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