#include <iostream>
#include <type_traits>
#include <iomanip>

template <typename Functor>
struct tester : std::integral_constant<int, 0>{};

template <typename Res, typename... Args>
struct tester<Res(Args...)> : std::integral_constant<int, 1>{};

template <typename Res, typename... Args>
struct tester<Res(Args......)> : std::integral_constant<int, 2>{};

#define STR_EXPAND(tok) #tok
#define STR(tok) STR_EXPAND(tok)
#define TEST_PARAM_1 void(*)(int, int)
#define TEST_PARAM_2 void(int, char, std::ostream&)
#define TEST_PARAM_3 void()

int main(){
    using std::setw;
    std::cout
    << setw(65)<< STR(TEST_PARAM_1) ": " << tester<TEST_PARAM_1>::value << "\n"
    << setw(65)<< STR(TEST_PARAM_2) ": " << tester<TEST_PARAM_2>::value << "\n"
    << setw(65)<< STR(TEST_PARAM_3) ": " << tester<TEST_PARAM_3>::value << "\n";
}