1// Concept-constrained comparison implementations -*- C++ -*-
2
3// Copyright (C) 2019-2021 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 __cpp_lib_concepts
59// Define this here, included by all the headers that need to define it.
60#define __cpp_lib_ranges 202106L
61
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 } // namespace __detail
79
80 // [range.cmp] Concept-constrained comparisons
81
82 // _GLIBCXX_RESOLVE_LIB_DEFECTS
83 // 3530 BUILTIN-PTR-MEOW should not opt the type out of syntactic checks
84
85 /// ranges::equal_to function object type.
86 struct equal_to
87 {
88 template<typename _Tp, typename _Up>
89 requires equality_comparable_with<_Tp, _Up>
90 constexpr bool
91 operator()(_Tp&& __t, _Up&& __u) const
92 noexcept(noexcept(std::declval<_Tp>() == std::declval<_Up>()))
93 { return std::forward<_Tp>(__t) == std::forward<_Up>(__u); }
94
95 using is_transparent = __is_transparent;
96 };
97
98 /// ranges::not_equal_to function object type.
99 struct not_equal_to
100 {
101 template<typename _Tp, typename _Up>
102 requires equality_comparable_with<_Tp, _Up>
103 constexpr bool
104 operator()(_Tp&& __t, _Up&& __u) const
105 noexcept(noexcept(std::declval<_Up>() == std::declval<_Tp>()))
106 { return !equal_to{}(std::forward<_Tp>(__t), std::forward<_Up>(__u)); }
107
108 using is_transparent = __is_transparent;
109 };
110
111 /// ranges::less function object type.
112 struct less
113 {
114 template<typename _Tp, typename _Up>
115 requires totally_ordered_with<_Tp, _Up>
116 constexpr bool
117 operator()(_Tp&& __t, _Up&& __u) const
118 noexcept(noexcept(std::declval<_Tp>() < std::declval<_Up>()))
119 {
120 if constexpr (__detail::__less_builtin_ptr_cmp<_Tp, _Up>)
121 {
122#ifdef __cpp_lib_is_constant_evaluated
123 if (std::is_constant_evaluated())
124 return __t < __u;
125#endif
126 auto __x = reinterpret_cast<__UINTPTR_TYPE__>(
127 static_cast<const volatile void*>(std::forward<_Tp>(__t)));
128 auto __y = reinterpret_cast<__UINTPTR_TYPE__>(
129 static_cast<const volatile void*>(std::forward<_Up>(__u)));
130 return __x < __y;
131 }
132 else
133 return std::forward<_Tp>(__t) < std::forward<_Up>(__u);
134 }
135
136 using is_transparent = __is_transparent;
137 };
138
139 /// ranges::greater function object type.
140 struct greater
141 {
142 template<typename _Tp, typename _Up>
143 requires totally_ordered_with<_Tp, _Up>
144 constexpr bool
145 operator()(_Tp&& __t, _Up&& __u) const
146 noexcept(noexcept(std::declval<_Up>() < std::declval<_Tp>()))
147 { return less{}(std::forward<_Up>(__u), std::forward<_Tp>(__t)); }
148
149 using is_transparent = __is_transparent;
150 };
151
152 /// ranges::greater_equal function object type.
153 struct greater_equal
154 {
155 template<typename _Tp, typename _Up>
156 requires totally_ordered_with<_Tp, _Up>
157 constexpr bool
158 operator()(_Tp&& __t, _Up&& __u) const
159 noexcept(noexcept(std::declval<_Tp>() < std::declval<_Up>()))
160 { return !less{}(std::forward<_Tp>(__t), std::forward<_Up>(__u)); }
161
162 using is_transparent = __is_transparent;
163 };
164
165 /// ranges::less_equal function object type.
166 struct less_equal
167 {
168 template<typename _Tp, typename _Up>
169 requires totally_ordered_with<_Tp, _Up>
170 constexpr bool
171 operator()(_Tp&& __t, _Up&& __u) const
172 noexcept(noexcept(std::declval<_Up>() < std::declval<_Tp>()))
173 { return !less{}(std::forward<_Up>(__u), std::forward<_Tp>(__t)); }
174
175 using is_transparent = __is_transparent;
176 };
177
178} // namespace ranges
179#endif // library concepts
180_GLIBCXX_END_NAMESPACE_VERSION
181} // namespace std
182#endif // C++20
183#endif // _RANGES_CMP_H
184

source code of include/c++/11/bits/ranges_cmp.h