include/__iterator/reverse_iterator.h - 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___ITERATOR_REVERSE_ITERATOR_H
 #define _LIBCPP___ITERATOR_REVERSE_ITERATOR_H

 #include <__algorithm/unwrap_iter.h>
 #include <__compare/compare_three_way_result.h>
 #include <__compare/three_way_comparable.h>
 #include <__concepts/convertible_to.h>
 #include <__config>
 #include <__iterator/advance.h>
 #include <__iterator/concepts.h>
 #include <__iterator/incrementable_traits.h>
 #include <__iterator/iter_move.h>
 #include <__iterator/iter_swap.h>
 #include <__iterator/iterator.h>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/next.h>
 #include <__iterator/prev.h>
 #include <__iterator/readable_traits.h>
 #include <__iterator/segmented_iterator.h>
 #include <__memory/addressof.h>
 #include <__ranges/access.h>
 #include <__ranges/concepts.h>
 #include <__ranges/subrange.h>
 #include <__type_traits/conditional.h>
 #include <__type_traits/enable_if.h>
 #include <__type_traits/is_assignable.h>
 #include <__type_traits/is_convertible.h>
 #include <__type_traits/is_nothrow_constructible.h>
 #include <__type_traits/is_pointer.h>
 #include <__type_traits/is_same.h>
 #include <__utility/declval.h>
 #include <__utility/move.h>

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

 _LIBCPP_BEGIN_NAMESPACE_STD

 _LIBCPP_SUPPRESS_DEPRECATED_PUSH
 template <class _Iter>
 class _LIBCPP_TEMPLATE_VIS reverse_iterator
 #if _LIBCPP_STD_VER <= 14 || !defined(_LIBCPP_ABI_NO_ITERATOR_BASES)
     : public iterator<typename iterator_traits<_Iter>::iterator_category,
                       typename iterator_traits<_Iter>::value_type,
                       typename iterator_traits<_Iter>::difference_type,
                       typename iterator_traits<_Iter>::pointer,
                       typename iterator_traits<_Iter>::reference>
 #endif
 {
   _LIBCPP_SUPPRESS_DEPRECATED_POP

 private:
 #ifndef _LIBCPP_ABI_NO_ITERATOR_BASES
   _Iter __t_; // no longer used as of LWG #2360, not removed due to ABI break
 #endif

 #if _LIBCPP_STD_VER >= 20
   static_assert(__has_bidirectional_iterator_category<_Iter>::value || bidirectional_iterator<_Iter>,
                 "reverse_iterator<It> requires It to be a bidirectional iterator.");
 #endif // _LIBCPP_STD_VER >= 20

 protected:
   _Iter current;

 public:
   using iterator_type = _Iter;

   using iterator_category =
       _If<__has_random_access_iterator_category<_Iter>::value,
           random_access_iterator_tag,
           typename iterator_traits<_Iter>::iterator_category>;
   using pointer = typename iterator_traits<_Iter>::pointer;
 #if _LIBCPP_STD_VER >= 20
   using iterator_concept = _If<random_access_iterator<_Iter>, random_access_iterator_tag, bidirectional_iterator_tag>;
   using value_type       = iter_value_t<_Iter>;
   using difference_type  = iter_difference_t<_Iter>;
   using reference        = iter_reference_t<_Iter>;
 #else
   using value_type      = typename iterator_traits<_Iter>::value_type;
   using difference_type = typename iterator_traits<_Iter>::difference_type;
   using reference       = typename iterator_traits<_Iter>::reference;
 #endif

 #ifndef _LIBCPP_ABI_NO_ITERATOR_BASES
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator() : __t_(), current() {}

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 explicit reverse_iterator(_Iter __x) : __t_(__x), current(__x) {}

   template <class _Up, __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value, int> = 0>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator(const reverse_iterator<_Up>& __u)
       : __t_(__u.base()), current(__u.base()) {}

   template <class _Up,
             __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value &&
                               is_assignable<_Iter&, _Up const&>::value,
                           int> = 0>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator=(const reverse_iterator<_Up>& __u) {
     __t_ = current = __u.base();
     return *this;
   }
 #else
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator() : current() {}

