GNU bug report logs - #12665
regexp fault for closing square bracket within character class

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

From: Panicz Maciej Godek <godek.maciek <at> gmail.com>
To: bug-guile <at> gnu.org
Subject: regexp fault for closing square bracket within character class
Date: Wed, 17 Oct 2012 21:33:58 +0200

guile 2.0.5-deb+1-1
(string-match "[\\[]" "[")
===> #("[" (0 . 1))
(string-match "[\\]]" "]")
===> #f

Message #10 received at 12665-done <at> debbugs.gnu.org (full text, mbox):

From: Mark H Weaver <mhw <at> netris.org>
To: Panicz Maciej Godek <godek.maciek <at> gmail.com>
Cc: 12665-done <at> debbugs.gnu.org
Subject: Re: bug#12665: regexp fault for closing square bracket within
	character class
Date: Thu, 18 Oct 2012 00:54:01 -0400

Panicz Maciej Godek <godek.maciek <at> gmail.com> writes:
> guile 2.0.5-deb+1-1
> (string-match "[\\[]" "[")
> ===> #("[" (0 . 1))
> (string-match "[\\]]" "]")
> ===> #f

As documented in "Syntax of Regular Expressions" of the Emacs manual
(to which section 6.15 of the Guile manual refers):

     To include a `]' in a character set, you must make it the first
     character.  For example, `[]a]' matches `]' or `a'.  To include a
     `-', write `-' as the first or last character of the set, or put
     it after a range.  Thus, `[]-]' matches both `]' and `-'.

For example:

  (string-match "[]\\]" "]")   ==>  #("]" (0 . 1))

Note that backslash is also a member of this character class, and of the
character class in your first example:

  (string-match "[]\\]" "\\")  ==>  #("\\" (0 . 1))
  (string-match "[\\[]" "\\")  ==>  #("\\" (0 . 1))

You might have been thinking that the backslash would escape the square
brackets in your class, but that's not how it works within character
classes.  '[' can be included anywhere in a character class without
being escaped, and ']' and '-' are handled as described above.

    Regards,
      Mark

Message #13 received at 12665-done <at> debbugs.gnu.org (full text, mbox):

From: Panicz Maciej Godek <godek.maciek <at> gmail.com>
To: Mark H Weaver <mhw <at> netris.org>
Cc: 12665-done <at> debbugs.gnu.org
Subject: Re: bug#12665: regexp fault for closing square bracket within
	character class
Date: Thu, 18 Oct 2012 11:44:30 +0200

> As documented in "Syntax of Regular Expressions" of the Emacs manual
> (to which section 6.15 of the Guile manual refers):
>
>      To include a `]' in a character set, you must make it the first
>      character.  For example, `[]a]' matches `]' or `a'.  To include a
>      `-', write `-' as the first or last character of the set, or put
>      it after a range.  Thus, `[]-]' matches both `]' and `-'.

OK, I see. I guess I got used to PCRE for too long :)
Sorry for my mistake.

Regards

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