Re: [Boost-users] RegEx Exception

From: Eric Niebler (eric_at_[hidden])
Date: 2006-03-28 01:48:57

Michael Primeaux wrote:
> I'm using the latest version of the boost regex libraries and am 
> receiving an exception when using the regex_replace function with the 
> following regular expression:
>  
> (?i)(?<!')((<\s*OBJECT\s*[^>]+classid="clsid:[^>]+?(?<!\s*/\s*)>[^*]+?<\s*/\s*OBJECT\s*>)|(<\s*OBJECT\s*[^>]+classid=\s*\"clsid:[^/>]+/))
>  
> ...which works in other industry standard regex library routines.
>  
> I seem to be failing on line 767 of basic_regex_creator.hpp.
>  
> Any assistance is appreciated.
>  

If I had to guess, I'd say the problem is "(?<!\\s*/\\s*)". This is a 
negative look-behind assertion. For most regex engines out there, 
look-behinds only work for fixed-width sub-expressions, like (?<!foo), 
which asserts that the previous 3 characters are not "foo". Your's is a 
variable-width look-behind, and I'm pretty sure Boost.Regex can't handle 
that.

Which other "industry standard" regex library handles this? Perl doesn't 
allow variable-width look-behinds. The only one I'm aware of which 
allows this is GRETA (which I wrote many moons ago).

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com