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 
10 #ifndef _LIBCPP___FUNCTIONAL_IDENTITY_H
11 #define _LIBCPP___FUNCTIONAL_IDENTITY_H
12 
13 #include <__config>
14 #include <utility>
15 
16 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
17 #pragma GCC system_header
18 #endif
19 
20 _LIBCPP_BEGIN_NAMESPACE_STD
21 
22 #if _LIBCPP_STD_VER > 17
23 
24 struct identity {
25     template<class _Tp>
operatoridentity26     _LIBCPP_NODISCARD_EXT constexpr _Tp&& operator()(_Tp&& __t) const noexcept
27     {
28         return _VSTD::forward<_Tp>(__t);
29     }
30 
31     using is_transparent = void;
32 };
33 #endif // _LIBCPP_STD_VER > 17
34 
35 _LIBCPP_END_NAMESPACE_STD
36 
37 #endif // _LIBCPP___FUNCTIONAL_IDENTITY_H
38