads = self.grammar.Follow[p.name]
+                            for a in laheads:
+                                actlist.append((a, p, 'reduce using rule %d (%s)' % (p.number, p)))
+                                r = st_action.get(a)
+                                if r is not None:
+                                    # Whoa. Have a shift/reduce or reduce/reduce conflict
+                                    if r > 0:
+                                        # Need to decide on shift or reduce here
+                                        # By default we favor shifting. Need to add
+                                        # some precedence rules here.
+                                        sprec, slevel = Productions[st_actionp[a].number].prec
+                                        rprec, rlevel = Precedence.get(a, ('right', 0))
+                                        if (slevel < rlevel) or ((slevel == rlevel) and (rprec == 'left')):
+                                            # We really need to reduce here.
+                                            st_action[a] = -p.number
+                                            st_actionp[a] = p
+                                            if not slevel and not rlevel:
+                                                log.info('  ! shift/reduce conflict for %s resolved as reduce', a)
+                                                self.sr_conflicts.append((st, a, 'reduce'))
+                                            Productions[p.number].reduced += 1
+                                        elif (slevel == rlevel) and (rprec == 'nonassoc'):
+                                            st_action[a] = None
+                                        else:
+                                            # Hmmm. Guess we'll keep the shift
+                                            if not rlevel:
+                                                log.info('  ! shift/reduce conflict for %s resolved as shift', a)
+                                                self.sr_conflicts.append((st, a, 'shift'))
+                                    elif r < 0:
+                                        # Reduce/reduce conflict.   In this case, we favor the rule
+                                        # that was defined first in the grammar file
+                                        oldp = Productions[-r]
+                                        pp = Productions[p.number]
+                                        if oldp.line > pp.line:
+                                            st_action[a] = -p.number
+                                            st_actionp[a] = p
+                                            chosenp, rejectp = pp, oldp
+                                            Productions[p.number].reduced += 1
+                                            Productions[oldp.number].reduced -= 1
+                                        else:
+                                            chosenp, rejectp = oldp, pp
+                                        self.rr_conflicts.append((st, chosenp, rejectp))
+                                        log.info('  ! reduce/reduce conflict for %s resolved using rule %d (%s)',
+                                                 a, st_actionp[a].number, st_actionp[a])
+                                    else:
+                                        raise LALRError('Unknown conflict in state %d' % st)
+                                else:
+                                    st_action[a] = -p.number
+                                    st_actionp[a] = p
+                                    Productions[p.number].reduced += 1
+                    else:
+                        i = p.lr_index
+                        a = p.prod[i+1]       # Get symbol right after the "."
+                        if a in self.grammar.Terminals:
+                            g = self.lr0_goto(I, a)
+                            j = self.lr0_cidhash.get(id(g), -1)
+                            if j >= 0:
+                                # We are in a shift state
+                                actlist.append((a, p, 'shift and go to state %d' % j))
+                                r = st_action.get(a)
+                                if r is not None:
+                                    # Whoa have a shift/reduce or shift/shift conflict
+                                    if r > 0:
+                                        if r != j:
+                                            raise LALRError('Shift/shift conflict in state %d' % st)
+                                    elif r < 0:
+                                        # Do a precedence check.
+                                        #   -  if precedence of reduce rule is higher, we reduce.
+                                        #   -  if precedence of reduce is same and left assoc, we reduce.
