justify use of flex vs. lex - summary

swl26@cas.org (Steve Layten x3451)
Mon, 1 Feb 1993 21:17:30 GMT

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justify use of flex vs. lex - summary swl26@cas.org (1993-02-01)
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Newsgroups: comp.compilers
From: swl26@cas.org (Steve Layten x3451)
Keywords: lex, summary
Organization: Compilers Central
Date: Mon, 1 Feb 1993 21:17:30 GMT

Original question:

I need to use flex instead of lex for a job I have that exceeds
capacities of some lex features. I want to put this into a
"production" job stream, and our current "standards" seem to
discourage use of public-domain code in production, the standard
managment argument being that we should use vendor-supported code
so we don't have to spend time maintaing the code ourselves. I
must justify the use of this "non-supported" code in production.

I would appreciate hearing comments from this community regarding
arguments for or against the use of flex vs. the vendor-supplied lex.
Some additional considerations which I think are important are:

[reasons deleted ]

Several persons, including the moderator indicated that flex contained
fewer bugs or had better support than lex: (ken@syd.dit.csiro.au (Ken Yap),
spot@hopeless.mess.cs.cmu.edu, zstern@adobe.com (Zalman Stern),
root@rwsys.wimsey.bc.ca (Randy Wright),
anton@mips.complang.tuwien.ac.at (Anton Ertl)).

One or two specifically mentioned performance:
(daniels@walleye.cse.ogi.edu (Scott David Daniels),
root@rwsys.wimsey.bc.ca (Randy Wright)).

Others indicated that I should consider paying others for support. Cygnus
Support (contact: don@cygnus.com (Don Rector), 415/903-1408) was mentioned
by three persons: (burley@gnu.ai.mit.edu (Craig Burley),
jbuck@forney.berkeley.edu (Joe Buck), (also gave
jbuck@ohm.berkeley.edu as e-mail address)
joe@modcomp.com (Joe Korty)).

Randy Wright (root@rwsys.wimsey.bc.ca) also pointed out some additional
features of flex:

>For example, I needed a re-entrant scanner to interpret ansi terminal
>codes into curses calls. It took an afternoon to modify flex to run
>in a re-entrant fashion.

>Flex has the exclusive start conditions that lex (at least my
>version) lacks. I have found the exclusive start condition feature
>very useful in state machine tasks.

Finally one person (Basile STARYNKEVITCH <basile@soleil.serma.cea.fr>)
suggested that I look at PCCTS:
"It is a lexical+syntaxical analyser generator having more
features than yacc+lex and their derivatives (flex, bison). PCCTS
is public domain, (not GPL copylefted) so you can use it for
commercial products without violating its notice, which explicitly
permit use for commerical or proprietary software (both prohibited
by bison&flex's copyright)."
He include a README file (fairly long, which I will not include), and
indicated that PCCTS files are available via anon ftp from
marvin.ecn.purdue.edu (128.46.179) in the subdirectory pub/pccts/1.06
(beginning December 1, 1992).

Thank-you all for your help,

Steve Layten
Steven W. Layten, Senior Engineer
Chemical Abstracts Service, PO Box 3012, Columbus, OH 43210 +1 614 447 3600
INET: swl26@cas.org BITNET: swl26@cas UUCP: osu-cis!chemabs!swl26

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