GNU bug report logs - #6743
Backslash regexp in Elisp manual

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Arni Magnusson <arnima <at> hafro.is>
To: bug-gnu-emacs <at> gnu.org
Subject: Backslash regexp in Elisp manual
Date: Tue, 27 Jul 2010 23:31:30 +0000 (UTC)

The current version (23.2) of the Elisp manual 
(http://www.gnu.org/software/emacs/manual/texi/elisp.texi.tar.gz) has a 
minor typo in Section 34.3.1.1 Special Characters in Regular Expressions 
(searching.texi) where

  Therefore, the read syntax for a regular expression matching
  @samp{\} is @code{"\\\\"}.

should be

  Therefore, the read syntax for a regular expression matching
  @samp{\\} is @code{"\\\\"}.

Arni

Message #8 received at 6743 <at> debbugs.gnu.org (full text, mbox):

From: Juanma Barranquero <lekktu <at> gmail.com>
To: Arni Magnusson <arnima <at> hafro.is>
Cc: 6743 <at> debbugs.gnu.org
Subject: Re: bug#6743: Backslash regexp in Elisp manual
Date: Wed, 28 Jul 2010 02:25:35 +0200

On Wed, Jul 28, 2010 at 01:31, Arni Magnusson <arnima <at> hafro.is> wrote:

>  Therefore, the read syntax for a regular expression matching
>  @samp{\} is @code{"\\\\"}.
>
> should be
>
>  Therefore, the read syntax for a regular expression matching
>  @samp{\\} is @code{"\\\\"}.

Why do you think so?

The section is talking about the read syntax. To match \, you need a
regexp with \\, and to write \\ in a string, you need \\\\.

Try

  emacs -Q
  \ <left>
  M-: (looking-at "\\") <RET>   => (invalid-regexp "Trailing backslash")
  q
  M-: (looking-at "\\\\") <RET> => t

Note that \\\\ is matching a single \ on the buffer, not \\

    Juanma

Message #11 received at 6743 <at> debbugs.gnu.org (full text, mbox):

From: Arni Magnusson <arnima <at> hafro.is>
To: Juanma Barranquero <lekktu <at> gmail.com>
Cc: 6743 <at> debbugs.gnu.org
Subject: Re: bug#6743: Backslash regexp in Elisp manual
Date: Wed, 28 Jul 2010 02:54:46 +0000 (GMT)

[Message part 1 (text/plain, inline)]

Sorry, my mistake. The sentence is correct in the manual.

Arni



On Wed, 28 Jul 2010, Juanma Barranquero wrote:

> On Wed, Jul 28, 2010 at 01:31, Arni Magnusson <arnima <at> hafro.is> wrote:
>
>>  Therefore, the read syntax for a regular expression matching
>>  @samp{\} is @code{"\\\\"}.
>>
>> should be
>>
>>  Therefore, the read syntax for a regular expression matching
>>  @samp{\\} is @code{"\\\\"}.
>
> Why do you think so?
>
> The section is talking about the read syntax. To match \, you need a 
> regexp with \\, and to write \\ in a string, you need \\\\.
>
> Try
>
>  emacs -Q
>  \ <left>
>  M-: (looking-at "\\") <RET>   => (invalid-regexp "Trailing backslash")
>  q
>  M-: (looking-at "\\\\") <RET> => t
>
> Note that \\\\ is matching a single \ on the buffer, not \\
>
>     Juanma
>

Message #16 received at 6743-done <at> debbugs.gnu.org (full text, mbox):

From: Juanma Barranquero <lekktu <at> gmail.com>
To: Arni Magnusson <arnima <at> hafro.is>
Cc: 6743-done <at> debbugs.gnu.org
Subject: Re: bug#6743: Backslash regexp in Elisp manual
Date: Wed, 28 Jul 2010 04:58:17 +0200

> Sorry, my mistake. The sentence is correct in the manual.

Thanks for the report anyway.

    Juanma

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