make_projected.h revision 1.1.1.1
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 <__type_traits/decay.h> 17#include <__type_traits/enable_if.h> 18#include <__type_traits/integral_constant.h> 19#include <__type_traits/is_member_pointer.h> 20#include <__type_traits/is_same.h> 21#include <__utility/declval.h> 22#include <__utility/forward.h> 23 24#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 25# pragma GCC system_header 26#endif 27 28_LIBCPP_BEGIN_NAMESPACE_STD 29 30template <class _Pred, class _Proj> 31struct _ProjectedPred { 32 _Pred& __pred; // Can be a unary or a binary predicate. 33 _Proj& __proj; 34 35 _LIBCPP_CONSTEXPR _ProjectedPred(_Pred& __pred_arg, _Proj& __proj_arg) : __pred(__pred_arg), __proj(__proj_arg) {} 36 37 template <class _Tp> 38 typename __invoke_of<_Pred&, 39 decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_Tp>())) 40 >::type 41 _LIBCPP_CONSTEXPR operator()(_Tp&& __v) const { 42 return std::__invoke(__pred, std::__invoke(__proj, std::forward<_Tp>(__v))); 43 } 44 45 template <class _T1, class _T2> 46 typename __invoke_of<_Pred&, 47 decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_T1>())), 48 decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_T2>())) 49 >::type 50 _LIBCPP_CONSTEXPR operator()(_T1&& __lhs, _T2&& __rhs) const { 51 return std::__invoke(__pred, 52 std::__invoke(__proj, std::forward<_T1>(__lhs)), 53 std::__invoke(__proj, std::forward<_T2>(__rhs))); 54 } 55 56}; 57 58template <class _Pred, class _Proj, class = void> 59struct __can_use_pristine_comp : false_type {}; 60 61template <class _Pred, class _Proj> 62struct __can_use_pristine_comp<_Pred, _Proj, __enable_if_t< 63 !is_member_pointer<typename decay<_Pred>::type>::value && ( 64#if _LIBCPP_STD_VER > 17 65 is_same<typename decay<_Proj>::type, identity>::value || 66#endif 67 is_same<typename decay<_Proj>::type, __identity>::value 68 ) 69> > : true_type {}; 70 71template <class _Pred, class _Proj> 72_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR static 73__enable_if_t< 74 !__can_use_pristine_comp<_Pred, _Proj>::value, 75 _ProjectedPred<_Pred, _Proj> 76> 77__make_projected(_Pred& __pred, _Proj& __proj) { 78 return _ProjectedPred<_Pred, _Proj>(__pred, __proj); 79} 80 81// Avoid creating the functor and just use the pristine comparator -- for certain algorithms, this would enable 82// optimizations that rely on the type of the comparator. Additionally, this results in less layers of indirection in 83// the call stack when the comparator is invoked, even in an unoptimized build. 84template <class _Pred, class _Proj> 85_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR static 86__enable_if_t< 87 __can_use_pristine_comp<_Pred, _Proj>::value, 88 _Pred& 89> 90__make_projected(_Pred& __pred, _Proj&) { 91 return __pred; 92} 93 94_LIBCPP_END_NAMESPACE_STD 95 96#if _LIBCPP_STD_VER > 17 97 98_LIBCPP_BEGIN_NAMESPACE_STD 99 100namespace ranges { 101 102template <class _Comp, class _Proj1, class _Proj2> 103_LIBCPP_HIDE_FROM_ABI constexpr static 104decltype(auto) __make_projected_comp(_Comp& __comp, _Proj1& __proj1, _Proj2& __proj2) { 105 if constexpr (same_as<decay_t<_Proj1>, identity> && same_as<decay_t<_Proj2>, identity> && 106 !is_member_pointer_v<decay_t<_Comp>>) { 107 // Avoid creating the lambda and just use the pristine comparator -- for certain algorithms, this would enable 108 // optimizations that rely on the type of the comparator. 109 return __comp; 110 111 } else { 112 return [&](auto&& __lhs, auto&& __rhs) { 113 return std::invoke(__comp, 114 std::invoke(__proj1, std::forward<decltype(__lhs)>(__lhs)), 115 std::invoke(__proj2, std::forward<decltype(__rhs)>(__rhs))); 116 }; 117 } 118} 119 120} // namespace ranges 121 122_LIBCPP_END_NAMESPACE_STD 123 124#endif // _LIBCPP_STD_VER > 17 125 126#endif // _LIBCPP___ALGORITHM_MAKE_PROJECTED_H 127