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