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 #pragma GCC diagnostic push
  38 #pragma GCC diagnostic ignored "-Wlong-long"
  39
  40 extern "C++" {
  41
  42 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  43 {
  44 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  45
  46   // Define a nested type if some predicate holds.
  47   template<bool, typename>
  48     struct __enable_if
  49     { };
  50
  51   template<typename _Tp>
  52     struct __enable_if<true, _Tp>
  53     { typedef _Tp __type; };
  54
  55
  56   // Conditional expression for types. If true, first, if false, second.
  57   template<bool _Cond, typename _Iftrue, typename _Iffalse>
  58     struct __conditional_type
  59     { typedef _Iftrue __type; };
  60
  61   template<typename _Iftrue, typename _Iffalse>
  62     struct __conditional_type<false, _Iftrue, _Iffalse>
  63     { typedef _Iffalse __type; };
  64
  65
  66   // Given an integral builtin type, return the corresponding unsigned type.
  67   template<typename _Tp>
  68     struct __add_unsigned
  69     {
  70     private:
  71       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
  72
  73     public:
  74       typedef typename __if_type::__type __type;
  75     };
  76
  77   template<>
  78     struct __add_unsigned<char>
  79     { typedef unsigned char __type; };
  80
  81   template<>
  82     struct __add_unsigned<signed char>
  83     { typedef unsigned char __type; };
  84
  85   template<>
  86     struct __add_unsigned<short>
  87     { typedef unsigned short __type; };
  88
  89   template<>
  90     struct __add_unsigned<int>
  91     { typedef unsigned int __type; };
  92
  93   template<>
  94     struct __add_unsigned<long>
  95     { typedef unsigned long __type; };
  96
  97   template<>
  98     struct __add_unsigned<long long>
  99     { typedef unsigned long long __type; };
 100
 101   // Declare but don't define.
 102   template<>
 103     struct __add_unsigned<bool>;
 104
 105   template<>
 106     struct __add_unsigned<wchar_t>;
 107
 108
 109   // Given an integral builtin type, return the corresponding signed type.
 110   template<typename _Tp>
 111     struct __remove_unsigned
 112     {
 113     private:
 114       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
 115
 116     public:
 117       typedef typename __if_type::__type __type;
 118     };
 119
 120   template<>
 121     struct __remove_unsigned<char>
 122     { typedef signed char __type; };
 123
 124   template<>
 125     struct __remove_unsigned<unsigned char>
 126     { typedef signed char __type; };
 127
 128   template<>
 129     struct __remove_unsigned<unsigned short>
 130     { typedef short __type; };
 131
 132   template<>
 133     struct __remove_unsigned<unsigned int>
 134     { typedef int __type; };
 135
 136   template<>
 137     struct __remove_unsigned<unsigned long>
 138     { typedef long __type; };
 139
 140   template<>
 141     struct __remove_unsigned<unsigned long long>
 142     { typedef long long __type; };
 143
 144   // Declare but don't define.
 145   template<>
 146     struct __remove_unsigned<bool>;
 147
 148   template<>
 149     struct __remove_unsigned<wchar_t>;
 150
 151
 152   // For use in string and vstring.
 153   template<typename _Type>
 154     _GLIBCXX_CONSTEXPR
 155     inline bool
 156     __is_null_pointer(_Type* __ptr)
 157     { return __ptr == 0; }
 158
 159   template<typename _Type>
 160     _GLIBCXX_CONSTEXPR
 161     inline bool
 162     __is_null_pointer(_Type)
 163     { return false; }
 164
 165 #if __cplusplus >= 201103L
 166   constexpr bool
 167   __is_null_pointer(std::nullptr_t)
 168   { return true; }
 169 #endif
 170
 171   // For arithmetic promotions in <complex> and <cmath>
 172
 173   template<typename _Tp, bool = std::__is_integer<_Tp>::__value>
 174     struct __promote
 175     { typedef double __type; };
 176
 177   // No nested __type member for non-integer non-floating point types,
 178   // allows this type to be used for SFINAE to constrain overloads in
 179   // <cmath> and <complex> to only the intended types.
