Why is flex pattern-matching of NULs slow?

Roger L Costello <costello@mitre.org>
Fri, 8 Apr 2022 11:06:00 +0000

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Why is flex pattern-matching of NULs slow? costello@mitre.org (Roger L Costello) (2022-04-08)
Why is flex pattern-matching of NULs slow? christopher.f.clark@compiler-resources.com (Christopher F Clark) (2022-04-09)
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From: Roger L Costello <costello@mitre.org>
Newsgroups: comp.compilers
Date: Fri, 8 Apr 2022 11:06:00 +0000
Organization: Compilers Central
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Posted-Date: 08 Apr 2022 11:48:17 EDT
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Hi Folks,

The Flex manual says this:

        Pattern-matching of NULs is substantially slower
        than matching other characters.

Why is that?

[My recollection is that zero is used as a flag value in internal
tables and there is some slow kludge to say that this is a nul not the
flag, but perhaps someone who has looked at the code more recently
will remember the details. -John]

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