libstdc++

type_traits.h
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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
159 // For complex and cmath
160 template<typename _Tp, bool = std::__is_integer<_Tp>::__value>
161 struct __promote
162 { typedef double __type; };
163
164 // No nested __type member for non-integer non-floating point types,
165 // allows this type to be used for SFINAE to constrain overloads in
166 // <cmath> and <complex> to only the intended types.
167 template<typename _Tp>
168 struct __promote<_Tp, false>
169 { };
170
171 template<>
172 struct __promote<long double>
173 { typedef long double __type; };
174
175 template<>
176 struct __promote<double>
177 { typedef double __type; };
178
179 template<>
180 struct __promote<float>
181 { typedef float __type; };
182
183 template<typename _Tp, typename _Up,
184 typename _Tp2 = typename __promote<_Tp>::__type,
185 typename _Up2 = typename __promote<_Up>::__type>
186 struct __promote_2
187 {
188 typedef __typeof__(_Tp2() + _Up2()) __type;
189 };
190
191 template<typename _Tp, typename _Up, typename _Vp,
192 typename _Tp2 = typename __promote<_Tp>::__type,
193 typename _Up2 = typename __promote<_Up>::__type,
194 typename _Vp2 = typename __promote<_Vp>::__type>
195 struct __promote_3
196 {
197 typedef __typeof__(_Tp2() + _Up2() + _Vp2()) __type;
198 };
199
200 template<typename _Tp, typename _Up, typename _Vp, typename _Wp,
201 typename _Tp2 = typename __promote<_Tp>::__type,
202 typename _Up2 = typename __promote<_Up>::__type,
203 typename _Vp2 = typename __promote<_Vp>::__type,
204 typename _Wp2 = typename __promote<_Wp>::__type>
205 struct __promote_4
206 {
207 typedef __typeof__(_Tp2() + _Up2() + _Vp2() + _Wp2()) __type;
208 };
209
210 _GLIBCXX_END_NAMESPACE_VERSION
211 } // namespace
212
213 #endif