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_FIND_INDEX_H 10 #define _LIBCPP___TUPLE_FIND_INDEX_H 11 12 #include <__config> 13 #include <__type_traits/is_same.h> 14 #include <cstddef> 15 16 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 17 # pragma GCC system_header 18 #endif 19 20 #if _LIBCPP_STD_VER >= 14 21 22 _LIBCPP_BEGIN_NAMESPACE_STD 23 24 namespace __find_detail { 25 26 static constexpr size_t __not_found = static_cast<size_t>(-1); 27 static constexpr size_t __ambiguous = __not_found - 1; 28 29 inline _LIBCPP_HIDE_FROM_ABI constexpr size_t __find_idx_return(size_t __curr_i, size_t __res, bool __matches) { 30 return !__matches ? __res : (__res == __not_found ? __curr_i : __ambiguous); 31 } 32 33 template <size_t _Nx> 34 inline _LIBCPP_HIDE_FROM_ABI constexpr size_t __find_idx(size_t __i, const bool (&__matches)[_Nx]) { 35 return __i == _Nx 36 ? __not_found 37 : __find_detail::__find_idx_return(__i, __find_detail::__find_idx(__i + 1, __matches), __matches[__i]); 38 } 39 40 template <class _T1, class... _Args> 41 struct __find_exactly_one_checked { 42 static constexpr bool __matches[sizeof...(_Args)] = {is_same<_T1, _Args>::value...}; 43 static constexpr size_t value = __find_detail::__find_idx(0, __matches); 44 static_assert(value != __not_found, "type not found in type list"); 45 static_assert(value != __ambiguous, "type occurs more than once in type list"); 46 }; 47 48 template <class _T1> 49 struct __find_exactly_one_checked<_T1> { 50 static_assert(!is_same<_T1, _T1>::value, "type not in empty type list"); 51 }; 52 53 } // namespace __find_detail 54 55 template <typename _T1, typename... _Args> 56 struct __find_exactly_one_t : public __find_detail::__find_exactly_one_checked<_T1, _Args...> {}; 57 58 _LIBCPP_END_NAMESPACE_STD 59 60 #endif // _LIBCPP_STD_VER >= 14 61 62 #endif // _LIBCPP___TUPLE_FIND_INDEX_H 63