From: Carsten Dominik <carsten.dominik@gmail.com>
To: Nicolas Goaziou <n.goaziou@gmail.com>
Cc: emacs-orgmode@gnu.org, Thorsten Jolitz <tjolitz@gmail.com>
Subject: Re: [BUG] in org-property-drawer-re?
Date: Wed, 2 Oct 2013 13:05:47 +0200 [thread overview]
Message-ID: <0A59AE22-E691-4319-9174-79761B4B025E@gmail.com> (raw)
In-Reply-To: <87li2ct2t3.fsf@gmail.com>
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On Oct 2, 2013, at 11:55 AM, Nicolas Goaziou <n.goaziou@gmail.com> wrote:
> Hello,
>
> Carsten Dominik <carsten.dominik@gmail.com> writes:
>
>> This is just a cheep way to match any character at all, because \000 should
>> not be part of any string (in C it indicates the end of a string).
>> In principle you could put any character you are sure will not turn up,
>> but \000 seems to be the safest choice. It is
>> faster (I think) than "\\(.\\|\n\\)*" because the first will
>> just run fast and streight with a table lookup while the
>> latter need to always alternate between two alternatives.
>> I have not timed it, though.
>
> On that topic, I would add that "^\000" must be used with care, as it
> can lead to a stack overflow in regexp matcher error quite easily. In
> particular, it may be safe to use it to match a property drawer, which
> will not be very large, but I think it's wrong to use it to match
> regular blocks or drawers, which can have arbitrary long size.
>
> For example a regexp like "[^\000]\\." will fail when matching around
> 500 lines (72 characters long). Of course, constructs like
> "\\(.\\|\n\\)*\\." will also fail, but my point is that it is tempting
> to use "^\000" even though a regexp may not be the correct answer to the
> problem.
Yes, I agree. This is why the real matching Org does is first looking for
a begin line, and then for the END line, in two independent searches.
Much better and safer.
- Carsten
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next prev parent reply other threads:[~2013-10-02 11:06 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-01 17:50 [BUG] in org-property-drawer-re? Thorsten Jolitz
2013-10-01 18:17 ` Carsten Dominik
2013-10-01 18:36 ` Thorsten Jolitz
2013-10-01 18:44 ` Carsten Dominik
2013-10-02 9:55 ` Nicolas Goaziou
2013-10-02 11:05 ` Carsten Dominik [this message]
2013-10-02 11:14 ` Nicolas Goaziou
2013-10-02 11:37 ` Carsten Dominik
2013-10-02 11:38 ` Thorsten Jolitz
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