+                                        #   -  otherwise we shift
+                                        rprec, rlevel = Productions[st_actionp[a].number].prec
+                                        sprec, slevel = Precedence.get(a, ('right', 0))
+                                        if (slevel > rlevel) or ((slevel == rlevel) and (rprec == 'right')):
+                                            # We decide to shift here... highest precedence to shift
+                                            Productions[st_actionp[a].number].reduced -= 1
+                                            st_action[a] = j
+                                            st_actionp[a] = p
+                                            if not rlevel:
+                                                log.info('  ! shift/reduce conflict for %s resolved as shift', a)
+                                                self.sr_conflicts.append((st, a, 'shift'))
+                                        elif (slevel == rlevel) and (rprec == 'nonassoc'):
+                                            st_action[a] = None
+                                        else:
+                                            # Hmmm. Guess we'll keep the reduce
+                                            if not slevel and not rlevel:
+                                                log.info('  ! shift/reduce conflict for %s resolved as reduce', a)
+                                                self.sr_conflicts.append((st, a, 'reduce'))
+
+                                    else:
+                                        raise LALRError('Unknown conflict in state %d' % st)
+                                else:
+                                    st_action[a] = j
+                                    st_actionp[a] = p
+
+            # Print the actions associated with each terminal
+            _actprint = {}
+            for a, p, m in actlist:
+                if a in st_action:
+                    if p is st_actionp[a]:
+                        log.info('    %-15s %s', a, m)
+                        _actprint[(a, m)] = 1
+            log.info('')
+            # Print the actions that were not used. (debugging)
+            not_used = 0
+            for a, p, m in actlist:
+                if a in st_action:
+                    if p is not st_actionp[a]:
+                        if not (a, m) in _actprint:
+                            log.debug('  ! %-15s [ %s ]', a, m)
+                            not_used = 1
+                            _actprint[(a, m)] = 1
+            if not_used:
+                log.debug('')
+
+            # Construct the goto table for this state
+
+            nkeys = {}
+            for ii in I:
+                for s in ii.usyms:
+                    if s in self.grammar.Nonterminals:
+                        nkeys[s] = None
+            for n in nkeys:
+                g = self.lr0_goto(I, n)
+                j = self.lr0_cidhash.get(id(g), -1)
+                if j >= 0:
+                    st_goto[n] = j
+                    log.info('    %-30s shift and go to state %d', n, j)
+
+            action[st] = st_action
+            actionp[st] = st_actionp
+            goto[st] = st_goto
+            st += 1
+
+    # -----------------------------------------------------------------------------
+    # write()
+    #
+    # This function writes the LR parsing tables to a file
+    # -----------------------------------------------------------------------------
+
+    def write_table(self, tabmodule, outputdir='', signature=''):
+        if isinstance(tabmodule, types.ModuleType):
+            raise IOError("Won't overwrite existing tabmodule")
+
+        basemodulename = tabmodule.split('.')[-1]
+        filename = os.path.join(outputdir, basemodulename) + '.py'
+        try:
+            f = open(filename, 'w')
+
+            f.write('''
+# %s
+# This file is automatically generated. Do not edit.
+_tabversion = %r
+
+_lr_method = %r
+
+_lr_signature = %r
+    ''' % (os.path.basename(filename), __tabversion__, self.lr_method, signature))
+
+            # Change smaller to 0 to go back to original tables
+            smaller = 1
+
+            # Factor out names to try and make smaller
+            if smaller:
+                items = {}
+
+                for s, nd in self.lr_action.items():
+                    for name, v in nd.items():
+                        i = items.get(name)
+                        if not i:
+                            i = ([], [])
+                            items[name] = i
+                        i[0].append(s)
+                        i[1].append(v)
+
+                f.write('\n_lr_action_items = {')
+                for k, v in items.items():
+                    f.write('%r:([' % k)
+                    for i in v[0]:
+                        f.write('%r,' % i)
+                    f.write('],[')
+                    for i in v[1]:
+                        f.write('%r,' % i)
+
+                    f.write(']),')
+                f.write('}\n')
+
+                f.write('''
+_lr_action = {}
+for _k, _v in _lr_action_items.items():
+   for _x,_y in zip(_v[0],_v[1]):
+      if not _x in _lr_action:  _lr_action[_x] = {}
+      _lr_action[_x][_k] = _y
+del _lr_action_items
+''')
+
+            else:
+                f.write('\n_lr_action = { ')
+                for k, v in self.lr_action.items():
+                    f.write('(%r,%r):%r,' % (k[0], k[1], v))
+                f.write('}\n')
+
+            if smaller:
+                # Factor out names to try and make smaller
+                items = {}
+
+                for s, nd in self.lr_goto.items():
+                    for name, v in nd.items():
+                        i = items.get(name)
+                        if not i:
+                            i = ([], [])
+                            items[name] = i
+                        i[0].append(s)
+                        i[1].append(v)
+
+                f.write('\n_lr_goto_items = {')
+                for k, v in items.items():
+                    f.write('%r:([' % k)
+                    for i in v[0]:
+                        f.write('%r,' % i)
+                    f.write('],[')
+                    for i in v[1]:
+                        f.write('%r,' % i)
+
+                    f.write(']),')
+                f.write('}\n')
+
+                f.write('''
+_lr_goto = {}
+for _k, _v in _lr_goto_items.items():
+   for _x, _y in zip(_v[0], _v[1]):
+       if not _x in _lr_goto: _lr_goto[_x] = {}
+       _lr_goto[_x][_k] = _y
+del _lr_goto_items
+''')
+            else:
+                f.write('\n_lr_goto = { ')
+                for k, v in self.lr_goto.items():
+                    f.write('(%r,%r):%r,' % (k[0], k[1], v))
+                f.write('}\n')
+
+            # Write production table
+            f.write('_lr_productions = [\n')
+            for p in self.lr_productions:
+                if p.func:
+                    f.write('  (%r,%r,%d,%r,%r,%d),\n' % (p.str, p.name, p.len,
+                                                          p.func, os.path.basename(p.file), p.line))
+                else:
+                    f.write('  (%r,%r,%d,None,None,None),\n' % (str(p), p.name, p.len))
+            f.write(']\n')
+            f.close()
+
+        except IOError as e:
+            raise
+
+
+    # -----------------------------------------------------------------------------
+    # pickle_table()
+    #
+    # This function pickles the LR parsing tables to a supplied file object
+    # -----------------------------------------------------------------------------
+
+    def pickle_table(self, filename, signature=''):
+        try:
+            import cPickle as pickle
+        except ImportError:
+            import pickle
+        with open(filename, 'wb') as outf:
+            pickle.dump(__tabversion__, outf, pickle_protocol)
+            pickle.dump(self.lr_method, outf, pickle_protocol)
+            pickle.dump(signature, outf, pickle_protocol)
+            pickle.dump(self.lr_action, outf, pickle_protocol)
+            pickle.dump(self.lr_goto, outf, pickle_protocol)
+
+            outp = []
+            for p in self.lr_productions:
+                if p.func:
+                    outp.append((p.str, p.name, p.len, p.func, os.path.basename(p.file), p.line))
+                else:
+                    outp.append((str(p), p.name, p.len, None, None, None))
+            pickle.dump(outp, outf, pickle_protocol)
+
+# -----------------------------------------------------------------------------
+#                            === INTROSPECTION ===
+#
+# The following functions and classes are used to implement the PLY
+# introspection features followed by the yacc() function itself.
+# -----------------------------------------------------------------------------
+
+# -----------------------------------------------------------------------------
+# get_caller_module_dict()
+#
+# This function returns a dictionary containing all of the symbols defined within
+# a caller further down the call stack.  This is used to get the environment
+# associated with the yacc() call if none was provided.
+# -----------------------------------------------------------------------------
+
+def get_caller_module_dict(levels):
+    f = sys._getframe(levels)
+    ldict = f.f_globals.copy()
+    if f.f_globals != f.f_locals:
+        ldict.update(f.f_locals)
+    return ldict
+
+# -----------------------------------------------------------------------------
+# parse_grammar()
+#
+# This takes a raw grammar rule string and parses it into production data
+# -----------------------------------------------------------------------------
+def parse_grammar(doc, file, line):
+    grammar = []
+    # Split the doc string into lines
+    pstrings = doc.splitlines()
+    lastp = None
+    dline = line
+    for ps in pstrings:
+        dline += 1
+        p = ps.split()
+        if not p:
+            continue
+        try:
+            if p[0] == '|':
+                # This is a continuation of a previous rule
+                if not lastp:
+                    raise SyntaxError("%s:%d: Misplaced '|'" % (file, dline))
+                prodname = lastp
+                syms = p[1:]
+            else:
+                prodname = p[0]
+                lastp = prodname
+                syms   = p[2:]
+                assign = p[1]
+                if assign != ':' and assign != '::=':
+                    raise SyntaxError("%s:%d: Syntax error. Expected ':'" % (file, dline))
+
+            grammar.append((file, dline, prodname, syms))
+        except SyntaxError:
+            raise
+        except Exception:
+            raise SyntaxError('%s:%d: Syntax error in rule %r' % (file, dline, ps.strip()))
+
+    return grammar
+
+# -----------------------------------------------------------------------------
+# ParserReflect()
+#
+# This class represents information extracted for building a parser including
+# start symbol, error function, tokens, precedence list, action functions,
+# etc.
