From: dkcombs@panix.com (David Combs)
To: help-gnu-emacs@gnu.org
Subject: Re: Performance tips when using regular expressions (regexps) in font-locking
Date: Sun, 16 Dec 2007 18:28:13 +0000 (UTC) [thread overview]
Message-ID: <fk3qnt$7mc$1@reader1.panix.com> (raw)
In-Reply-To: jwveje71yc7.fsf-monnier+gnu.emacs.help@gnu.org
In article <jwveje71yc7.fsf-monnier+gnu.emacs.help@gnu.org>,
Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>> 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
Friedel's "Regular Expressions" book (O'Reilly) (cheaper from Bookpool.com),
the *bible* on regexps (*hundreds* of pages long) has an entire chapter
devoted to optimizing your regexps. Essential reading.
(You may *think* you know something about regexps -- read that book,
and you'll know different! :-)
David
prev parent reply other threads:[~2007-12-16 18:28 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
2007-12-16 18:28 ` David Combs [this message]
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