yacc.py.wml
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yacc.py.wml
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	<protect>#-----------------------------------------------------------------------------
	# ply: yacc.py
	#
	# Author(s): David M. Beazley (beazley@cs.uchicago.edu)
	# Department of Computer Science
	# University of Chicago
	# Chicago, IL 60637
	#
	# Copyright (C) 2001-2004, David M. Beazley
	#
	# $Header$
	#
	# This library is free software; you can redistribute it and/or
	# modify it under the terms of the GNU Lesser General Public
	# License as published by the Free Software Foundation; either
	# version 2.1 of the License, or (at your option) any later version.
	#
	# This library is distributed in the hope that it will be useful,
	# but WITHOUT ANY WARRANTY; without even the implied warranty of
	# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	# Lesser General Public License for more details.
	#
	# You should have received a copy of the GNU Lesser General Public
	# License along with this library; if not, write to the Free Software
	# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	#
	# See the file COPYING for a complete copy of the LGPL.
	#
	#
	# This implements an LR parser that is constructed from grammar rules defined
	# as Python functions. Roughly speaking, this module is a cross between
	# John Aycock's Spark system 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 implemented by Elias Ioup (ezioup@alumni.uchicago.edu)
	# and hacked abit by Dave to run faster.
	#
	# :::::::: 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!
	# ----------------------------------------------------------------------------

	__version__ = "1.5"

	#-----------------------------------------------------------------------------
	# === User configurable parameters ===
	#
	# Change these to modify the default behavior of yacc (if you wish)
	#-----------------------------------------------------------------------------

	yaccdebug = 1 # 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 = 'SLR' # Default LR table generation method

	error_count = 3 # Number of symbols that must be shifted to leave recovery mode

	import re, types, sys, cStringIO, md5, os.path

	# Exception raised for yacc-related errors
	class YaccError(Exception): pass

	#-----------------------------------------------------------------------------
	# === 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)

	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.

	class YaccProduction:
	def __init__(self,s):
	self.slice = s
	self.pbstack = []

	def __getitem__(self,n):
	return self.slice[n].value

	def __setitem__(self,n,v):
	self.slice[n].value = v

	def __len__(self):
	return len(self.slice)

	def lineno(self,n):
	return getattr(self.slice[n],"lineno",0)

	def linespan(self,n):
	startline = getattr(self.slice[n],"lineno",0)
	endline = getattr(self.slice[n],"endlineno",startline)
	return startline,endline

	def pushback(self,n):
	if n <= 0:
	raise ValueError, "Expected a positive value"
	if n > (len(self.slice)-1):
	raise ValueError, "Can't push %d tokens. Only %d are available." % (n,len(self.slice)-1)
	for i in range(0,n):
	self.pbstack.append(self.slice[-i-1])

	# The LR Parsing engine. This is defined as a class so that multiple parsers
	# can exist in the same process. A user never instantiates this directly.
	# Instead, the global yacc() function should be used to create a suitable Parser
	# object.

	class Parser:
	def __init__(self,magic=None):

	# This is a hack to keep users from trying to instantiate a Parser
	# object directly.

	if magic != "xyzzy":
	raise YaccError, "Can't instantiate Parser. Use yacc() instead."

	# Reset internal state
	self.productions = None # List of productions
	self.errorfunc = None # Error handling function
	self.action = { } # LR Action table
	self.goto = { } # LR goto table
	self.require = { } # Attribute require table
	self.method = "Unknown LR" # Table construction method used

	def errok(self):
	self.errorcount = 0

	def restart(self):
	del self.statestack[:]
	del self.symstack[:]
	sym = YaccSymbol()
	sym.type = '$'
	self.symstack.append(sym)
	self.statestack.append(0)

	def parse(self,input=None,lexer=None,debug=0):
	lookahead = None # Current lookahead symbol
	lookaheadstack = [ ] # Stack of lookahead symbols
	actions = self.action # Local reference to action table
	goto = self.goto # Local reference to goto table
	prod = self.productions # Local reference to production list
	pslice = YaccProduction(None) # Production object passed to grammar rules
	pslice.parser = self # Parser object
	self.errorcount = 0 # Used during error recovery

	# If no lexer was given, we will try to use the lex module
	if not lexer:
	import lex as lexer

	pslice.lexer = lexer

	# If input was supplied, pass to lexer
	if input:
	lexer.input(input)

	# Tokenize function
	get_token = lexer.token

	statestack = [ ] # Stack of parsing states
	self.statestack = statestack
	symstack = [ ] # Stack of grammar symbols
	self.symstack = symstack

	errtoken = None # Err token

	# The start state is assumed to be (0,$)
	statestack.append(0)
	sym = YaccSymbol()
	sym.type = '$'
	symstack.append(sym)

	while 1:
	# 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 not lookahead:
	if not lookaheadstack:
	lookahead = get_token() # Get the next token
	else:
	lookahead = lookaheadstack.pop()
	if not lookahead:
	lookahead = YaccSymbol()
	lookahead.type = '$'
	if debug:
	errorlead = ("%s . %s" % (" ".join([xx.type for xx in symstack][1:]), str(lookahead))).lstrip()

	# Check the action table
	s = statestack[-1]
	ltype = lookahead.type
	t = actions.get((s,ltype),None)

	if t is not None:
	if t > 0:
	# shift a symbol on the stack
	if ltype == '$':
	# Error, end of input
	sys.stderr.write("yacc: Parse error. EOF\n")
	return
	statestack.append(t)
	if debug > 1:
	sys.stderr.write("%-60s shift state %s\n" % (errorlead, t))
	symstack.append(lookahead)
	lookahead = None

	# Decrease error count on successful shift
	if self.errorcount > 0:
	self.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 debug > 1:
	sys.stderr.write("%-60s reduce %d\n" % (errorlead, -t))

	if plen:
	targ = symstack[-plen-1:]
	targ[0] = sym
	try:
	sym.lineno = targ[1].lineno
	sym.endlineno = getattr(targ[-1],"endlineno",targ[-1].lineno)
	except AttributeError:
	sym.lineno = 0
	del symstack[-plen:]
	del statestack[-plen:]
	else:
	sym.lineno = 0
	targ = [ sym ]
	pslice.slice = targ
	pslice.pbstack = []
	# Call the grammar rule with our special slice object
	p.func(pslice)

	# If there was a pushback, put that on the stack
	if pslice.pbstack:
	lookaheadstack.append(lookahead)
	for _t in pslice.pbstack:
	lookaheadstack.append(_t)
	lookahead = None

	symstack.append(sym)
	statestack.append(goto[statestack[-1],pname])
	continue

	if t == 0:
	n = symstack[-1]
	return getattr(n,"value",None)
	sys.stderr.write(errorlead, "\n")

	if t == None:
	if debug:
	sys.stderr.write(errorlead + "\n")
	# 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 not self.errorcount:
	self.errorcount = error_count
	errtoken = lookahead
	if errtoken.type == '$':
	errtoken = None # End of file!
	if self.errorfunc:
	global errok,token,restart
	errok = self.errok # Set some special functions available in error recovery
	token = get_token
	restart = self.restart
	tok = self.errorfunc(errtoken)
	del errok, token, restart # Delete special functions

	if not self.errorcount:
	# 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:
	self.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 != '$':
	lookahead = None
	errtoken = None
	# 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 == '$':
	# 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
	t = YaccSymbol()
	t.type = 'error'
	if hasattr(lookahead,"lineno"):
	t.lineno = lookahead.lineno
	t.value = lookahead
	lookaheadstack.append(lookahead)
	lookahead = t
	else:
	symstack.pop()
	statestack.pop()

	continue

	# Call an error function here
	raise RuntimeError, "yacc: internal parser error!!!\n"

	# -----------------------------------------------------------------------------
	# === Parser Construction ===
	#
	# The following functions and variables are used to implement the yacc() function
	# itself. This is pretty hairy stuff involving lots of error checking,
	# construction of LR items, kernels, and so forth. Although a lot of
	# this work is done using global variables, the resulting Parser object
	# is completely self contained--meaning that it is safe to repeatedly
	# call yacc() with different grammars in the same application.
	# -----------------------------------------------------------------------------

