Mercurial > hg > expressionparser

comparison expr.py @ 12:835efd8acb04

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
add some vocab
author Jeff Hammel <jhammel@mozilla.com>
date Fri, 03 Jun 2011 11:09:08 -0700
parents e17a3464a0b9
children ec0e83ec329f
comparison
equal deleted inserted replaced
11:e17a3464a0b9 12:835efd8acb04
1 #!/usr/bin/env python
2
3 # Implements a top-down parser/evaluator for simple boolean expressions. 1 # Implements a top-down parser/evaluator for simple boolean expressions.
4 # ideas taken from http://effbot.org/zone/simple-top-down-parsing.htm 2 # ideas taken from http://effbot.org/zone/simple-top-down-parsing.htm
5 # 3 #
6 # Rough grammar: 4 # Rough grammar:
7 # expr := literal 5 # expr := literal
20 # IDENT := [A-Za-z_]\w* 18 # IDENT := [A-Za-z_]\w*
21 19
22 # Identifiers take their values from a mapping dictionary passed as the second 20 # Identifiers take their values from a mapping dictionary passed as the second
23 # argument. 21 # argument.
24 22
23 # Glossary (see above URL for details):
24 # - nud: null denotation
25 # - led: left detonation
26 # - lbp: left binding power
27 # - rbp: right binding power
28
25 __all__ = ['parse', 'ParseError', 'ExpressionParser'] 29 __all__ = ['parse', 'ParseError', 'ExpressionParser']
26 import re 30 import re
27 31
28 # token classes 32 # token classes
29 class token(object): 33 class token(object):