__cxx03/__algorithm/ranges_reverse.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___CXX03___ALGORITHM_RANGES_REVERSE_H
0010 #define _LIBCPP___CXX03___ALGORITHM_RANGES_REVERSE_H
0011
0012 #include <__cxx03/__config>
0013 #include <__cxx03/__iterator/concepts.h>
0014 #include <__cxx03/__iterator/iter_swap.h>
0015 #include <__cxx03/__iterator/next.h>
0016 #include <__cxx03/__iterator/permutable.h>
0017 #include <__cxx03/__ranges/access.h>
0018 #include <__cxx03/__ranges/concepts.h>
0019 #include <__cxx03/__ranges/dangling.h>
0020
0021 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0022 #  pragma GCC system_header
0023 #endif
0024
0025 #if _LIBCPP_STD_VER >= 20
0026
0027 _LIBCPP_BEGIN_NAMESPACE_STD
0028
0029 namespace ranges {
0030 namespace __reverse {
0031 struct __fn {
0032   template <bidirectional_iterator _Iter, sentinel_for<_Iter> _Sent>
0033     requires permutable<_Iter>
0034   _LIBCPP_HIDE_FROM_ABI constexpr _Iter operator()(_Iter __first, _Sent __last) const {
0035     if constexpr (random_access_iterator<_Iter>) {
0036       if (__first == __last)
0037         return __first;
0038
0039       auto __end = ranges::next(__first, __last);
0040       auto __ret = __end;
0041
0042       while (__first < --__end) {
0043         ranges::iter_swap(__first, __end);
0044         ++__first;
0045       }
0046       return __ret;
0047     } else {
0048       auto __end = ranges::next(__first, __last);
0049       auto __ret = __end;
0050
0051       while (__first != __end) {
0052         if (__first == --__end)
0053           break;
0054
0055         ranges::iter_swap(__first, __end);
0056         ++__first;
0057       }
0058       return __ret;
0059     }
0060   }
0061
0062   template <bidirectional_range _Range>
0063     requires permutable<iterator_t<_Range>>
0064   _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Range> operator()(_Range&& __range) const {
0065     return (*this)(ranges::begin(__range), ranges::end(__range));
0066   }
0067 };
0068 } // namespace __reverse
0069
0070 inline namespace __cpo {
0071 inline constexpr auto reverse = __reverse::__fn{};
0072 } // namespace __cpo
0073 } // namespace ranges
0074
0075 _LIBCPP_END_NAMESPACE_STD
0076
0077 #endif // _LIBCPP_STD_VER >= 20
0078
0079 #endif // _LIBCPP___CXX03___ALGORITHM_RANGES_REVERSE_H