Hi, Maybe I am misreading the documentation, but if I have an mpl::map and try and get an element associated with a key all's good, while if I assign a default - I get an error that mpl::at only takes 2 and not 3 template parameters. Simple example for sake of completness: using namespace boost::mpl; typedef map< pair<int, int_<0> > , pair<float, int_<1> > > m; at<m, float>::type::value; // Ok at<m, double, int_<2> >::type::value; // compiler error Indeed a look in boost/mpl/at.hpp even leads me to believe that mpl::at only takes two template parameters (maybe I mistaken), but documentation suggests otherwise. [Compiler: GCC-4.4.2 ; Boost-1.42] Am I doing something blatantly wrong? Cheers, -- Manfred