From: Stefan Monnier <monnier@iro.umontreal.ca>
To: help-gnu-emacs@gnu.org
Subject: Re: Any performance comparison/guide of/for Emacs regex?
Date: Tue, 18 Jan 2011 13:29:35 -0500 [thread overview]
Message-ID: <jwv8vyi2hm5.fsf-monnier+gnu.emacs.help@gnu.org> (raw)
In-Reply-To: mailman.16.1295365226.21909.help-gnu-emacs@gnu.org
> Any performance comparison/guide of/for Emacs regex?
Not really. What you need to know is that Emacs's regexp engine is
based on backtracking, so things like .*\\(.*\\).* is insanely
inefficient and will make you think Emacs is frozen.
Generally, you'll prefer to use regexps that don't require backtracking.
E.g. [^(\n]*( works much better than .*( since when encountering an open
parenthesis, the matcher will know for sure that it has to leave the *
loop, rather than having to try both cases in sequence.
Stefan
next parent reply other threads:[~2011-01-18 18:29 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.16.1295365226.21909.help-gnu-emacs@gnu.org>
2011-01-18 18:29 ` Stefan Monnier [this message]
2011-01-18 21:48 ` Any performance comparison/guide of/for Emacs regex? Oleksandr Gavenko
[not found] ` <mailman.3.1295387371.19799.help-gnu-emacs@gnu.org>
2011-01-19 1:22 ` Stefan Monnier
2011-01-18 21:27 ` Tim X
2011-01-18 15:38 Oleksandr Gavenko
2011-01-18 15:59 ` Deniz Dogan
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