include/__ranges/drop_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_DROP_VIEW_H
 #define _LIBCPP___RANGES_DROP_VIEW_H

 #include <__algorithm/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/distance.h>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/next.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/non_propagating_cache.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/conditional.h>
 #include <__type_traits/decay.h>
 #include <__type_traits/is_nothrow_constructible.h>
 #include <__type_traits/make_unsigned.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 drop_view : public view_interface<drop_view<_View>> {
   // We cache begin() whenever ranges::next is not guaranteed O(1) to provide an
   // amortized O(1) begin() method. If this is an input_range, then we cannot cache
   // begin because begin is not equality preserving.
   // Note: drop_view<input-range>::begin() is still trivially amortized O(1) because
   // one can't call begin() on it more than once.
   static constexpr bool _UseCache = forward_range<_View> && !(random_access_range<_View> && sized_range<_View>);
   using _Cache                    = _If<_UseCache, __non_propagating_cache<iterator_t<_View>>, __empty_cache>;
   _LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache();
   range_difference_t<_View> __count_               = 0;
   _View __base_                                    = _View();

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

   _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23
   drop_view(_View __base, range_difference_t<_View> __count)
       : __count_(__count), __base_(std::move(__base)) {
     _LIBCPP_ASSERT_UNCATEGORIZED(__count_ >= 0, "count must 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> && random_access_range<const _View> && sized_range<const _View>))
   {
     if constexpr (random_access_range<_View> && sized_range<_View>) {
       const auto __dist = std::min(ranges::distance(__base_), __count_);
       return ranges::begin(__base_) + __dist;
     }
     if constexpr (_UseCache)
       if (__cached_begin_.__has_value())
         return *__cached_begin_;

     auto __tmp = ranges::next(ranges::begin(__base_), __count_, ranges::end(__base_));
     if constexpr (_UseCache)
       __cached_begin_.__emplace(__tmp);
     return __tmp;
   }

   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
     requires random_access_range<const _View> && sized_range<const _View>
   {
     const auto __dist = std::min(ranges::distance(__base_), __count_);
     return ranges::begin(__base_) + __dist;
   }

   _LIBCPP_HIDE_FROM_ABI constexpr auto end()
     requires(!__simple_view<_View>)
   {
     return ranges::end(__base_);
   }

   _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
     requires range<const _View>
   {
     return ranges::end(__base_);
   }

   _LIBCPP_HIDE_FROM_ABI static constexpr auto __size(auto& __self) {
     const auto __s = ranges::size(__self.__base_);
     const auto __c = static_cast<decltype(__s)>(__self.__count_);
     return __s < __c ? 0 : __s - __c;
   }

   _LIBCPP_HIDE_FROM_ABI constexpr auto size()
     requires sized_range<_View>
   {
     return __size(*this);
   }

   _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
     requires sized_range<const _View>
   {
     return __size(*this);
   }
 };

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

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

 namespace views {
 namespace __drop {

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

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

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

 template <class _Iter, class _Sent, subrange_kind _Kind>
 inline constexpr bool __is_subrange_specialization_with_store_size<subrange<_Iter, _Sent, _Kind>> =
     subrange<_Iter, _Sent, _Kind>::_StoreSize;

 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 _Np, class _Bound>
 struct __passthrough_type<iota_view<_Np, _Bound>> {
   using type = iota_view<_Np, _Bound>;
 };

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

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

 struct __fn {
   // [range.drop.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.drop.overview]: the `span | basic_string_view | iota_view | subrange (StoreSize == false)` 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) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)), ranges::end(__rng))))
           -> decltype(__passthrough_type_t<_RawRange>(
               // Note: deliberately not forwarding `__rng` to guard against double moves.
               ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)),
               ranges::end(__rng))) {
     return __passthrough_type_t<_RawRange>(
         ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)), ranges::end(__rng));
   }

