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From: vern%lbl-helios@lbl-rtsg.arpa (Vern Paxson)
Newsgroups: comp.compilers
Subject: Re: Lex and Yacc - Availability?
Message-ID: <679@ima.ISC.COM>
Date: Thu, 20-Aug-87 01:31:37 EDT
Article-I.D.: ima.679
Posted: Thu Aug 20 01:31:37 1987
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>     At the Winter 1987 Usenix Van Jacobson of LBL labs presented a
> paper describing a much improved version of Lex...
> processing down to a single table lookup in memory!  (The rumor was
> that it was just marginally slower than 'cat').  I don't know what the
> current status of the project is; I would very much like either a copy
> of his paper or the program itself.  Anyone know more than I?

A student I'm supervising is adding Van's fast algorithm to my lex
re-write ("flex").  He's finished with the basics of the implementation,
but there's still a lot of tuning and clean-up before it'll be ready
for a beta-test and subsequent release.  (Details on distribution terms
are still being worked out, but it looks like it'll have a copyright that
says "freely redistribute, but don't make a significant enhancement
without contacting us first, and be willing to give UC rights to the
enhancement"; possibly it'll carry a more generous, GNU-like copyright.)

While there's still tuning to do, the preliminary results, done for a
C tokenizer, are (1) fast as cat?  No, not quite (I'll be going over
the implementation with Van to see where tuning might be needed); (2) fast
as a hand-coded scanner?  Well, as things stand now, it is about 15%
faster than PCC's tokenizer, which seems to have been done with some care.

	Vern Paxson				vern@lbl-csam.arpa
	Real Time Systems			ucbvax!lbl-csam.arpa!vern
	Lawrence Berkeley Laboratory		(415) 486-6411
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