include/__ranges/take_view.h - external/github.com/llvm/llvm-project/libcxx - Git at Google

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//

 #ifndef _LIBCPP___RANGES_TAKE_VIEW_H
 #define _LIBCPP___RANGES_TAKE_VIEW_H

 #include <__algorithm/min.h>
 #include <__algorithm/ranges_min.h>
 #include <__assert>
 #include <__concepts/constructible.h>
 #include <__concepts/convertible_to.h>
 #include <__config>
 #include <__functional/bind_back.h>
 #include <__fwd/span.h>
 #include <__fwd/string_view.h>
 #include <__iterator/concepts.h>
 #include <__iterator/counted_iterator.h>
 #include <__iterator/default_sentinel.h>
 #include <__iterator/distance.h>
 #include <__iterator/iterator_traits.h>
 #include <__ranges/access.h>
 #include <__ranges/all.h>
 #include <__ranges/concepts.h>
 #include <__ranges/empty_view.h>
 #include <__ranges/enable_borrowed_range.h>
 #include <__ranges/iota_view.h>
 #include <__ranges/range_adaptor.h>
 #include <__ranges/repeat_view.h>
 #include <__ranges/size.h>
 #include <__ranges/subrange.h>
 #include <__ranges/view_interface.h>
 #include <__type_traits/decay.h>
 #include <__type_traits/is_nothrow_constructible.h>
 #include <__type_traits/maybe_const.h>
 #include <__type_traits/remove_cvref.h>
 #include <__utility/auto_cast.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <cstddef>

 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif

 _LIBCPP_PUSH_MACROS
 #include <__undef_macros>

 _LIBCPP_BEGIN_NAMESPACE_STD

 #if _LIBCPP_STD_VER >= 20

 namespace ranges {

 template <view _View>
 class take_view : public view_interface<take_view<_View>> {
   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
   range_difference_t<_View> __count_      = 0;

   template <bool>
   class __sentinel;

 public:
   _LIBCPP_HIDE_FROM_ABI take_view()
     requires default_initializable<_View>
   = default;

   _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23
   take_view(_View __base, range_difference_t<_View> __count)
       : __base_(std::move(__base)), __count_(__count) {
     _LIBCPP_ASSERT_UNCATEGORIZED(__count >= 0, "count has to be greater than or equal to zero");
   }

   _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
     requires copy_constructible<_View>
   {
     return __base_;
   }

   _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }

   _LIBCPP_HIDE_FROM_ABI constexpr auto begin()
     requires(!__simple_view<_View>)
   {
     if constexpr (sized_range<_View>) {
       if constexpr (random_access_range<_View>) {
         return ranges::begin(__base_);
       } else {
         using _DifferenceT = range_difference_t<_View>;
         auto __size        = size();
         return counted_iterator(ranges::begin(__base_), static_cast<_DifferenceT>(__size));
       }
     } else {
       return counted_iterator(ranges::begin(__base_), __count_);
     }
   }

   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
     requires range<const _View>
   {
     if constexpr (sized_range<const _View>) {
       if constexpr (random_access_range<const _View>) {
         return ranges::begin(__base_);
       } else {
         using _DifferenceT = range_difference_t<const _View>;
         auto __size        = size();
         return counted_iterator(ranges::begin(__base_), static_cast<_DifferenceT>(__size));
       }
     } else {
       return counted_iterator(ranges::begin(__base_), __count_);
     }
   }

   _LIBCPP_HIDE_FROM_ABI constexpr auto end()
     requires(!__simple_view<_View>)
   {
     if constexpr (sized_range<_View>) {
       if constexpr (random_access_range<_View>) {
         return ranges::begin(__base_) + size();
       } else {
         return default_sentinel;
       }
     } else {
       return __sentinel<false>{ranges::end(__base_)};
     }
   }

   _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
     requires range<const _View>
   {
     if constexpr (sized_range<const _View>) {
       if constexpr (random_access_range<const _View>) {
         return ranges::begin(__base_) + size();
       } else {
         return default_sentinel;
       }
     } else {
       return __sentinel<true>{ranges::end(__base_)};
     }
   }

   _LIBCPP_HIDE_FROM_ABI constexpr auto size()
     requires sized_range<_View>
   {
     auto __n = ranges::size(__base_);
     return ranges::min(__n, static_cast<decltype(__n)>(__count_));
   }

