1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef _LIBCPP___TUPLE_TUPLE_ELEMENT_H
10 #define _LIBCPP___TUPLE_TUPLE_ELEMENT_H
11 
12 #include <__config>
13 #include <__tuple/tuple_indices.h>
14 #include <__tuple/tuple_types.h>
15 #include <__type_traits/add_const.h>
16 #include <__type_traits/add_cv.h>
17 #include <__type_traits/add_volatile.h>
18 #include <cstddef>
19 
20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
21 #  pragma GCC system_header
22 #endif
23 
24 _LIBCPP_BEGIN_NAMESPACE_STD
25 
26 template <size_t _Ip, class _Tp>
27 struct _LIBCPP_TEMPLATE_VIS tuple_element;
28 
29 template <size_t _Ip, class _Tp>
30 struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, const _Tp> {
31   typedef _LIBCPP_NODEBUG typename add_const<typename tuple_element<_Ip, _Tp>::type>::type type;
32 };
33 
34 template <size_t _Ip, class _Tp>
35 struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, volatile _Tp> {
36   typedef _LIBCPP_NODEBUG typename add_volatile<typename tuple_element<_Ip, _Tp>::type>::type type;
37 };
38 
39 template <size_t _Ip, class _Tp>
40 struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, const volatile _Tp> {
41   typedef _LIBCPP_NODEBUG typename add_cv<typename tuple_element<_Ip, _Tp>::type>::type type;
42 };
43 
44 #ifndef _LIBCPP_CXX03_LANG
45 
46 #  if !__has_builtin(__type_pack_element)
47 
48 namespace __indexer_detail {
49 
50 template <size_t _Idx, class _Tp>
51 struct __indexed {
52   using type _LIBCPP_NODEBUG = _Tp;
53 };
54 
55 template <class _Types, class _Indexes>
56 struct __indexer;
57 
58 template <class... _Types, size_t... _Idx>
59 struct __indexer<__tuple_types<_Types...>, __tuple_indices<_Idx...>> : __indexed<_Idx, _Types>... {};
60 
61 template <size_t _Idx, class _Tp>
62 __indexed<_Idx, _Tp> __at_index(__indexed<_Idx, _Tp> const&);
63 
64 } // namespace __indexer_detail
65 
66 template <size_t _Idx, class... _Types>
67 using __type_pack_element _LIBCPP_NODEBUG = typename decltype(__indexer_detail::__at_index<_Idx>(
68     __indexer_detail::__indexer< __tuple_types<_Types...>,
69                                  typename __make_tuple_indices<sizeof...(_Types)>::type >{}))::type;
70 #  endif
71 
72 template <size_t _Ip, class... _Types>
73 struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, __tuple_types<_Types...> > {
74   static_assert(_Ip < sizeof...(_Types), "tuple_element index out of range");
75   typedef _LIBCPP_NODEBUG __type_pack_element<_Ip, _Types...> type;
76 };
77 
78 #  if _LIBCPP_STD_VER >= 14
79 template <size_t _Ip, class... _Tp>
80 using tuple_element_t _LIBCPP_NODEBUG = typename tuple_element<_Ip, _Tp...>::type;
81 #  endif
82 
83 #endif // _LIBCPP_CXX03_LANG
84 
85 _LIBCPP_END_NAMESPACE_STD
86 
87 #endif // _LIBCPP___TUPLE_TUPLE_ELEMENT_H
88