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
_ProjectedPred_ProjectedPred35 _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&, decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_Tp>()))>::type
40 _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI
operator_ProjectedPred41 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>()))>::type _LIBCPP_CONSTEXPR
49 _LIBCPP_HIDE_FROM_ABI
operator_ProjectedPred50 operator()(_T1&& __lhs, _T2&& __rhs) const {
51 return std::__invoke(
52 __pred, std::__invoke(__proj, std::forward<_T1>(__lhs)), std::__invoke(__proj, std::forward<_T2>(__rhs)));
53 }
54 };
55
56 template <
57 class _Pred,
58 class _Proj,
59 __enable_if_t<!(!is_member_pointer<__decay_t<_Pred> >::value && __is_identity<__decay_t<_Proj> >::value), int> = 0>
__make_projected(_Pred & __pred,_Proj & __proj)60 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ProjectedPred<_Pred, _Proj> __make_projected(_Pred& __pred, _Proj& __proj) {
61 return _ProjectedPred<_Pred, _Proj>(__pred, __proj);
62 }
63
64 // Avoid creating the functor and just use the pristine comparator -- for certain algorithms, this would enable
65 // optimizations that rely on the type of the comparator. Additionally, this results in less layers of indirection in
66 // the call stack when the comparator is invoked, even in an unoptimized build.
67 template <
68 class _Pred,
69 class _Proj,
70 __enable_if_t<!is_member_pointer<__decay_t<_Pred> >::value && __is_identity<__decay_t<_Proj> >::value, int> = 0>
__make_projected(_Pred & __pred,_Proj &)71 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Pred& __make_projected(_Pred& __pred, _Proj&) {
72 return __pred;
73 }
74
75 _LIBCPP_END_NAMESPACE_STD
76
77 #if _LIBCPP_STD_VER >= 20
78
79 _LIBCPP_BEGIN_NAMESPACE_STD
80
81 namespace ranges {
82
83 template <class _Comp, class _Proj1, class _Proj2>
decltype(auto)84 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) __make_projected_comp(_Comp& __comp, _Proj1& __proj1, _Proj2& __proj2) {
85 if constexpr (__is_identity<decay_t<_Proj1>>::value && __is_identity<decay_t<_Proj2>>::value &&
86 !is_member_pointer_v<decay_t<_Comp>>) {
87 // Avoid creating the lambda and just use the pristine comparator -- for certain algorithms, this would enable
88 // optimizations that rely on the type of the comparator.
89 return __comp;
90
91 } else {
92 return [&](auto&& __lhs, auto&& __rhs) -> bool {
93 return std::invoke(__comp,
94 std::invoke(__proj1, std::forward<decltype(__lhs)>(__lhs)),
95 std::invoke(__proj2, std::forward<decltype(__rhs)>(__rhs)));
96 };
97 }
98 }
99
100 } // namespace ranges
101
102 _LIBCPP_END_NAMESPACE_STD
103
104 #endif // _LIBCPP_STD_VER >= 20
105
106 #endif // _LIBCPP___ALGORITHM_MAKE_PROJECTED_H
107