1fe6060f1SDimitry Andric // -*- C++ -*- 2fe6060f1SDimitry Andric //===----------------------------------------------------------------------===// 3fe6060f1SDimitry Andric // 4fe6060f1SDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5fe6060f1SDimitry Andric // See https://llvm.org/LICENSE.txt for license information. 6fe6060f1SDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7fe6060f1SDimitry Andric // 8fe6060f1SDimitry Andric //===----------------------------------------------------------------------===// 9fe6060f1SDimitry Andric 10fe6060f1SDimitry Andric #ifndef _LIBCPP___FUNCTIONAL_IDENTITY_H 11fe6060f1SDimitry Andric #define _LIBCPP___FUNCTIONAL_IDENTITY_H 12fe6060f1SDimitry Andric 13fe6060f1SDimitry Andric #include <__config> 14*06c3fb27SDimitry Andric #include <__type_traits/integral_constant.h> 1581ad6265SDimitry Andric #include <__utility/forward.h> 16fe6060f1SDimitry Andric 17fe6060f1SDimitry Andric #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 18fe6060f1SDimitry Andric # pragma GCC system_header 19fe6060f1SDimitry Andric #endif 20fe6060f1SDimitry Andric 21fe6060f1SDimitry Andric _LIBCPP_BEGIN_NAMESPACE_STD 22fe6060f1SDimitry Andric 23*06c3fb27SDimitry Andric template <class _Tp> 24*06c3fb27SDimitry Andric struct __is_identity : false_type {}; 25*06c3fb27SDimitry Andric 2681ad6265SDimitry Andric struct __identity { 2781ad6265SDimitry Andric template <class _Tp> 28*06c3fb27SDimitry Andric _LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Tp&& operator()(_Tp&& __t) const _NOEXCEPT { 2981ad6265SDimitry Andric return std::forward<_Tp>(__t); 3081ad6265SDimitry Andric } 3181ad6265SDimitry Andric 3281ad6265SDimitry Andric using is_transparent = void; 3381ad6265SDimitry Andric }; 3481ad6265SDimitry Andric 35*06c3fb27SDimitry Andric template <> 36*06c3fb27SDimitry Andric struct __is_identity<__identity> : true_type {}; 37*06c3fb27SDimitry Andric 38*06c3fb27SDimitry Andric #if _LIBCPP_STD_VER >= 20 39fe6060f1SDimitry Andric 40fe6060f1SDimitry Andric struct identity { 41fe6060f1SDimitry Andric template<class _Tp> 42*06c3fb27SDimitry Andric _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr _Tp&& operator()(_Tp&& __t) const noexcept 43fe6060f1SDimitry Andric { 44fe6060f1SDimitry Andric return _VSTD::forward<_Tp>(__t); 45fe6060f1SDimitry Andric } 46fe6060f1SDimitry Andric 47fe6060f1SDimitry Andric using is_transparent = void; 48fe6060f1SDimitry Andric }; 49*06c3fb27SDimitry Andric 50*06c3fb27SDimitry Andric template <> 51*06c3fb27SDimitry Andric struct __is_identity<identity> : true_type {}; 52*06c3fb27SDimitry Andric 53*06c3fb27SDimitry Andric #endif // _LIBCPP_STD_VER >= 20 54fe6060f1SDimitry Andric 55fe6060f1SDimitry Andric _LIBCPP_END_NAMESPACE_STD 56fe6060f1SDimitry Andric 57fe6060f1SDimitry Andric #endif // _LIBCPP___FUNCTIONAL_IDENTITY_H 58