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Re: fortran-fill-paragraph fails

From: Michaël Cadilhac
Subject: Re: fortran-fill-paragraph fails
Date: Sat, 30 Dec 2006 13:56:45 +0100
User-agent: Gnus/5.110006 (No Gnus v0.6) Emacs/22.0.90 (gnu/linux)

Richard Stallman <address@hidden> 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: address@hidden'                                   -  --'

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