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 explicit reverse_iterator(_Iter __x) : current(__x) {}

   template <class _Up, __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value, int> = 0>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator(const reverse_iterator<_Up>& __u)
       : current(__u.base()) {}

   template <class _Up,
             __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value &&
                               is_assignable<_Iter&, _Up const&>::value,
                           int> = 0>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator=(const reverse_iterator<_Up>& __u) {
     current = __u.base();
     return *this;
   }
 #endif
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _Iter base() const { return current; }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reference operator*() const {
     _Iter __tmp = current;
     return *--__tmp;
   }

 #if _LIBCPP_STD_VER >= 20
   _LIBCPP_HIDE_FROM_ABI constexpr pointer operator->() const
     requires is_pointer_v<_Iter> || requires(const _Iter __i) { __i.operator->(); }
   {
     if constexpr (is_pointer_v<_Iter>) {
       return std::prev(current);
     } else {
       return std::prev(current).operator->();
     }
   }
 #else
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pointer operator->() const { return std::addressof(operator*()); }
 #endif // _LIBCPP_STD_VER >= 20

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator++() {
     --current;
     return *this;
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator++(int) {
     reverse_iterator __tmp(*this);
     --current;
     return __tmp;
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator--() {
     ++current;
     return *this;
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator--(int) {
     reverse_iterator __tmp(*this);
     ++current;
     return __tmp;
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator+(difference_type __n) const {
     return reverse_iterator(current - __n);
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator+=(difference_type __n) {
     current -= __n;
     return *this;
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator-(difference_type __n) const {
     return reverse_iterator(current + __n);
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator-=(difference_type __n) {
     current += __n;
     return *this;
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reference operator[](difference_type __n) const {
     return *(*this + __n);
   }

 #if _LIBCPP_STD_VER >= 20
   _LIBCPP_HIDE_FROM_ABI friend constexpr iter_rvalue_reference_t<_Iter> iter_move(const reverse_iterator& __i) noexcept(
       is_nothrow_copy_constructible_v<_Iter>&& noexcept(ranges::iter_move(--std::declval<_Iter&>()))) {
     auto __tmp = __i.base();
     return ranges::iter_move(--__tmp);
   }

   template <indirectly_swappable<_Iter> _Iter2>
   _LIBCPP_HIDE_FROM_ABI friend constexpr void
   iter_swap(const reverse_iterator& __x, const reverse_iterator<_Iter2>& __y) noexcept(
       is_nothrow_copy_constructible_v<_Iter> &&
       is_nothrow_copy_constructible_v<_Iter2>&& noexcept(
           ranges::iter_swap(--std::declval<_Iter&>(), --std::declval<_Iter2&>()))) {
     auto __xtmp = __x.base();
     auto __ytmp = __y.base();
     ranges::iter_swap(--__xtmp, --__ytmp);
   }
 #endif // _LIBCPP_STD_VER >= 20
 };

 template <class _Iter1, class _Iter2>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
 operator==(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 #if _LIBCPP_STD_VER >= 20
   requires requires {
     { __x.base() == __y.base() } -> convertible_to<bool>;
   }
 #endif // _LIBCPP_STD_VER >= 20
 {
   return __x.base() == __y.base();
 }

 template <class _Iter1, class _Iter2>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
 operator<(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 #if _LIBCPP_STD_VER >= 20
   requires requires {
     { __x.base() > __y.base() } -> convertible_to<bool>;
   }
 #endif // _LIBCPP_STD_VER >= 20
 {
   return __x.base() > __y.base();
 }

 template <class _Iter1, class _Iter2>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
 operator!=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 #if _LIBCPP_STD_VER >= 20
   requires requires {
     { __x.base() != __y.base() } -> convertible_to<bool>;
   }
 #endif // _LIBCPP_STD_VER >= 20
 {
   return __x.base() != __y.base();
 }

 template <class _Iter1, class _Iter2>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
 operator>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 #if _LIBCPP_STD_VER >= 20
   requires requires {
     { __x.base() < __y.base() } -> convertible_to<bool>;
   }
 #endif // _LIBCPP_STD_VER >= 20
 {
   return __x.base() < __y.base();
 }

