Re: [Boost-users] case insensitive less_than string comparison

From: Pavol Droba (droba_at_[hidden])
Date: 2005-07-17 05:57:15

On Sat, Jul 16, 2005 at 06:17:28PM -0500, Thore Karlsen wrote:
> On Sat, 16 Jul 2005 18:46:33 +0200, Pavol Droba <droba_at_[hidden]>
> wrote:
> 
> >> I am aware that string_algo has an if_iequal functor. Is there also an 
> >> equivalent for a less-than comparison? I have to compare strings 
> >> ignoring the case but taking locales into account.
> >> Right now I'm calling boost::algorithm::to_lower on two copies of the 
> >> original strings. I'm not so sure if this is very efficient when I'm 
> >> comparing thousands of strings.
> >> 
> >> Here's the functor as it is now:
> >> 
> >>      struct FileLessNameA
> >>          : std::binary_function<const File&,const File&,bool> {
> >>          bool operator() (const File& lhs, const File& rhs) const {
> >>              std::string path1( lhs.get_name().c_str() );
> >>              std::string path2( rhs.get_name().c_str() );
> >>              boost::algorithm::to_lower( path1 );
> >>              boost::algorithm::to_lower( path2 );
> >>              return path1 < path2;
> >>          }
> >>      };
> >> 
> 
> >There is no such a function in string_algo lib. But you can easily use 
> >std::lexicographical_compare.
> >
> >There is a variant with a custom comparison predicate. For that you can use
> >boost::is_iequal defined in boost/algorithm/string/compare.hpp.
> 
> But is_iequal only tests for equality, it doesn't provide an ordering of
> the characters. He's looking for something like is_iless, which I think
> would be a nice addition too string_algo.
> 

I see. Sorry about that. Somehow I have overlooked this obvious aspect.

You are right, such a function can be usefull. I will add it (but it will have
to wait after the release)

Regards,
Pavol