+# -----------------------------------------------------------------------------
+class ParserReflect(object):
+    def __init__(self, pdict, log=None):
+        self.pdict      = pdict
+        self.start      = None
+        self.error_func = None
+        self.tokens     = None
+        self.modules    = set()
+        self.grammar    = []
+        self.error      = False
+
+        if log is None:
+            self.log = PlyLogger(sys.stderr)
+        else:
+            self.log = log
+
+    # Get all of the basic information
+    def get_all(self):
+        self.get_start()
+        self.get_error_func()
+        self.get_tokens()
+        self.get_precedence()
+        self.get_pfunctions()
+
+    # Validate all of the information
+    def validate_all(self):
+        self.validate_start()
+        self.validate_error_func()
+        self.validate_tokens()
+        self.validate_precedence()
+        self.validate_pfunctions()
+        self.validate_modules()
+        return self.error
+
+    # Compute a signature over the grammar
+    def signature(self):
+        try:
+            from hashlib import md5
+        except ImportError:
+            from md5 import md5
+        try:
+            sig = md5()
+            if self.start:
+                sig.update(self.start.encode('latin-1'))
+            if self.prec:
+                sig.update(''.join([''.join(p) for p in self.prec]).encode('latin-1'))
+            if self.tokens:
+                sig.update(' '.join(self.tokens).encode('latin-1'))
+            for f in self.pfuncs:
+                if f[3]:
+                    sig.update(f[3].encode('latin-1'))
+        except (TypeError, ValueError):
+            pass
+
+        digest = base64.b16encode(sig.digest())
+        if sys.version_info[0] >= 3:
+            digest = digest.decode('latin-1')
+        return digest
+
+    # -----------------------------------------------------------------------------
+    # validate_modules()
+    #
+    # This method checks to see if there are duplicated p_rulename() functions
+    # in the parser module file.  Without this function, it is really easy for
+    # users to make mistakes by cutting and pasting code fragments (and it's a real
+    # bugger to try and figure out why the resulting parser doesn't work).  Therefore,
+    # we just do a little regular expression pattern matching of def statements
+    # to try and detect duplicates.
+    # -----------------------------------------------------------------------------
+
+    def validate_modules(self):
+        # Match def p_funcname(
+        fre = re.compile(r'\s*def\s+(p_[a-zA-Z_0-9]*)\(')
+
+        for module in self.modules:
+            try:
+                lines, linen = inspect.getsourcelines(module)
+            except IOError:
+                continue
+
+            counthash = {}
+            for linen, line in enumerate(lines):
+                linen += 1
+                m = fre.match(line)
+                if m:
+                    name = m.group(1)
+                    prev = counthash.get(name)
+                    if not prev:
+                        counthash[name] = linen
+                    else:
+                        filename = inspect.getsourcefile(module)
+                        self.log.warning('%s:%d: Function %s redefined. Previously defined on line %d',
+                                         filename, linen, name, prev)
+
+    # Get the start symbol
+    def get_start(self):
+        self.start = self.pdict.get('start')
+
+    # Validate the start symbol
+    def validate_start(self):
+        if self.start is not None:
+            if not isinstance(self.start, string_types):
+                self.log.error("'start' must be a string")
+
+    # Look for error handler
+    def get_error_func(self):
+        self.error_func = self.pdict.get('p_error')
+
+    # Validate the error function
+    def validate_error_func(self):
+        if self.error_func:
+            if isinstance(self.error_func, types.FunctionType):
+                ismethod = 0
+            elif isinstance(self.error_func, types.MethodType):
+                ismethod = 1
+            else:
+                self.log.error("'p_error' defined, but is not a function or method")
+                self.error = True
+                return
+
+            eline = self.error_func.__code__.co_firstlineno
+            efile = self.error_func.__code__.co_filename
+            module = inspect.getmodule(self.error_func)
+            self.modules.add(module)
+
+            argcount = self.error_func.__code__.co_argcount - ismethod
+            if argcount != 1:
+                self.log.error('%s:%d: p_error() requires 1 argument', efile, eline)
+                self.error = True
+
+    # Get the tokens map
+    def get_tokens(self):
+        tokens = self.pdict.get('tokens')