	# -----------------------------------------------------------------------------
	# validate_file()
	#
	# This function 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_file(filename):
	base,ext = os.path.splitext(filename)
	if ext != '.py': return 1 # No idea. Assume it's okay.

	try:
	f = open(filename)
	lines = f.readlines()
	f.close()
	except IOError:
	return 1 # Oh well

	# Match def p_funcname(
	fre = re.compile(r'\sdef\s+(p_[a-zA-Z_0-9])\(')
	counthash = { }
	linen = 1
	noerror = 1
	for l in lines:
	m = fre.match(l)
	if m:
	name = m.group(1)
	prev = counthash.get(name)
	if not prev:
	counthash[name] = linen
	else:
	sys.stderr.write("%s:%d: Function %s redefined. Previously defined on line %d\n" % (filename,linen,name,prev))
	noerror = 0
	linen += 1
	return noerror

	# This function looks for functions that might be grammar rules, but which don't have the proper p_suffix.
	def validate_dict(d):
	for n,v in d.items():
	if n[0:2] == 'p_' and type(v) in (types.FunctionType, types.MethodType): continue
	if n[0:2] == 't_': continue

	if n[0:2] == 'p_':
	sys.stderr.write("yacc: Warning. '%s' not defined as a function\n" % n)
	if 1 and isinstance(v,types.FunctionType) and v.func_code.co_argcount == 1:
	try:
	doc = v.__doc__.split(" ")
	if doc[1] == ':':
	sys.stderr.write("%s:%d: Warning. Possible grammar rule '%s' defined without p_ prefix.\n" % (v.func_code.co_filename, v.func_code.co_firstlineno,n))
	except StandardError:
	pass

	# -----------------------------------------------------------------------------
	# === GRAMMAR FUNCTIONS ===
	#
	# The following global variables and functions are used to store, manipulate,
	# and verify the grammar rules specified by the user.
	# -----------------------------------------------------------------------------

	# Initialize all of the global variables used during grammar construction
	def initialize_vars():
	global Productions, Prodnames, Prodmap, Terminals
	global Nonterminals, First, Follow, Precedence, LRitems
	global Errorfunc, Signature, Requires

	# LALR(1) globals
	global Prodempty, TReductions, NTReductions, GotoSetNum, Canonical

	Productions = [None] # A list of all of the productions. The first
	# entry is always reserved for the purpose of
	# building an augmented grammar

	Prodnames = { } # A dictionary mapping the names of nonterminals to a list of all
	# productions of that nonterminal.

	Prodmap = { } # A dictionary that is only used to detect duplicate
	# productions.

	Terminals = { } # A dictionary mapping the names of terminal symbols to a
	# list of the rules where they are used.

	Nonterminals = { } # A dictionary mapping names of nonterminals to a list
	# of rule numbers where they are used.

	First = { } # A dictionary of precomputed FIRST(x) symbols

	Follow = { } # A dictionary of precomputed FOLLOW(x) symbols

	Precedence = { } # Precedence rules for each terminal. Contains tuples of the
	# form ('right',level) or ('nonassoc', level) or ('left',level)

	LRitems = [ ] # A list of all LR items for the grammar. These are the
	# productions with the "dot" like E -> E . PLUS E

	Errorfunc = None # User defined error handler

	Signature = md5.new() # Digital signature of the grammar rules, precedence
	# and other information. Used to determined when a
	# parsing table needs to be regenerated.

	Requires = { } # Requires list

	# LALR(1) Initialization
	Prodempty = { } # A dictionary of all productions that have an empty rule
	# of the form P : <empty>

	TReductions = { } # A dictionary of precomputer reductions from
	# nonterminals to terminals

	NTReductions = { } # A dictionary of precomputed reductions from
	# nonterminals to nonterminals

	GotoSetNum = { } # A dictionary that remembers goto sets based on
	# the state number and symbol

	Canonical = { } # A list of LR item sets. A LR item set is a list of LR
	# items that represent the state of the parser

	# File objects used when creating the parser.out debugging file
	global _vf, _vfc
	_vf = cStringIO.StringIO()
	_vfc = cStringIO.StringIO()

	# -----------------------------------------------------------------------------
	# class Production:
	#
	# This class stores the raw information about a single production or grammar rule.
	# It has a few required attributes:
	#
	# name - Name of the production (nonterminal)
	# prod - A list of symbols making up its production
	# number - Production number.
	#
	# In addition, a few additional attributes are used to help with debugging or
	# optimization of table generation.
	#
	# file - File where production action is defined.
	# lineno - Line number where action is defined
	# func - Action function
	# prec - Precedence level
	# lr_next - Next LR item. Example, if we are ' E -> E . PLUS E'
	# then lr_next refers to 'E -> E PLUS . E'
	# 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)
	# -----------------------------------------------------------------------------

	class Production:
	def __init__(self,**kw):
	for k,v in kw.items():
	setattr(self,k,v)
	self.lr_index = -1
	self.lr0_added = 0 # Flag indicating whether or not added to LR0 closure
	self.lr1_added = 0 # Flag indicating whether or not added to LR1
	self.usyms = [ ]
	self.lookaheads = { }
	self.lk_added = 0
	self.setnumbers = [ ]

	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 str(self)

	# Compute lr_items from the production
	def lr_item(self,n):
	if n > len(self.prod): return None
	p = Production()
	p.name = self.name
	p.prod = list(self.prod)
	p.number = self.number
	p.lr_index = n
	p.lookaheads = { }
	p.setnumbers = self.setnumbers
	p.prod.insert(n,".")
	p.prod = tuple(p.prod)
	p.len = len(p.prod)
	p.usyms = self.usyms

	# Precompute list of productions immediately following
	try:
	p.lrafter = Prodnames[p.prod[n+1]]
	except (IndexError,KeyError),e:
	p.lrafter = []
	try:
	p.lrbefore = p.prod[n-1]
	except IndexError:
	p.lrbefore = None

	return p

	class MiniProduction:
	pass

	# Utility function
	def is_identifier(s):
	for c in s:
	if not (c.isalnum() or c == '_'): return 0
	return 1

	# -----------------------------------------------------------------------------
	# add_production()
	#
	# Given an action function, this function assembles a production rule.
	# The production rule is assumed to be found in the function's docstring.
	# This rule has the general syntax:
	#
	# name1 ::= production1
	# \| production2
	# \| production3
	# ...
	# \| productionn
	# name2 ::= production1
	# \| production2
	# ...
	# -----------------------------------------------------------------------------

	def add_production(f,file,line,prodname,syms):

	if Terminals.has_key(prodname):
	sys.stderr.write("%s:%d: Illegal rule name '%s'. Already defined as a token.\n" % (file,line,prodname))
	return -1
	if prodname == 'error':
	sys.stderr.write("%s:%d: Illegal rule name '%s'. error is a reserved word.\n" % (file,line,prodname))
	return -1

	if not is_identifier(prodname):
	sys.stderr.write("%s:%d: Illegal rule name '%s'\n" % (file,line,prodname))
	return -1

	for s in syms:
	if not is_identifier(s) and s != '%prec':
	sys.stderr.write("%s:%d: Illegal name '%s' in rule '%s'\n" % (file,line,s, prodname))
	return -1

	# See if the rule is already in the rulemap
	map = "%s -> %s" % (prodname,syms)
	if Prodmap.has_key(map):
	m = Prodmap[map]
	sys.stderr.write("%s:%d: Duplicate rule %s.\n" % (file,line, m))
	sys.stderr.write("%s:%d: Previous definition at %s:%d\n" % (file,line, m.file, m.line))
	return -1

	p = Production()
	p.name = prodname
	p.prod = syms
	p.file = file
	p.line = line
	p.func = f
	p.number = len(Productions)


	Productions.append(p)
	Prodmap[map] = p
	if not Nonterminals.has_key(prodname):
	Nonterminals[prodname] = [ ]