 template <class _Iter1, class _Iter2>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
 operator>=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 #if _LIBCPP_STD_VER >= 20
   requires requires {
     { __x.base() <= __y.base() } -> convertible_to<bool>;
   }
 #endif // _LIBCPP_STD_VER >= 20
 {
   return __x.base() <= __y.base();
 }

 template <class _Iter1, class _Iter2>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
 operator<=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 #if _LIBCPP_STD_VER >= 20
   requires requires {
     { __x.base() >= __y.base() } -> convertible_to<bool>;
   }
 #endif // _LIBCPP_STD_VER >= 20
 {
   return __x.base() >= __y.base();
 }

 #if _LIBCPP_STD_VER >= 20
 template <class _Iter1, three_way_comparable_with<_Iter1> _Iter2>
 _LIBCPP_HIDE_FROM_ABI constexpr compare_three_way_result_t<_Iter1, _Iter2>
 operator<=>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
   return __y.base() <=> __x.base();
 }
 #endif // _LIBCPP_STD_VER >= 20

 #ifndef _LIBCPP_CXX03_LANG
 template <class _Iter1, class _Iter2>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 auto
 operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
     -> decltype(__y.base() - __x.base()) {
   return __y.base() - __x.base();
 }
 #else
 template <class _Iter1, class _Iter2>
 inline _LIBCPP_HIDE_FROM_ABI typename reverse_iterator<_Iter1>::difference_type
 operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
   return __y.base() - __x.base();
 }
 #endif

 template <class _Iter>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator<_Iter>
 operator+(typename reverse_iterator<_Iter>::difference_type __n, const reverse_iterator<_Iter>& __x) {
   return reverse_iterator<_Iter>(__x.base() - __n);
 }

 #if _LIBCPP_STD_VER >= 20
 template <class _Iter1, class _Iter2>
   requires(!sized_sentinel_for<_Iter1, _Iter2>)
 inline constexpr bool disable_sized_sentinel_for<reverse_iterator<_Iter1>, reverse_iterator<_Iter2>> = true;
 #endif // _LIBCPP_STD_VER >= 20

 #if _LIBCPP_STD_VER >= 14
 template <class _Iter>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator<_Iter> make_reverse_iterator(_Iter __i) {
   return reverse_iterator<_Iter>(__i);
 }
 #endif

 #if _LIBCPP_STD_VER >= 20
 template <ranges::bidirectional_range _Range>
 _LIBCPP_HIDE_FROM_ABI constexpr ranges::subrange<reverse_iterator<ranges::iterator_t<_Range>>,
                                                  reverse_iterator<ranges::iterator_t<_Range>>>
 __reverse_range(_Range&& __range) {
   auto __first = ranges::begin(__range);
   return {std::make_reverse_iterator(ranges::next(__first, ranges::end(__range))), std::make_reverse_iterator(__first)};
 }
 #endif

 template <class _Iter, bool __b>
 struct __unwrap_iter_impl<reverse_iterator<reverse_iterator<_Iter> >, __b> {
   using _UnwrappedIter  = decltype(__unwrap_iter_impl<_Iter>::__unwrap(std::declval<_Iter>()));
   using _ReverseWrapper = reverse_iterator<reverse_iterator<_Iter> >;

   static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ReverseWrapper
   __rewrap(_ReverseWrapper __orig_iter, _UnwrappedIter __unwrapped_iter) {
     return _ReverseWrapper(
         reverse_iterator<_Iter>(__unwrap_iter_impl<_Iter>::__rewrap(__orig_iter.base().base(), __unwrapped_iter)));
   }

   static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _UnwrappedIter __unwrap(_ReverseWrapper __i) _NOEXCEPT {
     return __unwrap_iter_impl<_Iter>::__unwrap(__i.base().base());
   }
 };

 _LIBCPP_END_NAMESPACE_STD

 #endif // _LIBCPP___ITERATOR_REVERSE_ITERATOR_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___ITERATOR_REVERSE_ITERATOR_H
	#define _LIBCPP___ITERATOR_REVERSE_ITERATOR_H

