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___UTILITY_EXCHANGE_H
10 #define _LIBCPP___UTILITY_EXCHANGE_H
11 
12 #include <__config>
13 #include <__type_traits/is_nothrow_assignable.h>
14 #include <__type_traits/is_nothrow_move_constructible.h>
15 #include <__utility/forward.h>
16 #include <__utility/move.h>
17 
18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19 #  pragma GCC system_header
20 #endif
21 
22 _LIBCPP_PUSH_MACROS
23 #include <__undef_macros>
24 
25 _LIBCPP_BEGIN_NAMESPACE_STD
26 
27 #if _LIBCPP_STD_VER >= 14
28 template<class _T1, class _T2 = _T1>
29 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
30 _T1 exchange(_T1& __obj, _T2&& __new_value)
31     noexcept(is_nothrow_move_constructible<_T1>::value && is_nothrow_assignable<_T1&, _T2>::value)
32 {
33     _T1 __old_value = _VSTD::move(__obj);
34     __obj = _VSTD::forward<_T2>(__new_value);
35     return __old_value;
36 }
37 #endif // _LIBCPP_STD_VER >= 14
38 
39 _LIBCPP_END_NAMESPACE_STD
40 
41 _LIBCPP_POP_MACROS
42 
43 #endif // _LIBCPP___UTILITY_EXCHANGE_H
44