Ho about this (replacement for yours, or just replace in PPChoiceParser - but it will result in different behavior for that method outside of your particular parser, so beware): parseOn: aStream "This is optimized code that avoids unnecessary block activations, do not change. When all choices fail, the last failure is answered." | element longest | longest := #( 0 nil ). 1 to: parsers size do: [ :index | element := (parsers at: index) parseOn: aStream. element isPetitFailure ifTrue: [ aStream position > longest first ifTrue: [ longest at: 1 put: aStream position; at: 2 put: element ] ] ifFalse: [ ^ element ] ]. aStream position: longest first. ^ element I had a need for it in the past (and, just now, in fact - so minimally tested just now). -cbc On Wed, Nov 20, 2013 at 2:15 AM, Norbert Hartl <norbert@hartl.name> wrote:
I talked to Lukas two years ago about parsing the longest match [1]. He committed it to PetitBeta back then. Now I need it and I had a look at the current parsers but didnât find one that can do the same. Is there a parser that can do longest match?
If not I would propose adding that to the default petit parser package. Lukasâ proposal back then was
LongestChoiceParser>>parseOn: aStream | start element longestEnd longestElement | start := aStream position. 1 to: parsers size do: [ :index | element := (parsers at: index) parseOn: aStream. (longestEnd isNil or: [ longestEnd < aStream position ]) ifTrue: [ longestEnd := aStream position. longestElement := element ]. aStream position: start ]. aStream position: longestEnd. ^ longestElement
Norbert
[1] http://www.iam.unibe.ch/pipermail/moose-dev/2011-July/009365.html