   _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
     requires sized_range<const _View>
   {
     auto __n = ranges::size(__base_);
     return ranges::min(__n, static_cast<decltype(__n)>(__count_));
   }
 };

 template <view _View>
 template <bool _Const>
 class take_view<_View>::__sentinel {
   using _Base = __maybe_const<_Const, _View>;
   template <bool _OtherConst>
   using _Iter                                        = counted_iterator<iterator_t<__maybe_const<_OtherConst, _View>>>;
   _LIBCPP_NO_UNIQUE_ADDRESS sentinel_t<_Base> __end_ = sentinel_t<_Base>();

   template <bool>
   friend class take_view<_View>::__sentinel;

 public:
   _LIBCPP_HIDE_FROM_ABI __sentinel() = default;

   _LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(sentinel_t<_Base> __end) : __end_(std::move(__end)) {}

   _LIBCPP_HIDE_FROM_ABI constexpr __sentinel(__sentinel<!_Const> __s)
     requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
       : __end_(std::move(__s.__end_)) {}

   _LIBCPP_HIDE_FROM_ABI constexpr sentinel_t<_Base> base() const { return __end_; }

   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const _Iter<_Const>& __lhs, const __sentinel& __rhs) {
     return __lhs.count() == 0 || __lhs.base() == __rhs.__end_;
   }

   template <bool _OtherConst = !_Const>
     requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const _Iter<_OtherConst>& __lhs, const __sentinel& __rhs) {
     return __lhs.count() == 0 || __lhs.base() == __rhs.__end_;
   }
 };

 template <class _Range>
 take_view(_Range&&, range_difference_t<_Range>) -> take_view<views::all_t<_Range>>;

 template <class _Tp>
 inline constexpr bool enable_borrowed_range<take_view<_Tp>> = enable_borrowed_range<_Tp>;

 namespace views {
 namespace __take {

 template <class _Tp>
 inline constexpr bool __is_empty_view = false;

 template <class _Tp>
 inline constexpr bool __is_empty_view<empty_view<_Tp>> = true;

 template <class _Tp>
 inline constexpr bool __is_passthrough_specialization = false;

 template <class _Tp, size_t _Extent>
 inline constexpr bool __is_passthrough_specialization<span<_Tp, _Extent>> = true;

 template <class _CharT, class _Traits>
 inline constexpr bool __is_passthrough_specialization<basic_string_view<_CharT, _Traits>> = true;

 template <class _Iter, class _Sent, subrange_kind _Kind>
 inline constexpr bool __is_passthrough_specialization<subrange<_Iter, _Sent, _Kind>> = true;

 template <class _Tp>
 inline constexpr bool __is_iota_specialization = false;

 template <class _Np, class _Bound>
 inline constexpr bool __is_iota_specialization<iota_view<_Np, _Bound>> = true;

 template <class _Tp>
 struct __passthrough_type;

 template <class _Tp, size_t _Extent>
 struct __passthrough_type<span<_Tp, _Extent>> {
   using type = span<_Tp>;
 };

 template <class _CharT, class _Traits>
 struct __passthrough_type<basic_string_view<_CharT, _Traits>> {
   using type = basic_string_view<_CharT, _Traits>;
 };

 template <class _Iter, class _Sent, subrange_kind _Kind>
   requires requires { typename subrange<_Iter>; }
 struct __passthrough_type<subrange<_Iter, _Sent, _Kind>> {
   using type = subrange<_Iter>;
 };

 template <class _Tp>
 using __passthrough_type_t = typename __passthrough_type<_Tp>::type;

 struct __fn {
   // [range.take.overview]: the `empty_view` case.
   template <class _Range, convertible_to<range_difference_t<_Range>> _Np>
     requires __is_empty_view<remove_cvref_t<_Range>>
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&&) const
       noexcept(noexcept(_LIBCPP_AUTO_CAST(std::forward<_Range>(__range))))
           -> decltype(_LIBCPP_AUTO_CAST(std::forward<_Range>(__range))) {
     return _LIBCPP_AUTO_CAST(std::forward<_Range>(__range));
   }

   // [range.take.overview]: the `span | basic_string_view | subrange` case.
   template <class _Range,
             convertible_to<range_difference_t<_Range>> _Np,
             class _RawRange = remove_cvref_t<_Range>,
             class _Dist     = range_difference_t<_Range>>
     requires(!__is_empty_view<_RawRange> && random_access_range<_RawRange> && sized_range<_RawRange> &&
              __is_passthrough_specialization<_RawRange>)
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto
   operator()(_Range&& __rng, _Np&& __n) const noexcept(noexcept(__passthrough_type_t<_RawRange>(
       ranges::begin(__rng), ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))))
       -> decltype(__passthrough_type_t<_RawRange>(
           // Note: deliberately not forwarding `__rng` to guard against double moves.
           ranges::begin(__rng),
           ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))) {
     return __passthrough_type_t<_RawRange>(
         ranges::begin(__rng), ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)));
   }

