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62 lines
2.1 KiB
C++
62 lines
2.1 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___TUPLE_FIND_INDEX_H
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#define _LIBCPP___TUPLE_FIND_INDEX_H
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#include <__config>
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#include <__type_traits/is_same.h>
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#include <cstddef>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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#if _LIBCPP_STD_VER >= 14
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_LIBCPP_BEGIN_NAMESPACE_STD
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namespace __find_detail {
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static constexpr size_t __not_found = static_cast<size_t>(-1);
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static constexpr size_t __ambiguous = __not_found - 1;
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inline _LIBCPP_HIDE_FROM_ABI constexpr size_t __find_idx_return(size_t __curr_i, size_t __res, bool __matches) {
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return !__matches ? __res : (__res == __not_found ? __curr_i : __ambiguous);
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}
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template <size_t _Nx>
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inline _LIBCPP_HIDE_FROM_ABI constexpr size_t __find_idx(size_t __i, const bool (&__matches)[_Nx]) {
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return __i == _Nx
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? __not_found
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: __find_detail::__find_idx_return(__i, __find_detail::__find_idx(__i + 1, __matches), __matches[__i]);
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}
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template <class _T1, class... _Args>
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struct __find_exactly_one_checked {
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static constexpr bool __matches[sizeof...(_Args)] = {is_same<_T1, _Args>::value...};
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static constexpr size_t value = __find_detail::__find_idx(0, __matches);
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static_assert(value != __not_found, "type not found in type list");
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static_assert(value != __ambiguous, "type occurs more than once in type list");
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};
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template <class _T1>
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struct __find_exactly_one_checked<_T1> {
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static_assert(!is_same<_T1, _T1>::value, "type not in empty type list");
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};
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} // namespace __find_detail
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template <typename _T1, typename... _Args>
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struct __find_exactly_one_t : public __find_detail::__find_exactly_one_checked<_T1, _Args...> {};
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP_STD_VER >= 14
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#endif // _LIBCPP___TUPLE_FIND_INDEX_H
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