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LSR/env/lib/python3.6/site-packages/hcl/ply/yacc.py

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2020-06-04 17:24:47 +02:00
# -----------------------------------------------------------------------------
# ply: yacc.py
#
# Copyright (C) 2001-2020
# David M. Beazley (Dabeaz LLC)
# All rights reserved.
#
# Latest version: https://github.com/dabeaz/ply
#
# 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 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 grammar 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 inspect
#-----------------------------------------------------------------------------
# === User configurable parameters ===
#
# Change these to modify the default behavior of yacc (if you wish)
#-----------------------------------------------------------------------------
yaccdebug = False # 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
error_count = 3 # Number of symbols that must be shifted to leave recovery mode
resultlimit = 40 # Size limit of results when running in debug mode.
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))
#-----------------------------------------------------------------------------
# === 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 set_lexpos(self, n, lexpos):
self.slice[n].lexpos = lexpos
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 = {}
# parse().
#
# This is the core parsing engine. To operate, it requires a lexer object.
# Two options are provided. The debug flag turns on debugging so that you can
# see the various rule reductions and parsing steps. tracking turns on position
# tracking. In this mode, symbols will record the starting/ending line number and
# character index.
def parse(self, input=None, lexer=None, debug=False, tracking=False):
# If debugging has been specified as a flag, turn it into a logging object
if isinstance(debug, int) and debug:
debug = PlyLogger(sys.stderr)
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 debug:
debug.info('PLY: PARSE DEBUG START')
# 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)
# Set the token function
get_token = self.token = lexer.token
# Set up the state and symbol stacks
statestack = self.statestack = [] # Stack of parsing states
symstack = self.symstack = [] # Stack of grammar symbols
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 = '$end'
symstack.append(sym)
state = 0
while True:
# Get the next symbol on the input. If a lookahead symbol
# is already set, we just use that. Otherwise, we'll pull
# the next token off of the lookaheadstack or from the lexer
if debug:
debug.debug('State : %s', state)
if state not in defaulted_states:
if not lookahead:
if not lookaheadstack:
lookahead = get_token() # Get the next token
else:
lookahead = lookaheadstack.pop()
if not lookahead:
lookahead = YaccSymbol()
lookahead.type = '$end'
# Check the action table
ltype = lookahead.type
t = actions[state].get(ltype)
else:
t = defaulted_states[state]
if debug:
debug.debug('Defaulted state %s: Reduce using %d', state, -t)
if debug:
debug.debug('Stack : %s',
('%s . %s' % (' '.join([xx.type for xx in symstack][1:]), str(lookahead))).lstrip())
if t is not None:
if t > 0:
# shift a symbol on the stack
statestack.append(t)
state = t
if debug:
debug.debug('Action : Shift and goto state %s', 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 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])
if plen:
targ = symstack[-plen-1:]
targ[0] = sym
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)
# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
# 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:]
if debug:
debug.info('Result : %s', format_result(pslice[0]))
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:
if tracking:
sym.lineno = lexer.lineno
sym.lexpos = lexer.lexpos
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)
if debug:
debug.info('Result : %s', format_result(pslice[0]))
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)
if debug:
debug.info('Done : Returning %s', format_result(result))
debug.info('PLY: PARSE DEBUG END')
return result
if t is None:
if debug:
debug.error('Error : %s',
('%s . %s' % (' '.join([xx.type for xx in symstack][1:]), str(lookahead))).lstrip())
# 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 == '$end':
errtoken = None # End of file!
if self.errorfunc:
if errtoken and not hasattr(errtoken, 'lexer'):
errtoken.lexer = lexer
self.state = state
tok = self.errorfunc(errtoken)
if self.errorok:
# User must have done some kind of panic
# mode recovery on their own. The
# returned token is the next lookahead
lookahead = tok
errtoken = None
continue
else:
if errtoken:
if hasattr(errtoken, 'lineno'):
lineno = lookahead.lineno
else:
lineno = 0
if lineno:
sys.stderr.write('yacc: Syntax error at line %d, token=%s\n' % (lineno, errtoken.type))
else:
sys.stderr.write('yacc: Syntax error, token=%s' % errtoken.type)
else:
sys.stderr.write('yacc: Parse error in input. EOF\n')
return
else:
