v1/__tuple/tuple_element.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___TUPLE_TUPLE_ELEMENT_H
0010 #define _LIBCPP___TUPLE_TUPLE_ELEMENT_H
0011
0012 #include <__config>
0013 #include <__cstddef/size_t.h>
0014 #include <__tuple/tuple_indices.h>
0015 #include <__tuple/tuple_types.h>
0016
0017 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0018 #  pragma GCC system_header
0019 #endif
0020
0021 _LIBCPP_BEGIN_NAMESPACE_STD
0022
0023 template <size_t _Ip, class _Tp>
0024 struct _LIBCPP_TEMPLATE_VIS tuple_element;
0025
0026 template <size_t _Ip, class _Tp>
0027 struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, const _Tp> {
0028   using type _LIBCPP_NODEBUG = const typename tuple_element<_Ip, _Tp>::type;
0029 };
0030
0031 template <size_t _Ip, class _Tp>
0032 struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, volatile _Tp> {
0033   using type _LIBCPP_NODEBUG = volatile typename tuple_element<_Ip, _Tp>::type;
0034 };
0035
0036 template <size_t _Ip, class _Tp>
0037 struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, const volatile _Tp> {
0038   using type _LIBCPP_NODEBUG = const volatile typename tuple_element<_Ip, _Tp>::type;
0039 };
0040
0041 #ifndef _LIBCPP_CXX03_LANG
0042
0043 template <size_t _Ip, class... _Types>
0044 struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, __tuple_types<_Types...> > {
0045   static_assert(_Ip < sizeof...(_Types), "tuple_element index out of range");
0046   using type _LIBCPP_NODEBUG = __type_pack_element<_Ip, _Types...>;
0047 };
0048
0049 #  if _LIBCPP_STD_VER >= 14
0050 template <size_t _Ip, class... _Tp>
0051 using tuple_element_t _LIBCPP_NODEBUG = typename tuple_element<_Ip, _Tp...>::type;
0052 #  endif
0053
0054 #endif // _LIBCPP_CXX03_LANG
0055
0056 _LIBCPP_END_NAMESPACE_STD
0057
0058 #endif // _LIBCPP___TUPLE_TUPLE_ELEMENT_H