Hi! The example in libs/mpl/example/tuple_from_list.cpp and gen_linear_hierarchy from http://aspn.activestate.com/ASPN/Mail/Message/boost/1166644 template< typename Types, typename Unit, typename Root = mpl::none > struct gen_linear_hierarchy { typedef typename mpl::fold<Types,Unit,Root> ::type type; // here }; /* usage example: template< class Base, class T > struct EventHander : public Base { virtual void OnEvent(T& obj, int eventID) = 0; }; typedef gen_linear_hierarchy< mpl::list<Window,Button,ScrollBar> , EventHander<_1,_2> > ::type v; */ all seem to me work fine with default constructible types. What I need is a type generator which provides a constructor, such that code like this one works for mpl::vectors (or other mpl::sequences) with arbitrary length: ------------- class C { C(std::string const & gaga) {} }; struct gen_linear_hierarchy_with_constructor // your idea missing here { // and here }; typedef gen_linear_hierarchy_with_constructor<mpl::vector<C, C> >::type mytuple; mytuple mt("test", "Thanks for your help"); ------------------ Markus P.S.: David and Aleksey, if you read this here: I could not find your "coming soon" book at awprofessional.com. What's the current state of the book I wait for so long already ...