constexpr explicit iterator(tuple<iterator_t<maybe-const<Const, Views>>...> current);
constexpr iterator(iterator<!Const> i)
requires Const && (convertible_to<iterator_t<Views>, iterator_t<const Views>> && ...);
constexpr auto operator*() const;
constexpr iterator& operator++();
constexpr void operator++(int);
constexpr iterator operator++(int) requires all-forward<Const, Views...>;
constexpr iterator& operator--() requires all-bidirectional<Const, Views...>;
constexpr iterator operator--(int) requires all-bidirectional<Const, Views...>;
constexpr iterator& operator+=(difference_type x)
requires all-random-access<Const, Views...>;
constexpr iterator& operator-=(difference_type x)
requires all-random-access<Const, Views...>;
constexpr auto operator[](difference_type n) const
requires all-random-access<Const, Views...>;
friend constexpr bool operator==(const iterator& x, const iterator& y)
requires (equality_comparable<iterator_t<maybe-const<Const, Views>>> && ...);
friend constexpr auto operator<=>(const iterator& x, const iterator& y)
requires all-random-access<Const, Views...>;
friend constexpr iterator operator+(const iterator& i, difference_type n)
requires all-random-access<Const, Views...>;
friend constexpr iterator operator+(difference_type n, const iterator& i)
requires all-random-access<Const, Views...>;
friend constexpr iterator operator-(const iterator& i, difference_type n)
requires all-random-access<Const, Views...>;
friend constexpr difference_type operator-(const iterator& x, const iterator& y)
requires (sized_sentinel_for<iterator_t<maybe-const<Const, Views>>,
iterator_t<maybe-const<Const, Views>>> && ...);
friend constexpr auto iter_move(const iterator& i) noexcept(see below);
friend constexpr void iter_swap(const iterator& l, const iterator& r) noexcept(see below)
requires (indirectly_swappable<iterator_t<maybe-const<Const, Views>>> && ...);