errorcount = error_count
# case 1: the statestack only has 1 entry on it. If we're in this state, the
# entire parse has been rolled back and we're completely hosed. The token is
# discarded and we just keep going.
if len(statestack) <= 1 and lookahead.type != '$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 == '$end':
# Whoa. We're really hosed here. Bail out
return
if lookahead.type != 'error':
sym = symstack[-1]
if sym.type == 'error':
# Hmmm. Error is on top of stack, we'll just nuke input
# symbol and continue
if tracking:
sym.endlineno = getattr(lookahead, 'lineno', sym.lineno)
sym.endlexpos = getattr(lookahead, 'lexpos', sym.lexpos)
lookahead = None
continue
# Create the error symbol for the first time and make it the new lookahead symbol
t = YaccSymbol()
t.type = 'error'
if hasattr(lookahead, 'lineno'):
t.lineno = t.endlineno = lookahead.lineno
if hasattr(lookahead, 'lexpos'):
t.lexpos = t.endlexpos = lookahead.lexpos
t.value = lookahead
lookaheadstack.append(lookahead)
lookahead = t
else:
sym = symstack.pop()
if tracking:
lookahead.lineno = sym.lineno
lookahead.lexpos = sym.lexpos
statestack.pop()
state = statestack[-1]
continue
# If we'r here, something really bad happened
raise RuntimeError('yacc: internal parser error!!!\n')
# -----------------------------------------------------------------------------
# === Grammar Representation ===
#
# The following functions, classes, and variables are used to represent and
# manipulate the rules that make up a grammar.
# -----------------------------------------------------------------------------
# regex matching identifiers
_is_identifier = re.compile(r'^[a-zA-Z0-9_-]+$')
# -----------------------------------------------------------------------------
# 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 = self.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]
# -----------------------------------------------------------------------------
# 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
# -----------------------------------------------------------------------------
# === 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
# -----------------------------------------------------------------------------
# == LRTable ==
#
# This class implements the LR table generation algorithm. There are no
# public methods.
# -----------------------------------------------------------------------------
class LRTable:
def __init__(self, grammar, log=None):
self.grammar = grammar
# 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
# Diagnostic 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()
# Bind all production function names to callable objects in pdict
def bind_callables(self, pdict):
for p in self.lr_productions:
p.bind(pdict)
# 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):
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)
# Step 1: Construct C = { I0, I1, ... IN}, collection of LR(0) items
# This determines the number of states
C = self.lr0_items()
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!
laheads = p.lookaheads[st]
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.
# Shift precedence comes from the token
sprec, slevel = Precedence.get(a, ('right', 0))
# Reduce precedence comes from rule being reduced (p)
rprec, rlevel = Productions[p.number].prec
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
# Shift precedence comes from the token
sprec, slevel = Precedence.get(a, ('right', 0))
# Reduce precedence comes from the rule that could have been reduced
rprec, rlevel = Productions[st_actionp[a].number].prec
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
# -----------------------------------------------------------------------------
# === 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):
parts = []
try:
if self.start:
parts.append(self.start)
if self.prec:
parts.append(''.join([''.join(p) for p in self.prec]))
if self.tokens:
parts.append(' '.join(self.tokens))
for f in self.pfuncs:
if f[3]:
parts.append(f[3])
except (TypeError, ValueError):
pass
return ''.join(parts)
# -----------------------------------------------------------------------------
# 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, str):
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 = sorted(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, str):
self.log.error('precedence associativity must be a string')
self.error = True
return
for term in p[1:]:
if not isinstance(term, str):
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(debug=yaccdebug, module=None, start=None,
check_recursion=True, optimize=False, debugfile=debug_file,
debuglog=None, errorlog=None):
# Reference to the parsing method of the last built parser
global parse
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__ or __package__ attributes are available, try to obtain them
# from the __module__ instead
if '__file__' not in pdict:
pdict['__file__'] = sys.modules[pdict['__module__']].__file__
if '__package__' not in pdict and '__module__' in pdict:
if hasattr(sys.modules[pdict['__module__']], '__package__'):
pdict['__package__'] = sys.modules[pdict['__module__']].__package__
else:
pdict = get_caller_module_dict(2)
# 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')
if debuglog is None:
if debug:
try:
debuglog = PlyLogger(open(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 (http://www.dabeaz.com/ply)')
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 LRTable on the grammar
lr = LRTable(grammar, 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)
# Build the parser
lr.bind_callables(pinfo.pdict)
parser = LRParser(lr, pinfo.error_func)
parse = parser.parse
return parser
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