simple variadic type_traits

variadic_traits.cpp

#include <iostream>
#include <tuple>
#include <type_traits>
#include <utility>
template <bool... Bs> using bool_sequence = std::integer_sequence<bool, Bs...>;

template <bool... Bs>
using bool_and =
    std::is_same<bool_sequence<Bs...>, bool_sequence<(Bs || true)...>>;

template <bool... Bs>
using bool_or = std::integral_constant<bool, !bool_and<!Bs...>::value>;

template <typename R, bool... Bs> // note: R first, no default :(
using enable_if_any = std::enable_if<bool_or<Bs...>::value, R>;

template <typename R, bool... Bs> // note: R first, no default :(
using enable_if_all = std::enable_if<bool_and<Bs...>::value, R>;

template <typename T, typename... Ts>
using are_same = bool_and<std::is_same<T, Ts>::value...>;

using namespace std;

int main() {
  cout << "Hello World!" << endl;
  cout << are_same<int, int, int>::value << endl;
  cout << are_same<int, int, float>::value << endl;
  cout << are_same<int, float, float>::value << endl;
  cout << are_same<float, float, float>::value << endl;
  cout << are_same<float, int, float>::value << endl;
  cout << are_same<float, int, int>::value << endl;
  return 0;
}