libstdc++
utility
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1 // <utility> -*- C++ -*-
2 
3 // Copyright (C) 2001-2023 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 /*
26  *
27  * Copyright (c) 1994
28  * Hewlett-Packard Company
29  *
30  * Permission to use, copy, modify, distribute and sell this software
31  * and its documentation for any purpose is hereby granted without fee,
32  * provided that the above copyright notice appear in all copies and
33  * that both that copyright notice and this permission notice appear
34  * in supporting documentation. Hewlett-Packard Company makes no
35  * representations about the suitability of this software for any
36  * purpose. It is provided "as is" without express or implied warranty.
37  *
38  *
39  * Copyright (c) 1996,1997
40  * Silicon Graphics Computer Systems, Inc.
41  *
42  * Permission to use, copy, modify, distribute and sell this software
43  * and its documentation for any purpose is hereby granted without fee,
44  * provided that the above copyright notice appear in all copies and
45  * that both that copyright notice and this permission notice appear
46  * in supporting documentation. Silicon Graphics makes no
47  * representations about the suitability of this software for any
48  * purpose. It is provided "as is" without express or implied warranty.
49  */
50 
51 /** @file include/utility
52  * This is a Standard C++ Library header.
53  */
54 
55 #ifndef _GLIBCXX_UTILITY
56 #define _GLIBCXX_UTILITY 1
57 
58 #pragma GCC system_header
59 
60 /**
61  * @defgroup utilities Utilities
62  *
63  * Basic function and class templates used with the rest of the library.
64  * Includes pair, swap, forward/move helpers, declval, integer_sequence.
65  */
66 
67 #include <bits/c++config.h>
68 #include <bits/stl_relops.h>
69 #include <bits/stl_pair.h>
70 
71 #if __cplusplus >= 201103L
72 
73 #include <initializer_list>
74 #include <type_traits>
75 #include <bits/move.h>
76 #include <bits/utility.h>
77 
78 #if __cplusplus >= 202002L
79 #include <ext/numeric_traits.h> // __is_standard_integer, __int_traits
80 #endif
81 
82 namespace std _GLIBCXX_VISIBILITY(default)
83 {
84 _GLIBCXX_BEGIN_NAMESPACE_VERSION
85 
86 #if __cplusplus >= 201402L
87 #define __cpp_lib_exchange_function 201304L
88 
89 #if __cplusplus > 201703L
90 # define __cpp_lib_constexpr_algorithms 201806L
91 #endif
92 
93  /// Assign @p __new_val to @p __obj and return its previous value.
94  template <typename _Tp, typename _Up = _Tp>
95  _GLIBCXX20_CONSTEXPR
96  inline _Tp
97  exchange(_Tp& __obj, _Up&& __new_val)
98  noexcept(__and_<is_nothrow_move_constructible<_Tp>,
99  is_nothrow_assignable<_Tp&, _Up>>::value)
100  { return std::__exchange(__obj, std::forward<_Up>(__new_val)); }
101 
102 #if __cplusplus >= 201703L
103 
104 #define __cpp_lib_as_const 201510L
105  template<typename _Tp>
106  [[nodiscard]]
107  constexpr add_const_t<_Tp>&
108  as_const(_Tp& __t) noexcept
109  { return __t; }
110 
111  template<typename _Tp>
112  void as_const(const _Tp&&) = delete;
113 
114 #if __cplusplus > 201703L
115 #define __cpp_lib_integer_comparison_functions 202002L
116 
117  template<typename _Tp, typename _Up>
118  constexpr bool
119  cmp_equal(_Tp __t, _Up __u) noexcept
120  {
121  static_assert(__is_standard_integer<_Tp>::value);
122  static_assert(__is_standard_integer<_Up>::value);
123 
124  if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
125  return __t == __u;
126  else if constexpr (is_signed_v<_Tp>)
127  return __t >= 0 && make_unsigned_t<_Tp>(__t) == __u;
128  else
129  return __u >= 0 && __t == make_unsigned_t<_Up>(__u);
130  }
131 
132  template<typename _Tp, typename _Up>
133  constexpr bool
134  cmp_not_equal(_Tp __t, _Up __u) noexcept
135  { return !std::cmp_equal(__t, __u); }
136 
137  template<typename _Tp, typename _Up>
138  constexpr bool
139  cmp_less(_Tp __t, _Up __u) noexcept
140  {
141  static_assert(__is_standard_integer<_Tp>::value);
142  static_assert(__is_standard_integer<_Up>::value);
143 
144  if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
145  return __t < __u;
146  else if constexpr (is_signed_v<_Tp>)
147  return __t < 0 || make_unsigned_t<_Tp>(__t) < __u;
148  else
149  return __u >= 0 && __t < make_unsigned_t<_Up>(__u);
150  }
151 
152  template<typename _Tp, typename _Up>
153  constexpr bool
154  cmp_greater(_Tp __t, _Up __u) noexcept
155  { return std::cmp_less(__u, __t); }
156 
157  template<typename _Tp, typename _Up>
158  constexpr bool
159  cmp_less_equal(_Tp __t, _Up __u) noexcept
160  { return !std::cmp_less(__u, __t); }
161 
162  template<typename _Tp, typename _Up>
163  constexpr bool
164  cmp_greater_equal(_Tp __t, _Up __u) noexcept
165  { return !std::cmp_less(__t, __u); }
166 
167  template<typename _Up, typename _Tp>
168  constexpr bool
169  in_range(_Tp __t) noexcept
170  {
171  static_assert(__is_standard_integer<_Up>::value);
172  static_assert(__is_standard_integer<_Tp>::value);
173  using __gnu_cxx::__int_traits;
174 
175  if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
176  return __int_traits<_Up>::__min <= __t
177  && __t <= __int_traits<_Up>::__max;
178  else if constexpr (is_signed_v<_Tp>)
179  return __t >= 0
180  && make_unsigned_t<_Tp>(__t) <= __int_traits<_Up>::__max;
181  else
182  return __t <= make_unsigned_t<_Up>(__int_traits<_Up>::__max);
183  }
184 
185 #if __cplusplus > 202002L
186 #define __cpp_lib_to_underlying 202102L
187  /// Convert an object of enumeration type to its underlying type.
188  template<typename _Tp>
189  [[nodiscard]]
190  constexpr underlying_type_t<_Tp>
191  to_underlying(_Tp __value) noexcept
192  { return static_cast<underlying_type_t<_Tp>>(__value); }
193 
194 #define __cpp_lib_unreachable 202202L
195  /// Informs the compiler that program control flow never reaches this point.
196  /**
197  * Evaluating a call to this function results in undefined behaviour.
198  * This can be used as an assertion informing the compiler that certain
199  * conditions are impossible, for when the compiler is unable to determine
200  * that by itself.
201  *
202  * For example, it can be used to prevent warnings about reaching the
203  * end of a non-void function without returning.
204  *
205  * @since C++23
206  */
207  [[noreturn,__gnu__::__always_inline__]]
208  inline void
209  unreachable()
210  {
211 #ifdef _GLIBCXX_DEBUG
212  std::__glibcxx_assert_fail(nullptr, 0, "std::unreachable()", nullptr);
213 #elif defined _GLIBCXX_ASSERTIONS
214  __builtin_trap();
215 #else
216  __builtin_unreachable();
217 #endif
218  }
219 #endif // C++23
220 #endif // C++20
221 #endif // C++17
222 #endif // C++14
223 
224 _GLIBCXX_END_NAMESPACE_VERSION
225 } // namespace
226 
227 #endif
228 
229 #endif /* _GLIBCXX_UTILITY */