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 = __can_borrow<_Tp> && requires(_Tp&& __t) {
  41   ranges::rbegin(__t);
  42   { _LIBCPP_AUTO_CAST(__t.rend()) } -> sentinel_for<decltype(ranges::rbegin(__t))>;
  43 };
  44
  45 void rend() = delete;
  46
  47 template <class _Tp>
  48 concept __unqualified_rend =
  49     !__member_rend<_Tp> && __can_borrow<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
  50       ranges::rbegin(__t);
  51       { _LIBCPP_AUTO_CAST(rend(__t)) } -> sentinel_for<decltype(ranges::rbegin(__t))>;
  52     };
  53
  54 template <class _Tp>
  55 concept __can_reverse = __can_borrow<_Tp> && !__member_rend<_Tp> && !__unqualified_rend<_Tp> && requires(_Tp&& __t) {
  56   { ranges::begin(__t) } -> same_as<decltype(ranges::end(__t))>;
  57   { ranges::begin(__t) } -> bidirectional_iterator;
  58 };
  59
  60 class __fn {
  61 public:
  62   template <class _Tp>
  63     requires __member_rend<_Tp>
  64   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
  65       noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.rend()))) {
  66     return _LIBCPP_AUTO_CAST(__t.rend());
  67   }
  68
  69   template <class _Tp>
  70     requires __unqualified_rend<_Tp>
  71   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
  72       noexcept(noexcept(_LIBCPP_AUTO_CAST(rend(__t)))) {
  73     return _LIBCPP_AUTO_CAST(rend(__t));
  74   }
  75
  76   template <class _Tp>
  77     requires __can_reverse<_Tp>
  78   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
  79       noexcept(noexcept(ranges::begin(__t))) {
  80     return std::make_reverse_iterator(ranges::begin(__t));
  81   }
  82
  83   void operator()(auto&&) const = delete;
  84 };
  85 } // namespace __rend
  86
  87 inline namespace __cpo {
  88 inline constexpr auto rend = __rend::__fn{};
  89 } // namespace __cpo
  90 } // namespace ranges
  91
  92 // [range.access.crend]
  93
  94 namespace ranges {
  95 namespace __crend {
  96 struct __fn {
  97   template <class _Tp>
  98     requires is_lvalue_reference_v<_Tp&&>
  99   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
 100       noexcept(noexcept(ranges::rend(static_cast<const remove_reference_t<_Tp>&>(__t))))
 101           -> decltype(ranges::rend(static_cast<const remove_reference_t<_Tp>&>(__t))) {
 102     return ranges::rend(static_cast<const remove_reference_t<_Tp>&>(__t));
 103   }
 104
 105   template <class _Tp>
 106     requires is_rvalue_reference_v<_Tp&&>
 107   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const noexcept(
 108       noexcept(ranges::rend(static_cast<const _Tp&&>(__t)))) -> decltype(ranges::rend(static_cast<const _Tp&&>(__t))) {
 109     return ranges::rend(static_cast<const _Tp&&>(__t));
 110   }
 111 };
 112 } // namespace __crend
 113
 114 inline namespace __cpo {
 115 inline constexpr auto crend = __crend::__fn{};
 116 } // namespace __cpo
 117 } // namespace ranges
 118
 119 #endif // _LIBCPP_STD_VER >= 20
 120
 121 _LIBCPP_END_NAMESPACE_STD
 122
 123 #endif // _LIBCPP___RANGES_REND_H