	# Add all terminals to Terminals
	i = 0
	while i < len(p.prod):
	t = p.prod[i]
	if t == '%prec':
	try:
	precname = p.prod[i+1]
	except IndexError:
	sys.stderr.write("%s:%d: Syntax error. Nothing follows %%prec.\n" % (p.file,p.line))
	return -1

	prec = Precedence.get(precname,None)
	if not prec:
	sys.stderr.write("%s:%d: Nothing known about the precedence of '%s'\n" % (p.file,p.line,precname))
	return -1
	else:
	p.prec = prec
	del p.prod[i]
	del p.prod[i]
	continue

	if Terminals.has_key(t):
	Terminals[t].append(p.number)
	# Is a terminal. We'll assign a precedence to p based on this
	if not hasattr(p,"prec"):
	p.prec = Precedence.get(t,('right',0))
	else:
	if not Nonterminals.has_key(t):
	Nonterminals[t] = [ ]
	Nonterminals[t].append(p.number)
	i += 1

	if not hasattr(p,"prec"):
	p.prec = ('right',0)

	# Set final length of productions
	p.len = len(p.prod)
	p.prod = tuple(p.prod)

	# Calculate unique syms in the production
	p.usyms = [ ]
	for s in p.prod:
	if s not in p.usyms:
	p.usyms.append(s)

	# Add to the global productions list
	try:
	Prodnames[p.name].append(p)
	except KeyError:
	Prodnames[p.name] = [ p ]
	return 0

	# Given a raw rule function, this function rips out its doc string
	# and adds rules to the grammar

	def add_function(f):
	line = f.func_code.co_firstlineno
	file = f.func_code.co_filename
	error = 0

	if isinstance(f,types.MethodType):
	reqdargs = 2
	else:
	reqdargs = 1

	if f.func_code.co_argcount > reqdargs:
	sys.stderr.write("%s:%d: Rule '%s' has too many arguments.\n" % (file,line,f.__name__))
	return -1

	if f.func_code.co_argcount < reqdargs:
	sys.stderr.write("%s:%d: Rule '%s' requires an argument.\n" % (file,line,f.__name__))
	return -1

	if f.__doc__:
	# Split the doc string into lines
	pstrings = f.__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:
	sys.stderr.write("%s:%d: Misplaced '\|'.\n" % (file,dline))
	return -1
	prodname = lastp
	if len(p) > 1:
	syms = p[1:]
	else:
	syms = [ ]
	else:
	prodname = p[0]
	lastp = prodname
	assign = p[1]
	if len(p) > 2:
	syms = p[2:]
	else:
	syms = [ ]
	if assign != ':' and assign != '::=':
	sys.stderr.write("%s:%d: Syntax error. Expected ':'\n" % (file,dline))
	return -1
	e = add_production(f,file,dline,prodname,syms)
	error += e
	except StandardError:
	sys.stderr.write("%s:%d: Syntax error in rule '%s'\n" % (file,dline,ps))
	error -= 1
	else:
	sys.stderr.write("%s:%d: No documentation string specified in function '%s'\n" % (file,line,f.__name__))
	return error


	# Cycle checking code (Michael Dyck)

	def compute_reachable():
	'''
	Find each symbol that can be reached from the start symbol.
	Print a warning for any nonterminals that can't be reached.
	(Unused terminals have already had their warning.)
	'''
	Reachable = { }
	for s in Terminals.keys() + Nonterminals.keys():
	Reachable[s] = 0

	mark_reachable_from( Productions[0].prod[0], Reachable )

	for s in Nonterminals.keys():
	if not Reachable[s]:
	sys.stderr.write("yacc: Symbol '%s' is unreachable.\n" % s)

	def mark_reachable_from(s, Reachable):
	'''
	Mark all symbols that are reachable from symbol s.
	'''
	if Reachable[s]:
	# We've already reached symbol s.
	return
	Reachable[s] = 1
	for p in Prodnames.get(s,[]):
	for r in p.prod:
	mark_reachable_from(r, Reachable)

	# -----------------------------------------------------------------------------
	# compute_terminates()
	#
	# 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 compute_terminates():
	'''
	Raise an error for any symbols that don't terminate.
	'''
	Terminates = {}

	# Terminals:
	for t in Terminals.keys():
	Terminates[t] = 1

	Terminates['$'] = 1

	# Nonterminals:

	# Initialize to false:
	for n in Nonterminals.keys():
	Terminates[n] = 0

	# Then propagate termination until no change:
	while 1:
	some_change = 0
	for (n,pl) in 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 = 0
	break
	else:
	# didn't break from the loop,
	# so every symbol s terminates
	# so production p terminates.
	p_terminates = 1

	if p_terminates:
	# symbol n terminates!
	if not Terminates[n]:
	Terminates[n] = 1
	some_change = 1
	# Don't need to consider any more productions for this n.
	break

	if not some_change:
	break

	some_error = 0
	for (s,terminates) in Terminates.items():
	if not terminates:
	if not Prodnames.has_key(s) and not Terminals.has_key(s) 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:
	sys.stderr.write("yacc: Infinite recursion detected for symbol '%s'.\n" % s)
	some_error = 1

	return some_error

	# -----------------------------------------------------------------------------
	# verify_productions()
	#
	# This function examines all of the supplied rules to see if they seem valid.
	# -----------------------------------------------------------------------------
	def verify_productions(cycle_check=1):
	error = 0
	for p in Productions:
	if not p: continue

	for s in p.prod:
	if not Prodnames.has_key(s) and not Terminals.has_key(s) and s != 'error':
	sys.stderr.write("%s:%d: Symbol '%s' used, but not defined as a token or a rule.\n" % (p.file,p.line,s))
	error = 1
	continue

	unused_tok = 0
	# Now verify all of the tokens
	if yaccdebug:
	_vf.write("Unused terminals:\n\n")
	for s,v in Terminals.items():
	if s != 'error' and not v:
	sys.stderr.write("yacc: Warning. Token '%s' defined, but not used.\n" % s)
	if yaccdebug: _vf.write(" %s\n"% s)
	unused_tok += 1

	# Print out all of the productions
	if yaccdebug:
	_vf.write("\nGrammar\n\n")
	for i in range(1,len(Productions)):
	_vf.write("Rule %-5d %s\n" % (i, Productions[i]))

	unused_prod = 0
	# Verify the use of all productions
	for s,v in Nonterminals.items():
	if not v:
	p = Prodnames[s][0]
	sys.stderr.write("%s:%d: Warning. Rule '%s' defined, but not used.\n" % (p.file,p.line, s))
	unused_prod += 1


	if unused_tok == 1:
	sys.stderr.write("yacc: Warning. There is 1 unused token.\n")
	if unused_tok > 1:
	sys.stderr.write("yacc: Warning. There are %d unused tokens.\n" % unused_tok)

	if unused_prod == 1:
	sys.stderr.write("yacc: Warning. There is 1 unused rule.\n")
	if unused_prod > 1:
	sys.stderr.write("yacc: Warning. There are %d unused rules.\n" % unused_prod)

	if yaccdebug:
	_vf.write("\nTerminals, with rules where they appear\n\n")
	ks = Terminals.keys()
	ks.sort()
	for k in ks:
	_vf.write("%-20s : %s\n" % (k, " ".join([str(s) for s in Terminals[k]])))
	_vf.write("\nNonterminals, with rules where they appear\n\n")
	ks = Nonterminals.keys()
	ks.sort()
	for k in ks:
	_vf.write("%-20s : %s\n" % (k, " ".join([str(s) for s in Nonterminals[k]])))

	if (cycle_check):
	compute_reachable()
	error += compute_terminates()
	# error += check_cycles()
	return error

	# -----------------------------------------------------------------------------
	# 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():
	for p in Productions:
	lastlri = p
	lri = p.lr_item(0)
	i = 0
	while 1:
	lri = p.lr_item(i)
	lastlri.lr_next = lri
	if not lri: break
	lri.lr_num = len(LRitems)
	LRitems.append(lri)
	lastlri = lri
	i += 1