+        if not tokens:
+            self.log.error('No token list is defined')
+            self.error = True
+            return
+
+        if not isinstance(tokens, (list, tuple)):
+            self.log.error('tokens must be a list or tuple')
+            self.error = True
+            return
+
+        if not tokens:
+            self.log.error('tokens is empty')
+            self.error = True
+            return
+
+        self.tokens = tokens
+
+    # Validate the tokens
+    def validate_tokens(self):
+        # Validate the tokens.
+        if 'error' in self.tokens:
+            self.log.error("Illegal token name 'error'. Is a reserved word")
+            self.error = True
+            return
+
+        terminals = set()
+        for n in self.tokens:
+            if n in terminals:
+                self.log.warning('Token %r multiply defined', n)
+            terminals.add(n)
+
+    # Get the precedence map (if any)
+    def get_precedence(self):
+        self.prec = self.pdict.get('precedence')
+
+    # Validate and parse the precedence map
+    def validate_precedence(self):
+        preclist = []
+        if self.prec:
+            if not isinstance(self.prec, (list, tuple)):
+                self.log.error('precedence must be a list or tuple')
+                self.error = True
+                return
+            for level, p in enumerate(self.prec):
+                if not isinstance(p, (list, tuple)):
+                    self.log.error('Bad precedence table')
+                    self.error = True
+                    return
+
+                if len(p) < 2:
+                    self.log.error('Malformed precedence entry %s. Must be (assoc, term, ..., term)', p)
+                    self.error = True
+                    return
+                assoc = p[0]
+                if not isinstance(assoc, string_types):
+                    self.log.error('precedence associativity must be a string')
+                    self.error = True
+                    return
+                for term in p[1:]:
+                    if not isinstance(term, string_types):
+                        self.log.error('precedence items must be strings')
+                        self.error = True
+                        return
+                    preclist.append((term, assoc, level+1))
+        self.preclist = preclist
+
+    # Get all p_functions from the grammar
+    def get_pfunctions(self):
+        p_functions = []
+        for name, item in self.pdict.items():
+            if not name.startswith('p_') or name == 'p_error':
+                continue
+            if isinstance(item, (types.FunctionType, types.MethodType)):
+                line = getattr(item, 'co_firstlineno', item.__code__.co_firstlineno)
+                module = inspect.getmodule(item)
+                p_functions.append((line, module, name, item.__doc__))
+
+        # Sort all of the actions by line number; make sure to stringify
+        # modules to make them sortable, since `line` may not uniquely sort all
+        # p functions
+        p_functions.sort(key=lambda p_function: (
+            p_function[0],
+            str(p_function[1]),
+            p_function[2],
+            p_function[3]))
+        self.pfuncs = p_functions
+
+    # Validate all of the p_functions
+    def validate_pfunctions(self):
+        grammar = []
+        # Check for non-empty symbols
+        if len(self.pfuncs) == 0:
+            self.log.error('no rules of the form p_rulename are defined')
+            self.error = True
+            return
+
+        for line, module, name, doc in self.pfuncs:
+            file = inspect.getsourcefile(module)
+            func = self.pdict[name]
+            if isinstance(func, types.MethodType):
+                reqargs = 2
+            else:
+                reqargs = 1
+            if func.__code__.co_argcount > reqargs:
+                self.log.error('%s:%d: Rule %r has too many arguments', file, line, func.__name__)
+                self.error = True
+            elif func.__code__.co_argcount < reqargs:
+                self.log.error('%s:%d: Rule %r requires an argument', file, line, func.__name__)
+                self.error = True
+            elif not func.__doc__:
+                self.log.warning('%s:%d: No documentation string specified in function %r (ignored)',
+                                 file, line, func.__name__)
+            else:
+                try:
+                    parsed_g = parse_grammar(doc, file, line)
+                    for g in parsed_g:
+                        grammar.append((name, g))
+                except SyntaxError as e:
+                    self.log.error(str(e))
+                    self.error = True
+
+                # Looks like a valid grammar rule
+                # Mark the file in which defined.
