[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Any performance comparison/guide of/for Emacs regex?
|
From: |
Stefan Monnier |
|
Subject: |
Re: Any performance comparison/guide of/for Emacs regex? |
|
Date: |
Tue, 18 Jan 2011 13:29:35 -0500 |
|
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.0.50 (gnu/linux) |
> 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