	# In order for the rest of the parser generator to work, we need to
	# guarantee that no more lritems are generated. Therefore, we nuke
	# the p.lr_item method. (Only used in debugging)
	# Production.lr_item = None

	# -----------------------------------------------------------------------------
	# add_precedence()
	#
	# Given a list of precedence rules, add to the precedence table.
	# -----------------------------------------------------------------------------

	def add_precedence(plist):
	plevel = 0
	error = 0
	for p in plist:
	plevel += 1
	try:
	prec = p[0]
	terms = p[1:]
	if prec != 'left' and prec != 'right' and prec != 'nonassoc':
	sys.stderr.write("yacc: Invalid precedence '%s'\n" % prec)
	return -1
	for t in terms:
	if Precedence.has_key(t):
	sys.stderr.write("yacc: Precedence already specified for terminal '%s'\n" % t)
	error += 1
	continue
	Precedence[t] = (prec,plevel)
	except:
	sys.stderr.write("yacc: Invalid precedence table.\n")
	error += 1

	return error

	# -----------------------------------------------------------------------------
	# augment_grammar()
	#
	# Compute the augmented grammar. This is just a rule S' -> start where start
	# is the starting symbol.
	# -----------------------------------------------------------------------------

	def augment_grammar(start=None):
	if not start:
	start = Productions[1].name
	Productions[0] = Production(name="S'",prod=[start],number=0,len=1,prec=('right',0),func=None)
	Productions[0].usyms = [ start ]
	Nonterminals[start].append(0)


	# -------------------------------------------------------------------------
	# 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(beta):

	# We are computing First(x1,x2,x3,...,xn)
	result = [ ]
	for x in beta:
	x_produces_empty = 0

	# Add all the non-<empty> symbols of First[x] to the result.
	for f in First[x]:
	if f == '<empty>':
	x_produces_empty = 1
	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


	# FOLLOW(x)
	# Given a non-terminal. This function computes the set of all symbols
	# that might follow it. Dragon book, p. 189.

	def compute_follow(start=None):
	# Add '$' to the follow list of the start symbol
	for k in Nonterminals.keys():
	Follow[k] = [ ]

	if not start:
	start = Productions[1].name

	Follow[start] = [ '$' ]

	while 1:
	didadd = 0
	for p in Productions[1:]:
	# Here is the production set
	for i in range(len(p.prod)):
	B = p.prod[i]
	if Nonterminals.has_key(B):
	# Okay. We got a non-terminal in a production
	fst = first(p.prod[i+1:])
	hasempty = 0
	for f in fst:
	if f != '<empty>' and f not in Follow[B]:
	Follow[B].append(f)
	didadd = 1
	if f == '<empty>':
	hasempty = 1
	if hasempty or i == (len(p.prod)-1):
	# Add elements of follow(a) to follow(b)
	for f in Follow[p.name]:
	if f not in Follow[B]:
	Follow[B].append(f)
	didadd = 1
	if not didadd: break

	if 0 and yaccdebug:
	_vf.write('\nFollow:\n')
	for k in Nonterminals.keys():
	_vf.write("%-20s : %s\n" % (k, " ".join([str(s) for s in Follow[k]])))

	# -------------------------------------------------------------------------
	# compute_first1()
	#
	# Compute the value of FIRST1(X) for all symbols
	# -------------------------------------------------------------------------
	def compute_first1():

	# Terminals:
	for t in Terminals.keys():
	First[t] = [t]

	First['$'] = ['$']
	First['#'] = ['#'] # what's this for?

	# Nonterminals:

	# Initialize to the empty set:
	for n in Nonterminals.keys():
	First[n] = []

	# Then propagate symbols until no change:
	while 1:
	some_change = 0
	for n in Nonterminals.keys():
	for p in Prodnames[n]:
	for f in first(p.prod):
	if f not in First[n]:
	First[n].append( f )
	some_change = 1
	if not some_change:
	break

	if 0 and yaccdebug:
	_vf.write('\nFirst:\n')
	for k in Nonterminals.keys():
	_vf.write("%-20s : %s\n" %
	(k, " ".join([str(s) for s in First[k]])))

	# -----------------------------------------------------------------------------
	# === SLR Generation ===
	#
	# The following functions are used to construct SLR (Simple LR) parsing tables
	# as described on p.221-229 of the dragon book.
	# -----------------------------------------------------------------------------

	# Global variables for the LR parsing engine
	def lr_init_vars():
	global _lr_action, _lr_goto, _lr_method
	global _lr_goto_cache

	_lr_action = { } # Action table
	_lr_goto = { } # Goto table
	_lr_method = "Unknown" # LR method used
	_lr_goto_cache = { }

	# Compute the LR(0) closure operation on I, where I is a set of LR(0) items.
	# prodlist is a list of productions.

	_add_count = 0 # Counter used to detect cycles

	def lr0_closure(I):
	global _add_count

	_add_count += 1
	prodlist = Productions

	# Add everything in I to J
	J = I[:]
	didadd = 1
	while didadd:
	didadd = 0
	for j in J:
	for x in j.lrafter:
	if x.lr0_added == _add_count: continue
	# Add B --> .G to J
	J.append(x.lr_next)
	x.lr0_added = _add_count
	didadd = 1

	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(I,x):
	# First we look for a previously cached entry
	g = _lr_goto_cache.get((id(I),x),None)
	if g: return g

	# Now we generate the goto set in a way that guarantees uniqueness
	# of the result

	s = _lr_goto_cache.get(x,None)
	if not s:
	s = { }
	_lr_goto_cache[x] = s

	gs = [ ]
	for p in I:
	n = p.lr_next
	if n and n.lrbefore == x:
	s1 = s.get(id(n),None)
	if not s1:
	s1 = { }
	s[id(n)] = s1
	gs.append(n)
	s = s1
	g = s.get('$',None)
	if not g:
	if gs:
	g = lr0_closure(gs)
	s['$'] = g
	else:
	s['$'] = gs
	_lr_goto_cache[(id(I),x)] = g
	return g

	# Added for LALR(1)

	# Given a setnumber of an lr0 state and a symbol return the setnumber of the goto state
	def lr0_goto_setnumber(I_setnumber, x):
	global Canonical
	global GotoSetNum

	if GotoSetNum.has_key((I_setnumber, x)):
	setnumber = GotoSetNum[(I_setnumber, x)]
	else:
	gset = lr0_goto(Canonical[I_setnumber], x)
	if not gset:
	return -1
	else:
	gsetlen = len(gset)
	for i in xrange(len(gset[0].setnumbers)):
	inall = 1
	for item in gset:
	if not item.setnumbers[i]:
	inall = 0
	break
	if inall and len(Canonical[i]) == gsetlen:
	setnumber = i
	break # Note: DB. I added this to improve performance.
	# Not sure if this breaks the algorithm (it doesn't appear to).

	GotoSetNum[(I_setnumber, x)] = setnumber

	return setnumber

	# Compute the kernel of a set of LR(0) items
	def lr0_kernel(I):
	KI = [ ]
	for p in I:
	if p.name == "S'" or p.lr_index > 0 or p.len == 0:
	KI.append(p)

	return KI

	_lr0_cidhash = { }

	# Compute the LR(0) sets of item function
	def lr0_items():

	C = [ lr0_closure([Productions[0].lr_next]) ]
	i = 0
	for I in C:
	_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.keys():
	g = lr0_goto(I,x)
	if not g: continue
	if _lr0_cidhash.has_key(id(g)): continue
	_lr0_cidhash[id(g)] = len(C)
	C.append(g)

	return C

	# -----------------------------------------------------------------------------
	# slr_parse_table()
	#
	# This function constructs an SLR table.
	# -----------------------------------------------------------------------------
	def slr_parse_table():
	global _lr_method
	goto = _lr_goto # Goto array
	action = _lr_action # Action array
	actionp = { } # Action production array (temporary)

	_lr_method = "SLR"

	n_srconflict = 0
	n_rrconflict = 0

	if yaccdebug:
	sys.stderr.write("yacc: Generating SLR parsing table...\n")
	_vf.write("\n\nParsing method: SLR\n\n")

