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

17 Jul 2005

      On Sat, Jul 16, 2005 at 06:17:28PM -0500, Thore Karlsen wrote:
...
On Sat, 16 Jul 2005 18:46:33 +0200, Pavol Droba 
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 {
         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