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
37extern "C++" {
38
39namespace __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 arithmetic promotions in <complex> and <cmath>
167
168 template<typename _Tp, bool = std::__is_integer<_Tp>::__value>
169 struct __promote
170 { typedef double __type; };
171
172 // No nested __type member for non-integer non-floating point types,
173 // allows this type to be used for SFINAE to constrain overloads in
174 // <cmath> and <complex> to only the intended types.
175 template<typename _Tp>
176 struct __promote<_Tp, false>
177 { };
178
179 template<>
180 struct __promote<long double>
181 { typedef long double __type; };
182
183 template<>
184 struct __promote<double>
185 { typedef double __type; };
186
187 template<>
188 struct __promote<float>
189 { typedef float __type; };
190
191#if __cpp_fold_expressions
192 template<typename... _Tp>
193 using __promoted_t = decltype((typename __promote<_Tp>::__type(0) + ...));
194#endif
195
196 template<typename _Tp, typename _Up,
197 typename _Tp2 = typename __promote<_Tp>::__type,
198 typename _Up2 = typename __promote<_Up>::__type>
199 struct __promote_2
200 {
201 typedef __typeof__(_Tp2() + _Up2()) __type;
202 };
203
204 template<typename _Tp, typename _Up, typename _Vp,
205 typename _Tp2 = typename __promote<_Tp>::__type,
206 typename _Up2 = typename __promote<_Up>::__type,
207 typename _Vp2 = typename __promote<_Vp>::__type>
208 struct __promote_3
209 {
210 typedef __typeof__(_Tp2() + _Up2() + _Vp2()) __type;
211 };
212
213 template<typename _Tp, typename _Up, typename _Vp, typename _Wp,
214 typename _Tp2 = typename __promote<_Tp>::__type,
215 typename _Up2 = typename __promote<_Up>::__type,
216 typename _Vp2 = typename __promote<_Vp>::__type,
217 typename _Wp2 = typename __promote<_Wp>::__type>
218 struct __promote_4
219 {
220 typedef __typeof__(_Tp2() + _Up2() + _Vp2() + _Wp2()) __type;
221 };
222
223_GLIBCXX_END_NAMESPACE_VERSION
224} // namespace
225} // extern "C++"
226
227#endif
228

source code of include/c++/11/ext/type_traits.h