   // [range.drop.overview]: the `subrange (StoreSize == true)` 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_subrange_specialization_with_store_size<_RawRange>)
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __rng, _Np&& __n) const noexcept(noexcept(
       _RawRange(ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)),
                 ranges::end(__rng),
                 std::__to_unsigned_like(ranges::distance(__rng) -
                                         std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n))))))
       -> decltype(_RawRange(
           // Note: deliberately not forwarding `__rng` to guard against double moves.
           ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)),
           ranges::end(__rng),
           std::__to_unsigned_like(ranges::distance(__rng) -
                                   std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n))))) {
     // Introducing local variables avoids calculating `min` and `distance` twice (at the cost of diverging from the
     // expression used in the `noexcept` clause and the return statement).
     auto __dist    = ranges::distance(__rng);
     auto __clamped = std::min<_Dist>(__dist, std::forward<_Np>(__n));
     return _RawRange(ranges::begin(__rng) + __clamped, ranges::end(__rng), std::__to_unsigned_like(__dist - __clamped));
   }
   // clang-format off
 #if _LIBCPP_STD_VER >= 23
   // [range.drop.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_, ranges::distance(__range) - std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n)))))
     -> decltype(      views::repeat(*__range.__value_, ranges::distance(__range) - std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n))))
     { return          views::repeat(*__range.__value_, ranges::distance(__range) - std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n))); }

   // [range.drop.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&&) 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)); }
 #endif
   // clang-format on

   // [range.drop.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_subrange_specialization_with_store_size<_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(drop_view(std::forward<_Range>(__range), std::forward<_Np>(__n))))
           -> decltype(drop_view(std::forward<_Range>(__range), std::forward<_Np>(__n))) {
     return drop_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 __drop

 inline namespace __cpo {
 inline constexpr auto drop = __drop::__fn{};
 } // namespace __cpo
 } // namespace views

 } // namespace ranges

 #endif // _LIBCPP_STD_VER >= 20

 _LIBCPP_END_NAMESPACE_STD

 _LIBCPP_POP_MACROS

 #endif // _LIBCPP___RANGES_DROP_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_DROP_VIEW_H
	#define _LIBCPP___RANGES_DROP_VIEW_H

	#include <__algorithm/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/distance.h>
	#include <__iterator/iterator_traits.h>
	#include <__iterator/next.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/non_propagating_cache.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/conditional.h>
	#include <__type_traits/decay.h>
	#include <__type_traits/is_nothrow_constructible.h>
	#include <__type_traits/make_unsigned.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 drop_view : public view_interface<drop_view<_View>> {
	// We cache begin() whenever ranges::next is not guaranteed O(1) to provide an
	// amortized O(1) begin() method. If this is an input_range, then we cannot cache
	// begin because begin is not equality preserving.
	// Note: drop_view<input-range>::begin() is still trivially amortized O(1) because
	// one can't call begin() on it more than once.
	static constexpr bool _UseCache = forward_range<_View> && !(random_access_range<_View> && sized_range<_View>);
	using _Cache = _If<_UseCache, __non_propagating_cache<iterator_t<_View>>, __empty_cache>;
	_LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache();
	range_difference_t<_View> __count_ = 0;
	_View __base_ = _View();

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

	_LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23
	drop_view(_View __base, range_difference_t<_View> __count)
	: __count_(__count), __base_(std::move(__base)) {
	_LIBCPP_ASSERT_UNCATEGORIZED(__count_ >= 0, "count must 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> && random_access_range<const _View> && sized_range<const _View>))
	{
	if constexpr (random_access_range<_View> && sized_range<_View>) {
	const auto __dist = std::min(ranges::distance(__base_), __count_);
	return ranges::begin(__base_) + __dist;
	}
	if constexpr (_UseCache)
	if (__cached_begin_.__has_value())
	return *__cached_begin_;

	auto __tmp = ranges::next(ranges::begin(__base_), __count_, ranges::end(__base_));
	if constexpr (_UseCache)
	__cached_begin_.__emplace(__tmp);
	return __tmp;
	}

	_LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
	requires random_access_range<const _View> && sized_range<const _View>
	{
	const auto __dist = std::min(ranges::distance(__base_), __count_);
	return ranges::begin(__base_) + __dist;
	}

