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# -*- coding: utf-8 -*-
#######################################################################
# Name: peg.py
# Purpose: Implementing PEG language
# Author: Igor R. Dejanovic <igor DOT dejanovic AT gmail DOT com>
# Copyright: (c) 2009 Igor R. Dejanovic <igor DOT dejanovic AT gmail DOT com>
# License: MIT License
#######################################################################
__all__ = ['ParserPEG']
from arpeggio import *
from arpeggio import RegExMatch as _
import logging
logger = logging.getLogger('arpeggio.peg')
# PEG Grammar
def grammar(): return OneOrMore(rule), EOF
def rule(): return identifier, LEFT_ARROW, ordered_choice, ";"
def ordered_choice(): return sequence, ZeroOrMore(SLASH, sequence)
def sequence(): return OneOrMore(prefix)
def prefix(): return Optional([AND,NOT]), sufix
def sufix(): return expression, Optional([QUESTION, STAR, PLUS])
def expression(): return [regex,(identifier, Not(LEFT_ARROW)),
(OPEN, ordered_choice, CLOSE),
literal]
def regex(): return "r", "'", _(r"(\\\'|[^\'])*"),"'"
def identifier(): return _(r"[a-zA-Z_]([a-zA-Z_]|[0-9])*")
#def literal(): return [_(r"\'(\\\'|[^\'])*\'"),_(r'"[^"]*"')]
def literal(): return _(r'(\'(\\\'|[^\'])*\')|("[^"]*")')
def LEFT_ARROW(): return "<-"
def SLASH(): return "/"
def STAR(): return "*"
def QUESTION(): return "?"
def PLUS(): return "+"
def AND(): return "&"
def NOT(): return "!"
def OPEN(): return "("
def CLOSE(): return ")"
def comment(): return "//", _(".*\n")
# ------------------------------------------------------------------
# PEG Semantic Actions
class PEGSemanticAction(SemanticAction):
def second_pass(self, parser, node):
if isinstance(node, Terminal):
return
for i,n in enumerate(node.nodes):
if isinstance(n, Terminal):
if parser.peg_rules.has_key(n.value):
node.nodes[i] = parser.peg_rules[n.value]
else:
raise SemanticError("Rule \"%s\" does not exists." % n)
class SemGrammar(SemanticAction):
def first_pass(self, parser, node, nodes):
return parser.peg_rules[parser.root_rule_name]
class SemRule(PEGSemanticAction):
def first_pass(self, parser, node, nodes):
rule_name = nodes[0].value
if len(nodes)>4:
retval = Sequence(nodes=nodes[2:-1])
else:
retval = nodes[2]
retval.rule = rule_name
retval.root = True
if not hasattr(parser, "peg_rules"):
parser.peg_rules = {} # Used for linking phase
parser.peg_rules["EndOfFile"] = EndOfFile()
parser.peg_rules[rule_name] = retval
return retval
class SemSequence(PEGSemanticAction):
def first_pass(self, parser, node, nodes):
if len(nodes)>1:
return Sequence(nodes=nodes)
else:
return nodes[0]
class SemOrderedChoice(PEGSemanticAction):
def first_pass(self, parser, node, nodes):
if len(nodes)>1:
retval = OrderedChoice(nodes=nodes[::2])
else:
retval = nodes[0]
return retval
class SemPrefix(PEGSemanticAction):
def first_pass(self, parser, node, nodes):
logger.debug("Prefix: %s " % str(nodes))
if len(nodes)==2:
if nodes[0] == NOT():
retval = Not()
else:
retval = And()
if type(nodes[1]) is list:
retval.nodes = nodes[1]
else:
retval.nodes = [nodes[1]]
else:
retval = nodes[0]
return retval
class SemSufix(PEGSemanticAction):
def first_pass(self, parser, node, nodes):
logger.debug("Sufix : %s" % str(nodes))
if len(nodes) == 2:
logger.debug("Sufix : %s" % str(nodes[1]))
if nodes[1] == STAR():
retval = ZeroOrMore(nodes[0])
elif nodes[1] == QUESTION():
retval = Optional(nodes[0])
else:
retval = OneOrMore(nodes[0])
if type(nodes[0]) is list:
retval.nodes = nodes[0]
else:
retval.nodes = [nodes[0]]
else:
retval = nodes[0]
return retval
class SemExpression(PEGSemanticAction):
def first_pass(self, parser, node, nodes):
logger.debug("Expression : %s" % str(nodes))
if len(nodes)==1:
return nodes[0]
else:
return nodes[1]
class SemIdentifier(SemanticAction):
def first_pass(self, parser, node, nodes):
logger.debug("Identifier %s." % node.value)
return node
class SemRegEx(SemanticAction):
def first_pass(self, parser, node, nodes):
logger.debug("RegEx %s." % nodes[2].value)
return RegExMatch(nodes[2].value)
class SemLiteral(SemanticAction):
def first_pass(self, parser, node, nodes):
logger.debug("Literal: %s" % node.value)
match_str = node.value[1:-1]
match_str = match_str.replace("\\'", "'")
match_str = match_str.replace("\\\\", "\\")
return StrMatch(match_str)
class SemTerminal(SemanticAction):
def first_pass(self, parser, node, nodes):
return StrMatch(node.value)
grammar.sem = SemGrammar()
rule.sem = SemRule()
ordered_choice.sem = SemOrderedChoice()
sequence.sem = SemSequence()
prefix.sem = SemPrefix()
sufix.sem = SemSufix()
expression.sem = SemExpression()
regex.sem = SemRegEx()
identifier.sem = SemIdentifier()
literal.sem = SemLiteral()
for sem in [LEFT_ARROW, SLASH, STAR, QUESTION, PLUS, AND, NOT, OPEN, CLOSE]:
sem.sem = SemTerminal()
class ParserPEG(Parser):
def __init__(self, language_def, root_rule_name, comment_rule_name=None, *args, **kwargs):
super(ParserPEG, self).__init__(*args, **kwargs)
self.root_rule_name = root_rule_name
# PEG Abstract Syntax Graph
self.parser_model = self._from_peg(language_def)
# Comments should be optional and there can be more of them
if self.comments_model: # and not isinstance(self.comments_model, ZeroOrMore):
self.comments_model.root = True
self.comments_model.rule = comment_rule_name
def _parse(self):
return self.parser_model.parse(self)
def _from_peg(self, language_def):
parser = ParserPython(grammar, comment)
parser.root_rule_name = self.root_rule_name
parse_tree = parser.parse(language_def)
return parser.getASG()
if __name__ == "__main__":
try:
logging.basicConfig(level=logging.DEBUG)
parser = ParserPython(grammar, None)
f = open("peg_parser_model.dot", "w")
f.write(str(DOTSerializator(parser.parser_model)))
f.close()
except NoMatch, e:
print "Expected %s at position %s." % (e.value, str(e.parser.pos_to_linecol(e.position)))