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#######################################################################
# Name: simple.py
# Purpose: Simple language based on example from pyPEG
# 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
#
# This example demonstrates grammar definition using python constructs.
# It is taken and adapted from pyPEG project (see http://www.fdik.org/pyPEG/).
#######################################################################
from arpeggio import *
from arpeggio.export import PMDOTExporter, PTDOTExporter
from arpeggio import RegExMatch as _
def comment(): return [_("//.*"), _("/\*.*\*/")]
def literal(): return _(r'\d*\.\d*|\d+|".*?"')
def symbol(): return _(r"\w+")
def operator(): return _(r"\+|\-|\*|\/|\=\=")
def operation(): return symbol, operator, [literal, functioncall]
def expression(): return [literal, operation, functioncall]
def expressionlist(): return expression, ZeroOrMore(",", expression)
def returnstatement(): return Kwd("return"), expression
def ifstatement(): return Kwd("if"), "(", expression, ")", block, Kwd("else"), block
def statement(): return [ifstatement, returnstatement], ";"
def block(): return "{", OneOrMore(statement), "}"
def parameterlist(): return "(", symbol, ZeroOrMore(",", symbol), ")"
def functioncall(): return symbol, "(", expressionlist, ")"
def function(): return Kwd("function"), symbol, parameterlist, block
def simpleLanguage(): return function
try:
# Parser instantiation. simpleLanguage is the definition of the root rule
# and comment is a grammar rule for comments.
parser = ParserPython(simpleLanguage, comment, debug=True)
# We save parser model to dot file in order to visualise it.
# We can make a png out of it using dot (part of graphviz) like this
# dot -Tpng -O simple_parser.dot
PMDOTExporter().exportFile(parser.parser_model,
"simple_parser_model.dot")
# Parser model for comments is handled as separate model
PMDOTExporter().exportFile(parser.comments_model,
"simple_parser_comments.dot")
input = """
function fak(n) {
if (n==0) {
// For 0! result is 0
return 0;
} else { /* And for n>0 result is calculated recursively */
return n * fak(n - 1);
};
}
"""
parse_tree = parser.parse(input)
PTDOTExporter().exportFile(parse_tree,
"simple_parse_tree.dot")
except NoMatch, e:
print "Expected %s at position %s." % (e.value, str(e.parser.pos_to_linecol(e.position)))