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 30 template <class _Pred, class _Proj> 31 struct _ProjectedPred { 32 _Pred& __pred; // Can be a unary or a binary predicate. 33 _Proj& __proj; 34 35 _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI _ProjectedPred(_Pred& __pred_arg, _Proj& __proj_arg) 36 : __pred(__pred_arg), __proj(__proj_arg) {} 37 38 template <class _Tp> 39 typename __invoke_of<_Pred&, 40 decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_Tp>())) 41 >::type 42 _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI operator()(_Tp&& __v) const { 43 return std::__invoke(__pred, std::__invoke(__proj, std::forward<_Tp>(__v))); 44 } 45 46 template <class _T1, class _T2> 47 typename __invoke_of<_Pred&, 48 decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_T1>())), 49 decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_T2>())) 50 >::type 51 _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI operator()(_T1&& __lhs, _T2&& __rhs) const { 52 return std::__invoke(__pred, 53 std::__invoke(__proj, std::forward<_T1>(__lhs)), 54 std::__invoke(__proj, std::forward<_T2>(__rhs))); 55 } 56 57 }; 58 59 template <class _Pred, 60 class _Proj, 61 __enable_if_t<!(!is_member_pointer<__decay_t<_Pred> >::value && 62 __is_identity<__decay_t<_Proj> >::value), 63 int> = 0> 64 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ProjectedPred<_Pred, _Proj> 65 __make_projected(_Pred& __pred, _Proj& __proj) { 66 return _ProjectedPred<_Pred, _Proj>(__pred, __proj); 67 } 68 69 // Avoid creating the functor and just use the pristine comparator -- for certain algorithms, this would enable 70 // optimizations that rely on the type of the comparator. Additionally, this results in less layers of indirection in 71 // the call stack when the comparator is invoked, even in an unoptimized build. 72 template <class _Pred, 73 class _Proj, 74 __enable_if_t<!is_member_pointer<__decay_t<_Pred> >::value && 75 __is_identity<__decay_t<_Proj> >::value, 76 int> = 0> 77 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Pred& __make_projected(_Pred& __pred, _Proj&) { 78 return __pred; 79 } 80 81 _LIBCPP_END_NAMESPACE_STD 82 83 #if _LIBCPP_STD_VER >= 20 84 85 _LIBCPP_BEGIN_NAMESPACE_STD 86 87 namespace ranges { 88 89 template <class _Comp, class _Proj1, class _Proj2> 90 _LIBCPP_HIDE_FROM_ABI constexpr 91 decltype(auto) __make_projected_comp(_Comp& __comp, _Proj1& __proj1, _Proj2& __proj2) { 92 if constexpr (__is_identity<decay_t<_Proj1>>::value && __is_identity<decay_t<_Proj2>>::value && 93 !is_member_pointer_v<decay_t<_Comp>>) { 94 // Avoid creating the lambda and just use the pristine comparator -- for certain algorithms, this would enable 95 // optimizations that rely on the type of the comparator. 96 return __comp; 97 98 } else { 99 return [&](auto&& __lhs, auto&& __rhs) { 100 return std::invoke(__comp, 101 std::invoke(__proj1, std::forward<decltype(__lhs)>(__lhs)), 102 std::invoke(__proj2, std::forward<decltype(__rhs)>(__rhs))); 103 }; 104 } 105 } 106 107 } // namespace ranges 108 109 _LIBCPP_END_NAMESPACE_STD 110 111 #endif // _LIBCPP_STD_VER >= 20 112 113 #endif // _LIBCPP___ALGORITHM_MAKE_PROJECTED_H 114