v1/__ranges/rbegin.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_RBEGIN_H
0011 #define _LIBCPP___RANGES_RBEGIN_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 <__type_traits/decay.h>
0021 #include <__type_traits/is_reference.h>
0022 #include <__type_traits/remove_cvref.h>
0023 #include <__type_traits/remove_reference.h>
0024 #include <__utility/auto_cast.h>
0025
0026 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0027 #  pragma GCC system_header
0028 #endif
0029
0030 _LIBCPP_BEGIN_NAMESPACE_STD
0031
0032 #if _LIBCPP_STD_VER >= 20
0033
0034 // [ranges.access.rbegin]
0035
0036 namespace ranges {
0037 namespace __rbegin {
0038 template <class _Tp>
0039 concept __member_rbegin = __can_borrow<_Tp> && requires(_Tp&& __t) {
0040   { _LIBCPP_AUTO_CAST(__t.rbegin()) } -> input_or_output_iterator;
0041 };
0042
0043 void rbegin() = delete;
0044
0045 template <class _Tp>
0046 concept __unqualified_rbegin =
0047     !__member_rbegin<_Tp> && __can_borrow<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
0048       { _LIBCPP_AUTO_CAST(rbegin(__t)) } -> input_or_output_iterator;
0049     };
0050
0051 template <class _Tp>
0052 concept __can_reverse =
0053     __can_borrow<_Tp> && !__member_rbegin<_Tp> && !__unqualified_rbegin<_Tp> && requires(_Tp&& __t) {
0054       { ranges::begin(__t) } -> same_as<decltype(ranges::end(__t))>;
0055       { ranges::begin(__t) } -> bidirectional_iterator;
0056     };
0057
0058 struct __fn {
0059   template <class _Tp>
0060     requires __member_rbegin<_Tp>
0061   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
0062       noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.rbegin()))) {
0063     return _LIBCPP_AUTO_CAST(__t.rbegin());
0064   }
0065
0066   template <class _Tp>
0067     requires __unqualified_rbegin<_Tp>
0068   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
0069       noexcept(noexcept(_LIBCPP_AUTO_CAST(rbegin(__t)))) {
0070     return _LIBCPP_AUTO_CAST(rbegin(__t));
0071   }
0072
0073   template <class _Tp>
0074     requires __can_reverse<_Tp>
0075   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const noexcept(noexcept(ranges::end(__t))) {
0076     return std::make_reverse_iterator(ranges::end(__t));
0077   }
0078
0079   void operator()(auto&&) const = delete;
0080 };
0081 } // namespace __rbegin
0082
0083 inline namespace __cpo {
0084 inline constexpr auto rbegin = __rbegin::__fn{};
0085 } // namespace __cpo
0086 } // namespace ranges
0087
0088 // [range.access.crbegin]
0089
0090 namespace ranges {
0091 namespace __crbegin {
0092 struct __fn {
0093   template <class _Tp>
0094     requires is_lvalue_reference_v<_Tp&&>
0095   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
0096       noexcept(noexcept(ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t))))
0097           -> decltype(ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t))) {
0098     return ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t));
0099   }
0100
0101   template <class _Tp>
0102     requires is_rvalue_reference_v<_Tp&&>
0103   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
0104       noexcept(noexcept(ranges::rbegin(static_cast<const _Tp&&>(__t))))
0105           -> decltype(ranges::rbegin(static_cast<const _Tp&&>(__t))) {
0106     return ranges::rbegin(static_cast<const _Tp&&>(__t));
0107   }
0108 };
0109 } // namespace __crbegin
0110
0111 inline namespace __cpo {
0112 inline constexpr auto crbegin = __crbegin::__fn{};
0113 } // namespace __cpo
0114 } // namespace ranges
0115
0116 #endif // _LIBCPP_STD_VER >= 20
0117
0118 _LIBCPP_END_NAMESPACE_STD
0119
0120 #endif // _LIBCPP___RANGES_RBEGIN_H