1 // -*- C++ -*- 2 //===----------------------------------------------------------------------===// 3 // 4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5 // See https://llvm.org/LICENSE.txt for license information. 6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7 // 8 //===----------------------------------------------------------------------===// 9 10 #ifndef _LIBCPP___VARIANT_MONOSTATE_H 11 #define _LIBCPP___VARIANT_MONOSTATE_H 12 13 #include <__config> 14 #include <__functional/hash.h> 15 #include <cstddef> 16 17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 18 #pragma GCC system_header 19 #endif 20 21 _LIBCPP_BEGIN_NAMESPACE_STD 22 23 #if _LIBCPP_STD_VER > 14 24 25 struct _LIBCPP_TEMPLATE_VIS monostate {}; 26 27 inline _LIBCPP_INLINE_VISIBILITY 28 constexpr bool operator<(monostate, monostate) noexcept { return false; } 29 30 inline _LIBCPP_INLINE_VISIBILITY 31 constexpr bool operator>(monostate, monostate) noexcept { return false; } 32 33 inline _LIBCPP_INLINE_VISIBILITY 34 constexpr bool operator<=(monostate, monostate) noexcept { return true; } 35 36 inline _LIBCPP_INLINE_VISIBILITY 37 constexpr bool operator>=(monostate, monostate) noexcept { return true; } 38 39 inline _LIBCPP_INLINE_VISIBILITY 40 constexpr bool operator==(monostate, monostate) noexcept { return true; } 41 42 inline _LIBCPP_INLINE_VISIBILITY 43 constexpr bool operator!=(monostate, monostate) noexcept { return false; } 44 45 template <> 46 struct _LIBCPP_TEMPLATE_VIS hash<monostate> { 47 using argument_type = monostate; 48 using result_type = size_t; 49 50 inline _LIBCPP_INLINE_VISIBILITY 51 result_type operator()(const argument_type&) const _NOEXCEPT { 52 return 66740831; // return a fundamentally attractive random value. 53 } 54 }; 55 56 #endif // _LIBCPP_STD_VER > 14 57 58 _LIBCPP_END_NAMESPACE_STD 59 60 #endif // _LIBCPP___VARIANT_MONOSTATE_H 61