1// Concept-constrained comparison implementations -*- C++ -*-
2
3// Copyright (C) 2019-2024 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file bits/ranges_cmp.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{functional}
28 */
29
30#ifndef _RANGES_CMP_H
31#define _RANGES_CMP_H 1
32
33#if __cplusplus > 201703L
34# include <bits/move.h>
35# include <concepts>
36
37namespace std _GLIBCXX_VISIBILITY(default)
38{
39_GLIBCXX_BEGIN_NAMESPACE_VERSION
40
41 struct __is_transparent; // not defined
42
43 // Define std::identity here so that <iterator> and <ranges>
44 // don't need to include <bits/stl_function.h> to get it.
45
46 /// [func.identity] The identity function.
47 struct identity
48 {
49 template<typename _Tp>
50 [[nodiscard]]
51 constexpr _Tp&&
52 operator()(_Tp&& __t) const noexcept
53 { return std::forward<_Tp>(__t); }
54
55 using is_transparent = __is_transparent;
56 };
57
58#ifdef __glibcxx_ranges // C++ >= 20
59namespace ranges
60{
61 namespace __detail
62 {
63 // BUILTIN-PTR-CMP(T, <, U)
64 // This determines whether t < u results in a call to a built-in operator<
65 // comparing pointers. It doesn't work for function pointers (PR 93628).
66 template<typename _Tp, typename _Up>
67 concept __less_builtin_ptr_cmp
68 = requires (_Tp&& __t, _Up&& __u) { { __t < __u } -> same_as<bool>; }
69 && convertible_to<_Tp, const volatile void*>
70 && convertible_to<_Up, const volatile void*>
71 && (! requires(_Tp&& __t, _Up&& __u)
72 { operator<(std::forward<_Tp>(__t), std::forward<_Up>(__u)); }
73 && ! requires(_Tp&& __t, _Up&& __u)
74 { std::forward<_Tp>(__t).operator<(std::forward<_Up>(__u)); });
75 } // namespace __detail
76
77 // [range.cmp] Concept-constrained comparisons
78
79 // _GLIBCXX_RESOLVE_LIB_DEFECTS
80 // 3530 BUILTIN-PTR-MEOW should not opt the type out of syntactic checks
81
82 /// ranges::equal_to function object type.
83 struct equal_to
84 {
85 template<typename _Tp, typename _Up>
86 requires equality_comparable_with<_Tp, _Up>
87 constexpr bool
88 operator()(_Tp&& __t, _Up&& __u) const
89 noexcept(noexcept(std::declval<_Tp>() == std::declval<_Up>()))
90 { return std::forward<_Tp>(__t) == std::forward<_Up>(__u); }
91
92 using is_transparent = __is_transparent;
93 };
94
95 /// ranges::not_equal_to function object type.
96 struct not_equal_to
97 {
98 template<typename _Tp, typename _Up>
99 requires equality_comparable_with<_Tp, _Up>
100 constexpr bool
101 operator()(_Tp&& __t, _Up&& __u) const
102 noexcept(noexcept(std::declval<_Up>() == std::declval<_Tp>()))
103 { return !equal_to{}(std::forward<_Tp>(__t), std::forward<_Up>(__u)); }
104
105 using is_transparent = __is_transparent;
106 };
107
108 /// ranges::less function object type.
109 struct less
110 {
111 template<typename _Tp, typename _Up>
112 requires totally_ordered_with<_Tp, _Up>
113 constexpr bool
114 operator()(_Tp&& __t, _Up&& __u) const
115 noexcept(noexcept(std::declval<_Tp>() < std::declval<_Up>()))
116 {
117 if constexpr (__detail::__less_builtin_ptr_cmp<_Tp, _Up>)
118 {
119 if (std::__is_constant_evaluated())
120 return __t < __u;
121
122 auto __x = reinterpret_cast<__UINTPTR_TYPE__>(
123 static_cast<const volatile void*>(std::forward<_Tp>(__t)));
124 auto __y = reinterpret_cast<__UINTPTR_TYPE__>(
125 static_cast<const volatile void*>(std::forward<_Up>(__u)));
126 return __x < __y;
127 }
128 else
129 return std::forward<_Tp>(__t) < std::forward<_Up>(__u);
130 }
131
132 using is_transparent = __is_transparent;
133 };
134
135 /// ranges::greater function object type.
136 struct greater
137 {
138 template<typename _Tp, typename _Up>
139 requires totally_ordered_with<_Tp, _Up>
140 constexpr bool
141 operator()(_Tp&& __t, _Up&& __u) const
142 noexcept(noexcept(std::declval<_Up>() < std::declval<_Tp>()))
143 { return less{}(std::forward<_Up>(__u), std::forward<_Tp>(__t)); }
144
145 using is_transparent = __is_transparent;
146 };
147
148 /// ranges::greater_equal function object type.
149 struct greater_equal
150 {
151 template<typename _Tp, typename _Up>
152 requires totally_ordered_with<_Tp, _Up>
153 constexpr bool
154 operator()(_Tp&& __t, _Up&& __u) const
155 noexcept(noexcept(std::declval<_Tp>() < std::declval<_Up>()))
156 { return !less{}(std::forward<_Tp>(__t), std::forward<_Up>(__u)); }
157
158 using is_transparent = __is_transparent;
159 };
160
161 /// ranges::less_equal function object type.
162 struct less_equal
163 {
164 template<typename _Tp, typename _Up>
165 requires totally_ordered_with<_Tp, _Up>
166 constexpr bool
167 operator()(_Tp&& __t, _Up&& __u) const
168 noexcept(noexcept(std::declval<_Up>() < std::declval<_Tp>()))
169 { return !less{}(std::forward<_Up>(__u), std::forward<_Tp>(__t)); }
170
171 using is_transparent = __is_transparent;
172 };
173
174} // namespace ranges
175#endif // __glibcxx_ranges
176_GLIBCXX_END_NAMESPACE_VERSION
177} // namespace std
178#endif // C++20
179#endif // _RANGES_CMP_H
180