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64 lines
2 KiB
C++
64 lines
2 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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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___VARIANT_MONOSTATE_H
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#define _LIBCPP___VARIANT_MONOSTATE_H
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#include <__compare/ordering.h>
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#include <__config>
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#include <__functional/hash.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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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER >= 17
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struct _LIBCPP_TEMPLATE_VIS monostate {};
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_LIBCPP_HIDE_FROM_ABI inline constexpr bool operator==(monostate, monostate) noexcept { return true; }
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# if _LIBCPP_STD_VER >= 20
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_LIBCPP_HIDE_FROM_ABI inline constexpr strong_ordering operator<=>(monostate, monostate) noexcept {
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return strong_ordering::equal;
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}
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# else // _LIBCPP_STD_VER >= 20
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_LIBCPP_HIDE_FROM_ABI inline constexpr bool operator!=(monostate, monostate) noexcept { return false; }
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_LIBCPP_HIDE_FROM_ABI inline constexpr bool operator<(monostate, monostate) noexcept { return false; }
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_LIBCPP_HIDE_FROM_ABI inline constexpr bool operator>(monostate, monostate) noexcept { return false; }
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_LIBCPP_HIDE_FROM_ABI inline constexpr bool operator<=(monostate, monostate) noexcept { return true; }
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_LIBCPP_HIDE_FROM_ABI inline constexpr bool operator>=(monostate, monostate) noexcept { return true; }
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# endif // _LIBCPP_STD_VER >= 20
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template <>
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struct _LIBCPP_TEMPLATE_VIS hash<monostate> {
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using argument_type = monostate;
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using result_type = size_t;
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inline _LIBCPP_HIDE_FROM_ABI result_type operator()(const argument_type&) const _NOEXCEPT {
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return 66740831; // return a fundamentally attractive random value.
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}
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};
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#endif // _LIBCPP_STD_VER >= 17
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___VARIANT_MONOSTATE_H
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