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 <__utility/forward.h>
14 #include <__utility/move.h>
15 
16 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
17 #pragma GCC system_header
18 #endif
19 
20 _LIBCPP_PUSH_MACROS
21 #include <__undef_macros>
22 
23 _LIBCPP_BEGIN_NAMESPACE_STD
24 
25 #if _LIBCPP_STD_VER > 11
26 template<class _T1, class _T2 = _T1>
27 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
28 _T1 exchange(_T1& __obj, _T2 && __new_value)
29 {
30     _T1 __old_value = _VSTD::move(__obj);
31     __obj = _VSTD::forward<_T2>(__new_value);
32     return __old_value;
33 }
34 #endif // _LIBCPP_STD_VER > 11
35 
36 _LIBCPP_END_NAMESPACE_STD
37 
38 _LIBCPP_POP_MACROS
39 
40 #endif // _LIBCPP___UTILITY_EXCHANGE_H
41