Re: Is YACC / PCCTS used in commercial compilers?

John Roberts (johnr@ims.com) wrote:
:
: What I'm trying to understand is:
:
: 1) What are the problems using YACC/PCCTS in commercial compilers?
: (i.e. why aren't they used?)


          One of the problems with yacc is that it's very hard to debug
complicated grammars because there's a `black box' step that produces
the parse table (i.e. transition matrix). There are no user
servicable parts inside because of its complexity, i.e. it's opaque to
someone who's trying to figure out what's wrong with his grammar.


          The advantage to these LALR techniques is that they're very efficient
when they work, and they work for most of the programming languages which
are of interest.


: 2) What techniques are used in place of YACC/PCCTS for commerical
: compiler parsing?


          The IBM compilers use what's called Syntax/Semantic Language (S/SL),
which has the advantage of being transparent to inspection in all phases
of the compilation process. I believe there is more information on S/SL
in the comp.compilers FAQ.


is all.
Mike O'Connor
--

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