libstdc++
tr2/type_traits
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1 // TR2 <type_traits> -*- C++ -*-
2 
3 // Copyright (C) 2011-2026 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
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU 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 tr2/type_traits
26  * This is a TR2 C++ Library header.
27  */
28 
29 #ifndef _GLIBCXX_TR2_TYPE_TRAITS
30 #define _GLIBCXX_TR2_TYPE_TRAITS 1
31 
32 #ifdef _GLIBCXX_SYSHDR
33 #pragma GCC system_header
34 #endif
35 #include <type_traits>
36 #include <bits/c++config.h>
37 
38 namespace std _GLIBCXX_VISIBILITY(default)
39 {
40 _GLIBCXX_BEGIN_NAMESPACE_VERSION
41 
42 namespace tr2
43 {
44  /**
45  * @addtogroup metaprogramming
46  * @{
47  */
48 
49  /**
50  * See N2965: Type traits and base classes
51  * by Michael Spertus
52  */
53 
54  /**
55  * Simple typelist. Compile-time list of types.
56  */
57  template<typename... _Elements>
58  struct __reflection_typelist;
59 
60  /// Specialization for an empty typelist.
61  template<>
62  struct __reflection_typelist<>
63  {
64  typedef std::true_type empty;
65  };
66 
67  /// Partial specialization.
68  template<typename _First, typename... _Rest>
69  struct __reflection_typelist<_First, _Rest...>
70  {
71  typedef std::false_type empty;
72 
73  struct first
74  {
75  typedef _First type;
76  };
77 
78  struct rest
79  {
80  typedef __reflection_typelist<_Rest...> type;
81  };
82  };
83 
84  /// Sequence abstraction metafunctions for manipulating a typelist.
85 
86 
87 #if __has_builtin(__bases)
88  /// Enumerate all the base classes of a class. Form of a typelist.
89  template<typename _Tp>
90  struct bases
91  {
92  typedef __reflection_typelist<__bases(_Tp)...> type;
93  };
94 #endif
95 
96 #if __has_builtin(__direct_bases)
97  /// Enumerate all the direct base classes of a class. Form of a typelist.
98  template<typename _Tp>
99  struct direct_bases
100  {
101  typedef __reflection_typelist<__direct_bases(_Tp)...> type;
102  };
103 #endif
104 
105  /// @} group metaprogramming
106 }
107 
108 _GLIBCXX_END_NAMESPACE_VERSION
109 }
110 
111 #endif // _GLIBCXX_TR2_TYPE_TRAITS
std::true_type
__bool_constant< true > true_type
The type used as a compile-time boolean with true value.
Definition: type_traits:119
std::empty
constexpr auto empty(const _Container &__cont) noexcept(noexcept(__cont.empty())) -> decltype(__cont.empty())
Return whether a container is empty.
Definition: range_access.h:294
std
ISO C++ entities toplevel namespace is std.
std::false_type
__bool_constant< false > false_type
The type used as a compile-time boolean with false value.
Definition: type_traits:122
std::tr2::direct_bases
Enumerate all the direct base classes of a class. Form of a typelist.
Definition: tr2/type_traits:99
std::tr2::bases
Sequence abstraction metafunctions for manipulating a typelist.
Definition: tr2/type_traits:90