   // [range.take.overview]: the `iota_view` case.
   // clang-format off
   template <class _Range,
             convertible_to<range_difference_t<_Range>> _Np,
             class _RawRange = remove_cvref_t<_Range>,
             class _Dist     = range_difference_t<_Range>>
     requires (!__is_empty_view<_RawRange> &&
               random_access_range<_RawRange> &&
               sized_range<_RawRange> &&
               __is_iota_specialization<_RawRange>)
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
   constexpr auto operator()(_Range&& __rng, _Np&& __n) const
     noexcept(noexcept(ranges::iota_view(
                               *ranges::begin(__rng),
                               *(ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))
                               )))
     -> decltype(      ranges::iota_view(
                               // Note: deliberately not forwarding `__rng` to guard against double moves.
                               *ranges::begin(__rng),
                               *(ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))
                               ))
     { return          ranges::iota_view(
                               *ranges::begin(__rng),
                               *(ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))
                               ); }

 #if _LIBCPP_STD_VER >= 23
   // [range.take.overview]: the `repeat_view` "_RawRange models sized_range" case.
   template <class _Range,
             convertible_to<range_difference_t<_Range>> _Np,
             class _RawRange = remove_cvref_t<_Range>,
             class _Dist     = range_difference_t<_Range>>
     requires(__is_repeat_specialization<_RawRange> && sized_range<_RawRange>)
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&& __n) const
     noexcept(noexcept(views::repeat(*__range.__value_, std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n)))))
     -> decltype(      views::repeat(*__range.__value_, std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n))))
     { return          views::repeat(*__range.__value_, std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n))); }

   // [range.take.overview]: the `repeat_view` "otherwise" case.
   template <class _Range,
             convertible_to<range_difference_t<_Range>> _Np,
             class _RawRange = remove_cvref_t<_Range>,
             class _Dist     = range_difference_t<_Range>>
     requires(__is_repeat_specialization<_RawRange> && !sized_range<_RawRange>)
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&& __n) const
     noexcept(noexcept(views::repeat(*__range.__value_, static_cast<_Dist>(__n))))
     -> decltype(      views::repeat(*__range.__value_, static_cast<_Dist>(__n)))
     { return          views::repeat(*__range.__value_, static_cast<_Dist>(__n)); }
 #endif
   // clang-format on

   // [range.take.overview]: the "otherwise" case.
   template <class _Range, convertible_to<range_difference_t<_Range>> _Np, class _RawRange = remove_cvref_t<_Range>>
   // Note: without specifically excluding the other cases, GCC sees this overload as ambiguous with the other
   // overloads.
     requires(!(__is_empty_view<_RawRange> ||
 #  if _LIBCPP_STD_VER >= 23
                __is_repeat_specialization<_RawRange> ||
 #  endif
                (__is_iota_specialization<_RawRange> && sized_range<_RawRange> && random_access_range<_RawRange>) ||
                (__is_passthrough_specialization<_RawRange> && sized_range<_RawRange> &&
                 random_access_range<_RawRange>)))
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&& __n) const
       noexcept(noexcept(take_view(std::forward<_Range>(__range), std::forward<_Np>(__n))))
           -> decltype(take_view(std::forward<_Range>(__range), std::forward<_Np>(__n))) {
     return take_view(std::forward<_Range>(__range), std::forward<_Np>(__n));
   }

   template <class _Np>
     requires constructible_from<decay_t<_Np>, _Np>
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Np&& __n) const
       noexcept(is_nothrow_constructible_v<decay_t<_Np>, _Np>) {
     return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Np>(__n)));
   }
 };

 } // namespace __take

 inline namespace __cpo {
 inline constexpr auto take = __take::__fn{};
 } // namespace __cpo
 } // namespace views

 } // namespace ranges

 #endif // _LIBCPP_STD_VER >= 20

 _LIBCPP_END_NAMESPACE_STD

 _LIBCPP_POP_MACROS

 #endif // _LIBCPP___RANGES_TAKE_VIEW_H
	// -- C++ --
	//===----------------------------------------------------------------------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//

