Re: Bison's Semantic Parser

[Hans Aberg]

At 20:01 +0200 2001/07/03, Akim Demaille wrote:
>Hans> About Bison's semantic parser ("hairy"), I think that in the
>Hans> near future one may have to remove it altogether from Bison for
>Hans> the following reasons: - I made a small example with it, and it
>Hans> did not parse correctly, so it seems broken.  - The "semantic
>Hans> parser" seems to have something with generating errors in
>Hans> midrule, but that can already be done by the use of Bison's
>Hans> YYERROR. So I do not think it will contributes to anything.  In
>Hans> addition nobody seems to really know about it, or have used it
>Hans> for a really long time (at least a decade).
>
>Part of the job of my students is to study this zombie code, and
>decide whether we can reactivate it, or simply remove it.

Good.

>Could you send your samples?

I figure you already have the example I posted to the Bison lists. I never
went further and figured out how to use the guards, even I looked a bit on
how figure that out.

>I don't think YYERROR can be compared to the guards, but again, I have
>only a small idea of what it is supposed to do.

Perhaps. What I really mean is that one should be able to attain the same
effects with YYERROR & actions in midrule.

But it would be good to know for sure what those guards do.

>Hans> Another feature that seems to be broken (right Akim?) is when
>Hans> using the non-yacc mode, where Bison is using its own token
>Hans> numbers. I think one can remove that one as well, as nobody
>Hans> seems to use it. Instead one might put in a Unicode mode that
>Hans> reserves numbers for the Unicode characters.
>
>I have already decided to remove this pseudo-feature.  It is not
>absolutely related to being non Yacc compatible, there are many other
>aspects.  The very one you are referring too, --raw, which has the
>token numbered from 3 instead of 257, was broken since at least 1.24.
>
>No one ever complained, and I see no reason to complicate Bison for
>free.

Right.

>So it will simply be removed.

OK. Fine. It didn't seem useful anyhow.

  Hans Aberg