From: luc.maranget@inria.fr (Luc Maranget)
To: skaller <skaller@users.sourceforge.net>
Cc: caml-list <caml-list@inria.fr>
Subject: Re: [Caml-list] Need NFA/DFA conversion help
Date: Wed, 15 Sep 2004 17:41:37 +0200 [thread overview]
Message-ID: <20040915154137.GB24717@yquem.inria.fr> (raw)
In-Reply-To: <1095260758.27775.1047.camel@pelican.wigram>
> I need some help understanding how to convert
> an NFA with *labelled* arcs into an equivalent DFA.
> I'm not even sure it is possible. Any advice,
> pointers to papers, or code appreciated. The main
> use will be in a set of regexp related tools intended
> to replace Ocamllex, Str, and PCRE with pure caml code,
> and then extend that with an RTN based parsing system.
>
> Ocamllex functionality is already available,
> however group extraction and friends seem
> to require labelled arcs (and RTNs definitely do).
> I'm using the naive algorithm (regexp->DFA) from
> the Dragon book with the pattern-recognition
> modification (which is enough for a tokeniser).
> I can't see how to modify it to keep track of
> the arcs (special marks in regexps like group
> brackets, lookahead operator, etc).
>
> --
> John Skaller, mailto:skaller@users.sf.net
> voice: 061-2-9660-0850,
> snail: PO BOX 401 Glebe NSW 2037 Australia
> Checkout the Felix programming language http://felix.sf.net
As regards ocamllex, I worked from various recent publications by
Ville Larikari.
Here is the relevent comment from ocamllex sources (lex/lexgen.ml)
(* To generate directly a NFA from a regular expression.
Confer Aho-Sethi-Ullman, dragon book, chap. 3
Extension to tagged automata.
Confer
Ville Larikari
``NFAs with Tagged Transitions, their Conversion to Deterministic
Automata and Application to Regular Expressions''.
Symposium on String Processing and Information Retrieval (SPIRE 2000),
<http://kouli.iki.fi/~vlaurika/spire2000-tnfa.ps>
(See also)
<http://kouli.iki.fi/~vlaurika/regex-submatch.ps.gz>
*)
To me, all that is far from being obvious...
Bon courage !
--Luc
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next prev parent reply other threads:[~2004-09-15 15:41 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-15 15:05 skaller
2004-09-15 15:41 ` Luc Maranget [this message]
2004-09-15 19:15 ` Alain Frisch
2004-09-15 17:50 ` Jason Hickey
2004-09-15 20:50 ` Jason Hickey
2004-09-15 23:35 ` skaller
2004-09-16 11:50 ` Diego Olivier Fernandez Pons
2004-09-16 12:07 ` Luc Maranget
2004-09-16 12:37 ` james woodyatt
2004-09-16 13:29 ` skaller
2004-09-16 12:57 ` skaller
2004-09-16 13:04 ` Diego Olivier Fernandez Pons
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