libstdc++-v3/include/ext/type_traits.h

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005-2025 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 terms
   7 // of the GNU General Public License as published by the Free Software
   8 // Foundation; either version 3, or (at your option) any later
   9 // version.
  10
  11 // This library is distributed in the hope that it will be useful, but
  12 // WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 // 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 ext/type_traits.h
  26  *  This file is a GNU extension to the Standard C++ Library.
  27  */
  28
  29 #ifndef _EXT_TYPE_TRAITS
  30 #define _EXT_TYPE_TRAITS 1
  31
  32 #ifdef _GLIBCXX_SYSHDR
  33 #pragma GCC system_header
  34 #endif
  35
  36 #include <bits/c++config.h>
  37 #include <bits/cpp_type_traits.h>
  38
  39 #pragma GCC diagnostic push
  40 #pragma GCC diagnostic ignored "-Wlong-long"
  41
  42 extern "C++" {
  43
  44 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  45 {
  46 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  47
  48   // Define a nested type if some predicate holds.
  49   template<bool, typename>
  50     struct __enable_if
  51     { };
  52
  53   template<typename _Tp>
  54     struct __enable_if<true, _Tp>
  55     { typedef _Tp __type; };
  56
  57
  58   // Conditional expression for types. If true, first, if false, second.
  59   template<bool _Cond, typename _Iftrue, typename _Iffalse>
  60     struct __conditional_type
  61     { typedef _Iftrue __type; };
  62
  63   template<typename _Iftrue, typename _Iffalse>
  64     struct __conditional_type<false, _Iftrue, _Iffalse>
  65     { typedef _Iffalse __type; };
  66
  67
  68   // Given an integral builtin type, return the corresponding unsigned type.
  69   template<typename _Tp>
  70     struct __add_unsigned
  71     {
  72     private:
  73       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
  74
  75     public:
  76       typedef typename __if_type::__type __type;
  77     };
  78
  79   template<>
  80     struct __add_unsigned<char>
  81     { typedef unsigned char __type; };
  82
  83   template<>
  84     struct __add_unsigned<signed char>
  85     { typedef unsigned char __type; };
  86
  87   template<>
  88     struct __add_unsigned<short>
  89     { typedef unsigned short __type; };
  90
  91   template<>
  92     struct __add_unsigned<int>
  93     { typedef unsigned int __type; };
  94
  95   template<>
  96     struct __add_unsigned<long>
  97     { typedef unsigned long __type; };
  98
  99   template<>
 100     struct __add_unsigned<long long>
 101     { typedef unsigned long long __type; };
 102
 103   // Declare but don't define.
 104   template<>
 105     struct __add_unsigned<bool>;
 106
 107   template<>
 108     struct __add_unsigned<wchar_t>;
 109
 110
 111   // Given an integral builtin type, return the corresponding signed type.
 112   template<typename _Tp>
 113     struct __remove_unsigned
 114     {
 115     private:
 116       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
 117
 118     public:
 119       typedef typename __if_type::__type __type;
 120     };
 121
 122   template<>
 123     struct __remove_unsigned<char>
 124     { typedef signed char __type; };
 125
 126   template<>
 127     struct __remove_unsigned<unsigned char>
 128     { typedef signed char __type; };
 129
 130   template<>
 131     struct __remove_unsigned<unsigned short>
 132     { typedef short __type; };
 133
 134   template<>
 135     struct __remove_unsigned<unsigned int>
 136     { typedef int __type; };
 137
 138   template<>
 139     struct __remove_unsigned<unsigned long>
 140     { typedef long __type; };
 141
 142   template<>
 143     struct __remove_unsigned<unsigned long long>
 144     { typedef long long __type; };
 145
 146   // Declare but don't define.
 147   template<>
 148     struct __remove_unsigned<bool>;
 149
 150   template<>
 151     struct __remove_unsigned<wchar_t>;
 152
 153
 154   // For use in string and vstring.
