constexpr explicit iterator(const T* value, index-type b = index-type());
constexpr const T& operator*() const noexcept;
constexpr iterator& operator++();
constexpr iterator operator++(int);
constexpr iterator& operator--();
constexpr iterator operator--(int);
constexpr iterator& operator+=(difference_type n);
constexpr iterator& operator-=(difference_type n);
constexpr const T& operator[](difference_type n) const noexcept;
friend constexpr bool operator==(const iterator& x, const iterator& y);
friend constexpr auto operator<=>(const iterator& x, const iterator& y);
friend constexpr iterator operator+(iterator i, difference_type n);
friend constexpr iterator operator+(difference_type n, iterator i);
friend constexpr iterator operator-(iterator i, difference_type n);
friend constexpr difference_type operator-(const iterator& x, const iterator& y);