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
__find_idx_return(size_t __curr_i,size_t __res,bool __matches)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>
__find_idx(size_t __i,const bool (& __matches)[_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