Thanks David, it works beautifully. Here is my code including conversion to fusion list plus printing of the foreign key fields. #include "boost/mpl/vector.hpp" #include <boost/mpl/find_if.hpp> #include <boost/mpl/at.hpp> #include <boost/mpl/filter_view.hpp> #include <boost/fusion/sequence.hpp> #include <boost/fusion/algorithm.hpp> using namespace std; using namespace boost; namespace fields { struct id { void print() { cout << "id" << endl; } }; struct name { void print() { cout << "name" << endl;} }; struct address { void print() { cout << "address" << endl; }}; struct birthday { void print() { cout << "birthday" << endl; }}; } namespace tags { struct primary {}; struct foreign {}; struct no_key {}; } typedef mpl::vector<fields::id , tags::primary> id_field_t; typedef mpl::vector<fields::name , tags::foreign> name_field_t; typedef mpl::vector<fields::address , tags::foreign> address_field_t; typedef mpl::vector<fields::birthday, tags::no_key> birthday_field_t; typedef mpl::vector< id_field_t , name_field_t , address_field_t , birthday_field_t > table; // find all foreign keys fields typedef mpl::filter_view<table, is_same<mpl::back<mpl::_>, tags::foreign> >::type iter_2; typedef fusion::result_of::as_list<iter_2>::type foreign_keys_t; struct print { template <typename T> void operator()( T const& vec ) const { fusion::at<mpl::int_<0> >(vec).print(); } }; int _tmain(int argc, _TCHAR* argv[]) { BOOST_STATIC_ASSERT(( is_same< mpl::deref<iter>::type, id_field_t
::value ));
foreign_keys_t foreign_keys; for_each( foreign_keys, do_something() ); return 0; }