Python pyparsing.operatorPrecedence() Examples

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Example #1

Source File: evaluator.py From manila with Apache License 2.0

4 votes

def _def_parser():
    # Enabling packrat parsing greatly speeds up the parsing.
    pyparsing.ParserElement.enablePackrat()

    alphas = pyparsing.alphas
    Combine = pyparsing.Combine
    Forward = pyparsing.Forward
    nums = pyparsing.nums
    oneOf = pyparsing.oneOf
    opAssoc = pyparsing.opAssoc
    operatorPrecedence = pyparsing.operatorPrecedence
    Word = pyparsing.Word

    integer = Word(nums)
    real = Combine(Word(nums) + '.' + Word(nums))
    variable = Word(alphas + '_' + '.')
    number = real | integer
    expr = Forward()
    fn = Word(alphas + '_' + '.')
    operand = number | variable | fn

    signop = oneOf('+ -')
    addop = oneOf('+ -')
    multop = oneOf('* /')
    comparisonop = oneOf(' '.join(EvalComparisonOp.operations.keys()))
    ternaryop = ('?', ':')
    boolandop = oneOf('AND and &&')
    boolorop = oneOf('OR or ||')
    negateop = oneOf('NOT not !')

    operand.setParseAction(EvalConstant)
    expr = operatorPrecedence(operand, [
        (fn, 1, opAssoc.RIGHT, EvalFunction),
        ("^", 2, opAssoc.RIGHT, EvalPowerOp),
        (signop, 1, opAssoc.RIGHT, EvalSignOp),
        (multop, 2, opAssoc.LEFT, EvalMultOp),
        (addop, 2, opAssoc.LEFT, EvalAddOp),
        (negateop, 1, opAssoc.RIGHT, EvalNegateOp),
        (comparisonop, 2, opAssoc.LEFT, EvalComparisonOp),
        (ternaryop, 3, opAssoc.LEFT, EvalTernaryOp),
        (boolandop, 2, opAssoc.LEFT, EvalBoolAndOp),
        (boolorop, 2, opAssoc.LEFT, EvalBoolOrOp),
        (',', 2, opAssoc.RIGHT, EvalCommaSeperator), ])

    return expr