Question

Consider:

template <typename Function, typename ...Args>
auto wrapper(Function&& f, Args&&... args) -> decltype(f(args...)) {
//...
}

Is there a way to partially specialize the above template for all the cases where decltype(f(args...)) is a pointer?

EDIT:
I think it can be done with an template helper class which takes decltype(f(args...)) as template argument, and specialize the helper class. If you know better solutions let me know.

Answer 1

An SFINAE-based solution:

#include <type_traits>

template<
    typename Functor
    , typename... Args
    , typename Result = decltype(std::declval<Functor&>()(std::declval<Args>()...))
    , typename std::enable_if<
        std::is_pointer<Result>::value
        , int
    >::type = 0
>
Result wrapper(Functor&& functor, Args&&... args)
{ /* ... */ }

template<
    typename Functor
    , typename... Args
    , typename Result = decltype(std::declval<Functor&>()(std::declval<Args>()...))
    , typename std::enable_if<
        !std::is_pointer<Result>::value
        , int
    >::type = 0
>
Result wrapper(Functor&& functor, Args&&... args)
{ /* ... */ }

You can adapt the test (here, std::is_pointer<Result>) to your needs.