From: Stefan Monnier <monnier@iro.umontreal.ca>
To: help-gnu-emacs@gnu.org
Subject: Re: Performance tips when using regular expressions (regexps) in font-locking
Date: Fri, 30 Nov 2007 11:42:29 -0500 [thread overview]
Message-ID: <jwveje71yc7.fsf-monnier+gnu.emacs.help@gnu.org> (raw)
In-Reply-To: c8c3a44f-d3be-4e4e-a50a-8853aba5450a@b15g2000hsa.googlegroups.com
> I have enhanced my cc-mode with extra font-locking for assignments,
> function calls, numerical literals, operators and even format strings
> to the [sf]?printf-functions. The regular expressions describing these
> context are quite complicated and as a result my cc-mode is no longer
> as snappy as without my enhancement. Does any have any tips on how to
> write regular expressions when performance is crucial? For example
> should I use [:space:] instead of [ \t]? Should I post the coden
> aswell?
I believe inmost cases micro-optimization such as choosing between
[[:space:]] and [ \t] will make no noticeable difference.
But you should pay attention to * and + operators, especially when
nested or when adjacent and make sure that there is no redundancy: there
should ideally be only one way for the regexp to match a given piece
of text.
E.g. avoid [ab]*a*
Stefan
next prev parent reply other threads:[~2007-11-30 16:42 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-21 17:00 Performance tips when using regular expressions (regexps) in font-locking Nordlöw
2007-11-30 16:42 ` Stefan Monnier [this message]
2007-12-16 18:28 ` David Combs
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