	#ifndef _LIBCPP___RANGES_TAKE_VIEW_H
	#define _LIBCPP___RANGES_TAKE_VIEW_H

	#include <__algorithm/min.h>
	#include <__algorithm/ranges_min.h>
	#include <__assert>
	#include <__concepts/constructible.h>
	#include <__concepts/convertible_to.h>
	#include <__config>
	#include <__functional/bind_back.h>
	#include <__fwd/span.h>
	#include <__fwd/string_view.h>
	#include <__iterator/concepts.h>
	#include <__iterator/counted_iterator.h>
	#include <__iterator/default_sentinel.h>
	#include <__iterator/distance.h>
	#include <__iterator/iterator_traits.h>
	#include <__ranges/access.h>
	#include <__ranges/all.h>
	#include <__ranges/concepts.h>
	#include <__ranges/empty_view.h>
	#include <__ranges/enable_borrowed_range.h>
	#include <__ranges/iota_view.h>
	#include <__ranges/range_adaptor.h>
	#include <__ranges/repeat_view.h>
	#include <__ranges/size.h>
	#include <__ranges/subrange.h>
	#include <__ranges/view_interface.h>
	#include <__type_traits/decay.h>
	#include <__type_traits/is_nothrow_constructible.h>
	#include <__type_traits/maybe_const.h>
	#include <__type_traits/remove_cvref.h>
	#include <__utility/auto_cast.h>
	#include <__utility/forward.h>
	#include <__utility/move.h>
	#include <cstddef>

	#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
	# pragma GCC system_header
	#endif

	_LIBCPP_PUSH_MACROS
	#include <__undef_macros>

	_LIBCPP_BEGIN_NAMESPACE_STD

	#if _LIBCPP_STD_VER >= 20

	namespace ranges {

	template <view _View>
	class take_view : public view_interface<take_view<_View>> {
	_LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
	range_difference_t<_View> __count_ = 0;

	template <bool>
	class __sentinel;

	public:
	_LIBCPP_HIDE_FROM_ABI take_view()
	requires default_initializable<_View>
	= default;

	_LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23
	take_view(_View __base, range_difference_t<_View> __count)
	: __base_(std::move(__base)), __count_(__count) {
	_LIBCPP_ASSERT_UNCATEGORIZED(__count >= 0, "count has to be greater than or equal to zero");
	}

	_LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
	requires copy_constructible<_View>
	{
	return __base_;
	}

	_LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }

	_LIBCPP_HIDE_FROM_ABI constexpr auto begin()
	requires(!__simple_view<_View>)
	{
	if constexpr (sized_range<_View>) {
	if constexpr (random_access_range<_View>) {
	return ranges::begin(__base_);
	} else {
	using _DifferenceT = range_difference_t<_View>;
	auto __size = size();
	return counted_iterator(ranges::begin(__base_), static_cast<_DifferenceT>(__size));
	}
	} else {
	return counted_iterator(ranges::begin(__base_), __count_);
	}
	}

	_LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
	requires range<const _View>
	{
	if constexpr (sized_range<const _View>) {
	if constexpr (random_access_range<const _View>) {
	return ranges::begin(__base_);
	} else {
	using _DifferenceT = range_difference_t<const _View>;
	auto __size = size();
	return counted_iterator(ranges::begin(__base_), static_cast<_DifferenceT>(__size));
	}
	} else {
	return counted_iterator(ranges::begin(__base_), __count_);
	}
	}

	_LIBCPP_HIDE_FROM_ABI constexpr auto end()
	requires(!__simple_view<_View>)
	{
	if constexpr (sized_range<_View>) {
	if constexpr (random_access_range<_View>) {
	return ranges::begin(__base_) + size();
	} else {
	return default_sentinel;
	}
	} else {
	return __sentinel<false>{ranges::end(__base_)};
	}
	}

	_LIBCPP_HIDE_FROM_ABI constexpr auto end() const
	requires range<const _View>
	{
	if constexpr (sized_range<const _View>) {
	if constexpr (random_access_range<const _View>) {
	return ranges::begin(__base_) + size();
	} else {
	return default_sentinel;
	}
	} else {
	return __sentinel<true>{ranges::end(__base_)};
	}
	}

	_LIBCPP_HIDE_FROM_ABI constexpr auto size()
	requires sized_range<_View>
	{
	auto __n = ranges::size(__base_);
	return ranges::min(__n, static_cast<decltype(__n)>(__count_));
	}