	_LIBCPP_HIDE_FROM_ABI constexpr auto end()
	requires(!__simple_view<_View>)
	{
	return ranges::end(__base_);
	}

	_LIBCPP_HIDE_FROM_ABI constexpr auto end() const
	requires range<const _View>
	{
	return ranges::end(__base_);
	}

	_LIBCPP_HIDE_FROM_ABI static constexpr auto __size(auto& __self) {
	const auto __s = ranges::size(__self.__base_);
	const auto __c = static_cast<decltype(__s)>(__self.__count_);
	return __s < __c ? 0 : __s - __c;
	}

	_LIBCPP_HIDE_FROM_ABI constexpr auto size()
	requires sized_range<_View>
	{
	return __size(*this);
	}

	_LIBCPP_HIDE_FROM_ABI constexpr auto size() const
	requires sized_range<const _View>
	{
	return __size(*this);
	}
	};

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

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

	namespace views {
	namespace __drop {

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

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

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

	template <class _Iter, class _Sent, subrange_kind _Kind>
	inline constexpr bool __is_subrange_specialization_with_store_size<subrange<_Iter, _Sent, _Kind>> =
	subrange<_Iter, _Sent, _Kind>::_StoreSize;

	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 _Np, class _Bound>
	struct __passthrough_type<iota_view<_Np, _Bound>> {
	using type = iota_view<_Np, _Bound>;
	};

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

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

	struct __fn {
	// [range.drop.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.drop.overview]: the `span \| basic_string_view \| iota_view \| subrange (StoreSize == false)` 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) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)), ranges::end(__rng))))
	-> decltype(__passthrough_type_t<_RawRange>(
	// Note: deliberately not forwarding `__rng` to guard against double moves.
	ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)),
	ranges::end(__rng))) {
	return __passthrough_type_t<_RawRange>(
	ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)), ranges::end(__rng));
	}

	// [range.drop.overview]: the `subrange (StoreSize == true)` 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_subrange_specialization_with_store_size<_RawRange>)
	[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __rng, _Np&& __n) const noexcept(noexcept(
	_RawRange(ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)),
	ranges::end(__rng),
	std::__to_unsigned_like(ranges::distance(__rng) -
	std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n))))))
	-> decltype(_RawRange(
	// Note: deliberately not forwarding `__rng` to guard against double moves.
	ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)),
	ranges::end(__rng),
	std::__to_unsigned_like(ranges::distance(__rng) -
	std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n))))) {
	// Introducing local variables avoids calculating `min` and `distance` twice (at the cost of diverging from the
	// expression used in the `noexcept` clause and the return statement).
	auto __dist = ranges::distance(__rng);
	auto __clamped = std::min<_Dist>(__dist, std::forward<_Np>(__n));
	return _RawRange(ranges::begin(__rng) + __clamped, ranges::end(__rng), std::__to_unsigned_like(__dist - __clamped));
	}
	// clang-format off
	#if _LIBCPP_STD_VER >= 23
	// [range.drop.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_, ranges::distance(__range) - std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n)))))
	-> decltype( views::repeat(*__range.__value_, ranges::distance(__range) - std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n))))
	{ return views::repeat(*__range.__value_, ranges::distance(__range) - std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n))); }

	// [range.drop.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&&) 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)); }
	#endif
	// clang-format on

	// [range.drop.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_subrange_specialization_with_store_size<_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(drop_view(std::forward<_Range>(__range), std::forward<_Np>(__n))))
	-> decltype(drop_view(std::forward<_Range>(__range), std::forward<_Np>(__n))) {
	return drop_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 __drop

	inline namespace __cpo {
	inline constexpr auto drop = __drop::__fn{};
	} // namespace __cpo
	} // namespace views

	} // namespace ranges

	#endif // _LIBCPP_STD_VER >= 20

	_LIBCPP_END_NAMESPACE_STD

	_LIBCPP_POP_MACROS

	#endif // _LIBCPP___RANGES_DROP_VIEW_H