#define __glibcxx_want_ranges_as_const
#define __glibcxx_want_ranges_as_rvalue
#define __glibcxx_want_ranges_cartesian_product
+#define __glibcxx_want_ranges_concat
#define __glibcxx_want_ranges_chunk
#define __glibcxx_want_ranges_chunk_by
#define __glibcxx_want_ranges_enumerate
} // namespace ranges
#endif // __cpp_lib_ranges_to_container
+#if __cpp_lib_ranges_concat // C++ >= C++26
+namespace ranges
+{
+ namespace __detail
+ {
+ template<typename... _Rs>
+ using __concat_reference_t = common_reference_t<range_reference_t<_Rs>...>;
+
+ template<typename... _Rs>
+ using __concat_value_t = common_type_t<range_value_t<_Rs>...>;
+
+ template<typename... _Rs>
+ using __concat_rvalue_reference_t
+ = common_reference_t<range_rvalue_reference_t<_Rs>...>;
+
+ template<typename _Ref, typename _RRef, typename _It>
+ concept __concat_indirectly_readable_impl = requires(const _It __it) {
+ { *__it } -> convertible_to<_Ref>;
+ { ranges::iter_move(__it) } -> convertible_to<_RRef>;
+ };
+
+ template<typename... _Rs>
+ concept __concat_indirectly_readable
+ = common_reference_with<__concat_reference_t<_Rs...>&&, __concat_value_t<_Rs...>&>
+ && common_reference_with<__concat_reference_t<_Rs...>&&,
+ __concat_rvalue_reference_t<_Rs...>&&>
+ && common_reference_with<__concat_rvalue_reference_t<_Rs...>&&,
+ __concat_value_t<_Rs...> const&>
+ && (__concat_indirectly_readable_impl<__concat_reference_t<_Rs...>,
+ __concat_rvalue_reference_t<_Rs...>,
+ iterator_t<_Rs>>
+ && ...);
+
+ template<typename... _Rs>
+ concept __concatable = requires {
+ typename __concat_reference_t<_Rs...>;
+ typename __concat_value_t<_Rs...>;
+ typename __concat_rvalue_reference_t<_Rs...>;
+ } && __concat_indirectly_readable<_Rs...>;
+
+ template<bool _Const, typename _Range, typename... _Rs>
+ struct __all_but_last_common
+ {
+ static inline constexpr bool value
+ = requires { requires (common_range<__maybe_const_t<_Const, _Range>>
+ && __all_but_last_common<_Const, _Rs...>::value); };
+ };
+
+ template<bool _Const, typename _Range>
+ struct __all_but_last_common<_Const, _Range>
+ { static inline constexpr bool value = true; };
+
+ template<bool _Const, typename... _Rs>
+ concept __concat_is_random_access = __all_random_access<_Const, _Rs...>
+ && __all_but_last_common<_Const, _Rs...>::value;
+
+ template<bool _Const, typename... _Rs>
+ concept __concat_is_bidirectional = __all_bidirectional<_Const, _Rs...>
+ && __all_but_last_common<_Const, _Rs...>::value;
+
+ template<typename _Range, typename... _Rs>
+ struct __last_is_common
+ { static inline constexpr bool value = __last_is_common<_Rs...>::value; };
+
+ template<typename _Range>
+ struct __last_is_common<_Range>
+ { static inline constexpr bool value = common_range<_Range>; };
+ } // namespace __detail
+
+ template<input_range... _Vs>
+ requires (view<_Vs> && ...) && (sizeof...(_Vs) > 0) && __detail::__concatable<_Vs...>
+ class concat_view : public view_interface<concat_view<_Vs...>>
+ {
+ tuple<_Vs...> _M_views;
+
+ template<bool _Const> class iterator;
+
+ public:
+ constexpr concat_view() = default;
+
+ constexpr explicit
+ concat_view(_Vs... __views)
+ : _M_views(std::move(__views)...)
