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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 <__config>
13#include <__functional/identity.h>
14#include <__functional/invoke.h>
15#include <__type_traits/decay.h>
16#include <__type_traits/enable_if.h>
17#include <__type_traits/invoke.h>
18#include <__type_traits/is_member_pointer.h>
19#include <__utility/declval.h>
20#include <__utility/forward.h>
21
22#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
23# pragma GCC system_header
24#endif
25
26_LIBCPP_BEGIN_NAMESPACE_STD
27
28template <class _Pred, class _Proj>
29struct _ProjectedPred {
30 _Pred& __pred; // Can be a unary or a binary predicate.
31 _Proj& __proj;
32
33 _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI _ProjectedPred(_Pred& __pred_arg, _Proj& __proj_arg)
34 : __pred(__pred_arg), __proj(__proj_arg) {}
35
36 template <class _Tp>
37 __invoke_result_t<_Pred&, decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_Tp>()))> _LIBCPP_CONSTEXPR
38 _LIBCPP_HIDE_FROM_ABI
39 operator()(_Tp&& __v) const {
40 return std::__invoke(__pred, std::__invoke(__proj, std::forward<_Tp>(__v)));
41 }
42
43 template <class _T1, class _T2>
44 __invoke_result_t<_Pred&,
45 decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_T1>())),
46 decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_T2>()))> _LIBCPP_CONSTEXPR
47 _LIBCPP_HIDE_FROM_ABI
48 operator()(_T1&& __lhs, _T2&& __rhs) const {
49 return std::__invoke(
50 __pred, std::__invoke(__proj, std::forward<_T1>(__lhs)), std::__invoke(__proj, std::forward<_T2>(__rhs)));
51 }
52};
53
54template <
55 class _Pred,
56 class _Proj,
57 __enable_if_t<!(!is_member_pointer<__decay_t<_Pred> >::value && __is_identity<__decay_t<_Proj> >::value), int> = 0>
58_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ProjectedPred<_Pred, _Proj> __make_projected(_Pred& __pred, _Proj& __proj) {
59 return _ProjectedPred<_Pred, _Proj>(__pred, __proj);
60}
61
62// Avoid creating the functor and just use the pristine comparator -- for certain algorithms, this would enable
63// optimizations that rely on the type of the comparator. Additionally, this results in less layers of indirection in
64// the call stack when the comparator is invoked, even in an unoptimized build.
65template <
66 class _Pred,
67 class _Proj,
68 __enable_if_t<!is_member_pointer<__decay_t<_Pred> >::value && __is_identity<__decay_t<_Proj> >::value, int> = 0>
69_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Pred& __make_projected(_Pred& __pred, _Proj&) {
70 return __pred;
71}
72
73_LIBCPP_END_NAMESPACE_STD
74
75#if _LIBCPP_STD_VER >= 20
76
77_LIBCPP_BEGIN_NAMESPACE_STD
78
79namespace ranges {
80
81template <class _Comp, class _Proj1, class _Proj2>
82_LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) __make_projected_comp(_Comp& __comp, _Proj1& __proj1, _Proj2& __proj2) {
83 if constexpr (__is_identity<decay_t<_Proj1>>::value && __is_identity<decay_t<_Proj2>>::value &&
84 !is_member_pointer_v<decay_t<_Comp>>) {
85 // Avoid creating the lambda and just use the pristine comparator -- for certain algorithms, this would enable
86 // optimizations that rely on the type of the comparator.
87 return __comp;
88
89 } else {
90 return [&](auto&& __lhs, auto&& __rhs) -> bool {
91 return std::invoke(__comp,
92 std::invoke(__proj1, std::forward<decltype(__lhs)>(__lhs)),
93 std::invoke(__proj2, std::forward<decltype(__rhs)>(__rhs)));
94 };
95 }
96}
97
98} // namespace ranges
99
100_LIBCPP_END_NAMESPACE_STD
101
102#endif // _LIBCPP_STD_VER >= 20
103
104#endif // _LIBCPP___ALGORITHM_MAKE_PROJECTED_H