	_LIBCPP_HIDE_FROM_ABI constexpr auto size() const
	requires sized_range<const _View>
	{
	auto __n = ranges::size(__base_);
	return ranges::min(__n, static_cast<decltype(__n)>(__count_));
	}
	};

	template <view _View>
	template <bool _Const>
	class take_view<_View>::__sentinel {
	using _Base = __maybe_const<_Const, _View>;
	template <bool _OtherConst>
	using _Iter = counted_iterator<iterator_t<__maybe_const<_OtherConst, _View>>>;
	_LIBCPP_NO_UNIQUE_ADDRESS sentinel_t<_Base> __end_ = sentinel_t<_Base>();

	template <bool>
	friend class take_view<_View>::__sentinel;

	public:
	_LIBCPP_HIDE_FROM_ABI __sentinel() = default;

	_LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(sentinel_t<_Base> __end) : __end_(std::move(__end)) {}

	_LIBCPP_HIDE_FROM_ABI constexpr __sentinel(__sentinel<!_Const> __s)
	requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
	: __end_(std::move(__s.__end_)) {}

	_LIBCPP_HIDE_FROM_ABI constexpr sentinel_t<_Base> base() const { return __end_; }

	_LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const _Iter<_Const>& __lhs, const __sentinel& __rhs) {
	return __lhs.count() == 0 \|\| __lhs.base() == __rhs.__end_;
	}

	template <bool _OtherConst = !_Const>
	requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
	_LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const _Iter<_OtherConst>& __lhs, const __sentinel& __rhs) {
	return __lhs.count() == 0 \|\| __lhs.base() == __rhs.__end_;
	}
	};

	template <class _Range>
	take_view(_Range&&, range_difference_t<_Range>) -> take_view<views::all_t<_Range>>;

	template <class _Tp>
	inline constexpr bool enable_borrowed_range<take_view<_Tp>> = enable_borrowed_range<_Tp>;

	namespace views {
	namespace __take {

	template <class _Tp>
	inline constexpr bool __is_empty_view = false;

	template <class _Tp>
	inline constexpr bool __is_empty_view<empty_view<_Tp>> = true;

	template <class _Tp>
	inline constexpr bool __is_passthrough_specialization = false;

	template <class _Tp, size_t _Extent>
	inline constexpr bool __is_passthrough_specialization<span<_Tp, _Extent>> = true;

	template <class _CharT, class _Traits>
	inline constexpr bool __is_passthrough_specialization<basic_string_view<_CharT, _Traits>> = true;

	template <class _Iter, class _Sent, subrange_kind _Kind>
	inline constexpr bool __is_passthrough_specialization<subrange<_Iter, _Sent, _Kind>> = true;

	template <class _Tp>
	inline constexpr bool __is_iota_specialization = false;

	template <class _Np, class _Bound>
	inline constexpr bool __is_iota_specialization<iota_view<_Np, _Bound>> = true;

	template <class _Tp>
	struct __passthrough_type;

	template <class _Tp, size_t _Extent>
	struct __passthrough_type<span<_Tp, _Extent>> {
	using type = span<_Tp>;
	};

	template <class _CharT, class _Traits>
	struct __passthrough_type<basic_string_view<_CharT, _Traits>> {
	using type = basic_string_view<_CharT, _Traits>;
	};

	template <class _Iter, class _Sent, subrange_kind _Kind>
	requires requires { typename subrange<_Iter>; }
	struct __passthrough_type<subrange<_Iter, _Sent, _Kind>> {
	using type = subrange<_Iter>;
	};

	template <class _Tp>
	using __passthrough_type_t = typename __passthrough_type<_Tp>::type;

	struct __fn {
	// [range.take.overview]: the `empty_view` case.
	template <class _Range, convertible_to<range_difference_t<_Range>> _Np>
	requires __is_empty_view<remove_cvref_t<_Range>>
	[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&&) const
	noexcept(noexcept(_LIBCPP_AUTO_CAST(std::forward<_Range>(__range))))
	-> decltype(_LIBCPP_AUTO_CAST(std::forward<_Range>(__range))) {
	return _LIBCPP_AUTO_CAST(std::forward<_Range>(__range));
	}