 155   template<typename _Type>
 156     _GLIBCXX_CONSTEXPR
 157     inline bool
 158     __is_null_pointer(_Type* __ptr)
 159     { return __ptr == 0; }
 160
 161   template<typename _Type>
 162     _GLIBCXX_CONSTEXPR
 163     inline bool
 164     __is_null_pointer(_Type)
 165     { return false; }
 166
 167 #if __cplusplus >= 201103L
 168   constexpr bool
 169   __is_null_pointer(std::nullptr_t)
 170   { return true; }
 171 #endif
 172
 173   // For arithmetic promotions in <complex> and <cmath>
 174
 175   template<typename _Tp, bool = std::__is_integer<_Tp>::__value>
 176     struct __promote
 177     { typedef double __type; };
 178
 179   // No nested __type member for non-integer non-floating point types,
 180   // allows this type to be used for SFINAE to constrain overloads in
 181   // <cmath> and <complex> to only the intended types.
 182   template<typename _Tp>
 183     struct __promote<_Tp, false>
 184     { };
 185
 186   template<>
 187     struct __promote<long double>
 188     { typedef long double __type; };
 189
 190   template<>
 191     struct __promote<double>
 192     { typedef double __type; };
 193
 194   template<>
 195     struct __promote<float>
 196     { typedef float __type; };
 197
 198 #ifdef __STDCPP_FLOAT16_T__
 199   template<>
 200     struct __promote<_Float16>
 201     { typedef _Float16 __type; };
 202 #endif
 203
 204 #ifdef __STDCPP_FLOAT32_T__
 205   template<>
 206     struct __promote<_Float32>
 207     { typedef _Float32 __type; };
 208 #endif
 209
 210 #ifdef __STDCPP_FLOAT64_T__
 211   template<>
 212     struct __promote<_Float64>
 213     { typedef _Float64 __type; };
 214 #endif
 215
 216 #ifdef __STDCPP_FLOAT128_T__
 217   template<>
 218     struct __promote<_Float128>
 219     { typedef _Float128 __type; };
 220 #endif
 221
 222 #ifdef __STDCPP_BFLOAT16_T__
 223   template<>
 224     struct __promote<__gnu_cxx::__bfloat16_t>
 225     { typedef __gnu_cxx::__bfloat16_t __type; };
 226 #endif
 227
 228 #if __cpp_fold_expressions
 229
 230   template<typename... _Tp>
 231     using __promoted_t = decltype((typename __promote<_Tp>::__type(0) + ...));
 232
 233   // Deducing the promoted type is done by __promoted_t<_Tp...>,
 234   // then __promote is used to provide the nested __type member.
 235   template<typename _Tp, typename _Up>
 236     using __promote_2 = __promote<__promoted_t<_Tp, _Up>>;
 237
 238   template<typename _Tp, typename _Up, typename _Vp>
 239     using __promote_3 = __promote<__promoted_t<_Tp, _Up, _Vp>>;
 240
 241   template<typename _Tp, typename _Up, typename _Vp, typename _Wp>
 242     using __promote_4 = __promote<__promoted_t<_Tp, _Up, _Vp, _Wp>>;
 243
 244 #else
 245
 246   template<typename _Tp, typename _Up,
 247            typename _Tp2 = typename __promote<_Tp>::__type,
 248            typename _Up2 = typename __promote<_Up>::__type>
 249     struct __promote_2
 250     {
 251       typedef __typeof__(_Tp2() + _Up2()) __type;
 252     };
 253
 254   template<typename _Tp, typename _Up, typename _Vp,
 255            typename _Tp2 = typename __promote<_Tp>::__type,
 256            typename _Up2 = typename __promote<_Up>::__type,
 257            typename _Vp2 = typename __promote<_Vp>::__type>
 258     struct __promote_3
 259     {
 260       typedef __typeof__(_Tp2() + _Up2() + _Vp2()) __type;
 261     };
 262
 263   template<typename _Tp, typename _Up, typename _Vp, typename _Wp,
 264            typename _Tp2 = typename __promote<_Tp>::__type,
 265            typename _Up2 = typename __promote<_Up>::__type,
 266            typename _Vp2 = typename __promote<_Vp>::__type,
 267            typename _Wp2 = typename __promote<_Wp>::__type>
 268     struct __promote_4
 269     {
 270       typedef __typeof__(_Tp2() + _Up2() + _Vp2() + _Wp2()) __type;
 271     };
 272 #endif
 273
 274 _GLIBCXX_END_NAMESPACE_VERSION
 275 } // namespace
 276 } // extern "C++"
 277
 278 #pragma GCC diagnostic pop
 279
 280 #endif