std::is_void

// is_void example
#include <iostream>
#include <type_traits>

int main() {
  std::cout << std::boolalpha;
  std::cout << "is_void:" << std::endl;
  std::cout << "int: " << std::is_void<int>::value << std::endl;
  std::cout << "void: " << std::is_void<void>::value << std::endl;
  return 0;
}