say I have a functor F which takes an argument of type

F::arg_type = quantity<time>

and returns a value of type

F::ret_type = quantity<velocity>

Now I want to write an integration function, which should return the correct type, something like

template<class F> F::ret_type*F::arg_type // only conceptually integrate(F& f, typename F::arg_type a, typename F::arg_type b);

so instantiating this with the above functor should produce a return type quantity<time*velocity==length>. How can I combine F::arg_type and F::ret_type to produce the correct return type for the function template?

Attempted to solve this with the help of boost.typeof: template<class F> BOOST_TYPEOF_TPL(F::ret_type() * F::arg_type()) integrate(F& f, typename F::arg_type a, typename F::arg_type b); but MVC9 produces a error C2064: term does not evaluate to a function taking 0 arguments for the default constructor calls in the macro argument. Any ideas welcome. Thanks -- Rupert Mazzucco <mazzucco@iiasa.ac.at> Research Scholar, Evolution and Ecology Program IIASA - Institute for Applied Systems Analysis Schlossplatz 1, 2361 Laxenburg, Austria Phone: +43 2236 807 522 Fax: +43 2236 713 13