1 //===- llvm/ADT/Identity.h - Provide std::identity from C++20 ---*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file provides an implementation of std::identity from C++20. 10 // 11 // No library is required when using these functions. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_ADT_IDENTITY_H 16 #define LLVM_ADT_IDENTITY_H 17 18 19 namespace llvm { 20 21 // Similar to `std::identity` from C++20. 22 template <class Ty> struct identity { 23 using is_transparent = void; 24 using argument_type = Ty; 25 operatoridentity26 Ty &operator()(Ty &self) const { 27 return self; 28 } operatoridentity29 const Ty &operator()(const Ty &self) const { 30 return self; 31 } 32 }; 33 34 } // end namespace llvm 35 36 #endif // LLVM_ADT_IDENTITY_H 37