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

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005-2013 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 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  38 {
  39 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  40
  41   // Define a nested type if some predicate holds.
  42   template<bool, typename>
  43     struct __enable_if
  44     { };
  45
  46   template<typename _Tp>
  47     struct __enable_if<true, _Tp>
  48     { typedef _Tp __type; };
  49
  50
  51   // Conditional expression for types. If true, first, if false, second.
  52   template<bool _Cond, typename _Iftrue, typename _Iffalse>
  53     struct __conditional_type
  54     { typedef _Iftrue __type; };
  55
  56   template<typename _Iftrue, typename _Iffalse>
  57     struct __conditional_type<false, _Iftrue, _Iffalse>
  58     { typedef _Iffalse __type; };
  59
  60
  61   // Given an integral builtin type, return the corresponding unsigned type.
  62   template<typename _Tp>
  63     struct __add_unsigned
  64     {
  65     private:
  66       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
  67
  68     public:
  69       typedef typename __if_type::__type __type;
  70     };
  71
  72   template<>
  73     struct __add_unsigned<char>
  74     { typedef unsigned char __type; };
  75
  76   template<>
  77     struct __add_unsigned<signed char>
  78     { typedef unsigned char __type; };
  79
  80   template<>
  81     struct __add_unsigned<short>
  82     { typedef unsigned short __type; };
  83
  84   template<>
  85     struct __add_unsigned<int>
  86     { typedef unsigned int __type; };
  87
  88   template<>
  89     struct __add_unsigned<long>
  90     { typedef unsigned long __type; };
  91
  92   template<>
  93     struct __add_unsigned<long long>
  94     { typedef unsigned long long __type; };
  95
  96   // Declare but don't define.
  97   template<>
  98     struct __add_unsigned<bool>;
  99
 100   template<>
 101     struct __add_unsigned<wchar_t>;
 102
 103
 104   // Given an integral builtin type, return the corresponding signed type.
 105   template<typename _Tp>
 106     struct __remove_unsigned
 107     {
 108     private:
 109       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
 110
 111     public:
 112       typedef typename __if_type::__type __type;
 113     };
 114
 115   template<>
 116     struct __remove_unsigned<char>
 117     { typedef signed char __type; };
 118
 119   template<>
 120     struct __remove_unsigned<unsigned char>
 121     { typedef signed char __type; };
 122
 123   template<>
 124     struct __remove_unsigned<unsigned short>
 125     { typedef short __type; };
 126
 127   template<>
 128     struct __remove_unsigned<unsigned int>
 129     { typedef int __type; };
 130
 131   template<>
 132     struct __remove_unsigned<unsigned long>
 133     { typedef long __type; };
 134
 135   template<>
 136     struct __remove_unsigned<unsigned long long>
 137     { typedef long long __type; };
 138
 139   // Declare but don't define.
 140   template<>
 141     struct __remove_unsigned<bool>;
 142
 143   template<>
 144     struct __remove_unsigned<wchar_t>;
 145
 146
 147   // For use in string and vstring.
 148   template<typename _Type>
 149     inline bool
 150     __is_null_pointer(_Type* __ptr)
 151     { return __ptr == 0; }
 152
 153   template<typename _Type>
 154     inline bool
 155     __is_null_pointer(_Type)
 156     { return false; }
 157
 158 #if __cplusplus >= 201103L
 159   inline bool
 160   __is_null_pointer(std::nullptr_t)
 161   { return true; }
 162 #endif
 163
 164   // For complex and cmath
 165   template<typename _Tp, bool = std::__is_integer<_Tp>::__value>
 166     struct __promote
 167     { typedef double __type; };
 168
 169   // No nested __type member for non-integer non-floating point types,
 170   // allows this type to be used for SFINAE to constrain overloads in
 171   // <cmath> and <complex> to only the intended types.
 172   template<typename _Tp>
 173     struct __promote<_Tp, false>
 174     { };
 175
 176   template<>
 177     struct __promote<long double>
 178     { typedef long double __type; };
 179
 180   template<>
 181     struct __promote<double>
 182     { typedef double __type; };
 183
 184   template<>
 185     struct __promote<float>
 186     { typedef float __type; };
 187
 188   template<typename _Tp, typename _Up,
 189            typename _Tp2 = typename __promote<_Tp>::__type,
 190            typename _Up2 = typename __promote<_Up>::__type>
 191     struct __promote_2
 192     {
 193       typedef __typeof__(_Tp2() + _Up2()) __type;
 194     };
 195
 196   template<typename _Tp, typename _Up, typename _Vp,
 197            typename _Tp2 = typename __promote<_Tp>::__type,
 198            typename _Up2 = typename __promote<_Up>::__type,
 199            typename _Vp2 = typename __promote<_Vp>::__type>
 200     struct __promote_3
 201     {
 202       typedef __typeof__(_Tp2() + _Up2() + _Vp2()) __type;
 203     };
 204
 205   template<typename _Tp, typename _Up, typename _Vp, typename _Wp,
 206            typename _Tp2 = typename __promote<_Tp>::__type,
 207            typename _Up2 = typename __promote<_Up>::__type,
 208            typename _Vp2 = typename __promote<_Vp>::__type,
 209            typename _Wp2 = typename __promote<_Wp>::__type>
 210     struct __promote_4
 211     {
 212       typedef __typeof__(_Tp2() + _Up2() + _Vp2() + _Wp2()) __type;
 213     };
 214
 215 _GLIBCXX_END_NAMESPACE_VERSION
 216 } // namespace
 217
 218 #endif