libcxx/include/__ranges/rend.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___RANGES_REND_H
  11 #define _LIBCPP___RANGES_REND_H
  12
  13 #include <__concepts/class_or_enum.h>
  14 #include <__concepts/same_as.h>
  15 #include <__config>
  16 #include <__iterator/concepts.h>
  17 #include <__iterator/readable_traits.h>
  18 #include <__iterator/reverse_iterator.h>
  19 #include <__ranges/access.h>
  20 #include <__ranges/rbegin.h>
  21 #include <__type_traits/decay.h>
  22 #include <__type_traits/is_reference.h>
  23 #include <__type_traits/remove_cvref.h>
  24 #include <__type_traits/remove_reference.h>
  25 #include <__utility/auto_cast.h>
  26
  27 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  28 #  pragma GCC system_header
  29 #endif
  30
  31 _LIBCPP_BEGIN_NAMESPACE_STD
  32
  33 #if _LIBCPP_STD_VER >= 20
  34
  35 // [range.access.rend]
  36
  37 namespace ranges {
  38 namespace __rend {
  39 template <class _Tp>
  40 concept __member_rend =
  41   __can_borrow<_Tp> &&
  42   __workaround_52970<_Tp> &&
  43   requires(_Tp&& __t) {
  44     ranges::rbegin(__t);
  45     { _LIBCPP_AUTO_CAST(__t.rend()) } -> sentinel_for<decltype(ranges::rbegin(__t))>;
  46   };
  47
  48 void rend(auto&) = delete;
  49 void rend(const auto&) = delete;
  50
  51 template <class _Tp>
  52 concept __unqualified_rend =
  53   !__member_rend<_Tp> &&
  54   __can_borrow<_Tp> &&
  55   __class_or_enum<remove_cvref_t<_Tp>> &&
  56   requires(_Tp&& __t) {
  57     ranges::rbegin(__t);
  58     { _LIBCPP_AUTO_CAST(rend(__t)) } -> sentinel_for<decltype(ranges::rbegin(__t))>;
  59   };
  60
  61 template <class _Tp>
  62 concept __can_reverse =
  63   __can_borrow<_Tp> &&
  64   !__member_rend<_Tp> &&
  65   !__unqualified_rend<_Tp> &&
  66   requires(_Tp&& __t) {
  67     { ranges::begin(__t) } -> same_as<decltype(ranges::end(__t))>;
  68     { ranges::begin(__t) } -> bidirectional_iterator;
  69   };
  70
  71 class __fn {
  72 public:
  73   template <class _Tp>
  74     requires __member_rend<_Tp>
  75   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
  76     noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.rend())))
  77   {
  78     return _LIBCPP_AUTO_CAST(__t.rend());
  79   }
  80
  81   template <class _Tp>
  82     requires __unqualified_rend<_Tp>
  83   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
  84     noexcept(noexcept(_LIBCPP_AUTO_CAST(rend(__t))))
  85   {
  86     return _LIBCPP_AUTO_CAST(rend(__t));
  87   }
  88
  89   template <class _Tp>
  90     requires __can_reverse<_Tp>
  91   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
  92     noexcept(noexcept(ranges::begin(__t)))
  93   {
  94     return std::make_reverse_iterator(ranges::begin(__t));
  95   }
  96
  97   void operator()(auto&&) const = delete;
  98 };
  99 } // namespace __rend
 100
 101 inline namespace __cpo {
 102   inline constexpr auto rend = __rend::__fn{};
 103 } // namespace __cpo
 104 } // namespace ranges
 105
 106 // [range.access.crend]
 107
 108 namespace ranges {
 109 namespace __crend {
 110 struct __fn {
 111   template <class _Tp>
 112     requires is_lvalue_reference_v<_Tp&&>
 113   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
 114   constexpr auto operator()(_Tp&& __t) const
 115     noexcept(noexcept(ranges::rend(static_cast<const remove_reference_t<_Tp>&>(__t))))
 116     -> decltype(      ranges::rend(static_cast<const remove_reference_t<_Tp>&>(__t)))
 117     { return          ranges::rend(static_cast<const remove_reference_t<_Tp>&>(__t)); }
 118
 119   template <class _Tp>
 120     requires is_rvalue_reference_v<_Tp&&>
 121   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
 122   constexpr auto operator()(_Tp&& __t) const
 123     noexcept(noexcept(ranges::rend(static_cast<const _Tp&&>(__t))))
 124     -> decltype(      ranges::rend(static_cast<const _Tp&&>(__t)))
 125     { return          ranges::rend(static_cast<const _Tp&&>(__t)); }
 126 };
 127 } // namespace __crend
 128
 129 inline namespace __cpo {
 130   inline constexpr auto crend = __crend::__fn{};
 131 } // namespace __cpo
 132 } // namespace ranges
 133
 134 #endif // _LIBCPP_STD_VER >= 20
 135
 136 _LIBCPP_END_NAMESPACE_STD
 137
 138 #endif // _LIBCPP___RANGES_REND_H