	// [range.take.overview]: the `span \| basic_string_view \| subrange` case.
	template <class _Range,
	convertible_to<range_difference_t<_Range>> _Np,
	class _RawRange = remove_cvref_t<_Range>,
	class _Dist = range_difference_t<_Range>>
	requires(!__is_empty_view<_RawRange> && random_access_range<_RawRange> && sized_range<_RawRange> &&
	__is_passthrough_specialization<_RawRange>)
	[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto
	operator()(_Range&& __rng, _Np&& __n) const noexcept(noexcept(__passthrough_type_t<_RawRange>(
	ranges::begin(__rng), ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))))
	-> decltype(__passthrough_type_t<_RawRange>(
	// Note: deliberately not forwarding `__rng` to guard against double moves.
	ranges::begin(__rng),
	ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))) {
	return __passthrough_type_t<_RawRange>(
	ranges::begin(__rng), ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)));
	}

	// [range.take.overview]: the `iota_view` case.
	// clang-format off
	template <class _Range,
	convertible_to<range_difference_t<_Range>> _Np,
	class _RawRange = remove_cvref_t<_Range>,
	class _Dist = range_difference_t<_Range>>
	requires (!__is_empty_view<_RawRange> &&
	random_access_range<_RawRange> &&
	sized_range<_RawRange> &&
	__is_iota_specialization<_RawRange>)
	[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
	constexpr auto operator()(_Range&& __rng, _Np&& __n) const
	noexcept(noexcept(ranges::iota_view(
	*ranges::begin(__rng),
	*(ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))
	)))
	-> decltype( ranges::iota_view(
	// Note: deliberately not forwarding `__rng` to guard against double moves.
	*ranges::begin(__rng),
	*(ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))
	))
	{ return ranges::iota_view(
	*ranges::begin(__rng),
	*(ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))
	); }

	#if _LIBCPP_STD_VER >= 23
	// [range.take.overview]: the `repeat_view` "_RawRange models sized_range" case.
	template <class _Range,
	convertible_to<range_difference_t<_Range>> _Np,
	class _RawRange = remove_cvref_t<_Range>,
	class _Dist = range_difference_t<_Range>>
	requires(__is_repeat_specialization<_RawRange> && sized_range<_RawRange>)
	[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&& __n) const
	noexcept(noexcept(views::repeat(*__range.__value_, std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n)))))
	-> decltype( views::repeat(*__range.__value_, std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n))))
	{ return views::repeat(*__range.__value_, std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n))); }

	// [range.take.overview]: the `repeat_view` "otherwise" case.
	template <class _Range,
	convertible_to<range_difference_t<_Range>> _Np,
	class _RawRange = remove_cvref_t<_Range>,
	class _Dist = range_difference_t<_Range>>
	requires(__is_repeat_specialization<_RawRange> && !sized_range<_RawRange>)
	[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&& __n) const
	noexcept(noexcept(views::repeat(*__range.__value_, static_cast<_Dist>(__n))))
	-> decltype( views::repeat(*__range.__value_, static_cast<_Dist>(__n)))
	{ return views::repeat(*__range.__value_, static_cast<_Dist>(__n)); }
	#endif
	// clang-format on

	// [range.take.overview]: the "otherwise" case.
	template <class _Range, convertible_to<range_difference_t<_Range>> _Np, class _RawRange = remove_cvref_t<_Range>>
	// Note: without specifically excluding the other cases, GCC sees this overload as ambiguous with the other
	// overloads.
	requires(!(__is_empty_view<_RawRange> \|\|
	# if _LIBCPP_STD_VER >= 23
	__is_repeat_specialization<_RawRange> \|\|
	# endif
	(__is_iota_specialization<_RawRange> && sized_range<_RawRange> && random_access_range<_RawRange>) \|\|
	(__is_passthrough_specialization<_RawRange> && sized_range<_RawRange> &&
	random_access_range<_RawRange>)))
	[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&& __n) const
	noexcept(noexcept(take_view(std::forward<_Range>(__range), std::forward<_Np>(__n))))
	-> decltype(take_view(std::forward<_Range>(__range), std::forward<_Np>(__n))) {
	return take_view(std::forward<_Range>(__range), std::forward<_Np>(__n));
	}

	template <class _Np>
	requires constructible_from<decay_t<_Np>, _Np>
	[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Np&& __n) const
	noexcept(is_nothrow_constructible_v<decay_t<_Np>, _Np>) {
	return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Np>(__n)));
	}
	};

	} // namespace __take

	inline namespace __cpo {
	inline constexpr auto take = __take::__fn{};
	} // namespace __cpo
	} // namespace views

	} // namespace ranges

	#endif // _LIBCPP_STD_VER >= 20

	_LIBCPP_END_NAMESPACE_STD

	_LIBCPP_POP_MACROS

	#endif // _LIBCPP___RANGES_TAKE_VIEW_H