hi, here's the problem i have: struct my{ template<typename UInt> struct apply{ typedef mpl::int_<UInt::value> type; }; }; template<int First,int Last> struct id_range{ typedef mpl::transform< mpl::range_c<int,First,Last> , my , mpl::back_inserter< mpl::vector<> > >::type type; /home/er/cpp/boost/random/mcmc/id_range.hpp|32|error: type ‘boost::mpl::transform<boost::mpl::range_c<int, First, Last>, boost::random::mcmc::<unnamed>::my, boost::mpl::back_inserter<boost::mpl::vector<mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na> >, mpl_::na>’ is not derived from type ‘boost::random::mcmc::id_range<First, Last>’| however, for example, this --instead-- compiles fine: struct id_range{ typedef mpl::transform< mpl::range_c<int,1,3> , my , mpl::back_inserter< mpl::vector<> > >::type type; }; any suggestion appreciated. thanks!