expressionparser: expr.py annotate

annotate expr.py @ 9:421e26c0299f

add a string token

author	Jeff Hammel <jhammel@mozilla.com>
date	Fri, 03 Jun 2011 08:36:55 -0700
parents	9b2bf000aeed
children	15fb1081784f

rev	line source
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	1 #!/usr/bin/env python
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	2
2 94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	3 # 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	4 # 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	5 #
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	6 # Rough grammar:
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	7 # expr := literal
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	8 # \| '(' 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 # \| expr '==' expr
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	12 # \| expr '!=' expr
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	13 # literal := BOOL
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	14 # \| INT
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	15 # \| STRING
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	16 # \| IDENT
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	17 # BOOL := true\|false
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	18 # INT := [0-9]+
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	19 # STRING := "[^"]*"
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	20 # IDENT := [A-Za-z_]\w*
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	21
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	22 # 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	23 # argument.
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	24
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	25 __all__ = ['parse', 'ParseError']
4 a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	26 import re
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	27
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	28 # token classes
4 a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	29 class ident_token(object):
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	30 def __init__(self, value):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	31 self.value = value
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	32 def nud(self, parser):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	33 # identifiers take their value from the value mappings passed
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	34 # to the parser
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	35 return parser.value(self.value)
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	36
4 a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	37 class literal_token(object):
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	38 def __init__(self, value):
3 5ac8eed85684 consolidate token classes Ted Mielczarek <ted.mielczarek@gmail.com> parents: 2 diff changeset	39 self.value = value
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	40 def nud(self, parser):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	41 return self.value
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	42
4 a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	43 class eq_op_token(object):
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	44 "=="
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	45 lbp = 20
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	46 def led(self, parser, left):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	47 return left == parser.expression(self.lbp)
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	48
4 a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	49 class neq_op_token(object):
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	50 "!="
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	51 lbp = 20
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 and_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 lbp = 11
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	58 def led(self, parser, left):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	59 right = parser.expression(self.lbp)
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	60 return left and right
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	61
4 a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	62 class or_op_token(object):
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	63 "\|\|"
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	64 lbp = 10
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	65 def led(self, parser, left):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	66 right = parser.expression(self.lbp)
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	67 return left or right
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	68
4 a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	69 class lparen_token(object):
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	70 "("
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	71 lbp = 50
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	72 def nud(self, parser):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	73 expr = parser.expression()
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	74 parser.advance(rparen_token)
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	75 return expr
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	76
4 a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	77 class rparen_token(object):
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	78 ")"
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	79 lbp = 0
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	80
4 a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	81 class end_token(object):
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	82 # lowest left binding power, always ends parsing
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	83 lbp = 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 ]
a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	106
2 94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	107 class ParseError(Exception):
4 a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	108 """errror parsing conditional expression"""
2 94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	109
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	110 class ExpressionParser(object):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	111 def __init__(self, text, valuemapping):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	112 """
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	113 Initialize the parser with input \|text\|, and \|valuemapping\| as
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	114 a dict mapping identifier names to values.
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 self.text = text
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	117 self.valuemapping = valuemapping
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 def _tokenize(self):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	120 """
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	121 Lex the input text into tokens and yield them in sequence.
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	122 """
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	123 # 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	124 def bool_(scanner, t): return bool_token(t)
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	125 def identifier(scanner, t): return ident_token(t)
8 9b2bf000aeed add an int token Jeff Hammel <jhammel@mozilla.com> parents: 7 diff changeset	126 def integer(scanner, t): return int_token(t)
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	127 def eq(scanner, t): return eq_op_token()
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	128 def neq(scanner, t): return neq_op_token()
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	129 def or_(scanner, t): return or_op_token()
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	130 def and_(scanner, t): return and_op_token()
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	131 def lparen(scanner, t): return lparen_token()
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	132 def rparen(scanner, t): return rparen_token()
9 421e26c0299f add a string token Jeff Hammel <jhammel@mozilla.com> parents: 8 diff changeset	133 def string_(scanner, t): return string_token(t)
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	134
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	135 scanner = re.Scanner([
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	136 (r"true\|false", bool_),
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	137 (r"[a-zA-Z_]\w*", identifier),
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	138 (r"[0-9]+", integer),
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	139 (r'"[^"]*"', string_),
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	140 (r"==", eq),
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	141 (r"!=", neq),
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	142 (r"\\|\\|", or_),
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	143 (r"&&", and_),
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	144 (r"\(", lparen),
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	145 (r"\)", rparen),
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	146 (r"\s+", None), # skip whitespace
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	147 ])
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	148 tokens, remainder = scanner.scan(self.text)
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	149 for t in tokens:
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	150 yield t
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	151 yield end_token()
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	152
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	153 def value(self, ident):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	154 """
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	155 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	156 constructor.
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 return self.valuemapping[ident]
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	159
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	160 def advance(self, expected):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	161 """
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	162 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	163 to the next token.
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 if not isinstance(self.token, expected):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	166 raise Exception, "Unexpected token!"
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	167 self.token = self.iter.next()
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	168
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	169 def expression(self, rbp=0):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	170 """
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	171 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	172 right binding power greater than rbp is encountered.
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 t = self.token
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	175 self.token = self.iter.next()
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	176 left = t.nud(self)
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	177 while rbp < self.token.lbp:
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	178 t = self.token
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	179 self.token = self.iter.next()
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	180 left = t.led(self, left)
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	181 return left
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	182
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	183 def parse(self):
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	184 """
ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	185 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	186 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	187 could not be parsed.
0 ae57e69e4b15 simple expression parser Ted Mielczarek <ted.mielczarek@gmail.com> parents: diff changeset	188 """
2 94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	189 try:
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	190 self.iter = self._tokenize()
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	191 self.token = self.iter.next()
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	192 return self.expression()
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	193 except:
4 a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	194 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	195
4 a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	196 __call__ = parse
a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	197
a42bb6dc2fa7 change parse mapping to *kwargs Jeff Hammel <jhammel@mozilla.com>* parents: 3 diff changeset	198 def parse(text, **values):
2 94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	199 """
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	200 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	201 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	202 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	203 """
94a293b914af add documentation, clean up interface slightly, tweak tests Ted Mielczarek <ted.mielczarek@gmail.com> parents: 1 diff changeset	204 return ExpressionParser(text, values).parse()

Mercurial > hg > expressionparser

annotate expr.py @ 9:421e26c0299f