v1/__ranges/rend.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___RANGES_REND_H
0011 #define _LIBCPP___RANGES_REND_H
0012
0013 #include <__concepts/class_or_enum.h>
0014 #include <__concepts/same_as.h>
0015 #include <__config>
0016 #include <__iterator/concepts.h>
0017 #include <__iterator/readable_traits.h>
0018 #include <__iterator/reverse_iterator.h>
0019 #include <__ranges/access.h>
0020 #include <__ranges/rbegin.h>
0021 #include <__type_traits/decay.h>
0022 #include <__type_traits/is_reference.h>
0023 #include <__type_traits/remove_cvref.h>
0024 #include <__type_traits/remove_reference.h>
0025 #include <__utility/auto_cast.h>
0026
0027 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0028 #  pragma GCC system_header
0029 #endif
0030
0031 _LIBCPP_BEGIN_NAMESPACE_STD
0032
0033 #if _LIBCPP_STD_VER >= 20
0034
0035 // [range.access.rend]
0036
0037 namespace ranges {
0038 namespace __rend {
0039 template <class _Tp>
0040 concept __member_rend = __can_borrow<_Tp> && requires(_Tp&& __t) {
0041   ranges::rbegin(__t);
0042   { _LIBCPP_AUTO_CAST(__t.rend()) } -> sentinel_for<decltype(ranges::rbegin(__t))>;
0043 };
0044
0045 void rend() = delete;
0046
0047 template <class _Tp>
0048 concept __unqualified_rend =
0049     !__member_rend<_Tp> && __can_borrow<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
0050       ranges::rbegin(__t);
0051       { _LIBCPP_AUTO_CAST(rend(__t)) } -> sentinel_for<decltype(ranges::rbegin(__t))>;
0052     };
0053
0054 template <class _Tp>
0055 concept __can_reverse = __can_borrow<_Tp> && !__member_rend<_Tp> && !__unqualified_rend<_Tp> && requires(_Tp&& __t) {
0056   { ranges::begin(__t) } -> same_as<decltype(ranges::end(__t))>;
0057   { ranges::begin(__t) } -> bidirectional_iterator;
0058 };
0059
0060 class __fn {
0061 public:
0062   template <class _Tp>
0063     requires __member_rend<_Tp>
0064   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
0065       noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.rend()))) {
0066     return _LIBCPP_AUTO_CAST(__t.rend());
0067   }
0068
0069   template <class _Tp>
0070     requires __unqualified_rend<_Tp>
0071   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
0072       noexcept(noexcept(_LIBCPP_AUTO_CAST(rend(__t)))) {
0073     return _LIBCPP_AUTO_CAST(rend(__t));
0074   }
0075
0076   template <class _Tp>
0077     requires __can_reverse<_Tp>
0078   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
0079       noexcept(noexcept(ranges::begin(__t))) {
0080     return std::make_reverse_iterator(ranges::begin(__t));
0081   }
0082
0083   void operator()(auto&&) const = delete;
0084 };
0085 } // namespace __rend
0086
0087 inline namespace __cpo {
0088 inline constexpr auto rend = __rend::__fn{};
0089 } // namespace __cpo
0090 } // namespace ranges
0091
0092 // [range.access.crend]
0093
0094 namespace ranges {
0095 namespace __crend {
0096 struct __fn {
0097   template <class _Tp>
0098     requires is_lvalue_reference_v<_Tp&&>
0099   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
0100       noexcept(noexcept(ranges::rend(static_cast<const remove_reference_t<_Tp>&>(__t))))
0101           -> decltype(ranges::rend(static_cast<const remove_reference_t<_Tp>&>(__t))) {
0102     return ranges::rend(static_cast<const remove_reference_t<_Tp>&>(__t));
0103   }
0104
0105   template <class _Tp>
0106     requires is_rvalue_reference_v<_Tp&&>
0107   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const noexcept(
0108       noexcept(ranges::rend(static_cast<const _Tp&&>(__t)))) -> decltype(ranges::rend(static_cast<const _Tp&&>(__t))) {
0109     return ranges::rend(static_cast<const _Tp&&>(__t));
0110   }
0111 };
0112 } // namespace __crend
0113
0114 inline namespace __cpo {
0115 inline constexpr auto crend = __crend::__fn{};
0116 } // namespace __cpo
0117 } // namespace ranges
0118
0119 #endif // _LIBCPP_STD_VER >= 20
0120
0121 _LIBCPP_END_NAMESPACE_STD
0122
0123 #endif // _LIBCPP___RANGES_REND_H