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 #ifndef _LIBCPP___ITERATOR_ITER_SWAP_H
10 #define _LIBCPP___ITERATOR_ITER_SWAP_H
11 
12 #include <__config>
13 #include <__iterator/concepts.h>
14 #include <__iterator/iter_move.h>
15 #include <__iterator/iterator_traits.h>
16 #include <__iterator/readable_traits.h>
17 #include <__utility/forward.h>
18 #include <__utility/move.h>
19 #include <concepts>
20 #include <type_traits>
21 
22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
23 #  pragma GCC system_header
24 #endif
25 
26 _LIBCPP_BEGIN_NAMESPACE_STD
27 
28 #if _LIBCPP_STD_VER > 17
29 
30 // [iter.cust.swap]
31 
32 namespace ranges {
33 namespace __iter_swap {
34   template<class _I1, class _I2>
35   void iter_swap(_I1, _I2) = delete;
36 
37   template<class _T1, class _T2>
38   concept __unqualified_iter_swap =
39     (__class_or_enum<remove_cvref_t<_T1>> || __class_or_enum<remove_cvref_t<_T2>>) &&
40     requires (_T1&& __x, _T2&& __y) {
41       iter_swap(_VSTD::forward<_T1>(__x), _VSTD::forward<_T2>(__y));
42     };
43 
44   template<class _T1, class _T2>
45   concept __readable_swappable =
46     indirectly_readable<_T1> && indirectly_readable<_T2> &&
47     swappable_with<iter_reference_t<_T1>, iter_reference_t<_T2>>;
48 
49   struct __fn {
50     template <class _T1, class _T2>
51       requires __unqualified_iter_swap<_T1, _T2>
52     _LIBCPP_HIDE_FROM_ABI
53     constexpr void operator()(_T1&& __x, _T2&& __y) const
54       noexcept(noexcept(iter_swap(_VSTD::forward<_T1>(__x), _VSTD::forward<_T2>(__y))))
55     {
56       (void)iter_swap(_VSTD::forward<_T1>(__x), _VSTD::forward<_T2>(__y));
57     }
58 
59     template <class _T1, class _T2>
60       requires (!__unqualified_iter_swap<_T1, _T2>) &&
61                __readable_swappable<_T1, _T2>
62     _LIBCPP_HIDE_FROM_ABI
63     constexpr void operator()(_T1&& __x, _T2&& __y) const
64       noexcept(noexcept(ranges::swap(*_VSTD::forward<_T1>(__x), *_VSTD::forward<_T2>(__y))))
65     {
66       ranges::swap(*_VSTD::forward<_T1>(__x), *_VSTD::forward<_T2>(__y));
67     }
68 
69     template <class _T1, class _T2>
70       requires (!__unqualified_iter_swap<_T1, _T2> &&
71                 !__readable_swappable<_T1, _T2>) &&
72                indirectly_movable_storable<_T1, _T2> &&
73                indirectly_movable_storable<_T2, _T1>
74     _LIBCPP_HIDE_FROM_ABI
75     constexpr void operator()(_T1&& __x, _T2&& __y) const
76       noexcept(noexcept(iter_value_t<_T2>(ranges::iter_move(__y))) &&
77                noexcept(*__y = ranges::iter_move(__x)) &&
78                noexcept(*_VSTD::forward<_T1>(__x) = declval<iter_value_t<_T2>>()))
79     {
80       iter_value_t<_T2> __old(ranges::iter_move(__y));
81       *__y = ranges::iter_move(__x);
82       *_VSTD::forward<_T1>(__x) = _VSTD::move(__old);
83     }
84   };
85 } // namespace __iter_swap
86 
87 inline namespace __cpo {
88   inline constexpr auto iter_swap = __iter_swap::__fn{};
89 } // namespace __cpo
90 } // namespace ranges
91 
92 template<class _I1, class _I2 = _I1>
93 concept indirectly_swappable =
94   indirectly_readable<_I1> && indirectly_readable<_I2> &&
95   requires(const _I1 __i1, const _I2 __i2) {
96     ranges::iter_swap(__i1, __i1);
97     ranges::iter_swap(__i2, __i2);
98     ranges::iter_swap(__i1, __i2);
99     ranges::iter_swap(__i2, __i1);
100   };
101 
102 #endif // _LIBCPP_STD_VER > 17
103 
104 _LIBCPP_END_NAMESPACE_STD
105 
106 #endif // _LIBCPP___ITERATOR_ITER_SWAP_H
107