PetitParser not distributive?

Question

Are rules in PetitParser distributive?

There were next rules:

integerLiteral --> hexIntegerLiteral / octalIntegerLiteral / decimalIntegerLiteral
  hexIntegerLiteral     --> hexNumeral , (integerTypeSuffix optional)
  octalIntegerLiteral   --> octalNumeral , (integerTypeSuffix optional)
  decimalIntegerLiteral --> decimalNumeral , (integerTypeSuffix optional)

if I change them to:

integerLiteral --> (hexIntegerLiteral / octalIntegerLiteral / decimalIntegerLiteral) , (integerTypeSuffix optional)
  hexIntegerLiteral     --> hexNumeral
  octalIntegerLiteral   --> octalNumeral
  decimalIntegerLiteral --> decimalNumeral

then 0777L is not parsed anymore. It should match octalNumeral , (integerTypeSuffix optional) or in new version octalIntegerLiteral , (integerTypeSuffix optional) but that isn't happening.

score 3 · Accepted Answer · answered Mar 20 '13 at 15:21

Yes, the ordered-choice in PetitParser is distributive. In your example there is some context missing, so I don't know why it doesn't work for you.

The PetitParser optimizer does the change you suggested automatically. The rewrite rule (in a slightly more general form) is defines as:

PPOptimizer>>#postfixChoice
    <optimize>

    | before prefix body1 body2 postfix after |
    before := PPListPattern any.
    prefix := PPPattern any.
    body1 := PPListPattern any.
    body2 := PPListPattern any.
    postfix := PPPattern any.
    after := PPListPattern any.
    rewriter
        replace: before / (prefix , body1) / (prefix , body2) / after
        with: before / (prefix , (body1 / body2)) / after.
    rewriter
        replace: before / (body1 , postfix) / (body2 , postfix) / after
        with: before / ((body1 / body2) , postfix) / after

PetitParser not distributive?

1 Answers1