1 // -*- C++ -*-
2 
3 // Copyright (C) 2005-2022 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 
_GLIBCXX_VISIBILITY(default)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     _GLIBCXX_CONSTEXPR
152     inline bool
153     __is_null_pointer(_Type* __ptr)
154     { return __ptr == 0; }
155 
156   template<typename _Type>
157     _GLIBCXX_CONSTEXPR
158     inline bool
159     __is_null_pointer(_Type)
160     { return false; }
161 
162 #if __cplusplus >= 201103L
163   constexpr bool
164   __is_null_pointer(std::nullptr_t)
165   { return true; }
166 #endif
167 
168   // For arithmetic promotions in <complex> and <cmath>
169 
170   template<typename _Tp, bool = std::__is_integer<_Tp>::__value>
171     struct __promote
172     { typedef double __type; };
173 
174   // No nested __type member for non-integer non-floating point types,
175   // allows this type to be used for SFINAE to constrain overloads in
176   // <cmath> and <complex> to only the intended types.
177   template<typename _Tp>
178     struct __promote<_Tp, false>
179     { };
180 
181   template<>
182     struct __promote<long double>
183     { typedef long double __type; };
184 
185   template<>
186     struct __promote<double>
187     { typedef double __type; };
188 
189   template<>
190     struct __promote<float>
191     { typedef float __type; };
192 
193 #if __cpp_fold_expressions
194 
195   template<typename... _Tp>
196     using __promoted_t = decltype((typename __promote<_Tp>::__type(0) + ...));
197 
198   // Deducing the promoted type is done by __promoted_t<_Tp...>,
199   // then __promote is used to provide the nested __type member.
200   template<typename _Tp, typename _Up>
201     using __promote_2 = __promote<__promoted_t<_Tp, _Up>>;
202 
203   template<typename _Tp, typename _Up, typename _Vp>
204     using __promote_3 = __promote<__promoted_t<_Tp, _Up, _Vp>>;
205 
206   template<typename _Tp, typename _Up, typename _Vp, typename _Wp>
207     using __promote_4 = __promote<__promoted_t<_Tp, _Up, _Vp, _Wp>>;
208 
209 #else
210 
211   template<typename _Tp, typename _Up,
212            typename _Tp2 = typename __promote<_Tp>::__type,
213            typename _Up2 = typename __promote<_Up>::__type>
214     struct __promote_2
215     {
216       typedef __typeof__(_Tp2() + _Up2()) __type;
217     };
218 
219   template<typename _Tp, typename _Up, typename _Vp,
220            typename _Tp2 = typename __promote<_Tp>::__type,
221            typename _Up2 = typename __promote<_Up>::__type,
222            typename _Vp2 = typename __promote<_Vp>::__type>
223     struct __promote_3
224     {
225       typedef __typeof__(_Tp2() + _Up2() + _Vp2()) __type;
226     };
227 
228   template<typename _Tp, typename _Up, typename _Vp, typename _Wp,
229            typename _Tp2 = typename __promote<_Tp>::__type,
230            typename _Up2 = typename __promote<_Up>::__type,
231            typename _Vp2 = typename __promote<_Vp>::__type,
232            typename _Wp2 = typename __promote<_Wp>::__type>
233     struct __promote_4
234     {
235       typedef __typeof__(_Tp2() + _Up2() + _Vp2() + _Wp2()) __type;
236     };
237 #endif
238 
239 _GLIBCXX_END_NAMESPACE_VERSION
240 } // namespace
241 } // extern "C++"
242 
243 #endif
244