Acts/Utilities/Identity.hpp

0001 // This file is part of the Acts project.
0002 //
0003 // Copyright (C) 2021 CERN for the benefit of the Acts project
0004 //
0005 // This Source Code Form is subject to the terms of the Mozilla Public
0006 // License, v. 2.0. If a copy of the MPL was not distributed with this
0007 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
0008
0009 #pragma once
0010
0011 #if __cplusplus >= 202002L
0012
0013 #include <functional>
0014
0015 namespace Acts {
0016 using Identity = std::identity;
0017 }
0018
0019 #else
0020
0021 #include <utility>
0022
0023 namespace Acts {
0024
0025 /// @brief Function object which maps a value to itself by perfect forwarding
0026 /// This is a backport of C++20's std::identity
0027 struct Identity {
0028   template <typename T>
0029   constexpr auto operator()(T &&v) const {
0030     return std::forward<T>(v);
0031   }
0032 };
0033
0034 }  // namespace Acts
0035
0036 #endif