libstdc++: type_traits Source File

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
38namespace std _GLIBCXX_VISIBILITY(default)
39{
40_GLIBCXX_BEGIN_NAMESPACE_VERSION
41
42namespace 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
c++config.h
std::true_type
__bool_constant< true > true_type
The type used as a compile-time boolean with true value.
Definition type_traits:119
std::false_type
__bool_constant< false > false_type
The type used as a compile-time boolean with false value.
Definition type_traits:122
std
ISO C++ entities toplevel namespace is std.
std::tr2
Namespace for non-standard "TR2" extensions.
std::tr2::__reflection_typelist
Definition tr2/type_traits:58
std::tr2::bases
Sequence abstraction metafunctions for manipulating a typelist.
Definition tr2/type_traits:91
std::tr2::direct_bases
Enumerate all the direct base classes of a class. Form of a typelist.
Definition tr2/type_traits:100
type_traits