Mercurial > hg > expressionparser

annotate expr.py @ 13:ec0e83ec329f

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
allow both kinds of strings
author Jeff Hammel <jhammel@mozilla.com>
date Fri, 03 Jun 2011 11:15:40 -0700
parents 835efd8acb04
children 6f0c032b65f5
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
2
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
1 # Implements a top-down parser/evaluator for simple boolean expressions.
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
2 # ideas taken from http://effbot.org/zone/simple-top-down-parsing.htm
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
3 #
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
4 # Rough grammar:
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
5 # expr := literal
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
6 # | '(' expr ')'
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
7 # | expr '&&' expr
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
8 # | expr '||' expr
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
9 # | expr '==' expr
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
10 # | expr '!=' expr
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
11 # literal := BOOL
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
12 # | INT
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
13 # | STRING
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
14 # | IDENT
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
15 # BOOL := true|false
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
16 # INT := [0-9]+
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
17 # STRING := "[^"]*"
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
18 # IDENT := [A-Za-z_]\w*
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
19
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
20 # Identifiers take their values from a mapping dictionary passed as the second
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
21 # argument.
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
22
12
835efd8acb04 add some vocab
Jeff Hammel <jhammel@mozilla.com>
parents: 11
diff changeset
23 # Glossary (see above URL for details):
835efd8acb04 add some vocab
Jeff Hammel <jhammel@mozilla.com>
parents: 11
diff changeset
24 # - nud: null denotation
835efd8acb04 add some vocab
Jeff Hammel <jhammel@mozilla.com>
parents: 11
diff changeset
25 # - led: left detonation
835efd8acb04 add some vocab
Jeff Hammel <jhammel@mozilla.com>
parents: 11
diff changeset
26 # - lbp: left binding power
835efd8acb04 add some vocab
Jeff Hammel <jhammel@mozilla.com>
parents: 11
diff changeset
27 # - rbp: right binding power
835efd8acb04 add some vocab
Jeff Hammel <jhammel@mozilla.com>
parents: 11
diff changeset
28
10
15fb1081784f add ExpressionParser to the exports
Jeff Hammel <jhammel@mozilla.com>
parents: 9
diff changeset
29 __all__ = ['parse', 'ParseError', 'ExpressionParser']
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
30 import re
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
31
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
32 # token classes
10
15fb1081784f add ExpressionParser to the exports
Jeff Hammel <jhammel@mozilla.com>
parents: 9
diff changeset
33 class token(object):
15fb1081784f add ExpressionParser to the exports
Jeff Hammel <jhammel@mozilla.com>
parents: 9
diff changeset
34 pass
15fb1081784f add ExpressionParser to the exports
Jeff Hammel <jhammel@mozilla.com>
parents: 9
diff changeset
35
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
36 class ident_token(object):
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
37 def __init__(self, value):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
38 self.value = value
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
39 def nud(self, parser):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
40 # identifiers take their value from the value mappings passed
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
41 # to the parser
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
42 return parser.value(self.value)
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
43
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
44 class literal_token(object):
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
45 def __init__(self, value):
3
5ac8eed85684 consolidate token classes
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 2
diff changeset
46 self.value = value
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
47 def nud(self, parser):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
48 return self.value
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
49
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
50 class eq_op_token(object):
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
51 "=="
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
52 def led(self, parser, left):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
53 return left == parser.expression(self.lbp)
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
54
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
55 class neq_op_token(object):
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
56 "!="
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
57 def led(self, parser, left):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
58 return left != parser.expression(self.lbp)
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
59
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
60 class and_op_token(object):
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
61 "&&"
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
62 def led(self, parser, left):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
63 right = parser.expression(self.lbp)
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
64 return left and right
