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bug#2881: 23.0.91; inconsistent regexps with "explicitly numbered group"
From: |
Andreas Schwab |
Subject: |
bug#2881: 23.0.91; inconsistent regexps with "explicitly numbered group" |
Date: |
Fri, 03 Apr 2009 21:55:42 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.0.92 (gnu/linux) |
Joe Corneli <holtzermann17@gmail.com> writes:
> Please execute the following forms with C-x C-e. Form 1
> and Form 3 return `t' (Yes, we are looking at the
> indicated regular expression), whereas Form 2 returns
> `nil' (even though from the Elisp reference page "34.3.1.3
> Backslash Constructs in Regular Expressions", it appears
> that this form ought to return `t' like the others).
`\|' applies to the largest possible surrounding expressions.
Only a surrounding `\( ... \)' grouping can limit the grouping
power of `\|'.
> (let ((possible-environments
> "\\(?1:lisp\\)\\|\\(?1:idea\\)\\|\\(?1:common\\)") )
> (looking-at
> (concat "\n*?\\\\begin{"
> possible-environments
> "}")))
The three alternatives of this regexp are "\n*?\\\\begin{\\(?1:lisp\\)",
"\\(?1:idea\\)" and "\\(?1:common\\)".
Andreas.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."