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From: michael@cadilhac.name (Michaël Cadilhac)
Cc: emacs-devel@gnu.org, Stefan Monnier <monnier@iro.umontreal.ca>,
	Roland.Winkler@physik.uni-erlangen.de
Subject: Re: fortran-fill-paragraph fails
Date: Sat, 30 Dec 2006 13:56:45 +0100	[thread overview]
Message-ID: <87ejqhwnhu.fsf@lrde.org> (raw)
In-Reply-To: E1H0XdS-00032t-Uo@fencepost.gnu.org


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Richard Stallman <rms@gnu.org> writes:

>     There's nothing specific to elisp there, and the \0 is just some
>     arbitrary char: a space would have probably worked just as well.
>
> What purpose does that character serve?  Is the aim to prevent the
> regexp from ever matching, in practice?

No!  The aim of \0 is to prevent the match when the regexp is "^C",
for example, but also "^x?C" (no mode does that AFAIK, but it's just
a security) where x is any non regexp-special char except \0.

Suppose commark is `C', we will have :
(string-match "^C" (concat "\0" commark "a")) -> nil
(string-match "C" (concat "\0" commark "a")) -> 1
(string-match "^ ?C" (concat "\0" commark "a")) -> nil

If ` ' was used instead of "\0", the last one would have returned 0.

Of course, it doesn't prevent a regexp like "^.C", but we can suppose,
IMO, that no mode will do that.  And IMO, it would be overkill to do
something to prevent that. "\0" is just a more secure char in this
precise context, at no cost :-) (except this thread ;-))

-- 
 |      Michaël `Micha' Cadilhac     |  In a World without Walls and Fences,  |
 |         Epita/LRDE Promo 2007     |     who needs Windows and Gates?       |
 |  http://michael.cadilhac.name     |          -- Dino Esposito              |
 `--JID: michael.cadilhac@gmail.com--'                                   -  --'

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  reply	other threads:[~2006-12-30 12:56 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <m3r6uq778w.fsf@tfkp07.physik.uni-erlangen.de>
2006-12-24  0:15 ` fortran-fill-paragraph fails Michaël Cadilhac
2006-12-24  1:35   ` Roland Winkler
2006-12-24 20:26   ` Michaël Cadilhac
2006-12-25 23:00   ` Stefan Monnier
2006-12-27 17:12     ` Roland Winkler
2006-12-29 21:06       ` Stefan Monnier
2006-12-29 22:43         ` Michaël Cadilhac
2006-12-30  6:24         ` Richard Stallman
2006-12-30 12:56           ` Michaël Cadilhac [this message]
2006-12-31  1:45             ` Richard Stallman
2007-01-02 23:22               ` Stefan Monnier
2007-01-03 21:11                 ` Richard Stallman
2007-01-07 20:12                   ` Stefan Monnier
2006-12-30 16:04         ` Roland Winkler

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