libstdc++
type_traits.h
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1 // -*- C++ -*-
2 
3 // Copyright (C) 2005-2014 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
GNU extensions for public use.