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

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005-2024 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 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 #pragma GCC system_header
  33
  34 #include <bits/c++config.h>
  35 #include <bits/cpp_type_traits.h>
  36
  37 extern "C++" {
  38
  39 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  40 {
  41 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  42
  43   // Define a nested type if some predicate holds.
  44   template<bool, typename>
  45     struct __enable_if
  46     { };
  47
  48   template<typename _Tp>
  49     struct __enable_if<true, _Tp>
  50     { typedef _Tp __type; };
  51
  52
  53   // Conditional expression for types. If true, first, if false, second.
  54   template<bool _Cond, typename _Iftrue, typename _Iffalse>
  55     struct __conditional_type
  56     { typedef _Iftrue __type; };
  57
  58   template<typename _Iftrue, typename _Iffalse>
  59     struct __conditional_type<false, _Iftrue, _Iffalse>
  60     { typedef _Iffalse __type; };
  61
  62
  63   // Given an integral builtin type, return the corresponding unsigned type.
  64   template<typename _Tp>
  65     struct __add_unsigned
  66     {
  67     private:
  68       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
  69
  70     public:
  71       typedef typename __if_type::__type __type;
  72     };
  73
  74   template<>
  75     struct __add_unsigned<char>
  76     { typedef unsigned char __type; };
  77
  78   template<>
  79     struct __add_unsigned<signed char>
  80     { typedef unsigned char __type; };
  81
  82   template<>
  83     struct __add_unsigned<short>
  84     { typedef unsigned short __type; };
  85
  86   template<>
  87     struct __add_unsigned<int>
  88     { typedef unsigned int __type; };
  89
  90   template<>
  91     struct __add_unsigned<long>
  92     { typedef unsigned long __type; };
  93
  94   template<>
  95     struct __add_unsigned<long long>
  96     { typedef unsigned long long __type; };
  97
  98   // Declare but don't define.
  99   template<>
 100     struct __add_unsigned<bool>;
 101
 102   template<>
 103     struct __add_unsigned<wchar_t>;
 104
 105
 106   // Given an integral builtin type, return the corresponding signed type.
 107   template<typename _Tp>
 108     struct __remove_unsigned
 109     {
 110     private:
 111       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
 112
 113     public:
 114       typedef typename __if_type::__type __type;
 115     };
 116
 117   template<>
 118     struct __remove_unsigned<char>
 119     { typedef signed char __type; };
 120
 121   template<>
 122     struct __remove_unsigned<unsigned char>
 123     { typedef signed char __type; };
 124
 125   template<>
 126     struct __remove_unsigned<unsigned short>
 127     { typedef short __type; };
 128
 129   template<>
 130     struct __remove_unsigned<unsigned int>
 131     { typedef int __type; };
 132
 133   template<>
 134     struct __remove_unsigned<unsigned long>
 135     { typedef long __type; };
 136
 137   template<>
 138     struct __remove_unsigned<unsigned long long>
 139     { typedef long long __type; };
 140
 141   // Declare but don't define.
 142   template<>
 143     struct __remove_unsigned<bool>;
 144
 145   template<>
 146     struct __remove_unsigned<wchar_t>;
 147
 148
 149   // For use in string and vstring.
 150   template<typename _Type>
 151     _GLIBCXX_CONSTEXPR
 152     inline bool
 153     __is_null_pointer(_Type* __ptr)
 154     { return __ptr == 0; }
 155
 156   template<typename _Type>
 157     _GLIBCXX_CONSTEXPR
 158     inline bool
 159     __is_null_pointer(_Type)
 160     { return false; }
 161
 162 #if __cplusplus >= 201103L
 163   constexpr bool
 164   __is_null_pointer(std::nullptr_t)
 165   { return true; }
 166 #endif
 167
 168   // For arithmetic promotions in <complex> and <cmath>
 169
 170   template<typename _Tp, bool = std::__is_integer<_Tp>::__value>
 171     struct __promote
 172     { typedef double __type; };
 173
 174   // No nested __type member for non-integer non-floating point types,
 175   // allows this type to be used for SFINAE to constrain overloads in
 176   // <cmath> and <complex> to only the intended types.
