Re: [Boost-users] Regex Bug in 1.33.1

From: Eric Niebler (eric_at_[hidden])
Date: 2006-03-19 09:54:05

Olaf Bachmann wrote:
> Hi,
> there seems to be a bug in version 1.33.1 of boost::regex:
> 
> boost::regex_replace(std::string("foo"), boost::regex(".*"), "bar") 
> returns "barbar"
> 
> whereas 1.31.0 returns just "bar" (as I would expect). Any fix or hints 
> out there?

I believe the behavior in 1.33.1 is correct. By default, regex_replace 
does a global search/replace. It should behave like the following perl:

   $str = 'foo';
   $str =~ s/.*/bar/g;
   print "$str\n";

This prints "barbar". The reason is that ".*" matches "foo" twice: the 
first time it matches "foo" and the second time it matches the 
zero-width character sequence after "foo".

If you only want the substitution to happen once, use 
match_flag_type::format_first_only, or change your pattern to ".+"

HTH,

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