+                self.modules.add(module)
+
+        # Secondary validation step that looks for p_ definitions that are not functions
+        # or functions that look like they might be grammar rules.
+
+        for n, v in self.pdict.items():
+            if n.startswith('p_') and isinstance(v, (types.FunctionType, types.MethodType)):
+                continue
+            if n.startswith('t_'):
+                continue
+            if n.startswith('p_') and n != 'p_error':
+                self.log.warning('%r not defined as a function', n)
+            if ((isinstance(v, types.FunctionType) and v.__code__.co_argcount == 1) or
+                   (isinstance(v, types.MethodType) and v.__func__.__code__.co_argcount == 2)):
+                if v.__doc__:
+                    try:
+                        doc = v.__doc__.split(' ')
+                        if doc[1] == ':':
+                            self.log.warning('%s:%d: Possible grammar rule %r defined without p_ prefix',
+                                             v.__code__.co_filename, v.__code__.co_firstlineno, n)
+                    except IndexError:
+                        pass
+
+        self.grammar = grammar
+
+# -----------------------------------------------------------------------------
+# yacc(module)
+#
+# Build a parser
+# -----------------------------------------------------------------------------
+
+def yacc(method='LALR', debug=yaccdebug, module=None, tabmodule=tab_module, start=None,
+         check_recursion=True, optimize=False, write_tables=True, debugfile=debug_file,
+         outputdir=None, debuglog=None, errorlog=None, picklefile=None):
+
+    if tabmodule is None:
+        tabmodule = tab_module
+
+    # Reference to the parsing method of the last built parser
+    global parse
+
+    # If pickling is enabled, table files are not created
+    if picklefile:
+        write_tables = 0
+
+    if errorlog is None:
+        errorlog = PlyLogger(sys.stderr)
+
+    # Get the module dictionary used for the parser
+    if module:
+        _items = [(k, getattr(module, k)) for k in dir(module)]
+        pdict = dict(_items)
+        # If no __file__ attribute is available, try to obtain it from the __module__ instead
+        if '__file__' not in pdict:
+            pdict['__file__'] = sys.modules[pdict['__module__']].__file__
+    else:
+        pdict = get_caller_module_dict(2)
+
+    if outputdir is None:
+        # If no output directory is set, the location of the output files
+        # is determined according to the following rules:
+        #     - If tabmodule specifies a package, files go into that package directory
+        #     - Otherwise, files go in the same directory as the specifying module
+        if isinstance(tabmodule, types.ModuleType):
+            srcfile = tabmodule.__file__
+        else:
+            if '.' not in tabmodule:
+                srcfile = pdict['__file__']
+            else:
+                parts = tabmodule.split('.')
+                pkgname = '.'.join(parts[:-1])
+                exec('import %s' % pkgname)
+                srcfile = getattr(sys.modules[pkgname], '__file__', '')
+        outputdir = os.path.dirname(srcfile)
+
+    # Determine if the module is package of a package or not.
