From: Marcin Borkowski <mbork@mbork.pl>
To: Barry Margolin <barmar@alum.mit.edu>
Cc: help-gnu-emacs@gnu.org
Subject: Re: looking-at-p slower than looking-at
Date: Wed, 25 Nov 2015 21:39:04 +0100 [thread overview]
Message-ID: <87egfdzudz.fsf@mbork.pl> (raw)
In-Reply-To: <barmar-B02DD0.10483925112015@88-209-239-213.giganet.hu>
On 2015-11-25, at 16:48, Barry Margolin <barmar@alum.mit.edu> wrote:
> In article <mailman.675.1448463102.31583.help-gnu-emacs@gnu.org>,
> Nicolas Richard <nrichard@ulb.ac.be> wrote:
>
>> Marcin Borkowski <mbork@mbork.pl> writes:
>>
>> > You might also (depending on your use-case) want to use looking-at-p,
>> > which is marginally slower than looking-at, but does not modify match
>> > data.
>>
>> Why is it slower and how much slower is it ? I don't see how it can
>> happen from its implementation:
>>
>> (defsubst looking-at-p (regexp)
>> "\
>> Same as `looking-at' except this function does not change the match data."
>> (let ((inhibit-changing-match-data t))
>> (looking-at regexp)))
>>
>> thanks,
>
> It takes a tiny amount of time to bind the variable
> inhibit-changing-match-data. That's why it's a little slower.
>
> On the other hand, it doesn't have to set the internal variables that
> hold the match data, so maybe they cancel out.
Ah, I didn't think of that. Stupid me. (That might be the answer to
the question why my benchmarks were inconclusive.)
Thanks,
--
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Faculty of Mathematics and Computer Science
Adam Mickiewicz University
next prev parent reply other threads:[~2015-11-25 20:39 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-14 16:11 How to test if the current line contains only white-spache? Rolf Ade
2015-11-14 18:42 ` Barry Margolin
2015-11-15 13:29 ` Marcin Borkowski
2015-11-16 21:15 ` Philipp Stephani
2015-11-25 13:58 ` looking-at-p slower than looking-at Nicolas Richard
2015-11-25 20:34 ` Marcin Borkowski
2015-11-25 21:28 ` Michael Heerdegen
2015-11-25 21:32 ` Marcin Borkowski
2015-11-26 13:37 ` Nicolas Richard
2015-11-25 22:39 ` Emanuel Berg
2015-11-26 13:58 ` Nicolas Richard
[not found] ` <mailman.675.1448463102.31583.help-gnu-emacs@gnu.org>
2015-11-25 15:48 ` Barry Margolin
2015-11-25 20:39 ` Marcin Borkowski [this message]
2015-11-15 19:18 ` How to test if the current line contains only white-spache? Rolf Ade
2015-11-17 0:26 ` Emanuel Berg
2015-11-17 20:38 ` Marcin Borkowski
[not found] ` <mailman.23.1447720376.31583.help-gnu-emacs@gnu.org>
2015-11-19 1:56 ` Rolf Ade
2015-11-19 2:05 ` Stefan Monnier
2015-11-19 2:18 ` Emanuel Berg
2015-11-19 2:23 ` Emanuel Berg
[not found] ` <mailman.202.1447899839.31583.help-gnu-emacs@gnu.org>
2015-11-19 13:54 ` Rolf Ade
2015-11-19 15:20 ` Marcin Borkowski
2015-11-19 23:58 ` Emanuel Berg
2015-11-20 6:14 ` Marcin Borkowski
2015-11-21 2:26 ` Emanuel Berg
[not found] ` <mailman.279.1447976946.31583.help-gnu-emacs@gnu.org>
2015-11-20 0:48 ` How to test if the current line contains only white-space? Rolf Ade
2015-11-20 0:48 ` Rolf Ade
2015-11-21 2:02 ` Emanuel Berg
[not found] ` <mailman.375.1448070734.31583.help-gnu-emacs@gnu.org>
2015-11-21 2:28 ` Rolf Ade
2015-11-24 3:01 ` Emanuel Berg
2015-11-26 17:51 ` How to test if the current line contains only white-spache? Alex Bennée
2015-11-26 23:59 ` predicates (was: Re: How to test if the current line contains only white-spache?) Emanuel Berg
[not found] ` <mailman.787.1448581762.31583.help-gnu-emacs@gnu.org>
2015-11-27 4:28 ` predicates Pascal J. Bourguignon
2015-11-27 19:52 ` predicates Emanuel Berg
2015-11-15 5:56 ` How to test if the current line contains only white-spache? Yuri Khan
2015-11-15 9:18 ` John Mastro
2015-11-25 14:04 ` Nicolas Richard
2015-11-25 20:36 ` Marcin Borkowski
2015-11-25 22:41 ` Emanuel Berg
[not found] ` <mailman.676.1448463105.31583.help-gnu-emacs@gnu.org>
2015-11-26 15:24 ` Rolf Ade
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