Re: Learning only one lexer made me blind to its hidden assumptions

George Neuner <gneuner2@comcast.net>
Thu, 14 Jul 2022 16:46:36 -0400

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From: George Neuner <gneuner2@comcast.net>
Newsgroups: comp.compilers
Date: Thu, 14 Jul 2022 16:46:36 -0400
Organization: A noiseless patient Spider
References: 22-07-006 22-07-010
Injection-Info: gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="49458"; mail-complaints-to="abuse@iecc.com"
Keywords: lex, performance
Posted-Date: 14 Jul 2022 22:18:15 EDT

On Wed, 13 Jul 2022 19:52:45 -0000 (UTC), antispam@math.uni.wroc.pl
wrote:


>Hmm, from flex manual:
>
>: -Ce, --ecs
>: construct equivalence classes
>:
>: -Cm, --meta-ecs
>: construct meta-equivalence classes
>
>If you want smaller tables use options above and flex DFA will
>work on character classes.


But note that Flex /may/ run considerably slower if you make heavy use
of equivalence classes. IIRC, that results in (moral equivalent of)
NFA rather than DFA.


George
[On modern computers it's hard to imagine a scanner so big that the space
savings from those two options are worth it. 64K PDP-11 and all that. -John]


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