From: Stefan Monnier <monnier@IRO.UMontreal.CA>
To: Helmut Eller <eller.helmut@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: Compiling Elisp to a native code with a GCC plugin
Date: Wed, 15 Sep 2010 16:59:31 +0200 [thread overview]
Message-ID: <jwv4odrm4xj.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <m2hbhrgjz9.fsf@gmail.com> (Helmut Eller's message of "Wed, 15 Sep 2010 16:27:38 +0200")
>> - The main problem with Emacs regexps right now is that they have
>> pathological cases where the match-time is enormous (potentially
>> exponential explosion in the size of the input string). To be
>> worthwhile a replacement should address this problem, which basically
>> needs it should not be based on backtracking.
> Is it possible (theoretically) to implement all of Emacs regexps without
> backtracking? In particular those with back-references (\N) seem
> problematic. Or is it necessary to recognize "optimizable" regexps
> before using a different regexp engine?
IIRC regexps without back-refs can be matched (and searched) in O(N)
where N is the length of the input. With back-refs, I think (not sure)
the theoretical bound is O(N^2), which requires
a non-backtracking algorithm.
So yes, we'd need to handle back-refs specially. Several regexp engines
do that already (they have a few different inner engines and choose
which one to use based on the particular regexp at hand).
Stefan
next prev parent reply other threads:[~2010-09-15 14:59 UTC|newest]
Thread overview: 97+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-14 19:12 Compiling Elisp to a native code with a GCC plugin Wojciech Meyer
2010-09-14 19:32 ` Tom Tromey
2010-09-14 19:45 ` Wojciech Meyer
2010-09-14 20:17 ` Lars Magne Ingebrigtsen
2010-09-14 20:52 ` Wojciech Meyer
2010-09-14 20:55 ` Tom Tromey
2010-09-14 21:05 ` Wojciech Meyer
2010-09-14 20:44 ` Tom Tromey
2010-09-14 21:00 ` Wojciech Meyer
2010-09-14 21:16 ` Tom Tromey
2010-09-14 21:29 ` Wojciech Meyer
2010-09-14 21:59 ` Tom Tromey
2010-09-14 22:37 ` Wojciech Meyer
2010-09-14 22:55 ` Tom Tromey
2010-09-14 23:33 ` Wojciech Meyer
2010-09-15 1:38 ` Tom Tromey
2010-09-14 22:49 ` Wojciech Meyer
2010-09-14 23:13 ` Thomas Lord
2010-09-14 23:42 ` Wojciech Meyer
2010-09-15 10:47 ` Leo
2010-09-15 11:41 ` Andreas Schwab
2010-09-15 12:10 ` Wojciech Meyer
2010-09-15 14:07 ` Stefan Monnier
2010-09-15 14:27 ` Helmut Eller
2010-09-15 14:59 ` Stefan Monnier [this message]
2010-09-15 15:09 ` Lars Magne Ingebrigtsen
2010-09-15 15:31 ` Andreas Schwab
2010-09-15 15:35 ` Lars Magne Ingebrigtsen
2010-09-15 16:28 ` Andreas Schwab
2010-09-16 16:57 ` Lars Magne Ingebrigtsen
2010-09-15 15:42 ` Stefan Monnier
2010-09-15 15:51 ` Lars Magne Ingebrigtsen
2010-09-15 15:57 ` Leo
2010-09-15 16:01 ` Lars Magne Ingebrigtsen
2010-09-15 16:05 ` David Kastrup
2010-09-15 16:23 ` Leo
2010-09-15 16:37 ` David Kastrup
2010-09-16 16:58 ` Lars Magne Ingebrigtsen
2010-09-16 21:11 ` Andreas Schwab
2010-09-16 23:17 ` Lars Magne Ingebrigtsen
2010-09-17 8:13 ` Eli Zaretskii
2010-09-17 13:17 ` Lars Magne Ingebrigtsen
2010-09-17 13:30 ` Eli Zaretskii
2010-09-17 13:34 ` Lars Magne Ingebrigtsen
2010-09-16 17:35 ` Lars Magne Ingebrigtsen
2010-09-16 2:57 ` Stephen J. Turnbull
2010-09-16 6:54 ` David Kastrup
2010-09-16 8:10 ` Stephen J. Turnbull
2010-09-16 8:31 ` David Kastrup
2010-09-16 17:01 ` Lars Magne Ingebrigtsen
2010-09-17 6:52 ` Stephen J. Turnbull
2010-09-17 13:09 ` Lars Magne Ingebrigtsen
2010-09-17 13:31 ` David Kastrup
2010-09-17 13:39 ` Lars Magne Ingebrigtsen
2010-09-17 13:55 ` David Kastrup
2010-09-17 14:18 ` Lars Magne Ingebrigtsen
2010-09-17 14:57 ` David Kastrup
2010-09-17 15:06 ` Lars Magne Ingebrigtsen
2010-09-17 15:24 ` Lars Magne Ingebrigtsen
2010-09-17 16:11 ` Eli Zaretskii
2010-09-17 16:33 ` David Kastrup
2010-09-17 16:41 ` Andreas Schwab
2010-09-17 17:17 ` David Kastrup
2010-09-17 18:24 ` David Kastrup
2010-09-17 20:30 ` David Kastrup
2010-09-17 20:49 ` Lars Magne Ingebrigtsen
2010-09-18 4:31 ` David Kastrup
2010-09-17 18:53 ` Stephen J. Turnbull
2010-09-17 20:57 ` Eli Zaretskii
2010-09-18 14:19 ` Stephen J. Turnbull
2010-09-18 15:46 ` Eli Zaretskii
2010-09-18 15:58 ` Stefan Monnier
2010-09-17 17:24 ` Lars Magne Ingebrigtsen
2010-09-17 16:11 ` David Kastrup
2010-09-17 16:18 ` Eli Zaretskii
2010-09-17 16:24 ` Lars Magne Ingebrigtsen
2010-09-17 16:39 ` Eli Zaretskii
2010-09-17 17:30 ` Lars Magne Ingebrigtsen
2010-09-17 18:49 ` Eli Zaretskii
2010-09-17 16:39 ` Eli Zaretskii
2010-09-17 13:49 ` Andreas Schwab
2010-09-17 13:55 ` Lars Magne Ingebrigtsen
2010-09-17 14:31 ` Wojciech Meyer
2010-09-17 14:40 ` Andreas Schwab
2010-09-17 14:47 ` Lars Magne Ingebrigtsen
2010-09-17 15:10 ` Andreas Schwab
2010-09-17 15:16 ` Lars Magne Ingebrigtsen
2010-09-17 15:39 ` Andreas Schwab
2010-09-17 15:42 ` Lars Magne Ingebrigtsen
2010-09-17 16:04 ` Andreas Schwab
2010-09-17 16:14 ` Eli Zaretskii
2010-09-17 19:22 ` James Cloos
2010-09-17 17:40 ` Stephen J. Turnbull
2010-09-17 19:40 ` Lars Magne Ingebrigtsen
2010-09-15 15:46 ` Helmut Eller
2010-09-15 16:28 ` Thomas Lord
2010-09-15 21:04 ` Leo
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