1 //===----------------------------------------------------------------------===// 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 #ifndef _LIBCPP___ALGORITHM_MAKE_PROJECTED_H 10 #define _LIBCPP___ALGORITHM_MAKE_PROJECTED_H 11 12 #include <__concepts/same_as.h> 13 #include <__config> 14 #include <__functional/identity.h> 15 #include <__functional/invoke.h> 16 #include <__utility/forward.h> 17 18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 19 # pragma GCC system_header 20 #endif 21 22 #if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 23 24 _LIBCPP_BEGIN_NAMESPACE_STD 25 26 namespace ranges { 27 28 template <class _Comp, class _Proj> 29 _LIBCPP_HIDE_FROM_ABI constexpr static 30 decltype(auto) __make_projected_comp(_Comp& __comp, _Proj& __proj) { 31 if constexpr (same_as<_Proj, identity>) { 32 // Avoid creating the lambda and just use the pristine comparator -- for certain algorithms, this would enable 33 // optimizations that rely on the type of the comparator. 34 return __comp; 35 36 } else { 37 return [&](auto&& __lhs, auto&& __rhs) { 38 return std::invoke(__comp, 39 std::invoke(__proj, std::forward<decltype(__lhs)>(__lhs)), 40 std::invoke(__proj, std::forward<decltype(__rhs)>(__rhs))); 41 }; 42 } 43 } 44 45 } // namespace ranges 46 47 _LIBCPP_END_NAMESPACE_STD 48 49 #endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 50 51 #endif // _LIBCPP___ALGORITHM_MAKE_PROJECTED_H 52