From: "Andreas Röhler" <andreas.roehler@online.de>
To: "Stephen J. Turnbull" <turnbull@sk.tsukuba.ac.jp>
Cc: Stefan Monnier <monnier@iro.umontreal.ca>,
Emacs developers <emacs-devel@gnu.org>
Subject: Re: Possible problem with looking-back function
Date: Thu, 19 Aug 2010 11:32:12 +0200 [thread overview]
Message-ID: <4C6CFA1C.7080609@online.de> (raw)
In-Reply-To: <8739ubug9r.fsf@uwakimon.sk.tsukuba.ac.jp>
Am 19.08.2010 11:02, schrieb Stephen J. Turnbull:
> Andreas Röhler writes:
>
> > that surprises me. Check must be done against the string already
> > found. So workload should grow lineary resp. slightly ascending.
>
> That's incorrect. In regexp matching abstractly defined, there is no
> "string already matched." In general backtracking must be done to get
> a correct POSIX match, and it's potentially very expensive. It would
> be sometimes possible (as in this case) to identify a non-backtracking
> algorithm as you suggest, but that would mean that different regexps
> would be treated differently, or that some regexps would be
> ridiculously expensive.
>
>
Hi,
just for the curious:
Coming upon the matter, as in markup languages point may be inside the
start tag.
Solved it whith function below
--begstr is the startup-tag
Sometimes begstr is used inside beg-end function quoted: (regexp-quote
begstr),
therefor the startup tag is delivered in both forms here, making
looking-at working
- not sure, if its really necessary btw--
(defun ar-leave-begstr-backward (begstr unquoted-beg)
(let* ((stringcount (length unquoted-beg))
(collected (char-to-string (char-after)))
(indx (string-match (regexp-quote collected) unquoted-beg)))
(while (and indx (not (ignore-errors (looking-at begstr)))(< 1
stringcount))
(forward-char -1)
(setq collected (concat (char-to-string (char-after)) collected))
(setq indx (string-match (regexp-quote collected) unquoted-beg))
(setq stringcount (1- stringcount)))))
See beg-end.el
at
https://code.launchpad.net/s-x-emacs-werkstatt/
next prev parent reply other threads:[~2010-08-19 9:32 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-19 1:15 Possible problem with looking-back function Vinicius Jose Latorre
2010-08-19 2:43 ` Davis Herring
2010-08-19 6:09 ` Andreas Röhler
2010-08-19 8:01 ` Stefan Monnier
2010-08-19 9:02 ` Stephen J. Turnbull
2010-08-19 9:32 ` Andreas Röhler [this message]
2010-08-20 2:11 ` Vinicius Jose Latorre
2010-08-20 13:07 ` Stefan Monnier
2010-08-21 0:08 ` Vinicius Jose Latorre
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