 180   template<typename _Tp>
 181     struct __promote<_Tp, false>
 182     { };
 183
 184   template<>
 185     struct __promote<long double>
 186     { typedef long double __type; };
 187
 188   template<>
 189     struct __promote<double>
 190     { typedef double __type; };
 191
 192   template<>
 193     struct __promote<float>
 194     { typedef float __type; };
 195
 196 #ifdef __STDCPP_FLOAT16_T__
 197   template<>
 198     struct __promote<_Float16>
 199     { typedef _Float16 __type; };
 200 #endif
 201
 202 #ifdef __STDCPP_FLOAT32_T__
 203   template<>
 204     struct __promote<_Float32>
 205     { typedef _Float32 __type; };
 206 #endif
 207
 208 #ifdef __STDCPP_FLOAT64_T__
 209   template<>
 210     struct __promote<_Float64>
 211     { typedef _Float64 __type; };
 212 #endif
 213
 214 #ifdef __STDCPP_FLOAT128_T__
 215   template<>
 216     struct __promote<_Float128>
 217     { typedef _Float128 __type; };
 218 #endif
 219
 220 #ifdef __STDCPP_BFLOAT16_T__
 221   template<>
 222     struct __promote<__gnu_cxx::__bfloat16_t>
 223     { typedef __gnu_cxx::__bfloat16_t __type; };
 224 #endif
 225
 226 #if __cpp_fold_expressions
 227
 228   template<typename... _Tp>
 229     using __promoted_t = decltype((typename __promote<_Tp>::__type(0) + ...));
 230
 231   // Deducing the promoted type is done by __promoted_t<_Tp...>,
 232   // then __promote is used to provide the nested __type member.
 233   template<typename _Tp, typename _Up>
 234     using __promote_2 = __promote<__promoted_t<_Tp, _Up>>;
 235
 236   template<typename _Tp, typename _Up, typename _Vp>
 237     using __promote_3 = __promote<__promoted_t<_Tp, _Up, _Vp>>;
 238
 239   template<typename _Tp, typename _Up, typename _Vp, typename _Wp>
 240     using __promote_4 = __promote<__promoted_t<_Tp, _Up, _Vp, _Wp>>;
 241
 242 #else
 243
 244   template<typename _Tp, typename _Up,
 245            typename _Tp2 = typename __promote<_Tp>::__type,
 246            typename _Up2 = typename __promote<_Up>::__type>
 247     struct __promote_2
 248     {
 249       typedef __typeof__(_Tp2() + _Up2()) __type;
 250     };
 251
 252   template<typename _Tp, typename _Up, typename _Vp,
 253            typename _Tp2 = typename __promote<_Tp>::__type,
 254            typename _Up2 = typename __promote<_Up>::__type,
 255            typename _Vp2 = typename __promote<_Vp>::__type>
 256     struct __promote_3
 257     {
 258       typedef __typeof__(_Tp2() + _Up2() + _Vp2()) __type;
 259     };
 260
 261   template<typename _Tp, typename _Up, typename _Vp, typename _Wp,
 262            typename _Tp2 = typename __promote<_Tp>::__type,
 263            typename _Up2 = typename __promote<_Up>::__type,
 264            typename _Vp2 = typename __promote<_Vp>::__type,
 265            typename _Wp2 = typename __promote<_Wp>::__type>
 266     struct __promote_4
 267     {
 268       typedef __typeof__(_Tp2() + _Up2() + _Vp2() + _Wp2()) __type;
 269     };
 270 #endif
 271
 272 _GLIBCXX_END_NAMESPACE_VERSION
 273 } // namespace
 274 } // extern "C++"
 275
 276 #pragma GCC diagnostic pop
 277
 278 #endif