1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9// UNSUPPORTED: c++03, c++11, c++14, c++17
10
11// <compare>
12// <functional>
13
14// compare_three_way
15
16#include <compare>
17#include <cassert>
18#include <limits>
19#include <type_traits>
20
21#include "pointer_comparison_test_helper.h"
22
23template<class T, class U>
24constexpr auto test_sfinae(T t, U u)
25 -> decltype(std::compare_three_way()(t, u), std::true_type{})
26 { return std::true_type{}; }
27
28constexpr auto test_sfinae(...)
29 { return std::false_type{}; }
30
31struct NotThreeWayComparable {
32 std::strong_ordering operator<=>(const NotThreeWayComparable&) const;
33};
34ASSERT_SAME_TYPE(std::compare_three_way_result_t<NotThreeWayComparable>, std::strong_ordering);
35static_assert(!std::three_way_comparable<NotThreeWayComparable>); // it lacks operator==
36
37struct WeaklyOrdered {
38 int i;
39 friend constexpr std::weak_ordering operator<=>(const WeaklyOrdered&, const WeaklyOrdered&) = default;
40};
41
42constexpr bool test()
43{
44 ASSERT_SAME_TYPE(decltype(std::compare_three_way()(1, 1)), std::strong_ordering);
45 assert(std::compare_three_way()(1, 2) == std::strong_ordering::less);
46 assert(std::compare_three_way()(1, 1) == std::strong_ordering::equal);
47 assert(std::compare_three_way()(2, 1) == std::strong_ordering::greater);
48
49 ASSERT_SAME_TYPE(decltype(std::compare_three_way()(WeaklyOrdered{1}, WeaklyOrdered{2})), std::weak_ordering);
50 assert(std::compare_three_way()(WeaklyOrdered{1}, WeaklyOrdered{2}) == std::weak_ordering::less);
51 assert(std::compare_three_way()(WeaklyOrdered{1}, WeaklyOrdered{1}) == std::weak_ordering::equivalent);
52 assert(std::compare_three_way()(WeaklyOrdered{2}, WeaklyOrdered{1}) == std::weak_ordering::greater);
53
54 ASSERT_SAME_TYPE(decltype(std::compare_three_way()(1.0, 1.0)), std::partial_ordering);
55 double nan = std::numeric_limits<double>::quiet_NaN();
56 assert(std::compare_three_way()(1.0, 2.0) == std::partial_ordering::less);
57 assert(std::compare_three_way()(1.0, 1.0) == std::partial_ordering::equivalent);
58 assert(std::compare_three_way()(2.0, 1.0) == std::partial_ordering::greater);
59 assert(std::compare_three_way()(nan, nan) == std::partial_ordering::unordered);
60
61 // Try heterogeneous comparison.
62 ASSERT_SAME_TYPE(decltype(std::compare_three_way()(42.0, 42)), std::partial_ordering);
63 assert(std::compare_three_way()(42.0, 42) == std::partial_ordering::equivalent);
64 ASSERT_SAME_TYPE(decltype(std::compare_three_way()(42, 42.0)), std::partial_ordering);
65 assert(std::compare_three_way()(42, 42.0) == std::partial_ordering::equivalent);
66
67 return true;
68}
69
70int main(int, char**)
71{
72 test();
73 static_assert(test());
74
75 do_pointer_comparison_test(std::compare_three_way());
76
77 static_assert(test_sfinae(1, 2));
78 static_assert(!test_sfinae(1, nullptr));
79 static_assert(!test_sfinae(NotThreeWayComparable(), NotThreeWayComparable()));
80
81 return 0;
82}
83

source code of libcxx/test/std/utilities/function.objects/comparisons/compare_three_way.pass.cpp