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# -*- coding: utf-8 -*-
##############################################################################
# Name: peg_peg.py
# Purpose: PEG parser definition using PEG itself.
# Author: Igor R. Dejanovic <igor DOT dejanovic AT gmail DOT com>
# Copyright: (c) 2009-2015 Igor R. Dejanovic <igor DOT dejanovic AT gmail DOT com>
# License: MIT License
#
# PEG can be used to describe PEG.
# This example demonstrates building PEG parser using PEG based grammar of PEG
# grammar definition language.
##############################################################################
from __future__ import unicode_literals
import os
from arpeggio import *
from arpeggio.export import PMDOTExporter
from arpeggio.peg import PEGVisitor, ParserPEG
def main(debug=False):
current_dir = os.path.dirname(__file__)
peg_grammar = open(os.path.join(current_dir, 'peg.peg')).read()
# ParserPEG will use ParserPython to parse peg_grammar definition and
# create parser_model for parsing PEG based grammars
# In debug mode dot (graphviz) files for parser model
# and parse tree will be created for visualization.
# Checkout current folder for .dot files.
parser = ParserPEG(peg_grammar, 'peggrammar', debug=debug)
# Now we will use created parser to parse the same peg_grammar used for
# parser initialization. We can parse peg_grammar because it is specified
# using PEG itself.
print("PARSING")
parse_tree = parser.parse(peg_grammar)
# ASG should be the same as parser.parser_model because semantic
# actions will create PEG parser (tree of ParsingExpressions).
parser_model, comment_model = visit_parse_tree(
parse_tree, PEGVisitor(root_rule_name='peggrammar',
comment_rule_name='comment',
ignore_case=False,
debug=debug))
if debug:
# This graph should be the same as peg_peg_parser_model.dot because
# they define the same parser.
PMDOTExporter().exportFile(parser_model,
"peg_peg_new_parser_model.dot")
# If we replace parser_mode with ASG constructed parser it will still
# parse PEG grammars
parser.parser_model = parser_model
parser.parse(peg_grammar)
if __name__ == '__main__':
main(debug=True)
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