+ { }
+
+ constexpr iterator<false>
+ begin() requires(!(__detail::__simple_view<_Vs> && ...))
+ {
+ iterator<false> __it(this, in_place_index<0>, ranges::begin(std::get<0>(_M_views)));
+ __it.template _M_satisfy<0>();
+ return __it;
+ }
+
+ constexpr iterator<true>
+ begin() const requires (range<const _Vs> && ...) && __detail::__concatable<const _Vs...>
+ {
+ iterator<true> __it(this, in_place_index<0>, ranges::begin(std::get<0>(_M_views)));
+ __it.template _M_satisfy<0>();
+ return __it;
+ }
+
+ constexpr auto
+ end() requires(!(__detail::__simple_view<_Vs> && ...))
+ {
+ if constexpr (__detail::__last_is_common<_Vs...>::value)
+ {
+ constexpr auto __n = sizeof...(_Vs);
+ return iterator<false>(this, in_place_index<__n - 1>,
+ ranges::end(std::get<__n - 1>(_M_views)));
+ }
+ else
+ return default_sentinel;
+ }
+
+ constexpr auto
+ end() const requires (range<const _Vs> && ...) && __detail::__concatable<const _Vs...>
+ {
+ if constexpr (__detail::__last_is_common<const _Vs...>::value)
+ {
+ constexpr auto __n = sizeof...(_Vs);
+ return iterator<true>(this, in_place_index<__n - 1>,
+ ranges::end(std::get<__n - 1>(_M_views)));
+ }
+ else
+ return default_sentinel;
+ }
+
+ constexpr auto
+ size() requires (sized_range<_Vs>&&...)
+ {
+ return std::apply([](auto... __sizes) {
+ using _CT = __detail::__make_unsigned_like_t<common_type_t<decltype(__sizes)...>>;
+ return (_CT(__sizes) + ...);
+ }, __detail::__tuple_transform(ranges::size, _M_views));
+ }
+
+ constexpr auto
+ size() const requires (sized_range<const _Vs>&&...)
+ {
+ return std::apply([](auto... __sizes) {
+ using _CT = __detail::__make_unsigned_like_t<common_type_t<decltype(__sizes)...>>;
+ return (_CT(__sizes) + ...);
+ }, __detail::__tuple_transform(ranges::size, _M_views));
+ }
+ };
+
+ template<typename... _Rs>
+ concat_view(_Rs&&...) -> concat_view<views::all_t<_Rs>...>;
+
+ namespace __detail
+ {
+ template<bool _Const, typename... _Vs>
+ struct __concat_view_iter_cat
+ { };
+
+ template<bool _Const, typename... _Vs>
+ requires __detail::__all_forward<_Const, _Vs...>
+ struct __concat_view_iter_cat<_Const, _Vs...>
+ {
+ static auto
+ _S_iter_cat()
+ {
+ if constexpr (!is_reference_v<__concat_reference_t<__maybe_const_t<_Const, _Vs>...>>)
+ return input_iterator_tag{};
+ else
+ return []<typename... _Cats>(_Cats... __cats) {
+ if constexpr ((derived_from<_Cats, random_access_iterator_tag> && ...)
+ && __concat_is_random_access<_Const, _Vs...>)
+ return random_access_iterator_tag{};
+ else if constexpr ((derived_from<_Cats, bidirectional_iterator_tag> && ...)
+ && __concat_is_bidirectional<_Const, _Vs...>)
+ return bidirectional_iterator_tag{};
+ else if constexpr ((derived_from<_Cats, forward_iterator_tag> && ...))
