[boost] Re: Regex-User: ISBN validation

From: Daniel Frey (d.frey_at_[hidden])
Date: 2005-04-10 05:02:12

Detlef wrote:
> we need to validate ISBN.
> With another REGEX-implementation we uses (?=.{13})\d{1,5}( 
> |\-)\d{1,7}\1\d{1,6}\1(\d|X).
> But this seem not to work.
> Only the shorter version "\d{1,5}( |\\-)?\\d{1,7}\\1\\d{1,6}\\1(\d|X)" 
> works, but how to check the 13 digits?

Have you tried \2 instead of \1 for the long expression? AFAICS from the 
documentation <http://www.boost.org/libs/regex/doc/syntax.html>, the 
first "Forward Lookahead Assert" is still a match, but you want to refer 
to the second parenthesis, right?

Regards, Daniel