expressionparser: expr.py annotate

annotate expr.py @ 12:835efd8acb04

add some vocab

author	Jeff Hammel <jhammel@mozilla.com>
date	Fri, 03 Jun 2011 11:09:08 -0700
parents	e17a3464a0b9
children	ec0e83ec329f

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),
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	142 (r'"[^"]*"', string_),
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()

Mercurial > hg > expressionparser

annotate expr.py @ 12:835efd8acb04