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
65
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
66 class or_op_token(object):
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
67 "||"
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
68 def led(self, parser, left):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
69 right = parser.expression(self.lbp)
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
70 return left or right
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
71
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
72 class lparen_token(object):
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
73 "("
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
74 def nud(self, parser):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
75 expr = parser.expression()
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
76 parser.advance(rparen_token)
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
77 return expr
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
78
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
79 class rparen_token(object):
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
80 ")"
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
81
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
82 class end_token(object):
11
e17a3464a0b9 get precedence from a list position vs magic constants
Jeff Hammel <jhammel@mozilla.com>
parents: 10
diff changeset
83 """always ends parsing"""
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
84
8
9b2bf000aeed add an int token
Jeff Hammel <jhammel@mozilla.com>
parents: 7
diff changeset
85 ### derived literal tokens
9b2bf000aeed add an int token
Jeff Hammel <jhammel@mozilla.com>
parents: 7
diff changeset
86
7
325dccc38308 begin using subclasses for tokens; the eventual goal is that a token class will know everything it can about what it is and the parser just knows about what tokens are
Jeff Hammel <jhammel@mozilla.com>
parents: 4
diff changeset
87 class bool_token(literal_token):
325dccc38308 begin using subclasses for tokens; the eventual goal is that a token class will know everything it can about what it is and the parser just knows about what tokens are
Jeff Hammel <jhammel@mozilla.com>
parents: 4
diff changeset
88 def __init__(self, value):
325dccc38308 begin using subclasses for tokens; the eventual goal is that a token class will know everything it can about what it is and the parser just knows about what tokens are
Jeff Hammel <jhammel@mozilla.com>
parents: 4
diff changeset
89 value = {'true':True, 'false':False}[value]
325dccc38308 begin using subclasses for tokens; the eventual goal is that a token class will know everything it can about what it is and the parser just knows about what tokens are
Jeff Hammel <jhammel@mozilla.com>
parents: 4
diff changeset
90 literal_token.__init__(self, value)
325dccc38308 begin using subclasses for tokens; the eventual goal is that a token class will know everything it can about what it is and the parser just knows about what tokens are
Jeff Hammel <jhammel@mozilla.com>
parents: 4
diff changeset
91
8
9b2bf000aeed add an int token
Jeff Hammel <jhammel@mozilla.com>
parents: 7
diff changeset
92 class int_token(literal_token):
9b2bf000aeed add an int token
Jeff Hammel <jhammel@mozilla.com>
parents: 7
diff changeset
93 def __init__(self, value):
9b2bf000aeed add an int token
Jeff Hammel <jhammel@mozilla.com>
parents: 7
diff changeset
94 literal_token.__init__(self, int(value))
9b2bf000aeed add an int token
Jeff Hammel <jhammel@mozilla.com>
parents: 7
diff changeset
95
9
421e26c0299f add a string token
Jeff Hammel <jhammel@mozilla.com>
parents: 8
diff changeset
96 class string_token(literal_token):
421e26c0299f add a string token
Jeff Hammel <jhammel@mozilla.com>
parents: 8
diff changeset
97 def __init__(self, value):
421e26c0299f add a string token
Jeff Hammel <jhammel@mozilla.com>
parents: 8
diff changeset
98 literal_token.__init__(self, value[1:-1])
421e26c0299f add a string token
Jeff Hammel <jhammel@mozilla.com>
parents: 8
diff changeset
99
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
100 precedence = [(end_token, rparen_token),
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
101 (or_op_token,),
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
102 (and_op_token,),
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
103 (eq_op_token, neq_op_token),
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
104 (lparen_token,),
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
105 ]
11
e17a3464a0b9 get precedence from a list position vs magic constants
Jeff Hammel <jhammel@mozilla.com>
parents: 10
diff changeset
106 for index, rank in enumerate(precedence):
e17a3464a0b9 get precedence from a list position vs magic constants
Jeff Hammel <jhammel@mozilla.com>
parents: 10
diff changeset
107 for token in rank:
e17a3464a0b9 get precedence from a list position vs magic constants
Jeff Hammel <jhammel@mozilla.com>
parents: 10
diff changeset
108 token.lbp = index # lbp = lowest left binding power
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
109
2
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
110 class ParseError(Exception):
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
111 """errror parsing conditional expression"""
2
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
112
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
113 class ExpressionParser(object):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
114 def __init__(self, text, valuemapping):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
115 """
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
116 Initialize the parser with input |text|, and |valuemapping| as
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
117 a dict mapping identifier names to values.
