Backtracking yacc

Jarmo Raiha <jarmo@ksvltd.FI>
Thu, 10 Sep 1992 23:01:10 GMT

          From comp.compilers

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Backtracking yacc jarmo@ksvltd.FI (Jarmo Raiha) (1992-09-10)
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Newsgroups: comp.compilers
From: Jarmo Raiha <jarmo@ksvltd.FI>
Organization: Compilers Central
Date: Thu, 10 Sep 1992 23:01:10 GMT
Keywords: yacc, parse, question, comment

Has anybody seen such a thing as backtracking yacc? What I had in mind
was a LALR parser that resolves ambiquity by backtracking to the point
where it had multiple routes to go. It would parse the input until it
encounters a dead end, and after that it would try an alternative path.


I know this would not solve much. Resolving the the conflicts 'the wrong
way' can still result to an errorless parsing, but I would like to know if
there have been any study about this approach. Is this a completely dead
idea ?


Jarmo Raiha
[That might help for conflicts in an unambiguous grammar that needs more than
one token lookahead, but not for the more common case that a conflict is due
to a truly ambiguous grammar. Besides, isn't there a theorem that says that
any LR(k) grammar can be rewritten as LR(1)? -John]
--


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