namespace std {
template<class To, class From>
constexpr To bit_cast(const From& from) noexcept;
template<class T>
constexpr bool has_single_bit(T x) noexcept;
template<class T>
constexpr T bit_ceil(T x);
template<class T>
constexpr T bit_floor(T x) noexcept;
template<class T>
constexpr T bit_width(T x) noexcept;
template<class T>
[[nodiscard]] constexpr T rotl(T x, int s) noexcept;
template<class T>
[[nodiscard]] constexpr T rotr(T x, int s) noexcept;
template<class T>
constexpr int countl_zero(T x) noexcept;
template<class T>
constexpr int countl_one(T x) noexcept;
template<class T>
constexpr int countr_zero(T x) noexcept;
template<class T>
constexpr int countr_one(T x) noexcept;
template<class T>
constexpr int popcount(T x) noexcept;
enum class endian {
little = see below,
big = see below,
native = see below
};
}