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
118 """
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
119 self.text = text
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
120 self.valuemapping = valuemapping
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
121
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
122 def _tokenize(self):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
123 """
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
124 Lex the input text into tokens and yield them in sequence.
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
125 """
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
126 # scanner callbacks
7
325dccc38308 begin using subclasses for tokens; the eventual goal is that a token class will know everything it can about what it is and the parser just knows about what tokens are
Jeff Hammel <jhammel@mozilla.com>
parents: 4
diff changeset
127 def bool_(scanner, t): return bool_token(t)
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
128 def identifier(scanner, t): return ident_token(t)
8
9b2bf000aeed add an int token
Jeff Hammel <jhammel@mozilla.com>
parents: 7
diff changeset
129 def integer(scanner, t): return int_token(t)
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
130 def eq(scanner, t): return eq_op_token()
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
131 def neq(scanner, t): return neq_op_token()
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
132 def or_(scanner, t): return or_op_token()
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
133 def and_(scanner, t): return and_op_token()
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
134 def lparen(scanner, t): return lparen_token()
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
135 def rparen(scanner, t): return rparen_token()
9
421e26c0299f add a string token
Jeff Hammel <jhammel@mozilla.com>
parents: 8
diff changeset
136 def string_(scanner, t): return string_token(t)
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
137
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
138 scanner = re.Scanner([
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
139 (r"true|false", bool_),
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
140 (r"[a-zA-Z_]\w*", identifier),
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
141 (r"[0-9]+", integer),
13
ec0e83ec329f allow both kinds of strings
Jeff Hammel <jhammel@mozilla.com>
parents: 12
diff changeset
142 (r'("[^"]*")|(\'[^\']*\')', string_),
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
143 (r"==", eq),
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
144 (r"!=", neq),
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
145 (r"\|\|", or_),
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
146 (r"&&", and_),
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
147 (r"\(", lparen),
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
148 (r"\)", rparen),
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
149 (r"\s+", None), # skip whitespace
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
150 ])
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
151 tokens, remainder = scanner.scan(self.text)
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
152 for t in tokens:
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
153 yield t
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
154 yield end_token()
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
155
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
156 def value(self, ident):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
157 """
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
158 Look up the value of |ident| in the value mapping passed in the
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
159 constructor.
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
160 """
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
161 return self.valuemapping[ident]
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
162
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
163 def advance(self, expected):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
164 """
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
165 Assert that the next token is an instance of |expected|, and advance
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
166 to the next token.
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
167 """
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
168 if not isinstance(self.token, expected):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
169 raise Exception, "Unexpected token!"
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
170 self.token = self.iter.next()
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
171
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
172 def expression(self, rbp=0):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
173 """
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
174 Parse and return the value of an expression until a token with
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
175 right binding power greater than rbp is encountered.
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
176 """
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
177 t = self.token
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
178 self.token = self.iter.next()
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
179 left = t.nud(self)
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
180 while rbp < self.token.lbp:
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
181 t = self.token
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
182 self.token = self.iter.next()
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
183 left = t.led(self, left)
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
184 return left
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
185
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
186 def parse(self):
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
187 """
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
188 Parse and return the value of the expression in the text
2
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
189 passed to the constructor. Raises a ParseError if the expression
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
190 could not be parsed.
0
ae57e69e4b15 simple expression parser
Ted Mielczarek <ted.mielczarek@gmail.com>
parents:
diff changeset
191 """
2
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
192 try:
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
193 self.iter = self._tokenize()
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
194 self.token = self.iter.next()
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
195 return self.expression()
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
196 except:
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
197 raise ParseError("could not parse: %s" % self.text)
2
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
198
4
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
199 __call__ = parse
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
200
a42bb6dc2fa7 change parse mapping to **kwargs
Jeff Hammel <jhammel@mozilla.com>
parents: 3
diff changeset
201 def parse(text, **values):
2
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
202 """
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
203 Parse and evaluate a boolean expression in |text|. Use |values| to look
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
204 up the value of identifiers referenced in the expression. Returns the final
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
205 value of the expression. A ParseError will be raised if parsing fails.
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
206 """
94a293b914af add documentation, clean up interface slightly, tweak tests
Ted Mielczarek <ted.mielczarek@gmail.com>
parents: 1
diff changeset
207 return ExpressionParser(text, values).parse()