Re: [boost] Re: Interest in a Recursive Descent Parsing Library

From: Andreas Pokorny (dieMumiee_at_[hidden])
Date: 2004-12-26 04:37:56

Joel de Guzman wrote:
> >>An alternative scheme is to let the user switch
> >>strategies (possibly using spirit directives).
> >>
> >>Another scheme, used by PCCTS, is to make the parser predictive
> >>by default, and allow the user to use syntactic and semantic
> >>predicates with arbitrary lookahead on specific points in
> >>the grammar.
> > 
> > 
> > Eewww, I smell a kludge ;-)
> 
> Not really. There's a big problem with backtracking in general:
> backtracking and semantic actions do not mix well (e.g. false
> triggering). In a syntactic and semantic predicate, all actions
> are intentionally inhibited.

Thats up to now the only problem I had, when using spirit. Are there plans, 
to allow defering of semantic actions? E.g like the phrase and character
level directives that can be used switch the parsers behaviour at certain 
positions within rules, maybe that could be done for semantic actions too.
Such that all semantic actions are triggered after the rules within the
directive returned sucess.

Maybe there are better solutions.

Regards,
Andreas Pokorny

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