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___TYPE_TRAITS_TYPE_LIST_H 10 #define _LIBCPP___TYPE_TRAITS_TYPE_LIST_H 11 12 #include <__config> 13 #include <__cstddef/size_t.h> 14 15 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 16 # pragma GCC system_header 17 #endif 18 19 _LIBCPP_BEGIN_NAMESPACE_STD 20 21 template <class... _Types> 22 struct __type_list {}; 23 24 template <class> 25 struct __type_list_head; 26 27 template <class _Head, class... _Tail> 28 struct __type_list_head<__type_list<_Head, _Tail...> > { 29 using type _LIBCPP_NODEBUG = _Head; 30 }; 31 32 template <class _TypeList, size_t _Size, bool = _Size <= sizeof(typename __type_list_head<_TypeList>::type)> 33 struct __find_first; 34 35 template <class _Head, class... _Tail, size_t _Size> 36 struct __find_first<__type_list<_Head, _Tail...>, _Size, true> { 37 using type _LIBCPP_NODEBUG = _Head; 38 }; 39 40 template <class _Head, class... _Tail, size_t _Size> 41 struct __find_first<__type_list<_Head, _Tail...>, _Size, false> { 42 using type _LIBCPP_NODEBUG = typename __find_first<__type_list<_Tail...>, _Size>::type; 43 }; 44 45 _LIBCPP_END_NAMESPACE_STD 46 47 #endif // _LIBCPP___TYPE_TRAITS_TYPE_LIST_H 48