[boost] [iterator] why isn't there a mapped_type iterator adaptor in boost?

Subject: [boost] [iterator] why isn't there a mapped_type iterator adaptor in boost?
From: Mostafa (mostafa_working_away_at_[hidden])
Date: 2010-05-14 17:33:07

Hi all,

Why isn't there a mapped_type/key_type iterator adaptor in boost?  (Just  
in case it's not clear, something which allow one to iterator over the  
keys or the mapped-values of a map/multimap.)  I would think this is a  
pretty common need.

By the way, going through the archives this is all I could dig up:

http://thread.gmane.org/gmane.comp.lib.boost.devel/117946

Additionaly something with a clearer syntax than the following would be  
great:

        make_transform_iterator(
                map.begin(),
                boost::bind( &MAP_TYPE::value_type::first, _1 ))

ie, something along the lines of:

        take_mapped_type(map.begin())

Thanks,

-Mostafa