From: "Andreas Röhler" <andreas.roehler@easy-emacs.de>
To: help-gnu-emacs@gnu.org
Subject: Re: Numbered regexps throw invalid regex error
Date: Wed, 25 Jan 2012 21:02:13 +0100 [thread overview]
Message-ID: <4F205FC5.90106@easy-emacs.de> (raw)
In-Reply-To: <loom.20120125T184906-790@post.gmane.org>
Am 25.01.2012 18:51, schrieb Tom:
> Andreas Röhler<andreas.roehler<at> easy-emacs.de> writes:
>
>>
>> Am 25.01.2012 11:17, schrieb Tom:
>>> (looking-at "\\(a\\c(?1:b\\)\\)")
>>>
>> AFAIU there are serveral errors,
>>
>> think you can't refer to first match inside itself
>>
>
> You misunderstand the feature.
>
> It's not a backreference. It's an explicit numbering of
> the group, so it doesn't change if you add more parens:
>
> `\(?NUM: ... \)'
> is the "explicitly numbered group" construct. Normal groups get
> their number implicitly, based on their position, which can be
> inconvenient. This construct allows you to force a particular
> group number. There is no particular restriction on the numbering,
> e.g. you can have several groups with the same number in which case
> the last one to match (i.e. the rightmost match) will win.
> Implicitly numbered groups always get the smallest integer larger
> than the one of any previous group.
>
>
>
>
Okay, next try :)
you can't assign a group number already assigned automatically
that would work:
(looking-at "\\(?2:a\\(?1:b\\)c\\)")
next prev parent reply other threads:[~2012-01-25 20:02 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-25 10:17 Numbered regexps throw invalid regex error Tom
2012-01-25 17:21 ` Andreas Röhler
2012-01-25 17:51 ` Tom
2012-01-25 20:02 ` Andreas Röhler [this message]
2012-01-25 20:14 ` Tom
2012-01-25 20:37 ` Andreas Röhler
2012-01-26 8:30 ` Tom
2012-01-26 9:29 ` Andreas Röhler
2012-01-26 11:52 ` Tim Landscheidt
2012-01-26 14:36 ` Tom
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