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Re: Bison back-tracking
From: |
Akim Demaille |
Subject: |
Re: Bison back-tracking |
Date: |
24 Nov 2000 11:03:03 +0100 |
User-agent: |
Gnus/5.0807 (Gnus v5.8.7) XEmacs/21.1 (Channel Islands) |
>>>>> "Hans" == Hans Aberg <address@hidden> writes:
Hans> Is Bison deterministic or does sometimes Bison back-track? If
Hans> Bison sometimes back-track, is there a way to know when Bison is
Hans> back-tracking or to enforce determinism?
It does not backtrack, it is fully deterministic. Look for Btyacc for
a back tracking Yacc. It's funny to see that Corbett worked on it,
and pretty many files are common with Bison :)
Hans> By back-tracking, I mean that there are rules
Hans> <variable>: <rule 1> { ... } | <rule 2> { ... } ...
Hans> where Bison first investigates <rule 1> and in that course
Hans> executes some of the associated actions, then decides that rule
Hans> 1 is not applicable, and then decides for <rule 2> instead.
This cannot happen. Nevertheless, if you insert actions between the
symbols, and you have `error' tokens then something somewhat similar
can happen. See the nodes about lexical tie-ins in the documentation.