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) -> bool {
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