+ return forward_iterator_tag{};
+ else
+ return input_iterator_tag{};
+ }(typename iterator_traits<iterator_t<__maybe_const_t<_Const, _Vs>>>
+ ::iterator_category{}...);
+ }
+ };
+ }
+
+ template<input_range... _Vs>
+ requires (view<_Vs> && ...) && (sizeof...(_Vs) > 0) && __detail::__concatable<_Vs...>
+ template<bool _Const>
+ class concat_view<_Vs...>::iterator
+ : public __detail::__concat_view_iter_cat<_Const, _Vs...>
+ {
+ static auto
+ _S_iter_concept()
+ {
+ if constexpr (__detail::__concat_is_random_access<_Const, _Vs...>)
+ return random_access_iterator_tag{};
+ else if constexpr (__detail::__concat_is_bidirectional<_Const, _Vs...>)
+ return bidirectional_iterator_tag{};
+ else if constexpr (__detail::__all_forward<_Const, _Vs...>)
+ return forward_iterator_tag{};
+ else
+ return input_iterator_tag{};
+ }
+
+ friend concat_view;
+ friend iterator<!_Const>;
+
+ public:
+ // iterator_category defined in __concat_view_iter_cat
+ using iterator_concept = decltype(_S_iter_concept());
+ using value_type = __detail::__concat_value_t<__maybe_const_t<_Const, _Vs>...>;
+ using difference_type = common_type_t<range_difference_t<__maybe_const_t<_Const, _Vs>>...>;
+
+ private:
+ using __base_iter = variant<iterator_t<__maybe_const_t<_Const, _Vs>>...>;
+
+ __maybe_const_t<_Const, concat_view>* _M_parent = nullptr;
+ __base_iter _M_it;
+
+ template<size_t _Nm>
+ constexpr void
+ _M_satisfy()
+ {
+ if constexpr (_Nm < (sizeof...(_Vs) - 1))
+ {
+ if (std::get<_Nm>(_M_it) == ranges::end(std::get<_Nm>(_M_parent->_M_views)))
+ {
+ _M_it.template emplace<_Nm + 1>(ranges::begin
+ (std::get<_Nm + 1>(_M_parent->_M_views)));
+ _M_satisfy<_Nm + 1>();
+ }
+ }
+ }
+
+ template<size_t _Nm>
+ constexpr void
+ _M_prev()
+ {
+ if constexpr (_Nm == 0)
+ --std::get<0>(_M_it);
+ else
+ {
+ if (std::get<_Nm>(_M_it) == ranges::begin(std::get<_Nm>(_M_parent->_M_views)))
+ {
+ _M_it.template emplace<_Nm - 1>(ranges::end
+ (std::get<_Nm - 1>(_M_parent->_M_views)));
+ _M_prev<_Nm - 1>();
+ }
+ else
+ --std::get<_Nm>(_M_it);
+ }
+ }
+
+ template<size_t _Nm>
+ constexpr void
+ _M_advance_fwd(difference_type __offset, difference_type __steps)
+ {
+ using _Dt = iter_difference_t<variant_alternative_t<_Nm, __base_iter>>;
+ if constexpr (_Nm == sizeof...(_Vs) - 1)
+ std::get<_Nm>(_M_it) += static_cast<_Dt>(__steps);
+ else
+ {
+ auto __n_size = ranges::distance(std::get<_Nm>(_M_parent->_M_views));
+ if (__offset + __steps < __n_size)
+ std::get<_Nm>(_M_it) += static_cast<_Dt>(__steps);
+ else
+ {
+ _M_it.template emplace<_Nm + 1>(ranges::begin
+ (std::get<_Nm + 1>(_M_parent->_M_views)));
+ _M_advance_fwd<_Nm + 1>(0, __offset + __steps - __n_size);
+ }
+ }
+ }
+
+ template<size_t _Nm>
+ constexpr void
+ _M_advance_bwd(difference_type __offset, difference_type __steps)
+ {
+ using _Dt = iter_difference_t<variant_alternative_t<_Nm, __base_iter>>;
+ if constexpr (_Nm == 0)
+ std::get<_Nm>(_M_it) -= static_cast<_Dt>(__steps);
+ else {
+ if (__offset >= __steps)
+ std::get<_Nm>(_M_it) -= static_cast<_Dt>(__steps);
+ else
+ {
+ auto __prev_size = ranges::distance(std::get<_Nm - 1>(_M_parent->_M_views));
+ _M_it.template emplace<_Nm - 1>(ranges::end
+ (std::get<_Nm - 1>(_M_parent->_M_views)));
+ _M_advance_bwd<_Nm - 1>(__prev_size, __steps - __offset);
+ }
+ }
+ }
+
+ // Invoke the function object __f, which has a call operator with a size_t
+ // template parameter (corresponding to an index into the pack of views),
+ // using the runtime value of __index as the template argument.