+    # If so, fix the tabmodule setting so that tables load correctly
+    pkg = pdict.get('__package__')
+    if pkg and isinstance(tabmodule, str):
+        if '.' not in tabmodule:
+            tabmodule = pkg + '.' + tabmodule
+
+
+
+    # Set start symbol if it's specified directly using an argument
+    if start is not None:
+        pdict['start'] = start
+
+    # Collect parser information from the dictionary
+    pinfo = ParserReflect(pdict, log=errorlog)
+    pinfo.get_all()
+
+    if pinfo.error:
+        raise YaccError('Unable to build parser')
+
+    # Check signature against table files (if any)
+    signature = pinfo.signature()
+
+    # Read the tables
+    try:
+        lr = LRTable()
+        if picklefile:
+            read_signature = lr.read_pickle(picklefile)
+        else:
+            read_signature = lr.read_table(tabmodule)
+        if optimize or (read_signature == signature):
+            try:
+                lr.bind_callables(pinfo.pdict)
+                parser = LRParser(lr, pinfo.error_func)
+                parse = parser.parse
+                return parser
+            except Exception as e:
+                errorlog.warning('There was a problem loading the table file: %r', e)
+    except VersionError as e:
+        errorlog.warning(str(e))
+    except ImportError:
+        pass
+
+    if debuglog is None:
+        if debug:
+            try:
+                debuglog = PlyLogger(open(os.path.join(outputdir, debugfile), 'w'))
+            except IOError as e:
+                errorlog.warning("Couldn't open %r. %s" % (debugfile, e))
+                debuglog = NullLogger()
+        else:
+            debuglog = NullLogger()
+
+    debuglog.info('Created by PLY version %s (http://www.dabeaz.com/ply)', __version__)
+
+    errors = False
+
+    # Validate the parser information
+    if pinfo.validate_all():
+        raise YaccError('Unable to build parser')
+
+    if not pinfo.error_func:
+        errorlog.warning('no p_error() function is defined')
+
+    # Create a grammar object
+    grammar = Grammar(pinfo.tokens)
+
+    # Set precedence level for terminals
+    for term, assoc, level in pinfo.preclist:
+        try:
+            grammar.set_precedence(term, assoc, level)
+        except GrammarError as e:
+            errorlog.warning('%s', e)
+
+    # Add productions to the grammar
+    for funcname, gram in pinfo.grammar:
+        file, line, prodname, syms = gram
+        try:
+            grammar.add_production(prodname, syms, funcname, file, line)
+        except GrammarError as e:
+            errorlog.error('%s', e)
+            errors = True
+
+    # Set the grammar start symbols
+    try:
+        if start is None:
+            grammar.set_start(pinfo.start)
+        else:
+            grammar.set_start(start)
+    except GrammarError as e:
+        errorlog.error(str(e))
+        errors = True
+
+    if errors:
+        raise YaccError('Unable to build parser')
+
+    # Verify the grammar structure
+    undefined_symbols = grammar.undefined_symbols()
+    for sym, prod in undefined_symbols:
+        errorlog.error('%s:%d: Symbol %r used, but not defined as a token or a rule', prod.file, prod.line, sym)
+        errors = True
+
+    unused_terminals = grammar.unused_terminals()
+    if unused_terminals:
+        debuglog.info('')
+        debuglog.info('Unused terminals:')
+        debuglog.info('')
+        for term in unused_terminals:
+            errorlog.warning('Token %r defined, but not used', term)
+            debuglog.info('    %s', term)
+
+    # Print out all productions to the debug log
+    if debug:
+        debuglog.info('')
+        debuglog.info('Grammar')
+        debuglog.info('')
+        for n, p in enumerate(grammar.Productions):
+            debuglog.info('Rule %-5d %s', n, p)
+
+    # Find unused non-terminals
+    unused_rules = grammar.unused_rules()
+    for prod in unused_rules:
+        errorlog.warning('%s:%d: Rule %r defined, but not used', prod.file, prod.line, prod.name)
+
+    if len(unused_terminals) == 1:
+        errorlog.warning('There is 1 unused token')
+    if len(unused_terminals) > 1:
+        errorlog.warning('There are %d unused tokens', len(unused_terminals))