	# Step 1: Construct C = { I0, I1, ... IN}, collection of LR(0) items
	# This determines the number of states

	C = lr0_items()

	# Build the parser table, state by state
	st = 0
	for I in C:
	# Loop over each production in I
	actlist = [ ] # List of actions

	if yaccdebug:
	_vf.write("\nstate %d\n\n" % st)
	for p in I:
	_vf.write(" (%d) %s\n" % (p.number, str(p)))
	_vf.write("\n")

	for p in I:
	try:
	if p.prod[-1] == ".":
	if p.name == "S'":
	# Start symbol. Accept!
	action[st,"$"] = 0
	actionp[st,"$"] = p
	else:
	# We are at the end of a production. Reduce!
	for a in Follow[p.name]:
	actlist.append((a,p,"reduce using rule %d (%s)" % (p.number,p)))
	r = action.get((st,a),None)
	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[actionp[st,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.
	action[st,a] = -p.number
	actionp[st,a] = p
	if not slevel and not rlevel:
	_vfc.write("shift/reduce conflict in state %d resolved as reduce.\n" % st)
	_vf.write(" ! shift/reduce conflict for %s resolved as reduce.\n" % a)
	n_srconflict += 1
	elif (slevel == rlevel) and (rprec == 'nonassoc'):
	action[st,a] = None
	else:
	# Hmmm. Guess we'll keep the shift
	if not slevel and not rlevel:
	_vfc.write("shift/reduce conflict in state %d resolved as shift.\n" % st)
	_vf.write(" ! shift/reduce conflict for %s resolved as shift.\n" % a)
	n_srconflict +=1
	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:
	action[st,a] = -p.number
	actionp[st,a] = p
	# sys.stderr.write("Reduce/reduce conflict in state %d\n" % st)
	n_rrconflict += 1
	_vfc.write("reduce/reduce conflict in state %d resolved using rule %d (%s).\n" % (st, actionp[st,a].number, actionp[st,a]))
	_vf.write(" ! reduce/reduce conflict for %s resolved using rule %d (%s).\n" % (a,actionp[st,a].number, actionp[st,a]))
	else:
	sys.stderr.write("Unknown conflict in state %d\n" % st)
	else:
	action[st,a] = -p.number
	actionp[st,a] = p
	else:
	i = p.lr_index
	a = p.prod[i+1] # Get symbol right after the "."
	if Terminals.has_key(a):
	g = lr0_goto(I,a)
	j = _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 = action.get((st,a),None)
	if r is not None:
	# Whoa have a shift/reduce or shift/shift conflict
	if r > 0:
	if r != j:
	sys.stderr.write("Shift/shift conflict in state %d\n" % 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[actionp[st,a].number].prec
	sprec,slevel = Precedence.get(a,('right',0))
	if (slevel > rlevel) or ((slevel == rlevel) and (rprec != 'left')):
	# We decide to shift here... highest precedence to shift
	action[st,a] = j
	actionp[st,a] = p
	if not slevel and not rlevel:
	n_srconflict += 1
	_vfc.write("shift/reduce conflict in state %d resolved as shift.\n" % st)
	_vf.write(" ! shift/reduce conflict for %s resolved as shift.\n" % a)
	elif (slevel == rlevel) and (rprec == 'nonassoc'):
	action[st,a] = None
	else:
	# Hmmm. Guess we'll keep the reduce
	if not slevel and not rlevel:
	n_srconflict +=1
	_vfc.write("shift/reduce conflict in state %d resolved as reduce.\n" % st)
	_vf.write(" ! shift/reduce conflict for %s resolved as reduce.\n" % a)

	else:
	sys.stderr.write("Unknown conflict in state %d\n" % st)
	else:
	action[st,a] = j
	actionp[st,a] = p

	except StandardError,e:
	raise YaccError, "Hosed in slr_parse_table", e

	# Print the actions associated with each terminal
	if yaccdebug:
	_actprint = { }
	for a,p,m in actlist:
	if action.has_key((st,a)):
	if p is actionp[st,a]:
	_vf.write(" %-15s %s\n" % (a,m))
	_actprint[(a,m)] = 1
	_vf.write("\n")
	for a,p,m in actlist:
	if action.has_key((st,a)):
	if p is not actionp[st,a]:
	if not _actprint.has_key((a,m)):
	_vf.write(" ! %-15s [ %s ]\n" % (a,m))
	_actprint[(a,m)] = 1

	# Construct the goto table for this state
	if yaccdebug:
	_vf.write("\n")
	nkeys = { }
	for ii in I:
	for s in ii.usyms:
	if Nonterminals.has_key(s):
	nkeys[s] = None
	for n in nkeys.keys():
	g = lr0_goto(I,n)
	j = _lr0_cidhash.get(id(g),-1)
	if j >= 0:
	goto[st,n] = j
	if yaccdebug:
	_vf.write(" %-30s shift and go to state %d\n" % (n,j))

	st += 1

	if yaccdebug:
	if n_srconflict == 1:
	sys.stderr.write("yacc: %d shift/reduce conflict\n" % n_srconflict)
	if n_srconflict > 1:
	sys.stderr.write("yacc: %d shift/reduce conflicts\n" % n_srconflict)
	if n_rrconflict == 1:
	sys.stderr.write("yacc: %d reduce/reduce conflict\n" % n_rrconflict)
	if n_rrconflict > 1:
	sys.stderr.write("yacc: %d reduce/reduce conflicts\n" % n_rrconflict)



	# -----------------------------------------------------------------------------
	# ==== LALR(1) Parsing ====
	# FINISHED! 5/20/2003 by Elias Ioup
	# -----------------------------------------------------------------------------


	# Compute the lr1_closure of a set I. I is a list of productions and setnumber
	# is the state that you want the lr items that are made from the to come from.

	_lr1_add_count = 0

	def lr1_closure(I, setnumber = 0):
	global _add_count
	global Nonterminals

	_add_count += 1
	prodlist = Productions

	# Add everything in I to J
	J = I[:]
	Jhash = { }
	for j in J:
	Jhash[id(j)] = 1

	didadd = 1
	while didadd:
	didadd = 0
	for j in J:
	jprod = j.prod
	jlr_index = j.lr_index
	jprodslice = jprod[jlr_index+2:]

	if jlr_index < len(jprod) - 1 and Nonterminals.has_key(jprod[jlr_index+1]):
	first_syms = []
	if j.lk_added < len(j.lookaheads[setnumber]):
	for a in j.lookaheads[setnumber][j.lk_added:]:
	# find b in FIRST(Xa) if j = [A->a.BX,a]
	temp_first_syms = first(jprodslice + (a,))
	for x in temp_first_syms:
	if x not in first_syms:
	first_syms.append(x)

	j.lk_added = len(j.lookaheads[setnumber])

	for x in j.lrafter:

	# Add B --> .G to J
	if x.lr_next.lookaheads.has_key(setnumber):
	_xlook = x.lr_next.lookaheads[setnumber]
	for s in first_syms:
	if s not in _xlook:
	_xlook.append(s)
	didadd = 1
	else:
	didadd = 0
	else:
	x.lr_next.lookaheads[setnumber] = first_syms
	didadd = 1

	nid = id(x.lr_next)
	if not Jhash.has_key(nid):
	J.append(x.lr_next)
	Jhash[nid] = 1

	return J

	def add_lookaheads(K):
	spontaneous = []
	propogate = []

	for setnumber in range(len(K)):
	for kitem in K[setnumber]:
	kitem.lookaheads[setnumber] = ['#']
	J = lr1_closure([kitem], setnumber)

