Hi, here's another result_of question: Given a function object struct f { template< typename T > r<T> operator()(T const &) const; template< typename T > r<T&> operator()(T &) const; template< typename Sig > struct result; }; , result_of< f(some_obj &) >::type // is r<T&> result_of< f(some_obj const & >::type // is r<T> but what about: result_of< f(some_obj) >::type // is r<T>? That's what I'd do intuitively. I also found an example (written by Dave) on the net that seems to do the same: http://tinyurl.com/yzeenu But wait: the TR1 text is talking about lvalues so I probably should let F::result return r<T&>?! Thanks a lot for clarification. Regards, Tobias