+
+    if len(unused_rules) == 1:
+        errorlog.warning('There is 1 unused rule')
+    if len(unused_rules) > 1:
+        errorlog.warning('There are %d unused rules', len(unused_rules))
+
+    if debug:
+        debuglog.info('')
+        debuglog.info('Terminals, with rules where they appear')
+        debuglog.info('')
+        terms = list(grammar.Terminals)
+        terms.sort()
+        for term in terms:
+            debuglog.info('%-20s : %s', term, ' '.join([str(s) for s in grammar.Terminals[term]]))
+
+        debuglog.info('')
+        debuglog.info('Nonterminals, with rules where they appear')
+        debuglog.info('')
+        nonterms = list(grammar.Nonterminals)
+        nonterms.sort()
+        for nonterm in nonterms:
+            debuglog.info('%-20s : %s', nonterm, ' '.join([str(s) for s in grammar.Nonterminals[nonterm]]))
+        debuglog.info('')
+
+    if check_recursion:
+        unreachable = grammar.find_unreachable()
+        for u in unreachable:
+            errorlog.warning('Symbol %r is unreachable', u)
+
+        infinite = grammar.infinite_cycles()
+        for inf in infinite:
+            errorlog.error('Infinite recursion detected for symbol %r', inf)
+            errors = True
+
+    unused_prec = grammar.unused_precedence()
+    for term, assoc in unused_prec:
+        errorlog.error('Precedence rule %r defined for unknown symbol %r', assoc, term)
+        errors = True
+
+    if errors:
+        raise YaccError('Unable to build parser')
+
+    # Run the LRGeneratedTable on the grammar
+    if debug:
+        errorlog.debug('Generating %s tables', method)
+
+    lr = LRGeneratedTable(grammar, method, debuglog)
+
+    if debug:
+        num_sr = len(lr.sr_conflicts)
+
+        # Report shift/reduce and reduce/reduce conflicts
+        if num_sr == 1:
+            errorlog.warning('1 shift/reduce conflict')
+        elif num_sr > 1:
+            errorlog.warning('%d shift/reduce conflicts', num_sr)
+
+        num_rr = len(lr.rr_conflicts)
+        if num_rr == 1:
+            errorlog.warning('1 reduce/reduce conflict')
+        elif num_rr > 1:
+            errorlog.warning('%d reduce/reduce conflicts', num_rr)
+
+    # Write out conflicts to the output file
+    if debug and (lr.sr_conflicts or lr.rr_conflicts):
+        debuglog.warning('')
+        debuglog.warning('Conflicts:')
+        debuglog.warning('')
+
+        for state, tok, resolution in lr.sr_conflicts:
+            debuglog.warning('shift/reduce conflict for %s in state %d resolved as %s',  tok, state, resolution)
+
+        already_reported = set()
+        for state, rule, rejected in lr.rr_conflicts:
+            if (state, id(rule), id(rejected)) in already_reported:
+                continue
+            debuglog.warning('reduce/reduce conflict in state %d resolved using rule (%s)', state, rule)
+            debuglog.warning('rejected rule (%s) in state %d', rejected, state)
+            errorlog.warning('reduce/reduce conflict in state %d resolved using rule (%s)', state, rule)
+            errorlog.warning('rejected rule (%s) in state %d', rejected, state)
+            already_reported.add((state, id(rule), id(rejected)))
+
+        warned_never = []
+        for state, rule, rejected in lr.rr_conflicts:
+            if not rejected.reduced and (rejected not in warned_never):
+                debuglog.warning('Rule (%s) is never reduced', rejected)
+                errorlog.warning('Rule (%s) is never reduced', rejected)
+                warned_never.append(rejected)
+
+    # Write the table file if requested
+    if write_tables:
+        try:
+            lr.write_table(tabmodule, outputdir, signature)
+        except IOError as e:
+            errorlog.warning("Couldn't create %r. %s" % (tabmodule, e))
+
+    # Write a pickled version of the tables
+    if picklefile:
+        try:
+            lr.pickle_table(picklefile, signature)
+        except IOError as e:
+            errorlog.warning("Couldn't create %r. %s" % (picklefile, e))
+
+    # Build the parser
+    lr.bind_callables(pinfo.pdict)
+    parser = LRParser(lr, pinfo.error_func)
+
+    parse = parser.parse
+    return parser