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From: cinsk <cinsky@gmail.com>
To: help-gnu-emacs@gnu.org
Subject: efficient regular expression that never matches
Date: Fri, 20 Nov 2015 01:35:32 -0800 (PST)	[thread overview]
Message-ID: <c2e414ce-cc63-4270-9452-b0dc517d1a95@googlegroups.com> (raw)

hi,

Is there any special regular expression string that never matches
anything?

I'm thinking of "$a", but it should scan all the string until end
of the string, so it may not be efficient.

Is there any short, efficient regular expression that never
matches anything? (it's okay with Emacs-specific regular
expression, since I'm going to use it with `directory-files' or
`string-match' function)
 
Thank you.


             reply	other threads:[~2015-11-20  9:35 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-20  9:35 cinsk [this message]
2015-11-20 15:13 ` efficient regular expression that never matches Stefan Monnier
2015-11-20 15:59   ` John Wiegley
     [not found]   ` <mailman.342.1448035187.31583.help-gnu-emacs@gnu.org>
2015-11-21  5:52     ` cinsk
2015-11-21 15:04       ` Stefan Monnier

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