1// Concept-constrained comparison implementations -*- C++ -*-
2
3// Copyright (C) 2019-2025 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 && std::__detail::__not_overloaded_spaceship<_Tp, _Up>;
76 } // namespace __detail
77
78 // [range.cmp] Concept-constrained comparisons
79
80 // _GLIBCXX_RESOLVE_LIB_DEFECTS
81 // 3530 BUILTIN-PTR-MEOW should not opt the type out of syntactic checks
82
83 /// ranges::equal_to function object type.
84 struct equal_to
85 {
86 template<typename _Tp, typename _Up>
87 requires equality_comparable_with<_Tp, _Up>
88 constexpr bool
89 operator()(_Tp&& __t, _Up&& __u) const
90 noexcept(noexcept(std::declval<_Tp>() == std::declval<_Up>()))
91 { return std::forward<_Tp>(__t) == std::forward<_Up>(__u); }
92
93 using is_transparent = __is_transparent;
94 };
95
96 /// ranges::not_equal_to function object type.
97 struct not_equal_to
98 {
99 template<typename _Tp, typename _Up>
100 requires equality_comparable_with<_Tp, _Up>
101 constexpr bool
102 operator()(_Tp&& __t, _Up&& __u) const
103 noexcept(noexcept(std::declval<_Tp>() == std::declval<_Up>()))
104 { return !equal_to{}(std::forward<_Tp>(__t), std::forward<_Up>(__u)); }
105
106 using is_transparent = __is_transparent;
107 };
108
109 /// ranges::less function object type.
110 struct less
111 {
112 template<typename _Tp, typename _Up>
113 requires totally_ordered_with<_Tp, _Up>
114 constexpr bool
115 operator()(_Tp&& __t, _Up&& __u) const
116 noexcept(noexcept(std::declval<_Tp>() < std::declval<_Up>()))
117 {
118 if constexpr (__detail::__less_builtin_ptr_cmp<_Tp, _Up>)
119 {
120 if (std::__is_constant_evaluated())
121 return __t < __u;
122
123 auto __x = reinterpret_cast<__UINTPTR_TYPE__>(
124 static_cast<const volatile void*>(std::forward<_Tp>(__t)));
125 auto __y = reinterpret_cast<__UINTPTR_TYPE__>(
126 static_cast<const volatile void*>(std::forward<_Up>(__u)));
127 return __x < __y;
128 }
129 else
130 return std::forward<_Tp>(__t) < std::forward<_Up>(__u);
131 }
132
133 using is_transparent = __is_transparent;
134 };
135
136 /// ranges::greater function object type.
137 struct greater
138 {
139 template<typename _Tp, typename _Up>
140 requires totally_ordered_with<_Tp, _Up>
141 constexpr bool
142 operator()(_Tp&& __t, _Up&& __u) const
143 noexcept(noexcept(std::declval<_Up>() < std::declval<_Tp>()))
144 { return less{}(std::forward<_Up>(__u), std::forward<_Tp>(__t)); }
145
146 using is_transparent = __is_transparent;
147 };
148
149 /// ranges::greater_equal function object type.
150 struct greater_equal
151 {
152 template<typename _Tp, typename _Up>
153 requires totally_ordered_with<_Tp, _Up>
154 constexpr bool
155 operator()(_Tp&& __t, _Up&& __u) const
156 noexcept(noexcept(std::declval<_Tp>() < std::declval<_Up>()))
157 { return !less{}(std::forward<_Tp>(__t), std::forward<_Up>(__u)); }
158
159 using is_transparent = __is_transparent;
160 };
161
162 /// ranges::less_equal function object type.
163 struct less_equal
164 {
165 template<typename _Tp, typename _Up>
166 requires totally_ordered_with<_Tp, _Up>
167 constexpr bool
168 operator()(_Tp&& __t, _Up&& __u) const
169 noexcept(noexcept(std::declval<_Up>() < std::declval<_Tp>()))
170 { return !less{}(std::forward<_Up>(__u), std::forward<_Tp>(__t)); }
171
172 using is_transparent = __is_transparent;
173 };
174
175} // namespace ranges
176#endif // __glibcxx_ranges
177_GLIBCXX_END_NAMESPACE_VERSION
178} // namespace std
179#endif // C++20
180#endif // _RANGES_CMP_H
181