forked from OSchip/llvm-project
52 lines
1.6 KiB
C++
52 lines
1.6 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___COMPARE_SYNTH_THREE_WAY_H
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#define _LIBCPP___COMPARE_SYNTH_THREE_WAY_H
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#include <__compare/ordering.h>
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#include <__compare/three_way_comparable.h>
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#include <__concepts/boolean_testable.h>
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#include <__config>
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#include <__utility/declval.h>
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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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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
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// [expos.only.func]
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_LIBCPP_HIDE_FROM_ABI inline constexpr auto __synth_three_way =
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[]<class _Tp, class _Up>(const _Tp& __t, const _Up& __u)
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requires requires {
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{ __t < __u } -> __boolean_testable;
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{ __u < __t } -> __boolean_testable;
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}
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{
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if constexpr (three_way_comparable_with<_Tp, _Up>) {
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return __t <=> __u;
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} else {
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if (__t < __u) return weak_ordering::less;
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if (__u < __t) return weak_ordering::greater;
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return weak_ordering::equivalent;
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}
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};
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template <class _Tp, class _Up = _Tp>
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using __synth_three_way_result = decltype(__synth_three_way(declval<_Tp&>(), declval<_Up&>()));
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#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___COMPARE_SYNTH_THREE_WAY_H
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