	#include <__algorithm/unwrap_iter.h>
	#include <__compare/compare_three_way_result.h>
	#include <__compare/three_way_comparable.h>
	#include <__concepts/convertible_to.h>
	#include <__config>
	#include <__iterator/advance.h>
	#include <__iterator/concepts.h>
	#include <__iterator/incrementable_traits.h>
	#include <__iterator/iter_move.h>
	#include <__iterator/iter_swap.h>
	#include <__iterator/iterator.h>
	#include <__iterator/iterator_traits.h>
	#include <__iterator/next.h>
	#include <__iterator/prev.h>
	#include <__iterator/readable_traits.h>
	#include <__iterator/segmented_iterator.h>
	#include <__memory/addressof.h>
	#include <__ranges/access.h>
	#include <__ranges/concepts.h>
	#include <__ranges/subrange.h>
	#include <__type_traits/conditional.h>
	#include <__type_traits/enable_if.h>
	#include <__type_traits/is_assignable.h>
	#include <__type_traits/is_convertible.h>
	#include <__type_traits/is_nothrow_constructible.h>
	#include <__type_traits/is_pointer.h>
	#include <__type_traits/is_same.h>
	#include <__utility/declval.h>
	#include <__utility/move.h>

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

	_LIBCPP_BEGIN_NAMESPACE_STD

	_LIBCPP_SUPPRESS_DEPRECATED_PUSH
	template <class _Iter>
	class _LIBCPP_TEMPLATE_VIS reverse_iterator
	#if _LIBCPP_STD_VER <= 14 \|\| !defined(_LIBCPP_ABI_NO_ITERATOR_BASES)
	: public iterator<typename iterator_traits<_Iter>::iterator_category,
	typename iterator_traits<_Iter>::value_type,
	typename iterator_traits<_Iter>::difference_type,
	typename iterator_traits<_Iter>::pointer,
	typename iterator_traits<_Iter>::reference>
	#endif
	{
	_LIBCPP_SUPPRESS_DEPRECATED_POP

	private:
	#ifndef _LIBCPP_ABI_NO_ITERATOR_BASES
	_Iter __t_; // no longer used as of LWG #2360, not removed due to ABI break
	#endif

	#if _LIBCPP_STD_VER >= 20
	static_assert(__has_bidirectional_iterator_category<_Iter>::value \|\| bidirectional_iterator<_Iter>,
	"reverse_iterator<It> requires It to be a bidirectional iterator.");
	#endif // _LIBCPP_STD_VER >= 20

	protected:
	_Iter current;

	public:
	using iterator_type = _Iter;

	using iterator_category =
	_If<__has_random_access_iterator_category<_Iter>::value,
	random_access_iterator_tag,
	typename iterator_traits<_Iter>::iterator_category>;
	using pointer = typename iterator_traits<_Iter>::pointer;
	#if _LIBCPP_STD_VER >= 20
	using iterator_concept = _If<random_access_iterator<_Iter>, random_access_iterator_tag, bidirectional_iterator_tag>;
	using value_type = iter_value_t<_Iter>;
	using difference_type = iter_difference_t<_Iter>;
	using reference = iter_reference_t<_Iter>;
	#else
	using value_type = typename iterator_traits<_Iter>::value_type;
	using difference_type = typename iterator_traits<_Iter>::difference_type;
	using reference = typename iterator_traits<_Iter>::reference;
	#endif

	#ifndef _LIBCPP_ABI_NO_ITERATOR_BASES
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator() : __t_(), current() {}

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 explicit reverse_iterator(_Iter __x) : __t_(__x), current(__x) {}

	template <class _Up, __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value, int> = 0>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator(const reverse_iterator<_Up>& __u)
	: __t_(__u.base()), current(__u.base()) {}

	template <class _Up,
	__enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value &&
	is_assignable<_Iter&, _Up const&>::value,
	int> = 0>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator=(const reverse_iterator<_Up>& __u) {
	__t_ = current = __u.base();
	return *this;
	}
	#else
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator() : current() {}

