How do I get the argument types of a function pointer in a variadic template class?

This is a follow up of this problem: Generic functor for functions with any argument list

I have this functor class (full code see link above):

template<typename... ARGS>
class Foo
{
    std::function<void(ARGS...)> m_f;
public:
    Foo(std::function<void(ARGS...)> f) : m_f(f) {}
    void operator()(ARGS... args) const { m_f(args...); }
};

In operator() I can access the args... easily with a recursive "peeling" function as described in Stroustrup's C++11 FAQ

My problem is: I want to access the types of the arguments of f, i.e. ARGS..., in the constructor. Obviously I can't access values because there are none so far, but the argument type list is somehow burried in f, isn't it?