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_RANGES_MINMAX_H
10#define _LIBCPP___ALGORITHM_RANGES_MINMAX_H
11
12#include <__algorithm/min_max_result.h>
13#include <__algorithm/minmax_element.h>
14#include <__assert>
15#include <__concepts/copyable.h>
16#include <__concepts/same_as.h>
17#include <__config>
18#include <__functional/identity.h>
19#include <__functional/invoke.h>
20#include <__functional/ranges_operations.h>
21#include <__iterator/concepts.h>
22#include <__iterator/next.h>
23#include <__iterator/projected.h>
24#include <__ranges/access.h>
25#include <__ranges/concepts.h>
26#include <__type_traits/desugars_to.h>
27#include <__type_traits/is_reference.h>
28#include <__type_traits/is_trivially_copyable.h>
29#include <__type_traits/remove_cvref.h>
30#include <__utility/forward.h>
31#include <__utility/move.h>
32#include <__utility/pair.h>
33#include <initializer_list>
34
35#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
36# pragma GCC system_header
37#endif
38
39#if _LIBCPP_STD_VER >= 20
40
41_LIBCPP_PUSH_MACROS
42# include <__undef_macros>
43
44_LIBCPP_BEGIN_NAMESPACE_STD
45
46namespace ranges {
47template <class _T1>
48using minmax_result = min_max_result<_T1>;
49
50namespace __minmax {
51struct __fn {
52 template <class _Type,
53 class _Proj = identity,
54 indirect_strict_weak_order<projected<const _Type*, _Proj>> _Comp = ranges::less>
55 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr ranges::minmax_result<const _Type&>
56 operator()(_LIBCPP_LIFETIMEBOUND const _Type& __a,
57 _LIBCPP_LIFETIMEBOUND const _Type& __b,
58 _Comp __comp = {},
59 _Proj __proj = {}) const {
60 if (std::invoke(__comp, std::invoke(__proj, __b), std::invoke(__proj, __a)))
61 return {__b, __a};
62 return {__a, __b};
63 }
64
65 template <copyable _Type,
66 class _Proj = identity,
67 indirect_strict_weak_order<projected<const _Type*, _Proj>> _Comp = ranges::less>
68 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr ranges::minmax_result<_Type>
69 operator()(initializer_list<_Type> __il, _Comp __comp = {}, _Proj __proj = {}) const {
70 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
71 __il.begin() != __il.end(), "initializer_list has to contain at least one element");
72 auto __iters = std::__minmax_element_impl(__il.begin(), __il.end(), __comp, __proj);
73 return ranges::minmax_result<_Type>{*__iters.first, *__iters.second};
74 }
75
76 template <input_range _Range,
77 class _Proj = identity,
78 indirect_strict_weak_order<projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less>
79 requires indirectly_copyable_storable<iterator_t<_Range>, range_value_t<_Range>*>
80 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr ranges::minmax_result<range_value_t<_Range>>
81 operator()(_Range&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
82 auto __first = ranges::begin(__r);
83 auto __last = ranges::end(__r);
84 using _ValueT = range_value_t<_Range>;
85
86 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__first != __last, "range has to contain at least one element");
87
88 // This optimiation is not in minmax_element because clang doesn't see through the pointers and as a result doesn't
89 // vectorize the code.
90 if constexpr (contiguous_range<_Range> && is_integral_v<_ValueT> &&
91 __is_cheap_to_copy<_ValueT> & __is_identity<_Proj>::value &&
92 __desugars_to_v<__less_tag, _Comp, _ValueT, _ValueT>) {
93 minmax_result<_ValueT> __result = {__r[0], __r[0]};
94 for (auto __e : __r) {
95 if (__e < __result.min)
96 __result.min = __e;
97 if (__result.max < __e)
98 __result.max = __e;
99 }
100 return __result;
101 } else if constexpr (forward_range<_Range>) {
102 // Special-case the one element case. Avoid repeatedly initializing objects from the result of an iterator
103 // dereference when doing so might not be idempotent. The `if constexpr` avoids the extra branch in cases where
104 // it's not needed.
105 if constexpr (!same_as<remove_cvref_t<range_reference_t<_Range>>, _ValueT> ||
106 is_rvalue_reference_v<range_reference_t<_Range>>) {
107 if (ranges::next(__first) == __last) {
108 // During initialization, members are allowed to refer to already initialized members
109 // (see http://eel.is/c++draft/dcl.init.aggr#6)
110 minmax_result<_ValueT> __result = {*__first, __result.min};
111 return __result;
112 }
113 }
114 auto __result = std::__minmax_element_impl(__first, __last, __comp, __proj);
115 return {*__result.first, *__result.second};
116 } else {
117 // input_iterators can't be copied, so the implementation for input_iterators has to store
118 // the values instead of a pointer to the correct values
119 auto __less = [&](auto&& __a, auto&& __b) -> bool {
120 return std::invoke(__comp,
121 std::invoke(__proj, std::forward<decltype(__a)>(__a)),
122 std::invoke(__proj, std::forward<decltype(__b)>(__b)));
123 };
124
125 // During initialization, members are allowed to refer to already initialized members
126 // (see http://eel.is/c++draft/dcl.init.aggr#6)
127 ranges::minmax_result<_ValueT> __result = {*__first, __result.min};
128 if (__first == __last || ++__first == __last)
129 return __result;
130
131 if (__less(*__first, __result.min))
132 __result.min = *__first;
133 else
134 __result.max = *__first;
135
136 while (++__first != __last) {
137 _ValueT __i = *__first;
138 if (++__first == __last) {
139 if (__less(__i, __result.min))
140 __result.min = __i;
141 else if (!__less(__i, __result.max))
142 __result.max = __i;
143 return __result;
144 }
145
146 if (__less(*__first, __i)) {
147 if (__less(*__first, __result.min))
148 __result.min = *__first;
149 if (!__less(__i, __result.max))
150 __result.max = std::move(__i);
151 } else {
152 if (__less(__i, __result.min))
153 __result.min = std::move(__i);
154 if (!__less(*__first, __result.max))
155 __result.max = *__first;
156 }
157 }
158 return __result;
159 }
160 }
161};
162} // namespace __minmax
163
164inline namespace __cpo {
165inline constexpr auto minmax = __minmax::__fn{};
166} // namespace __cpo
167} // namespace ranges
168
169_LIBCPP_END_NAMESPACE_STD
170
171_LIBCPP_POP_MACROS
172
173#endif // _LIBCPP_STD_VER >= 20
174
175#endif // _LIBCPP___ALGORITHM_RANGES_MINMAX_H
176