From: Ilya Zakharevich <nospam-abuse@ilyaz.org>
To: help-gnu-emacs@gnu.org
Subject: Re: will we ever have zero width assertions in regexps?
Date: Tue, 8 Feb 2011 22:41:18 +0000 (UTC) [thread overview]
Message-ID: <slrnil3hke.80t.nospam-abuse@powdermilk.math.berkeley.edu> (raw)
In-Reply-To: jwvd3n3twxv.fsf-monnier+gnu.emacs.help@gnu.org
On 2011-02-07, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>> Hmm, I thought about a different scenario: if the bit is set, then one
>> switches to a DIFFERENT REx designed for a multi-line case. Otherwise
>> why not just run it against the rest of the buffer, instead of
>> one-line?
>
> Because we don't want to match those regexps against the whole buffer
> every time the buffer is modified (the buffer may be large).
I think there is some confusion here: I did not want to mean that you
run "another REx" via re-search(), but via looking-at() at the
corresponding position... Essentially: do you want the REx to start
match on the current line, or end match on the current line?
Or maybe you mean a different thing, and
WANT e.g. [^a-z] to actually "mean" [^a-z\n] ? (So only an explicit
non-negated \n in a REx may match \n in a buffer?)
> BTW, another reason to want a non-backtracking matcher can be seen in
> the recent thread "Stack overflow in regexp matcher".
I think this is a red herring. Try to stack-overflow the Perl
matcher... (Possible, but one must be very malicious to hit these
situations.)
Ilya
next prev parent reply other threads:[~2011-02-08 22:41 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.1.1296054361.23496.help-gnu-emacs@gnu.org>
2011-01-26 15:58 ` will we ever have zero width assertions in regexps? Stefan Monnier
2011-01-27 1:45 ` Le Wang
[not found] ` <mailman.6.1296092730.6982.help-gnu-emacs@gnu.org>
2011-01-27 2:21 ` Stefan Monnier
2011-01-27 6:34 ` Ilya Zakharevich
2011-01-27 16:10 ` Stefan Monnier
2011-01-28 23:49 ` Ilya Zakharevich
2011-01-29 2:51 ` Stefan Monnier
2011-01-29 22:28 ` Ilya Zakharevich
2011-01-31 16:08 ` Stefan Monnier
2011-01-31 17:10 ` Ilya Zakharevich
2011-01-31 21:29 ` Stefan Monnier
2011-02-02 15:09 ` Ilya Zakharevich
2011-02-07 20:30 ` Stefan Monnier
2011-02-08 22:41 ` Ilya Zakharevich [this message]
2011-01-26 14:55 Le Wang
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