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/forward.h> 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 struct __identity { 23 template <class _Tp> 24 _LIBCPP_NODISCARD _LIBCPP_CONSTEXPR _Tp&& operator()(_Tp&& __t) const _NOEXCEPT { 25 return std::forward<_Tp>(__t); 26 } 27 28 using is_transparent = void; 29 }; 30 31 #if _LIBCPP_STD_VER > 17 32 33 struct identity { 34 template<class _Tp> 35 _LIBCPP_NODISCARD_EXT constexpr _Tp&& operator()(_Tp&& __t) const noexcept 36 { 37 return _VSTD::forward<_Tp>(__t); 38 } 39 40 using is_transparent = void; 41 }; 42 #endif // _LIBCPP_STD_VER > 17 43 44 _LIBCPP_END_NAMESPACE_STD 45 46 #endif // _LIBCPP___FUNCTIONAL_IDENTITY_H 47