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___OPTIONAL_NULLOPT_T_H
11#define _LIBCPP___OPTIONAL_NULLOPT_T_H
12
13#include <__compare/ordering.h>
14#include <__config>
15
16#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
17# pragma GCC system_header
18#endif
19
20_LIBCPP_PUSH_MACROS
21#include <__undef_macros>
22
23#if _LIBCPP_STD_VER >= 17
24
25_LIBCPP_BEGIN_NAMESPACE_STD
26
27struct nullopt_t {
28 struct __secret_tag {
29 explicit __secret_tag() = default;
30 };
31 _LIBCPP_HIDE_FROM_ABI constexpr explicit nullopt_t(__secret_tag, __secret_tag) noexcept {}
32
33# if _LIBCPP_STD_VER >= 20
34
35 _LIBCPP_HIDE_FROM_ABI constexpr friend strong_ordering operator<=>(nullopt_t, nullopt_t) = default;
36
37# else
38
39 _LIBCPP_HIDE_FROM_ABI constexpr friend bool operator==(nullopt_t, nullopt_t) noexcept { return true; }
40 _LIBCPP_HIDE_FROM_ABI constexpr friend bool operator!=(nullopt_t, nullopt_t) noexcept { return false; }
41 _LIBCPP_HIDE_FROM_ABI constexpr friend bool operator>(nullopt_t, nullopt_t) noexcept { return false; }
42 _LIBCPP_HIDE_FROM_ABI constexpr friend bool operator<(nullopt_t, nullopt_t) noexcept { return false; }
43 _LIBCPP_HIDE_FROM_ABI constexpr friend bool operator>=(nullopt_t, nullopt_t) noexcept { return true; }
44 _LIBCPP_HIDE_FROM_ABI constexpr friend bool operator<=(nullopt_t, nullopt_t) noexcept { return true; }
45
46# endif // _LIBCPP_STD_VER >= 20
47};
48
49inline constexpr nullopt_t nullopt{nullopt_t::__secret_tag{}, nullopt_t::__secret_tag{}};
50
51_LIBCPP_END_NAMESPACE_STD
52
53#endif // _LIBCPP_STD_VER >= 17
54
55_LIBCPP_POP_MACROS
56#endif // _LIBCPP___OPTIONAL_NULLOPT_T_H
57