libstdc++: ranges_cmp.h Source File

libstdc++

ranges_cmp.h
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1// Concept-constrained comparison implementations -*- C++ -*-
2
3// Copyright (C) 2019-2026 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#pragma GCC diagnostic push
50#pragma GCC diagnostic ignored "-Wc++23-extensions" // static operator()
51 template<typename _Tp>
52 [[nodiscard]]
53 static constexpr _Tp&&
54 operator()(_Tp&& __t) noexcept
55 { return std::forward<_Tp>(__t); }
56#pragma GCC diagnostic pop
57
58 using is_transparent = __is_transparent;
59 };
60
61#ifdef __glibcxx_ranges // C++ >= 20
62namespace ranges
63{
64 namespace __detail
65 {
66 // BUILTIN-PTR-CMP(T, <, U)
67 // This determines whether t < u results in a call to a built-in operator<
68 // comparing pointers. It doesn't work for function pointers (PR 93628).
69 template<typename _Tp, typename _Up>
70 concept __less_builtin_ptr_cmp
71 = requires (_Tp&& __t, _Up&& __u) { { __t < __u } -> same_as<bool>; }
72 && convertible_to<_Tp, const volatile void*>
73 && convertible_to<_Up, const volatile void*>
74 && ! requires(_Tp&& __t, _Up&& __u)
75 { operator<(std::forward<_Tp>(__t), std::forward<_Up>(__u)); }
76 && ! requires(_Tp&& __t, _Up&& __u)
77 { std::forward<_Tp>(__t).operator<(std::forward<_Up>(__u)); }
78 && std::__detail::__not_overloaded_spaceship<_Tp, _Up>;
79 } // namespace __detail
80
81 // [range.cmp] Concept-constrained comparisons
82
83 // _GLIBCXX_RESOLVE_LIB_DEFECTS
84 // 3530 BUILTIN-PTR-MEOW should not opt the type out of syntactic checks
85
86#pragma GCC diagnostic push
87#pragma GCC diagnostic ignored "-Wc++23-extensions" // static operator()
88 /// ranges::equal_to function object type.
89 struct equal_to
90 {
91 template<typename _Tp, typename _Up>
92 requires equality_comparable_with<_Tp, _Up>
93 static constexpr bool
94 operator()(_Tp&& __t, _Up&& __u)
95 noexcept(noexcept(std::declval<_Tp>() == std::declval<_Up>()))
96 { return std::forward<_Tp>(__t) == std::forward<_Up>(__u); }
97
98 using is_transparent = __is_transparent;
99 };
100
101 /// ranges::not_equal_to function object type.
102 struct not_equal_to
103 {
104 template<typename _Tp, typename _Up>
105 requires equality_comparable_with<_Tp, _Up>
106 static constexpr bool
107 operator()(_Tp&& __t, _Up&& __u)
108 noexcept(noexcept(std::declval<_Tp>() == std::declval<_Up>()))
109 { return !equal_to{}(std::forward<_Tp>(__t), std::forward<_Up>(__u)); }
110
111 using is_transparent = __is_transparent;
112 };
113
114 /// ranges::less function object type.
115 struct less
116 {
117 template<typename _Tp, typename _Up>
118 requires totally_ordered_with<_Tp, _Up>
119 static constexpr bool
120 operator()(_Tp&& __t, _Up&& __u)
121 noexcept(noexcept(std::declval<_Tp>() < std::declval<_Up>()))
122 {
123 if constexpr (__detail::__less_builtin_ptr_cmp<_Tp, _Up>)
124 {
125 if (std::__is_constant_evaluated())
126 return __t < __u;
127
128 auto __x = reinterpret_cast<__UINTPTR_TYPE__>(
129 static_cast<const volatile void*>(std::forward<_Tp>(__t)));
130 auto __y = reinterpret_cast<__UINTPTR_TYPE__>(
131 static_cast<const volatile void*>(std::forward<_Up>(__u)));
132 return __x < __y;
133 }
134 else
135 return std::forward<_Tp>(__t) < std::forward<_Up>(__u);
136 }
137
138 using is_transparent = __is_transparent;
139 };
140
141 /// ranges::greater function object type.
142 struct greater
143 {
144 template<typename _Tp, typename _Up>
145 requires totally_ordered_with<_Tp, _Up>
146 static constexpr bool
147 operator()(_Tp&& __t, _Up&& __u)
148 noexcept(noexcept(std::declval<_Up>() < std::declval<_Tp>()))
149 { return less{}(std::forward<_Up>(__u), std::forward<_Tp>(__t)); }
150
151 using is_transparent = __is_transparent;
152 };
153
154 /// ranges::greater_equal function object type.
155 struct greater_equal
156 {
157 template<typename _Tp, typename _Up>
158 requires totally_ordered_with<_Tp, _Up>
159 static constexpr bool
160 operator()(_Tp&& __t, _Up&& __u)
161 noexcept(noexcept(std::declval<_Tp>() < std::declval<_Up>()))
162 { return !less{}(std::forward<_Tp>(__t), std::forward<_Up>(__u)); }
163
164 using is_transparent = __is_transparent;
165 };
166
167 /// ranges::less_equal function object type.
168 struct less_equal
169 {
170 template<typename _Tp, typename _Up>
171 requires totally_ordered_with<_Tp, _Up>
172 static constexpr bool
173 operator()(_Tp&& __t, _Up&& __u)
174 noexcept(noexcept(std::declval<_Up>() < std::declval<_Tp>()))
175 { return !less{}(std::forward<_Up>(__u), std::forward<_Tp>(__t)); }
176
177 using is_transparent = __is_transparent;
178 };
179#pragma GCC diagnostic pop
180
181} // namespace ranges
182#endif // __glibcxx_ranges
183_GLIBCXX_END_NAMESPACE_VERSION
184} // namespace std
185#endif // C++20
186#endif // _RANGES_CMP_H
concepts
move.h
std::declval
auto declval() noexcept -> decltype(__declval< _Tp >(0))
Definition type_traits:2714
std::forward
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition move.h:72
std
ISO C++ entities toplevel namespace is std.
std::__detail
Implementation details not part of the namespace std interface.
std::identity
[func.identity] The identity function.
Definition ranges_cmp.h:48
std::ranges::equal_to
ranges::equal_to function object type.
Definition ranges_cmp.h:90
std::ranges::not_equal_to
ranges::not_equal_to function object type.
Definition ranges_cmp.h:103
std::ranges::less
ranges::less function object type.
Definition ranges_cmp.h:116
std::ranges::greater
ranges::greater function object type.
Definition ranges_cmp.h:143
std::ranges::greater_equal
ranges::greater_equal function object type.
Definition ranges_cmp.h:156
std::ranges::less_equal
ranges::less_equal function object type.
Definition ranges_cmp.h:169