	# find the lookaheads that are spontaneously created from closures
	# and the propogations of lookaheads between lr items
	for item in J:
	if item.lr_index < len(item.prod)-1:
	for lookahead in item.lookaheads[setnumber]:
	if lookahead != '#':
	goto_setnumber = lr0_goto_setnumber(setnumber, item.prod[item.lr_index+1])
	next = None
	if item.lr_next in K[goto_setnumber]:
	next = item.lr_next
	if next:
	spontaneous.append((next, (lookahead, goto_setnumber)))
	else:
	goto_setnumber = lr0_goto_setnumber(setnumber, item.prod[item.lr_index+1])
	next = None
	if goto_setnumber > -1:
	if item.lr_next in K[goto_setnumber]:
	next = item.lr_next

	if next:
	propogate.append(((kitem, setnumber), (next, goto_setnumber)))



	for x in K[setnumber]:
	x.lookaheads[setnumber] = []

	for x in spontaneous:
	if x[1][0] not in x[0].lookaheads[x[1][1]]:
	x[0].lookaheads[x[1][1]].append(x[1][0])

	K[0][0].lookaheads[0] = ['$']

	pitems = {}
	for x in propogate:
	if pitems.has_key(x[0]):
	pitems[x[0]].append(x[1])
	else:
	pitems[x[0]] = []
	pitems[x[0]].append(x[1])

	# propogate the lookaheads that were spontaneously generated
	# based on the propogations produced above
	stop = 0

	while not stop:
	stop = 1
	kindex = 0
	for set in K:
	for item in set:
	pkey = (item, kindex)
	if pitems.has_key(pkey):
	for propogation in pitems[pkey]:
	gitem = propogation[0]
	gsetnumber = propogation[1]
	glookaheads = gitem.lookaheads[gsetnumber]
	for lookahead in item.lookaheads[kindex]:
	if lookahead not in glookaheads:
	glookaheads.append(lookahead)
	stop = 0
	kindex += 1

	def ReduceNonterminals():
	global Nonterminals

	global TReductions
	global NTReductions

	for nt in Nonterminals.keys():
	TReductions[nt] = []
	NTReductions[nt] = []

	for nt in Nonterminals.keys():
	terms = ReduceToTerminals(nt)
	TReductions[nt].extend(terms)
	if not NTReductions.has_key(nt):
	ReduceToNonterminals(nt)



	def ReduceToTerminals(nt):
	global Prodnames
	global Terminals
	reducedterminals = []

	for p in Prodnames[nt]:
	if len(p.prod) > 0:
	if Terminals.has_key(p.prod[0]):
	if p.prod[0] not in reducedterminals:
	reducedterminals.append(p.prod[0])
	else:
	if p.prod[0] != nt:
	terms = ReduceToTerminals(p.prod[0])
	for t in terms:
	if t not in reducedterminals:
	reducedterminals.append(t)

	return reducedterminals


	def ReduceToNonterminals(nt):
	global Prodnames
	global Nonterminals
	global NTReductions
	reducednonterminals = []

	for p in Prodnames[nt]:
	if len(p.prod) > 0:
	if Nonterminals.has_key(p.prod[0]):
	if p.prod[0] not in reducednonterminals:
	reducednonterminals.append(p.prod[0])
	if p.prod[0] != nt:
	if not NTReductions.has_key(p.prod[0]):
	ReduceToNonterminals(p.prod[0])

	nterms = NTReductions[p.prod[0]]
	for nt in nterms:
	if nt not in reducednonterminals:
	reducednonterminals.append(nt)


	NTReductions[nt] = reducednonterminals

	# -----------------------------------------------------------------------------
	# lalr_parse_table()
	#
	# This function constructs an LALR table.
	# -----------------------------------------------------------------------------
	def lalr_parse_table():
	global _lr_method
	goto = _lr_goto # Goto array
	action = _lr_action # Action array
	actionp = { } # Action production array (temporary)
	goto_cache = _lr_goto_cache
	cid_hash = _lr0_cidhash

	_lr_method = "LALR"

	n_srconflict = 0
	n_rrconflict = 0

	if yaccdebug:
	sys.stderr.write("yacc: Generating LALR(1) parsing table...\n")
	_vf.write("\n\nParsing method: LALR(1)\n\n")

	# Step 1: Construct C = { I0, I1, ... IN}, collection of LR(0) items
	# This determines the number of states

	C = lr0_items()

	global Canonical
	Canonical = C

	###
	# Create the kernel states.
	###
	K = []
	setC = [0]*len(C)
	for x in C:
	K.append(lr0_kernel(x))
	for y in x:
	y.setnumbers = setC[:]

	_cindex = 0
	for x in C:
	for y in x:
	y.lookaheads[_cindex] = []
	y.setnumbers[_cindex] = 1
	_cindex = _cindex + 1

	###
	# Add lookaheads to the lr items
	###

	add_lookaheads(K)

	###
	# Do the reductions for parsing first and keep them in globals
	###

	ReduceNonterminals()

	global TReductions
	global NTReductions
	global Prodempty

	EmptyAncestors = {}
	for y in Prodempty.keys():
	EmptyAncestors[y] = []
	for x in NTReductions.items():
	for y in x[1]:
	if Prodempty.has_key(y):
	EmptyAncestors[y].append(x[0])


	# Build the parser table, state by state
	st = 0
	for I in C:
	# Loop over each production in I
	actlist = [ ] # List of actions
	acthash = { }

	idI = id(I)

	if yaccdebug:
	_vf.write("\nstate %d\n\n" % st)
	for p in I:
	_vf.write(" (%d) %s\n" % (p.number, str(p)))
	_vf.write("\n")

	global First
	for p in I:
	try:
	if p.prod[-1] == ".":
	if p.name == "S'":
	# Start symbol. Accept!
	action[st,"$"] = 0
	actionp[st,"$"] = p
	elif len(p.prod) == 0:
	ancestors = EmptyAncestors[p.name]
	for i in ancestors:
	for s in K:
	if i in s:
	input_list = []
	plist = Productions[i.name]
	for x in plist:
	if len(x.prod) > 0 and x.prod[0] == p.name:
	n = p.prod[1:]
	d = x.prod[lr_index+2:]
	for l in x.lookaheads.items():
	flist = First[tuple(n+d+[l])]
	for f in flist:
	if f not in input_list and f in p.lookaheads[st]:
	input_list.append(f)

	# We are at the end of a production. Reduce!
	#print "input_list: %s" % input_list
	#print "Follow[p.name]: %s" % Follow[p.name]
	for a in input_list:
	actlist.append((a,p,"reduce using rule %d (%s) " % (p.number,p)))
	r = action.get((st,a),None)
	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[actionp[st,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.
	action[st,a] = -p.number
	actionp[st,a] = p
	if not slevel and not rlevel:
	_vfc.write("shift/reduce conflict in state %d resolved as reduce.\n" % st)
	_vf.write(" ! shift/reduce conflict for %s resolved as reduce.\n" % a)
	n_srconflict += 1
	elif (slevel == rlevel) and (rprec == 'nonassoc'):
	action[st,a] = None
	else:
	# Hmmm. Guess we'll keep the shift
	if not slevel and not rlevel:
	_vfc.write("shift/reduce conflict in state %d resolved as shift.\n" % st)
	_vf.write(" ! shift/reduce conflict for %s resolved as shift.\n" % a)
	n_srconflict +=1
	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:
	action[st,a] = -p.number
	actionp[st,a] = p
	# print "Reduce/reduce conflict in state %d" % st
	n_rrconflict += 1
	_vfc.write("reduce/reduce conflict in state %d resolved using rule %d.\n" % (st, actionp[st,a].number))
	_vf.write(" ! reduce/reduce conflict for %s resolved using rule %d.\n" % (a,actionp[st,a].number))
	else:
	sys.stderr.write("Unknown conflict in state %d\n" % st)
	else:
	action[st,a] = -p.number
	actionp[st,a] = p

	break # break out of the for s in K loop because we only want to make
	# sure that a production is in the Kernel

	else:
	# We are at the end of a production. Reduce!

