libstdc++
type_traits.h
Go to the documentation of this file.
1 // -*- C++ -*-
2 
3 // Copyright (C) 2005-2021 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  inline bool
152  __is_null_pointer(_Type* __ptr)
153  { return __ptr == 0; }
154 
155  template<typename _Type>
156  inline bool
157  __is_null_pointer(_Type)
158  { return false; }
159 
160 #if __cplusplus >= 201103L
161  inline bool
162  __is_null_pointer(std::nullptr_t)
163  { return true; }
164 #endif
165 
166  // For complex and cmath
167  template<typename _Tp, bool = std::__is_integer<_Tp>::__value>
168  struct __promote
169  { typedef double __type; };
170 
171  // No nested __type member for non-integer non-floating point types,
172  // allows this type to be used for SFINAE to constrain overloads in
173  // <cmath> and <complex> to only the intended types.
174  template<typename _Tp>
175  struct __promote<_Tp, false>
176  { };
177 
178  template<>
179  struct __promote<long double>
180  { typedef long double __type; };
181 
182  template<>
183  struct __promote<double>
184  { typedef double __type; };
185 
186  template<>
187  struct __promote<float>
188  { typedef float __type; };
189 
190  template<typename _Tp, typename _Up,
191  typename _Tp2 = typename __promote<_Tp>::__type,
192  typename _Up2 = typename __promote<_Up>::__type>
193  struct __promote_2
194  {
195  typedef __typeof__(_Tp2() + _Up2()) __type;
196  };
197 
198  template<typename _Tp, typename _Up, typename _Vp,
199  typename _Tp2 = typename __promote<_Tp>::__type,
200  typename _Up2 = typename __promote<_Up>::__type,
201  typename _Vp2 = typename __promote<_Vp>::__type>
202  struct __promote_3
203  {
204  typedef __typeof__(_Tp2() + _Up2() + _Vp2()) __type;
205  };
206 
207  template<typename _Tp, typename _Up, typename _Vp, typename _Wp,
208  typename _Tp2 = typename __promote<_Tp>::__type,
209  typename _Up2 = typename __promote<_Up>::__type,
210  typename _Vp2 = typename __promote<_Vp>::__type,
211  typename _Wp2 = typename __promote<_Wp>::__type>
212  struct __promote_4
213  {
214  typedef __typeof__(_Tp2() + _Up2() + _Vp2() + _Wp2()) __type;
215  };
216 
217 _GLIBCXX_END_NAMESPACE_VERSION
218 } // namespace
219 } // extern "C++"
220 
221 #endif
GNU extensions for public use.