Have MapMaker store a reference to map. (Warning untested code)
typedef std::map<std::size_t, std::size_t> map_type;
struct MapMaker { map_type& m; template<class T> void operator()(T) const { func_map[U::first::value]=U::second::value; } };
template<class MplMap> map_type makeMap() { map_type result; MapMaker f = { result }; boost::mpl::for_each<MplMap>(f); return result; }
Yes, since I wasn't able to send a reference directly, you're suggesting including a reference within the object being passed to mpl::for_each. This is a nice straightforward solution and in some ways cleaner. I was looking for a way of sending the reference directly. I think I've found it by using boost::ref. typedef std::map<std::size_t, std::size_t> map_type; struct MapMaker { map_type m; template<class T> void operator()(T) const { m[U::first::value]=U::second::value; } }; template<class MplMap> map_type makeMap() { MapMaker f; boost::mpl::for_each<MplMap>(boost::ref(f)); return f.m; } Luke Skelly