Re:Bermudez-Logothetis LALR(1) Lookahead Algorithm

Rob Thorpe <>
9 Mar 2003 17:24:08 -0500

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Bermudez-Logothetis LALR(1) Lookahead Algorithm (Rob Arthan) (2003-02-21)
Re: Bermudez-Logothetis LALR(1) Lookahead Algorithm (Rob Arthan) (2003-02-24)
Re:Bermudez-Logothetis LALR(1) Lookahead Algorithm (Rob Thorpe) (2003-03-09)
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From: Rob Thorpe <>
Newsgroups: comp.compilers
Date: 9 Mar 2003 17:24:08 -0500
Organization: Compilers Central
References: 03-02-126 03-02-152
Keywords: parse, LALR
Posted-Date: 09 Mar 2003 17:24:08 EST

> Rob Arthan wrote:

> This all turns out to be wonderfully easy to implement - it only adds about
> 300 non-comment lines of Standard ML code to my earlier SLR(1)-based
> parser generator (and about 80 of those are for diagnostics and listings).
> I have been put off implementing LALR(1) for over 10 years because of the
> uninspiring description of the over-complex (and slow) yacc algorithm in
> Aho & Ullman - drat that dragon!

Though I don't properly understand it, the algorithm in yacc is quite
short, only 400 lines of C. In Standard ML it would probably be a
similar length or shorter.
That said algorithms that work in complex ways, such as any parser
construction algorithm should be completely documented in the source or
in a reference manual. So it's best to pick the one that is easiest to

Robert Thorpe
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