libstdc++
ranges_cmp.h
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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 
37 namespace 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
59 namespace 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.
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
ISO C++ entities toplevel namespace is std.
[func.identity] The identity function.
Definition: ranges_cmp.h:48
ranges::equal_to function object type.
Definition: ranges_cmp.h:84
ranges::not_equal_to function object type.
Definition: ranges_cmp.h:97
ranges::less function object type.
Definition: ranges_cmp.h:110
ranges::greater function object type.
Definition: ranges_cmp.h:137
ranges::greater_equal function object type.
Definition: ranges_cmp.h:150
ranges::less_equal function object type.
Definition: ranges_cmp.h:163