+ template<typename _Fp>
+ static constexpr auto
+ _S_invoke_with_runtime_index(_Fp&& __f, size_t __index)
+ {
+ return [&__f, __index]<size_t _Idx>(this auto&& __self) {
+ if (_Idx == __index)
+ return __f.template operator()<_Idx>();
+ if constexpr (_Idx + 1 < sizeof...(_Vs))
+ return __self.template operator()<_Idx + 1>();
+ }.template operator()<0>();
+ }
+
+ template<typename _Fp>
+ constexpr auto
+ _M_invoke_with_runtime_index(_Fp&& __f)
+ { return _S_invoke_with_runtime_index(std::forward<_Fp>(__f), _M_it.index()); }
+
+ template<typename... _Args>
+ explicit constexpr
+ iterator(__maybe_const_t<_Const, concat_view>* __parent, _Args&&... __args)
+ requires constructible_from<__base_iter, _Args&&...>
+ : _M_parent(__parent), _M_it(std::forward<_Args>(__args)...)
+ { }
+
+ public:
+ iterator() = default;
+
+ constexpr
+ iterator(iterator<!_Const> __it)
+ requires _Const && (convertible_to<iterator_t<_Vs>, iterator_t<const _Vs>> && ...)
+ : _M_parent(__it._M_parent)
+ {
+ _M_invoke_with_runtime_index([this, &__it]<size_t _Idx>() {
+ _M_it.template emplace<_Idx>(std::get<_Idx>(std::move(__it._M_it)));
+ });
+ }
+
+ constexpr decltype(auto)
+ operator*() const
+ {
+ __glibcxx_assert(!_M_it.valueless_by_exception());
+ using reference = __detail::__concat_reference_t<__maybe_const_t<_Const, _Vs>...>;
+ return std::visit([](auto&& __it) -> reference { return *__it; }, _M_it);
+ }
+
+ constexpr iterator&
+ operator++()
+ {
+ _M_invoke_with_runtime_index([this]<size_t _Idx>() {
+ ++std::get<_Idx>(_M_it);
+ _M_satisfy<_Idx>();
+ });
+ return *this;
+ }
+
+ constexpr void
+ operator++(int)
+ { ++*this; }
+
+ constexpr iterator
+ operator++(int)
+ requires __detail::__all_forward<_Const, _Vs...>
+ {
+ auto __tmp = *this;
+ ++*this;
+ return __tmp;
+ }
+
+ constexpr iterator&
+ operator--()
+ requires __detail::__concat_is_bidirectional<_Const, _Vs...>
+ {
+ __glibcxx_assert(!_M_it.valueless_by_exception());
+ _M_invoke_with_runtime_index([this]<size_t _Idx>() {
+ _M_prev<_Idx>();
+ });
+ return *this;
+ }
+
+ constexpr iterator
+ operator--(int)
+ requires __detail::__concat_is_bidirectional<_Const, _Vs...>
+ {
+ auto __tmp = *this;
+ --*this;
+ return __tmp;
+ }
+
+ constexpr iterator&
+ operator+=(difference_type __n)
+ requires __detail::__concat_is_random_access<_Const, _Vs...>
+ {
+ __glibcxx_assert(!_M_it.valueless_by_exception());
+ _M_invoke_with_runtime_index([this, __n]<size_t _Idx>() {
+ auto __begin = ranges::begin(std::get<_Idx>(_M_parent->_M_views));
+ if (__n > 0)
+ _M_advance_fwd<_Idx>(std::get<_Idx>(_M_it) - __begin, __n);
+ else if (__n < 0)
+ _M_advance_bwd<_Idx>(std::get<_Idx>(_M_it) - __begin, -__n);
+ });
+ return *this;
+ }
+
+ constexpr iterator&
+ operator-=(difference_type __n)
+ requires __detail::__concat_is_random_access<_Const, _Vs...>
+ {
+ *this += -__n;
+ return *this;
+ }
+
+ constexpr decltype(auto)
+ operator[](difference_type __n) const
+ requires __detail::__concat_is_random_access<_Const, _Vs...>
+ { return *((*this) + __n); }
+
+ friend constexpr bool
+ operator==(const iterator& __x, const iterator& __y)
+ requires (equality_comparable<iterator_t<__maybe_const_t<_Const, _Vs>>> && ...)
