Re: Bison's Semantic Parser

[Akim Demaille]

>>>>> "Hans" == Hans Aberg <address@hidden> writes:

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.

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.

Could you send your samples?

Hans> So the strategy I suggest is to keep it in the current version
Hans> 1.29 that Akim is working on, and perhaps the next one if that
Hans> is only to add C++ support, but then make a permanent archiving
Hans> of the last version containing the semantic parser and then
Hans> remove it. If somebody then wants to go back and study it, they
Hans> can still do that, without the semantic parser being a bother in
Hans> future development of Bison.

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.

So it will simply be removed.


I'm sorry for the delays, I've been under pressure lately, and I
expect to be back to Bison in the next couple of months.