#include <array>
 
template <typename E, class T, E N>
class enum_array : public std::array<T, static_cast<std::size_t>(N)> {
 public:
  T& operator[](E e) {
    return std::array<T, static_cast<std::size_t>(N)>::operator[](
        static_cast<std::size_t>(e));
  }
 
  const T& operator[](E e) const {
    return std::array<T, static_cast<std::size_t>(N)>::operator[](
        static_cast<std::size_t>(e));
  }
};
 
enum class ENUM { a, b, c, last };
 
int main() {
  enum_array<ENUM, int, ENUM::last> t;
  return t.size();
}

How to use a C++ enum class enumerator as std::array index without an explicit cast Archive du 25/12/2017 le 03/02/2023