+ {
+ __glibcxx_assert(!__x._M_it.valueless_by_exception());
+ __glibcxx_assert(!__y._M_it.valueless_by_exception());
+ return __x._M_it == __y._M_it;
+ }
+
+ friend constexpr bool
+ operator==(const iterator& __it, default_sentinel_t)
+ {
+ __glibcxx_assert(!__it._M_it.valueless_by_exception());
+ constexpr auto __last_idx = sizeof...(_Vs) - 1;
+ return (__it._M_it.index() == __last_idx
+ && (std::get<__last_idx>(__it._M_it)
+ == ranges::end(std::get<__last_idx>(__it._M_parent->_M_views))));
+ }
+
+ friend constexpr bool
+ operator<(const iterator& __x, const iterator& __y)
+ requires __detail::__all_random_access<_Const, _Vs...>
+ { return __x._M_it < __y._M_it; }
+
+ friend constexpr bool
+ operator>(const iterator& __x, const iterator& __y)
+ requires __detail::__all_random_access<_Const, _Vs...>
+ { return __x._M_it > __y._M_it; }
+
+ friend constexpr bool
+ operator<=(const iterator& __x, const iterator& __y)
+ requires __detail::__all_random_access<_Const, _Vs...>
+ { return __x._M_it <= __y._M_it; }
+
+ friend constexpr bool
+ operator>=(const iterator& __x, const iterator& __y)
+ requires __detail::__all_random_access<_Const, _Vs...>
+ { return __x._M_it >= __y._M_it; }
+
+ friend constexpr auto
+ operator<=>(const iterator& __x, const iterator& __y)
+ requires __detail::__all_random_access<_Const, _Vs...>
+ && (three_way_comparable<iterator_t<__maybe_const_t<_Const, _Vs>>> && ...)
+ { return __x._M_it <=> __y._M_it; }
+
+ friend constexpr iterator
+ operator+(const iterator& __it, difference_type __n)
+ requires __detail::__concat_is_random_access<_Const, _Vs...>
+ { return auto(__it) += __n; }
+
+ friend constexpr iterator
+ operator+(difference_type __n, const iterator& __it)
+ requires __detail::__concat_is_random_access<_Const, _Vs...>
+ { return __it + __n; }
+
+ friend constexpr iterator
+ operator-(const iterator& __it, difference_type __n)
+ requires __detail::__concat_is_random_access<_Const, _Vs...>
+ { return auto(__it) -= __n; }
+
+ friend constexpr difference_type
+ operator-(const iterator& __x, const iterator& __y)
+ requires __detail::__concat_is_random_access<_Const, _Vs...>
+ {
+ return _S_invoke_with_runtime_index([&]<size_t _Ix>() -> difference_type {
+ return _S_invoke_with_runtime_index([&]<size_t _Iy>() -> difference_type {
+ if constexpr (_Ix > _Iy)
+ {
+ auto __dy = ranges::distance(std::get<_Iy>(__y._M_it),
+ ranges::end(std::get<_Iy>(__y._M_parent
+ ->_M_views)));
+ auto __dx = ranges::distance(ranges::begin(std::get<_Ix>(__x._M_parent
+ ->_M_views)),
+ std::get<_Ix>(__x._M_it));
+ difference_type __s = 0;
+ [&]<size_t _Idx = _Iy + 1>(this auto&& __self) {
+ if constexpr (_Idx < _Ix)
+ {