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 explicit reverse_iterator(_Iter __x) : current(__x) {}

	template <class _Up, __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value, int> = 0>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator(const reverse_iterator<_Up>& __u)
	: current(__u.base()) {}

	template <class _Up,
	__enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value &&
	is_assignable<_Iter&, _Up const&>::value,
	int> = 0>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator=(const reverse_iterator<_Up>& __u) {
	current = __u.base();
	return *this;
	}
	#endif
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _Iter base() const { return current; }
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reference operator*() const {
	_Iter __tmp = current;
	return *--__tmp;
	}

	#if _LIBCPP_STD_VER >= 20
	_LIBCPP_HIDE_FROM_ABI constexpr pointer operator->() const
	requires is_pointer_v<_Iter> \|\| requires(const _Iter __i) { __i.operator->(); }
	{
	if constexpr (is_pointer_v<_Iter>) {
	return std::prev(current);
	} else {
	return std::prev(current).operator->();
	}
	}
	#else
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pointer operator->() const { return std::addressof(operator*()); }
	#endif // _LIBCPP_STD_VER >= 20

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator++() {
	--current;
	return *this;
	}
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator++(int) {
	reverse_iterator __tmp(*this);
	--current;
	return __tmp;
	}
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator--() {
	++current;
	return *this;
	}
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator--(int) {
	reverse_iterator __tmp(*this);
	++current;
	return __tmp;
	}
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator+(difference_type __n) const {
	return reverse_iterator(current - __n);
	}
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator+=(difference_type __n) {
	current -= __n;
	return *this;
	}
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator-(difference_type __n) const {
	return reverse_iterator(current + __n);
	}
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator-=(difference_type __n) {
	current += __n;
	return *this;
	}
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reference operator[](difference_type __n) const {
	return (this + __n);
	}

	#if _LIBCPP_STD_VER >= 20
	_LIBCPP_HIDE_FROM_ABI friend constexpr iter_rvalue_reference_t<_Iter> iter_move(const reverse_iterator& __i) noexcept(
	is_nothrow_copy_constructible_v<_Iter>&& noexcept(ranges::iter_move(--std::declval<_Iter&>()))) {
	auto __tmp = __i.base();
	return ranges::iter_move(--__tmp);
	}

	template <indirectly_swappable<_Iter> _Iter2>
	_LIBCPP_HIDE_FROM_ABI friend constexpr void
	iter_swap(const reverse_iterator& __x, const reverse_iterator<_Iter2>& __y) noexcept(
	is_nothrow_copy_constructible_v<_Iter> &&
	is_nothrow_copy_constructible_v<_Iter2>&& noexcept(
	ranges::iter_swap(--std::declval<_Iter&>(), --std::declval<_Iter2&>()))) {
	auto __xtmp = __x.base();
	auto __ytmp = __y.base();
	ranges::iter_swap(--__xtmp, --__ytmp);
	}
	#endif // _LIBCPP_STD_VER >= 20
	};

	template <class _Iter1, class _Iter2>
	inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
	operator==(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
	#if _LIBCPP_STD_VER >= 20
	requires requires {
	{ __x.base() == __y.base() } -> convertible_to<bool>;
	}
	#endif // _LIBCPP_STD_VER >= 20
	{
	return __x.base() == __y.base();
	}

	template <class _Iter1, class _Iter2>
	inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
	operator<(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
	#if _LIBCPP_STD_VER >= 20
	requires requires {
	{ __x.base() > __y.base() } -> convertible_to<bool>;
	}
	#endif // _LIBCPP_STD_VER >= 20
	{
	return __x.base() > __y.base();
	}

	template <class _Iter1, class _Iter2>
	inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
	operator!=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
	#if _LIBCPP_STD_VER >= 20
	requires requires {
	{ __x.base() != __y.base() } -> convertible_to<bool>;
	}
	#endif // _LIBCPP_STD_VER >= 20
	{
	return __x.base() != __y.base();
	}

	template <class _Iter1, class _Iter2>
	inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
	operator>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
	#if _LIBCPP_STD_VER >= 20
	requires requires {
	{ __x.base() < __y.base() } -> convertible_to<bool>;
	}
	#endif // _LIBCPP_STD_VER >= 20
	{
	return __x.base() < __y.base();
	}

