template <typename _Enum>
  struct define_bitwise_ops
  {
    using value_type = _Enum;
    using basic_type = std::underlying_type_t<_Enum>;
    friend constexpr value_type operator | (value_type a, value_type b)
    {
      return static_cast<value_type> (static_cast<basic_type>(a)|static_cast<basic_type>(b));
    }
    friend constexpr value_type operator & (value_type a, value_type b)
    {
      return static_cast<value_type> (static_cast<basic_type>(a)&static_cast<basic_type>(b));
    }
    friend constexpr value_type operator ^ (value_type a, value_type b)
    {
      return static_cast<value_type> (static_cast<basic_type>(a)^static_cast<basic_type>(b));
    }
    friend constexpr value_type operator ~ (value_type a)
    {
      return static_cast<value_type> (~static_cast<basic_type>(a));
    }
  };