+ __s += ranges::size(std::get<_Idx>(__x._M_parent->_M_views));
+ __self.template operator()<_Idx + 1>();
+ }
+ }();
+ return __dy + __s + __dx;
+ }
+ else if constexpr (_Ix < _Iy)
+ return -(__y - __x);
+ else
+ return std::get<_Ix>(__x._M_it) - std::get<_Iy>(__y._M_it);
+ }, __y._M_it.index());
+ }, __x._M_it.index());
+ }
+
+ friend constexpr difference_type
+ operator-(const iterator& __x, default_sentinel_t)
+ requires __detail::__concat_is_random_access<_Const, _Vs...>
+ && __detail::__last_is_common<__maybe_const_t<_Const, _Vs>...>::value
+ {
+ return _S_invoke_with_runtime_index([&]<size_t _Ix>() -> difference_type {
+ auto __dx = ranges::distance(std::get<_Ix>(__x._M_it),
+ ranges::end(std::get<_Ix>(__x._M_parent->_M_views)));
+ difference_type __s = 0;
+ [&]<size_t _Idx = _Ix + 1>(this auto&& __self) {
+ if constexpr (_Idx < sizeof...(_Vs))
+ {
+ __s += ranges::size(std::get<_Idx>(__x._M_parent->_M_views));
+ __self.template operator()<_Idx + 1>();
+ }
+ }();
+ return -(__dx + __s);
+ }, __x._M_it.index());
+ }
+
+ friend constexpr difference_type
+ operator-(default_sentinel_t, const iterator& __x)
+ requires __detail::__concat_is_random_access<_Const, _Vs...>
+ && __detail::__last_is_common<__maybe_const_t<_Const, _Vs>...>::value
+ { return -(__x - default_sentinel); }
+
+ friend constexpr decltype(auto)
+ iter_move(const iterator& __it)
+ {
+ using _Res = __detail::__concat_rvalue_reference_t<__maybe_const_t<_Const, _Vs>...>;
+ return std::visit([](const auto& __i) -> _Res {
+ return ranges::iter_move(__i);
+ }, __it._M_it);
+ }
+
+ friend constexpr void
+ iter_swap(const iterator& __x, const iterator& __y)
+ requires swappable_with<iter_reference_t<iterator>, iter_reference_t<iterator>>
+ && (... && indirectly_swappable<iterator_t<__maybe_const_t<_Const, _Vs>>>)
+ {
+ std::visit([&]<typename _Tp, typename _Up>(const _Tp& __it1, const _Up& __it2) {
+ if constexpr (is_same_v<_Tp, _Up>)
+ ranges::iter_swap(__it1, __it2);
+ else
+ ranges::swap(*__it1, *__it2);
+ }, __x._M_it, __y._M_it);
+ }
+ };
+
+ namespace views
+ {
+ namespace __detail
+ {
+ template<typename... _Ts>
+ concept __can_concat_view = requires { concat_view(std::declval<_Ts>()...); };
+ }
+
+ struct _Concat
+ {
+ template<typename... _Ts>
+ requires __detail::__can_concat_view<_Ts...>
+ constexpr auto
+ operator() [[nodiscard]] (_Ts&&... __ts) const
+ {
+ if constexpr (sizeof...(_Ts) == 1)
+ return views::all(std::forward<_Ts>(__ts)...);
+ else
+ return concat_view(std::forward<_Ts>(__ts)...);
+ }
+ };
+
+ inline constexpr _Concat concat;
+ }
+
+} // namespace ranges
+#endif // __cpp_lib_ranges_concat
+
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // library concepts