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Re: c-forward-sws: Is the code right?

From: Stefan Monnier
Subject: Re: c-forward-sws: Is the code right?
Date: Tue, 03 Apr 2018 17:03:46 -0400
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux)

>>> I've just commented these "a\\`"s everywhere, and committed the fixes to
>>> master.
>> Maybe we should have a
>>     (defconst empty-regexp "\\`\\'a"
>>       "Regular expression which cannot match anything.")
>> in subr.el?
> Perhaps "nomatch-regexp" would be a better name ? There are several
> regexp constructs that match an empty string, rather than failing to
> match anything.

Right, I was thinking of regexps in the mathematical sense where they
describe a "set of strings", hence the "nomatch" regexp corresponds to
an "empty" regexp.  IIRC Brzozovski used ∅ for this empty regexp and
ε for the regexp which matches the empty string.

"nomatch" would be less confusing, indeed.


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