1// <utility> -*- C++ -*-
2
3// Copyright (C) 2001-2024 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/*
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#define __glibcxx_want_addressof_constexpr
83#define __glibcxx_want_as_const
84#define __glibcxx_want_constexpr_algorithms
85#define __glibcxx_want_constexpr_utility
86#define __glibcxx_want_exchange_function
87#define __glibcxx_want_forward_like
88#define __glibcxx_want_integer_comparison_functions
89#define __glibcxx_want_integer_sequence
90#define __glibcxx_want_ranges_zip
91#define __glibcxx_want_to_underlying
92#define __glibcxx_want_tuple_element_t
93#define __glibcxx_want_tuples_by_type
94#define __glibcxx_want_unreachable
95#define __glibcxx_want_tuple_like
96#include <bits/version.h>
97
98namespace std _GLIBCXX_VISIBILITY(default)
99{
100_GLIBCXX_BEGIN_NAMESPACE_VERSION
101
102#ifdef __cpp_lib_exchange_function // C++ >= 14
103 /// Assign @p __new_val to @p __obj and return its previous value.
104 template <typename _Tp, typename _Up = _Tp>
105 _GLIBCXX20_CONSTEXPR
106 inline _Tp
107 exchange(_Tp& __obj, _Up&& __new_val)
108 noexcept(__and_<is_nothrow_move_constructible<_Tp>,
109 is_nothrow_assignable<_Tp&, _Up>>::value)
110 { return std::__exchange(__obj, std::forward<_Up>(__new_val)); }
111#endif
112
113#ifdef __cpp_lib_as_const // C++ >= 17
114 template<typename _Tp>
115 [[nodiscard]]
116 constexpr add_const_t<_Tp>&
117 as_const(_Tp& __t) noexcept
118 { return __t; }
119
120 template<typename _Tp>
121 void as_const(const _Tp&&) = delete;
122#endif
123
124#ifdef __cpp_lib_integer_comparison_functions // C++ >= 20
125 template<typename _Tp, typename _Up>
126 constexpr bool
127 cmp_equal(_Tp __t, _Up __u) noexcept
128 {
129 static_assert(__is_standard_integer<_Tp>::value);
130 static_assert(__is_standard_integer<_Up>::value);
131
132 if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
133 return __t == __u;
134 else if constexpr (is_signed_v<_Tp>)
135 return __t >= 0 && make_unsigned_t<_Tp>(__t) == __u;
136 else
137 return __u >= 0 && __t == make_unsigned_t<_Up>(__u);
138 }
139
140 template<typename _Tp, typename _Up>
141 constexpr bool
142 cmp_not_equal(_Tp __t, _Up __u) noexcept
143 { return !std::cmp_equal(__t, __u); }
144
145 template<typename _Tp, typename _Up>
146 constexpr bool
147 cmp_less(_Tp __t, _Up __u) noexcept
148 {
149 static_assert(__is_standard_integer<_Tp>::value);
150 static_assert(__is_standard_integer<_Up>::value);
151
152 if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
153 return __t < __u;
154 else if constexpr (is_signed_v<_Tp>)
155 return __t < 0 || make_unsigned_t<_Tp>(__t) < __u;
156 else
157 return __u >= 0 && __t < make_unsigned_t<_Up>(__u);
158 }
159
160 template<typename _Tp, typename _Up>
161 constexpr bool
162 cmp_greater(_Tp __t, _Up __u) noexcept
163 { return std::cmp_less(__u, __t); }
164
165 template<typename _Tp, typename _Up>
166 constexpr bool
167 cmp_less_equal(_Tp __t, _Up __u) noexcept
168 { return !std::cmp_less(__u, __t); }
169
170 template<typename _Tp, typename _Up>
171 constexpr bool
172 cmp_greater_equal(_Tp __t, _Up __u) noexcept
173 { return !std::cmp_less(__t, __u); }
174
175 template<typename _Res, typename _Tp>
176 constexpr bool
177 in_range(_Tp __t) noexcept
178 {
179 static_assert(__is_standard_integer<_Res>::value);
180 static_assert(__is_standard_integer<_Tp>::value);
181 using __gnu_cxx::__int_traits;
182
183 if constexpr (is_signed_v<_Tp> == is_signed_v<_Res>)
184 return __int_traits<_Res>::__min <= __t
185 && __t <= __int_traits<_Res>::__max;
186 else if constexpr (is_signed_v<_Tp>)
187 return __t >= 0
188 && make_unsigned_t<_Tp>(__t) <= __int_traits<_Res>::__max;
189 else
190 return __t <= make_unsigned_t<_Res>(__int_traits<_Res>::__max);
191 }
192#endif // __cpp_lib_integer_comparison_functions
193
194#ifdef __cpp_lib_to_underlying // C++ >= 23
195 /// Convert an object of enumeration type to its underlying type.
196 template<typename _Tp>
197 [[nodiscard]]
198 constexpr underlying_type_t<_Tp>
199 to_underlying(_Tp __value) noexcept
200 { return static_cast<underlying_type_t<_Tp>>(__value); }
201#endif
202
203#ifdef __cpp_lib_unreachable // C++ >= 23
204 /// Informs the compiler that program control flow never reaches this point.
205 /**
206 * Evaluating a call to this function results in undefined behaviour.
207 * This can be used as an assertion informing the compiler that certain
208 * conditions are impossible, for when the compiler is unable to determine
209 * that by itself.
210 *
211 * For example, it can be used to prevent warnings about reaching the
212 * end of a non-void function without returning.
213 *
214 * @since C++23
215 */
216 [[noreturn,__gnu__::__always_inline__]]
217 inline void
218 unreachable()
219 {
220#ifdef _GLIBCXX_DEBUG
221 std::__glibcxx_assert_fail(nullptr, 0, "std::unreachable()", nullptr);
222#elif defined _GLIBCXX_ASSERTIONS
223 __builtin_trap();
224#else
225 __builtin_unreachable();
226#endif
227 }
228#endif
229
230_GLIBCXX_END_NAMESPACE_VERSION
231} // namespace
232
233#endif
234
235#endif /* _GLIBCXX_UTILITY */
236