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___CXX03___FUNCTIONAL_IDENTITY_H 11 #define _LIBCPP___CXX03___FUNCTIONAL_IDENTITY_H 12 13 #include <__cxx03/__config> 14 #include <__cxx03/__fwd/functional.h> 15 #include <__cxx03/__type_traits/integral_constant.h> 16 #include <__cxx03/__utility/forward.h> 17 18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 19 # pragma GCC system_header 20 #endif 21 22 _LIBCPP_BEGIN_NAMESPACE_STD 23 24 template <class _Tp> 25 struct __is_identity : false_type {}; 26 27 struct __identity { 28 template <class _Tp> operator__identity29 _LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI _Tp&& operator()(_Tp&& __t) const _NOEXCEPT { 30 return std::forward<_Tp>(__t); 31 } 32 33 using is_transparent = void; 34 }; 35 36 template <> 37 struct __is_identity<__identity> : true_type {}; 38 template <> 39 struct __is_identity<reference_wrapper<__identity> > : true_type {}; 40 template <> 41 struct __is_identity<reference_wrapper<const __identity> > : true_type {}; 42 43 _LIBCPP_END_NAMESPACE_STD 44 45 #endif // _LIBCPP___CXX03___FUNCTIONAL_IDENTITY_H 46