libcxx/include/__ranges/rbegin.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_RBEGIN_H
  11 #define _LIBCPP___RANGES_RBEGIN_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 <__type_traits/decay.h>
  21 #include <__type_traits/is_reference.h>
  22 #include <__type_traits/remove_cvref.h>
  23 #include <__type_traits/remove_reference.h>
  24 #include <__utility/auto_cast.h>
  25
  26 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  27 #  pragma GCC system_header
  28 #endif
  29
  30 _LIBCPP_BEGIN_NAMESPACE_STD
  31
  32 #if _LIBCPP_STD_VER >= 20
  33
  34 // [ranges.access.rbegin]
  35
  36 namespace ranges {
  37 namespace __rbegin {
  38 template <class _Tp>
  39 concept __member_rbegin =
  40   __can_borrow<_Tp> &&
  41   __workaround_52970<_Tp> &&
  42   requires(_Tp&& __t) {
  43     { _LIBCPP_AUTO_CAST(__t.rbegin()) } -> input_or_output_iterator;
  44   };
  45
  46 void rbegin(auto&) = delete;
  47 void rbegin(const auto&) = delete;
  48
  49 template <class _Tp>
  50 concept __unqualified_rbegin =
  51   !__member_rbegin<_Tp> &&
  52   __can_borrow<_Tp> &&
  53   __class_or_enum<remove_cvref_t<_Tp>> &&
  54   requires(_Tp&& __t) {
  55     { _LIBCPP_AUTO_CAST(rbegin(__t)) } -> input_or_output_iterator;
  56   };
  57
  58 template <class _Tp>
  59 concept __can_reverse =
  60   __can_borrow<_Tp> &&
  61   !__member_rbegin<_Tp> &&
  62   !__unqualified_rbegin<_Tp> &&
  63   requires(_Tp&& __t) {
  64     { ranges::begin(__t) } -> same_as<decltype(ranges::end(__t))>;
  65     { ranges::begin(__t) } -> bidirectional_iterator;
  66   };
  67
  68 struct __fn {
  69   template <class _Tp>
  70     requires __member_rbegin<_Tp>
  71   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
  72     noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.rbegin())))
  73   {
  74     return _LIBCPP_AUTO_CAST(__t.rbegin());
  75   }
  76
  77   template <class _Tp>
  78     requires __unqualified_rbegin<_Tp>
  79   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
  80     noexcept(noexcept(_LIBCPP_AUTO_CAST(rbegin(__t))))
  81   {
  82     return _LIBCPP_AUTO_CAST(rbegin(__t));
  83   }
  84
  85   template <class _Tp>
  86     requires __can_reverse<_Tp>
  87   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
  88     noexcept(noexcept(ranges::end(__t)))
  89   {
  90     return std::make_reverse_iterator(ranges::end(__t));
  91   }
  92
  93   void operator()(auto&&) const = delete;
  94 };
  95 } // namespace __rbegin
  96
  97 inline namespace __cpo {
  98   inline constexpr auto rbegin = __rbegin::__fn{};
  99 } // namespace __cpo
 100 } // namespace ranges
 101
 102 // [range.access.crbegin]
 103
 104 namespace ranges {
 105 namespace __crbegin {
 106 struct __fn {
 107   template <class _Tp>
 108     requires is_lvalue_reference_v<_Tp&&>
 109   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
 110   constexpr auto operator()(_Tp&& __t) const
 111     noexcept(noexcept(ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t))))
 112     -> decltype(      ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t)))
 113     { return          ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t)); }
 114
 115   template <class _Tp>
 116     requires is_rvalue_reference_v<_Tp&&>
 117   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
 118   constexpr auto operator()(_Tp&& __t) const
 119     noexcept(noexcept(ranges::rbegin(static_cast<const _Tp&&>(__t))))
 120     -> decltype(      ranges::rbegin(static_cast<const _Tp&&>(__t)))
 121     { return          ranges::rbegin(static_cast<const _Tp&&>(__t)); }
 122 };
 123 } // namespace __crbegin
 124
 125 inline namespace __cpo {
 126   inline constexpr auto crbegin = __crbegin::__fn{};
 127 } // namespace __cpo
 128 } // namespace ranges
 129
 130 #endif // _LIBCPP_STD_VER >= 20
 131
 132 _LIBCPP_END_NAMESPACE_STD
 133
 134 #endif // _LIBCPP___RANGES_RBEGIN_H