3 // Copyright (C) 2005-2023 Free Software Foundation, Inc.
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
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.
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.
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/>.
25 /** @file ext/type_traits.h
26 * This file is a GNU extension to the Standard C++ Library.
29 #ifndef _EXT_TYPE_TRAITS
30 #define _EXT_TYPE_TRAITS 1
32 #pragma GCC system_header
34 #include <bits/c++config.h>
35 #include <bits/cpp_type_traits.h>
39 namespace __gnu_cxx
_GLIBCXX_VISIBILITY(default)
41 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43 // Define a nested type if some predicate holds.
44 template<bool, typename
>
48 template<typename _Tp
>
49 struct __enable_if
<true, _Tp
>
50 { typedef _Tp __type
; };
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
; };
58 template<typename _Iftrue
, typename _Iffalse
>
59 struct __conditional_type
<false, _Iftrue
, _Iffalse
>
60 { typedef _Iffalse __type
; };
63 // Given an integral builtin type, return the corresponding unsigned type.
64 template<typename _Tp
>
68 typedef __enable_if
<std::__is_integer
<_Tp
>::__value
, _Tp
> __if_type
;
71 typedef typename
__if_type::__type __type
;
75 struct __add_unsigned
<char>
76 { typedef unsigned char __type
; };
79 struct __add_unsigned
<signed char>
80 { typedef unsigned char __type
; };
83 struct __add_unsigned
<short>
84 { typedef unsigned short __type
; };
87 struct __add_unsigned
<int>
88 { typedef unsigned int __type
; };
91 struct __add_unsigned
<long>
92 { typedef unsigned long __type
; };
95 struct __add_unsigned
<long long>
96 { typedef unsigned long long __type
; };
98 // Declare but don't define.
100 struct __add_unsigned
<bool>;
103 struct __add_unsigned
<wchar_t>;
106 // Given an integral builtin type, return the corresponding signed type.
107 template<typename _Tp
>
108 struct __remove_unsigned
111 typedef __enable_if
<std::__is_integer
<_Tp
>::__value
, _Tp
> __if_type
;
114 typedef typename
__if_type::__type __type
;
118 struct __remove_unsigned
<char>
119 { typedef signed char __type
; };
122 struct __remove_unsigned
<unsigned char>
123 { typedef signed char __type
; };
126 struct __remove_unsigned
<unsigned short>
127 { typedef short __type
; };
130 struct __remove_unsigned
<unsigned int>
131 { typedef int __type
; };
134 struct __remove_unsigned
<unsigned long>
135 { typedef long __type
; };
138 struct __remove_unsigned
<unsigned long long>
139 { typedef long long __type
; };
141 // Declare but don't define.
143 struct __remove_unsigned
<bool>;
146 struct __remove_unsigned
<wchar_t>;
149 // For use in string and vstring.
150 template<typename _Type
>
153 __is_null_pointer(_Type
* __ptr
)
154 { return __ptr
== 0; }
156 template<typename _Type
>
159 __is_null_pointer(_Type
)
162 #if __cplusplus >= 201103L
164 __is_null_pointer(std::nullptr_t
)
168 // For arithmetic promotions in <complex> and <cmath>
170 template<typename _Tp
, bool = std::__is_integer
<_Tp
>::__value
>
172 { typedef double __type
; };
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>
182 struct __promote
<long double>
183 { typedef long double __type
; };
186 struct __promote
<double>
187 { typedef double __type
; };
190 struct __promote
<float>
191 { typedef float __type
; };
193 #ifdef __STDCPP_FLOAT16_T__
195 struct __promote
<_Float16
>
196 { typedef _Float16 __type
; };
199 #ifdef __STDCPP_FLOAT32_T__
201 struct __promote
<_Float32
>
202 { typedef _Float32 __type
; };
205 #ifdef __STDCPP_FLOAT64_T__
207 struct __promote
<_Float64
>
208 { typedef _Float64 __type
; };
211 #ifdef __STDCPP_FLOAT128_T__
213 struct __promote
<_Float128
>
214 { typedef _Float128 __type
; };
217 #ifdef __STDCPP_BFLOAT16_T__
219 struct __promote
<__gnu_cxx::__bfloat16_t
>
220 { typedef __gnu_cxx::__bfloat16_t __type
; };
223 #if __cpp_fold_expressions
225 template<typename
... _Tp
>
226 using __promoted_t
= decltype((typename __promote
<_Tp
>::__type(0) + ...));
228 // Deducing the promoted type is done by __promoted_t<_Tp...>,
229 // then __promote is used to provide the nested __type member.
230 template<typename _Tp
, typename _Up
>
231 using __promote_2
= __promote
<__promoted_t
<_Tp
, _Up
>>;
233 template<typename _Tp
, typename _Up
, typename _Vp
>
234 using __promote_3
= __promote
<__promoted_t
<_Tp
, _Up
, _Vp
>>;
236 template<typename _Tp
, typename _Up
, typename _Vp
, typename _Wp
>
237 using __promote_4
= __promote
<__promoted_t
<_Tp
, _Up
, _Vp
, _Wp
>>;
241 template<typename _Tp
, typename _Up
,
242 typename _Tp2
= typename __promote
<_Tp
>::__type
,
243 typename _Up2
= typename __promote
<_Up
>::__type
>
246 typedef __typeof__(_Tp2() + _Up2()) __type
;
249 template<typename _Tp
, typename _Up
, typename _Vp
,
250 typename _Tp2
= typename __promote
<_Tp
>::__type
,
251 typename _Up2
= typename __promote
<_Up
>::__type
,
252 typename _Vp2
= typename __promote
<_Vp
>::__type
>
255 typedef __typeof__(_Tp2() + _Up2() + _Vp2()) __type
;
258 template<typename _Tp
, typename _Up
, typename _Vp
, typename _Wp
,
259 typename _Tp2
= typename __promote
<_Tp
>::__type
,
260 typename _Up2
= typename __promote
<_Up
>::__type
,
261 typename _Vp2
= typename __promote
<_Vp
>::__type
,
262 typename _Wp2
= typename __promote
<_Wp
>::__type
>
265 typedef __typeof__(_Tp2() + _Up2() + _Vp2() + _Wp2()) __type
;
269 _GLIBCXX_END_NAMESPACE_VERSION