Idiomatic C++11 type promotion

Question

There is a great paper on C++ for scientific computing where the author (T. Veldhuizen) suggests a traits-based approach to address type promotion. I have used such app

Answer 1

I think you can use decltype for this:

template 
void product(T t, U u) 
{
    std::cout << typeid(decltype(t * u)).name() << std::endl;
}

Or with declval:

#include 
template 
void product() 
{
    std::cout << typeid(decltype(std::declval() * std::declval())).name() << std::endl;
}

EDIT For T ans = T(a) * T(b); you can just use auto, auto ans = T(a) * T(b);