backtracking yacc

["Anthony J Heading" <heading_anthony at jpmorgan dot com>]

Hi,
     I was interested by the plan to replace the C++ parser with a hand-crafted
recursive descent one.   Seemed to be a change in perspective from when I read
the original Dragon book many years back, but my expertise is no deeper than a
cursory read of that so I've not got anything to contribute.

But my attention was grabbed some time earlier this year though by "BackTracking
Yacc"   http://www.siber.org/btyacc,  and just thought I'd mention it in case it
was of possible use as maybe an alternative solution

From the readme:

> BTYACC is a modified version of yacc that supports automatic backtracking and
semantic disambiguation to parse ambiguous grammars...

>  BTYACC was originally written to make it easy to write a
>  C++ parser (my goal was to be able to use the grammar out
>  of the back of the ARM with as few modifications as
>  possible).  Anyone who has ever looked at Jim Roskind
>  public domain C++ yacc grammar, or the yacc-based grammar
>  used in g++ knows how difficult this is.

It may be that this doesn't help with any of the things that Gaby and Mark
mentioned as desirables  - better error messages and so on.   But just in case
it's of interest...

Anthony




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