libstdc++-v3/include/std/utility

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