 177   template<typename _Tp>
 178     struct __promote<_Tp, false>
 179     { };
 180
 181   template<>
 182     struct __promote<long double>
 183     { typedef long double __type; };
 184
 185   template<>
 186     struct __promote<double>
 187     { typedef double __type; };
 188
 189   template<>
 190     struct __promote<float>
 191     { typedef float __type; };
 192
 193 #ifdef __STDCPP_FLOAT16_T__
 194   template<>
 195     struct __promote<_Float16>
 196     { typedef _Float16 __type; };
 197 #endif
 198
 199 #ifdef __STDCPP_FLOAT32_T__
 200   template<>
 201     struct __promote<_Float32>
 202     { typedef _Float32 __type; };
 203 #endif
 204
 205 #ifdef __STDCPP_FLOAT64_T__
 206   template<>
 207     struct __promote<_Float64>
 208     { typedef _Float64 __type; };
 209 #endif
 210
 211 #ifdef __STDCPP_FLOAT128_T__
 212   template<>
 213     struct __promote<_Float128>
 214     { typedef _Float128 __type; };
 215 #endif
 216
 217 #ifdef __STDCPP_BFLOAT16_T__
 218   template<>
 219     struct __promote<__gnu_cxx::__bfloat16_t>
 220     { typedef __gnu_cxx::__bfloat16_t __type; };
 221 #endif
 222
 223 #if __cpp_fold_expressions
 224
 225   template<typename... _Tp>
 226     using __promoted_t = decltype((typename __promote<_Tp>::__type(0) + ...));
 227
 228   // Deducing the promoted type is done by __promoted_t<_Tp...>,
 229   // then __promote is used to provide the nested __type member.
 230   template<typename _Tp, typename _Up>
 231     using __promote_2 = __promote<__promoted_t<_Tp, _Up>>;
 232
 233   template<typename _Tp, typename _Up, typename _Vp>
 234     using __promote_3 = __promote<__promoted_t<_Tp, _Up, _Vp>>;
 235
 236   template<typename _Tp, typename _Up, typename _Vp, typename _Wp>
 237     using __promote_4 = __promote<__promoted_t<_Tp, _Up, _Vp, _Wp>>;
 238
 239 #else
 240
 241   template<typename _Tp, typename _Up,
 242            typename _Tp2 = typename __promote<_Tp>::__type,
 243            typename _Up2 = typename __promote<_Up>::__type>
 244     struct __promote_2
 245     {
 246       typedef __typeof__(_Tp2() + _Up2()) __type;
 247     };
 248
 249   template<typename _Tp, typename _Up, typename _Vp,
 250            typename _Tp2 = typename __promote<_Tp>::__type,
 251            typename _Up2 = typename __promote<_Up>::__type,
 252            typename _Vp2 = typename __promote<_Vp>::__type>
 253     struct __promote_3
 254     {
 255       typedef __typeof__(_Tp2() + _Up2() + _Vp2()) __type;
 256     };
 257
 258   template<typename _Tp, typename _Up, typename _Vp, typename _Wp,
 259            typename _Tp2 = typename __promote<_Tp>::__type,
 260            typename _Up2 = typename __promote<_Up>::__type,
 261            typename _Vp2 = typename __promote<_Vp>::__type,
 262            typename _Wp2 = typename __promote<_Wp>::__type>
 263     struct __promote_4
 264     {
 265       typedef __typeof__(_Tp2() + _Up2() + _Vp2() + _Wp2()) __type;
 266     };
 267 #endif
 268
 269 _GLIBCXX_END_NAMESPACE_VERSION
 270 } // namespace
 271 } // extern "C++"
 272
 273 #endif