Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.compilers > #3710 > unrolled thread

LALR look-ahead sets from item right context grammar?

Back to article view | Back to comp.compilers

Contents

  LALR look-ahead sets from item right context grammar? Richard Rogers <rprogers@seanet.com> - 2026-01-29 18:25 -0500
    LALR look-ahead sets from item right context grammar? Chris Clark <cclark@imachinesinc.com> - 2026-01-31 01:30 +0000

#3710 — LALR look-ahead sets from item right context grammar?

In discussing LR-Regular parsing, Grune [1] gives an algorithm for computing
the CFG of LR(0) item right contexts. I wondered if LALR(1) look-ahead sets
are just the FIRST of the item right context grammar?

1. @book{Grune:1990:PTP:130365,
 author = {Grune, Dick and Jacobs, Ceriel J. H.},
 title = {Parsing Techniques: A Practical Guide},
 year = {1990},
 isbn = {0-13-651431-6},
 publisher = {Ellis Horwood},
 address = {Upper Saddle River, NJ, USA},
}

[toc] | [next] | [standalone]

#3712

While I haven't read the book you reference, and thus am not familiar with the
details of the "right context grammar", I would suggest you look to verify
that in cases where there are nullable non-terminals in the right context
grammar, that it would also include the "follow" set and not just the "first'
set.  We did something similar to that in our version of  "Yacc++ and the
Language Objects Library" but our algorithm is a non-standard implementation
of the technology.  Still the LR(0) machine has more information in it than is
generally assumed.

[toc] | [prev] | [standalone]

Back to top | Article view | comp.compilers

csiph-web