libstdc++
ranges_cmp.h
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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 
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 __cpp_lib_concepts
59 // Define this here, included by all the headers that need to define it.
60 #define __cpp_lib_ranges 201911L
61 
62 namespace 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