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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___COMPARE_COMMON_COMPARISON_CATEGORY_H
#define _LIBCPP___COMPARE_COMMON_COMPARISON_CATEGORY_H
#include <__compare/ordering.h>
#include <__config>
#include <__cstddef/size_t.h>
#include <__type_traits/is_same.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER >= 20
namespace __comp_detail {
enum _ClassifyCompCategory : unsigned { _None, _PartialOrd, _WeakOrd, _StrongOrd, _CCC_Size };
template <class _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr _ClassifyCompCategory __type_to_enum() noexcept {
if (is_same_v<_Tp, partial_ordering>)
return _PartialOrd;
if (is_same_v<_Tp, weak_ordering>)
return _WeakOrd;
if (is_same_v<_Tp, strong_ordering>)
return _StrongOrd;
return _None;
}
template <size_t _Size>
_LIBCPP_HIDE_FROM_ABI constexpr _ClassifyCompCategory
__compute_comp_type(const _ClassifyCompCategory (&__types)[_Size]) {
int __seen[_CCC_Size] = {};
for (auto __type : __types)
++__seen[__type];
if (__seen[_None])
return _None;
if (__seen[_PartialOrd])
return _PartialOrd;
if (__seen[_WeakOrd])
return _WeakOrd;
return _StrongOrd;
}
template <class... _Ts, bool _False = false>
_LIBCPP_HIDE_FROM_ABI constexpr auto __get_comp_type() {
using _CCC = _ClassifyCompCategory;
constexpr _CCC __type_kinds[] = {_StrongOrd, __type_to_enum<_Ts>()...};
constexpr _CCC __cat = __comp_detail::__compute_comp_type(__type_kinds);
if constexpr (__cat == _None)
return void();
else if constexpr (__cat == _PartialOrd)
return partial_ordering::equivalent;
else if constexpr (__cat == _WeakOrd)
return weak_ordering::equivalent;
else if constexpr (__cat == _StrongOrd)
return strong_ordering::equivalent;
else
static_assert(_False, "unhandled case");
}
} // namespace __comp_detail
// [cmp.common], common comparison category type
template <class... _Ts>
struct _LIBCPP_TEMPLATE_VIS common_comparison_category {
using type = decltype(__comp_detail::__get_comp_type<_Ts...>());
};
template <class... _Ts>
using common_comparison_category_t = typename common_comparison_category<_Ts...>::type;
#endif // _LIBCPP_STD_VER >= 20
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___COMPARE_COMMON_COMPARISON_CATEGORY_H
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