1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef _LIBCPP___ALGORITHM_RANGES_REVERSE_H
10#define _LIBCPP___ALGORITHM_RANGES_REVERSE_H
11
12#include <__config>
13#include <__iterator/concepts.h>
14#include <__iterator/iter_swap.h>
15#include <__iterator/next.h>
16#include <__iterator/permutable.h>
17#include <__ranges/access.h>
18#include <__ranges/concepts.h>
19#include <__ranges/dangling.h>
20
21#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
22# pragma GCC system_header
23#endif
24
25#if _LIBCPP_STD_VER >= 20
26
27_LIBCPP_BEGIN_NAMESPACE_STD
28
29namespace ranges {
30namespace __reverse {
31struct __fn {
32 template <bidirectional_iterator _Iter, sentinel_for<_Iter> _Sent>
33 requires permutable<_Iter>
34 _LIBCPP_HIDE_FROM_ABI constexpr _Iter operator()(_Iter __first, _Sent __last) const {
35 if constexpr (random_access_iterator<_Iter>) {
36 if (__first == __last)
37 return __first;
38
39 auto __end = ranges::next(__first, __last);
40 auto __ret = __end;
41
42 while (__first < --__end) {
43 ranges::iter_swap(__first, __end);
44 ++__first;
45 }
46 return __ret;
47 } else {
48 auto __end = ranges::next(__first, __last);
49 auto __ret = __end;
50
51 while (__first != __end) {
52 if (__first == --__end)
53 break;
54
55 ranges::iter_swap(__first, __end);
56 ++__first;
57 }
58 return __ret;
59 }
60 }
61
62 template <bidirectional_range _Range>
63 requires permutable<iterator_t<_Range>>
64 _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Range> operator()(_Range&& __range) const {
65 return (*this)(ranges::begin(__range), ranges::end(__range));
66 }
67};
68} // namespace __reverse
69
70inline namespace __cpo {
71inline constexpr auto reverse = __reverse::__fn{};
72} // namespace __cpo
73} // namespace ranges
74
75_LIBCPP_END_NAMESPACE_STD
76
77#endif // _LIBCPP_STD_VER >= 20
78
79#endif // _LIBCPP___ALGORITHM_RANGES_REVERSE_H
80