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> 26 _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