[regex-coach] Possessive Quantifier + Problem with the Regex Coach

[Edi Weitz]

On Fri, 16 Apr 2004 14:01:23 -0400, "Seen Sai Yang" <whollyanointed at hotmail.com> wrote:

> I tried an example from the Regex Tutorial
> (http://www.regular-expressions.com/atomic.html) with the following
> regex (at the bottom of the page):
>
> \d++6 gave an error "Quantifier '+' not allowed at position 3"
>
> The same regex worked in PowerGREP.

Hi!

The Regex Coach tries to be compatible with Perl. Perl does not allow
the '++' notation for 'possesive' quantifiers, you have to use
'(?>...)' instead:

  edi at bird:~ > perl -v

  This is perl, v5.8.1 built for i586-linux-thread-multi

  Copyright 1987-2003, Larry Wall

  Perl may be copied only under the terms of either the Artistic License or the
  GNU General Public License, which may be found in the Perl 5 source kit.

  Complete documentation for Perl, including FAQ lists, should be found on
  this system using `man perl' or `perldoc perl'.  If you have access to the
  Internet, point your browser at http://www.perl.com/, the Perl Home Page.

  edi at bird:~ > perl -le 'print 1 if "123456" =~ /\d++6/'
  Nested quantifiers in regex; marked by <-- HERE in m/\d++ <-- HERE 6/ at -e line 1.
  edi at bird:~ > perl -le 'print 1 if "123456" =~ /(?>\d+)6/'
  edi at bird:~ > perl -le 'print 1 if "123456" =~ /(?>\d+)/'
  1
  edi at bird:~ > perl -le 'print 1 if "123456" =~ /\d+6/'
  1

Cheers,
Edi.