#include <tuple>

template<typename T>
struct function_traits;

template<typename R, typename ...Args>
struct function_traits<R(Args...)>
{
    typedef R return_type;
    struct args{
        template <size_t i>
        using type = typename std::tuple_element<i, std::tuple<Args...>>::type;
        static const size_t count = sizeof...(Args);
    };
};



int f(int a){
    return a;
}
double e(int a, double c){
    return a + c;
}

int main(int , char **){

    //declare a with same type as return type from f
    function_traits<decltype(f)>::return_type a;

    //declare first with same type as first argument of e
    //declare second with same type as second argument of e
    function_traits<decltype(e)>::args::type<0> first;
    function_traits<decltype(e)>::args::type<1> second;

    std::cout << "Function e have" << function_traits<decltype(e)>::args::count << " parameter/s";


    std::cout << std::is_same< function_traits<decltype(f)>::args::type<0>, int >::value << std::endl;
    return 0;
}