	for a in p.lookaheads[st]:
	actlist.append((a,p,"reduce using rule %d (%s)" % (p.number,p)))
	r = action.get((st,a),None)
	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[actionp[st,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.
	action[st,a] = -p.number
	actionp[st,a] = p
	if not slevel and not rlevel:
	_vfc.write("shift/reduce conflict in state %d resolved as reduce.\n" % st)
	_vf.write(" ! shift/reduce conflict for %s resolved as reduce.\n" % a)
	n_srconflict += 1
	elif (slevel == rlevel) and (rprec == 'nonassoc'):
	action[st,a] = None
	else:
	# Hmmm. Guess we'll keep the shift
	if not slevel and not rlevel:
	_vfc.write("shift/reduce conflict in state %d resolved as shift.\n" % st)
	_vf.write(" ! shift/reduce conflict for %s resolved as shift.\n" % a)
	n_srconflict +=1
	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:
	action[st,a] = -p.number
	actionp[st,a] = p
	# print "Reduce/reduce conflict in state %d" % st
	n_rrconflict += 1
	_vfc.write("reduce/reduce conflict in state %d resolved using rule %d.\n" % (st, actionp[st,a].number))
	_vf.write(" ! reduce/reduce conflict for %s resolved using rule %d.\n" % (a,actionp[st,a].number))
	else:
	print "Unknown conflict in state %d" % st
	else:
	action[st,a] = -p.number
	actionp[st,a] = p
	else:
	i = p.lr_index
	a = p.prod[i+1] # Get symbol right after the "."
	if Terminals.has_key(a):
	g = goto_cache[(idI,a)]
	j = cid_hash.get(id(g),-1)
	if j >= 0:
	# We are in a shift state
	_k = (a,j)
	if not acthash.has_key(_k):
	actlist.append((a,p,"shift and go to state %d" % j))
	acthash[_k] = 1
	r = action.get((st,a),None)
	if r is not None:
	# Whoa have a shift/reduce or shift/shift conflict
	if r > 0:
	if r != j:
	sys.stderr.write("Shift/shift conflict in state %d\n" % 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[actionp[st,a].number].prec
	sprec,slevel = Precedence.get(a,('right',0))
	if (slevel > rlevel) or ((slevel == rlevel) and (rprec != 'left')):
	# We decide to shift here... highest precedence to shift
	action[st,a] = j
	actionp[st,a] = p
	if not slevel and not rlevel:
	n_srconflict += 1
	_vfc.write("shift/reduce conflict in state %d resolved as shift.\n" % st)
	_vf.write(" ! shift/reduce conflict for %s resolved as shift.\n" % a)
	elif (slevel == rlevel) and (rprec == 'nonassoc'):
	action[st,a] = None
	else:
	# Hmmm. Guess we'll keep the reduce
	if not slevel and not rlevel:
	n_srconflict +=1
	_vfc.write("shift/reduce conflict in state %d resolved as reduce.\n" % st)
	_vf.write(" ! shift/reduce conflict for %s resolved as reduce.\n" % a)

	else:
	sys.stderr.write("Unknown conflict in state %d\n" % st)
	else:
	action[st,a] = j
	actionp[st,a] = p
	else:
	nonterminal = a
	term_list = TReductions[nonterminal]
	# DB: This loop gets executed a lot. Try to optimize
	for a in term_list:
	g = goto_cache[(idI,a)]
	j = cid_hash[id(g)]
	if j >= 0:
	# We are in a shift state
	# Don't put repeated shift actions on action list (performance hack)
	_k = (a,j)
	if not acthash.has_key(_k):
	actlist.append((a,p,"shift and go to state "+str(j)))
	acthash[_k] = 1

	r = action.get((st,a),None)
	if r is not None:
	# Whoa have a shift/reduce or shift/shift conflict
	if r > 0:
	if r != j:
	sys.stderr.write("Shift/shift conflict in state %d\n" % st)
	continue
	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[actionp[st,a].number].prec
	sprec,slevel = Precedence.get(a,('right',0))
	if (slevel > rlevel) or ((slevel == rlevel) and (rprec != 'left')):
	# We decide to shift here... highest precedence to shift
	action[st,a] = j
	actionp[st,a] = p
	if not slevel and not rlevel:
	n_srconflict += 1
	_vfc.write("shift/reduce conflict in state %d resolved as shift.\n" % st)
	_vf.write(" ! shift/reduce conflict for %s resolved as shift.\n" % a)
	elif (slevel == rlevel) and (rprec == 'nonassoc'):
	action[st,a] = None
	else:
	# Hmmm. Guess we'll keep the reduce
	if not slevel and not rlevel:
	n_srconflict +=1
	_vfc.write("shift/reduce conflict in state %d resolved as reduce.\n" % st)
	_vf.write(" ! shift/reduce conflict for %s resolved as reduce.\n" % a)

	else:
	sys.stderr.write("Unknown conflict in state %d\n" % st)
	else:
	action[st,a] = j
	actionp[st,a] = p

	except StandardError,e:
	raise YaccError, "Hosed in lalr_parse_table", e

	# Print the actions associated with each terminal
	if yaccdebug:
	for a,p,m in actlist:
	if action.has_key((st,a)):
	if p is actionp[st,a]:
	_vf.write(" %-15s %s\n" % (a,m))
	_vf.write("\n")

	for a,p,m in actlist:
	if action.has_key((st,a)):
	if p is not actionp[st,a]:
	_vf.write(" ! %-15s [ %s ]\n" % (a,m))

	# Construct the goto table for this state
	nkeys = { }
	for ii in I:
	for s in ii.usyms:
	if Nonterminals.has_key(s):
	nkeys[s] = None

	# Construct the goto table for this state
	for n in nkeys.keys():
	g = lr0_goto(I,n)
	j = cid_hash.get(id(g),-1)
	if j >= 0:
	goto[st,n] = j
	if yaccdebug:
	_vf.write(" %-30s shift and go to state %d\n" % (n,j))

	st += 1
	if yaccdebug:
	if n_srconflict == 1:
	sys.stderr.write("yacc: %d shift/reduce conflict\n" % n_srconflict)
	if n_srconflict > 1:
	sys.stderr.write("yacc: %d shift/reduce conflicts\n" % n_srconflict)
	if n_rrconflict == 1:
	sys.stderr.write("yacc: %d reduce/reduce conflict\n" % n_rrconflict)
	if n_rrconflict > 1:
	sys.stderr.write("yacc: %d reduce/reduce conflicts\n" % n_rrconflict)


	# -----------------------------------------------------------------------------
	# ==== LR Utility functions ====
	# -----------------------------------------------------------------------------

	# -----------------------------------------------------------------------------
	# _lr_write_tables()
	#
	# This function writes the LR parsing tables to a file
	# -----------------------------------------------------------------------------

	def lr_write_tables(modulename=tab_module):
	filename = modulename + ".py"
	try:
	f = open(filename,"w")

	f.write("""
	# %s
	# This file is automatically generated. Do not edit.

	_lr_method = %s

	_lr_signature = %s
	""" % (filename, repr(_lr_method), repr(Signature.digest())))

	# Change smaller to 0 to go back to original tables
	smaller = 1

	# Factor out names to try and make smaller
	if smaller:
	items = { }

	for k,v in _lr_action.items():
	i = items.get(k[1])
	if not i:
	i = ([],[])
	items[k[1]] = i
	i[0].append(k[0])
	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]):
	_lr_action[(_x,_k)] = _y
	del _lr_action_items
	""")

	else:
	f.write("\n_lr_action = { ");
	for k,v in _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 k,v in _lr_goto.items():
	i = items.get(k[1])
	if not i:
	i = ([],[])
	items[k[1]] = i
	i[0].append(k[0])
	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]):
	_lr_goto[(_x,_k)] = _y
	del _lr_goto_items
	""")
	else:
	f.write("\n_lr_goto = { ");
	for k,v in _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 Productions:
	if p:
	if (p.func):
	f.write(" (%r,%d,%r,%r,%d),\n" % (p.name, p.len, p.func.__name__,p.file,p.line))
	else:
	f.write(" (%r,%d,None,None,None),\n" % (p.name, p.len))
	else:
	f.write(" None,\n")
	f.write("]\n")
	f.close()

	except IOError,e:
	print "Unable to create '%s'" % filename
	print e
	return

	def lr_read_tables(module=tab_module,optimize=0):
	global _lr_action, _lr_goto, _lr_productions, _lr_method
	try:
	exec "import %s as parsetab" % module

