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From: Robert Dewar <robert_dewar@my-deja.com>
Subject: Re: Ayacc/Aflex "entropy" (P2Ada)
Date: 1999/10/27
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In article <3816331A.99C596D2@mitre.org>,
  "Robert I. Eachus" <eachus@mitre.org> wrote:
>     One alternative would be to use a parser generator which
uses
> Early's algorithm.  Early's algorithm will cheerfully accept
any LR(k)
> grammar, and parse it quite fast, but it can also accept and
recognize
> ambiguous grammars, but the performance degrades to O(n**3).



I think the parsing algorithm is less of an issue than error
recovery, the error recovery of YACC is pathetic. It is
surprising what can be done with automatic generators in
this area. See some of the papers from Fisher and Charles from
the early days of the NYU Ada/Ed project. Many commercial Ada/83
compilers made use of this work, and the syntactic error
recovery of Ada/Ed was really quite good (not as good as GNAT,
but GNAT has a lot of careful hand coded heuristic stuff that
I doubt any automatic system could fully match).

Robert Dewar


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