	template <class _Iter1, class _Iter2>
	inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
	operator>=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
	#if _LIBCPP_STD_VER >= 20
	requires requires {
	{ __x.base() <= __y.base() } -> convertible_to<bool>;
	}
	#endif // _LIBCPP_STD_VER >= 20
	{
	return __x.base() <= __y.base();
	}

	template <class _Iter1, class _Iter2>
	inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
	operator<=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
	#if _LIBCPP_STD_VER >= 20
	requires requires {
	{ __x.base() >= __y.base() } -> convertible_to<bool>;
	}
	#endif // _LIBCPP_STD_VER >= 20
	{
	return __x.base() >= __y.base();
	}

	#if _LIBCPP_STD_VER >= 20
	template <class _Iter1, three_way_comparable_with<_Iter1> _Iter2>
	_LIBCPP_HIDE_FROM_ABI constexpr compare_three_way_result_t<_Iter1, _Iter2>
	operator<=>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
	return __y.base() <=> __x.base();
	}
	#endif // _LIBCPP_STD_VER >= 20

	#ifndef _LIBCPP_CXX03_LANG
	template <class _Iter1, class _Iter2>
	inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 auto
	operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
	-> decltype(__y.base() - __x.base()) {
	return __y.base() - __x.base();
	}
	#else
	template <class _Iter1, class _Iter2>
	inline _LIBCPP_HIDE_FROM_ABI typename reverse_iterator<_Iter1>::difference_type
	operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
	return __y.base() - __x.base();
	}
	#endif

	template <class _Iter>
	inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator<_Iter>
	operator+(typename reverse_iterator<_Iter>::difference_type __n, const reverse_iterator<_Iter>& __x) {
	return reverse_iterator<_Iter>(__x.base() - __n);
	}

	#if _LIBCPP_STD_VER >= 20
	template <class _Iter1, class _Iter2>
	requires(!sized_sentinel_for<_Iter1, _Iter2>)
	inline constexpr bool disable_sized_sentinel_for<reverse_iterator<_Iter1>, reverse_iterator<_Iter2>> = true;
	#endif // _LIBCPP_STD_VER >= 20

	#if _LIBCPP_STD_VER >= 14
	template <class _Iter>
	inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator<_Iter> make_reverse_iterator(_Iter __i) {
	return reverse_iterator<_Iter>(__i);
	}
	#endif

	#if _LIBCPP_STD_VER >= 20
	template <ranges::bidirectional_range _Range>
	_LIBCPP_HIDE_FROM_ABI constexpr ranges::subrange<reverse_iterator<ranges::iterator_t<_Range>>,
	reverse_iterator<ranges::iterator_t<_Range>>>
	__reverse_range(_Range&& __range) {
	auto __first = ranges::begin(__range);
	return {std::make_reverse_iterator(ranges::next(__first, ranges::end(__range))), std::make_reverse_iterator(__first)};
	}
	#endif

	template <class _Iter, bool __b>
	struct __unwrap_iter_impl<reverse_iterator<reverse_iterator<_Iter> >, __b> {
	using _UnwrappedIter = decltype(__unwrap_iter_impl<_Iter>::__unwrap(std::declval<_Iter>()));
	using _ReverseWrapper = reverse_iterator<reverse_iterator<_Iter> >;

	static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ReverseWrapper
	__rewrap(_ReverseWrapper __orig_iter, _UnwrappedIter __unwrapped_iter) {
	return _ReverseWrapper(
	reverse_iterator<_Iter>(__unwrap_iter_impl<_Iter>::__rewrap(__orig_iter.base().base(), __unwrapped_iter)));
	}

	static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _UnwrappedIter __unwrap(_ReverseWrapper __i) _NOEXCEPT {
	return __unwrap_iter_impl<_Iter>::__unwrap(__i.base().base());
	}
	};

	_LIBCPP_END_NAMESPACE_STD

	#endif // _LIBCPP___ITERATOR_REVERSE_ITERATOR_H