	if (optimize) or (Signature.digest() == parsetab._lr_signature):
	_lr_action = parsetab._lr_action
	_lr_goto = parsetab._lr_goto
	_lr_productions = parsetab._lr_productions
	_lr_method = parsetab._lr_method
	return 1
	else:
	return 0

	except (ImportError,AttributeError):
	return 0

	# -----------------------------------------------------------------------------
	# yacc(module)
	#
	# Build the parser module
	# -----------------------------------------------------------------------------

	def yacc(method=default_lr, debug=yaccdebug, module=None, tabmodule=tab_module, start=None, check_recursion=1, optimize=0,write_tables=1,debugfile=debug_file):
	global yaccdebug
	yaccdebug = debug

	initialize_vars()
	files = { }
	error = 0

	# Add starting symbol to signature
	if start:
	Signature.update(start)

	# Add parsing method to signature
	Signature.update(method)

	# If a "module" parameter was supplied, extract its dictionary.
	# Note: a module may in fact be an instance as well.

	if module:
	# User supplied a module object.
	if isinstance(module, types.ModuleType):
	ldict = module.__dict__
	elif isinstance(module, types.InstanceType):
	_items = [(k,getattr(module,k)) for k in dir(module)]
	ldict = { }
	for i in _items:
	ldict[i[0]] = i[1]
	else:
	raise ValueError,"Expected a module"

	else:
	# No module given. We might be able to get information from the caller.
	# Throw an exception and unwind the traceback to get the globals

	try:
	raise RuntimeError
	except RuntimeError:
	e,b,t = sys.exc_info()
	f = t.tb_frame
	f = f.f_back # Walk out to our calling function
	ldict = f.f_globals # Grab its globals dictionary

	# If running in optimized mode. We're going to

	if (optimize and lr_read_tables(tabmodule,1)):
	# Read parse table
	del Productions[:]
	for p in _lr_productions:
	if not p:
	Productions.append(None)
	else:
	m = MiniProduction()
	m.name = p[0]
	m.len = p[1]
	m.file = p[3]
	m.line = p[4]
	if p[2]:
	m.func = ldict[p[2]]
	Productions.append(m)

	else:
	# Get the tokens map
	if (module and isinstance(module,types.InstanceType)):
	tokens = getattr(module,"tokens",None)
	else:
	tokens = ldict.get("tokens",None)

	if not tokens:
	raise YaccError,"module does not define a list 'tokens'"
	if not (isinstance(tokens,types.ListType) or isinstance(tokens,types.TupleType)):
	raise YaccError,"tokens must be a list or tuple."

	# Check to see if a requires dictionary is defined.
	requires = ldict.get("require",None)
	if requires:
	if not (isinstance(requires,types.DictType)):
	raise YaccError,"require must be a dictionary."

	for r,v in requires.items():
	try:
	if not (isinstance(v,types.ListType)):
	raise TypeError
	v1 = [x.split(".") for x in v]
	Requires[r] = v1
	except StandardError:
	print "Invalid specification for rule '%s' in require. Expected a list of strings" % r


	# Build the dictionary of terminals. We a record a 0 in the
	# dictionary to track whether or not a terminal is actually
	# used in the grammar

	if 'error' in tokens:
	print "yacc: Illegal token 'error'. Is a reserved word."
	raise YaccError,"Illegal token name"

	for n in tokens:
	if Terminals.has_key(n):
	print "yacc: Warning. Token '%s' multiply defined." % n
	Terminals[n] = [ ]

	Terminals['error'] = [ ]

	# Get the precedence map (if any)
	prec = ldict.get("precedence",None)
	if prec:
	if not (isinstance(prec,types.ListType) or isinstance(prec,types.TupleType)):
	raise YaccError,"precedence must be a list or tuple."
	add_precedence(prec)
	Signature.update(repr(prec))

	for n in tokens:
	if not Precedence.has_key(n):
	Precedence[n] = ('right',0) # Default, right associative, 0 precedence

	# Look for error handler
	ef = ldict.get('p_error',None)
	if ef:
	if isinstance(ef,types.FunctionType):
	ismethod = 0
	elif isinstance(ef, types.MethodType):
	ismethod = 1
	else:
	raise YaccError,"'p_error' defined, but is not a function or method."
	eline = ef.func_code.co_firstlineno
	efile = ef.func_code.co_filename
	files[efile] = None

	if (ef.func_code.co_argcount != 1+ismethod):
	raise YaccError,"%s:%d: p_error() requires 1 argument." % (efile,eline)
	global Errorfunc
	Errorfunc = ef
	else:
	print "yacc: Warning. no p_error() function is defined."

	# Get the list of built-in functions with p_ prefix
	symbols = [ldict[f] for f in ldict.keys()
	if (type(ldict[f]) in (types.FunctionType, types.MethodType) and ldict[f].__name__[:2] == 'p_'
	and ldict[f].__name__ != 'p_error')]

	# Check for non-empty symbols
	if len(symbols) == 0:
	raise YaccError,"no rules of the form p_rulename are defined."

	# Sort the symbols by line number
	symbols.sort(lambda x,y: cmp(x.func_code.co_firstlineno,y.func_code.co_firstlineno))

	# Add all of the symbols to the grammar
	for f in symbols:
	if (add_function(f)) < 0:
	error += 1
	else:
	files[f.func_code.co_filename] = None

	# Make a signature of the docstrings
	for f in symbols:
	if f.__doc__:
	Signature.update(f.__doc__)

	lr_init_vars()

	if error:
	raise YaccError,"Unable to construct parser."

	if not lr_read_tables(tabmodule):

	# Validate files
	for filename in files.keys():
	if not validate_file(filename):
	error = 1

	# Validate dictionary
	validate_dict(ldict)

	if start and not Prodnames.has_key(start):
	raise YaccError,"Bad starting symbol '%s'" % start

	augment_grammar(start)
	error = verify_productions(cycle_check=check_recursion)
	otherfunc = [ldict[f] for f in ldict.keys()
	if (type(f) in (types.FunctionType,types.MethodType) and ldict[f].__name__[:2] != 'p_')]

	if error:
	raise YaccError,"Unable to construct parser."

	build_lritems()
	compute_first1()
	compute_follow(start)

	if method == 'SLR':
	slr_parse_table()
	elif method == 'LALR':
	lalr_parse_table()
	else:
	raise YaccError, "Unknown parsing method '%s'" % method

	if write_tables:
	lr_write_tables(tabmodule)

	if yaccdebug:
	try:
	f = open(debugfile,"w")
	f.write(_vfc.getvalue())
	f.write("\n\n")
	f.write(_vf.getvalue())
	f.close()
	except IOError,e:
	print "yacc: can't create '%s'" % debugfile,e

	# Made it here. Create a parser object and set up its internal state.
	# Set global parse() method to bound method of parser object.

	p = Parser("xyzzy")
	p.productions = Productions
	p.errorfunc = Errorfunc
	p.action = _lr_action
	p.goto = _lr_goto
	p.method = _lr_method
	p.require = Requires

	global parse
	parse = p.parse

	# Clean up all of the globals we created
	if (not optimize):
	yacc_cleanup()
	return p

	# yacc_cleanup function. Delete all of the global variables
	# used during table construction

	def yacc_cleanup():
	global _lr_action, _lr_goto, _lr_method, _lr_goto_cache
	del _lr_action, _lr_goto, _lr_method, _lr_goto_cache

	global Productions, Prodnames, Prodmap, Terminals
	global Nonterminals, First, Follow, Precedence, LRitems
	global Errorfunc, Signature, Requires
	global Prodempty, TReductions, NTReductions, GotoSetNum, Canonical

	del Productions, Prodnames, Prodmap, Terminals
	del Nonterminals, First, Follow, Precedence, LRitems
	del Errorfunc, Signature, Requires
	del Prodempty, TReductions, NTReductions, GotoSetNum, Canonical

	global _vf, _vfc
	del _vf, _vfc


	# Stub that raises an error if parsing is attempted without first calling yacc()
	def parse(args,*kwargs):
	raise YaccError, "yacc: No parser built with yacc()"

	</protect>

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