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 // UNSUPPORTED: libcpp-no-concepts
11 
12 // <compare>
13 // <functional>
14 
15 // compare_three_way
16 
17 #include <compare>
18 #include <cassert>
19 #include <limits>
20 #include <type_traits>
21 
22 #include "pointer_comparison_test_helper.h"
23 
24 template<class T, class U>
25 constexpr auto test_sfinae(T t, U u)
26     -> decltype(std::compare_three_way()(t, u), std::true_type{})
27     { return std::true_type{}; }
28 
29 constexpr auto test_sfinae(...)
30     { return std::false_type{}; }
31 
32 struct NotThreeWayComparable {
33     std::strong_ordering operator<=>(const NotThreeWayComparable&) const;
34 };
35 ASSERT_SAME_TYPE(std::compare_three_way_result_t<NotThreeWayComparable>, std::strong_ordering);
36 static_assert(!std::three_way_comparable<NotThreeWayComparable>);  // it lacks operator==
37 
38 struct WeaklyOrdered {
39     int i;
40     friend constexpr std::weak_ordering operator<=>(const WeaklyOrdered&, const WeaklyOrdered&) = default;
41 };
42 
43 constexpr bool test()
44 {
45     ASSERT_SAME_TYPE(decltype(std::compare_three_way()(1, 1)), std::strong_ordering);
46     assert(std::compare_three_way()(1, 2) == std::strong_ordering::less);
47     assert(std::compare_three_way()(1, 1) == std::strong_ordering::equal);
48     assert(std::compare_three_way()(2, 1) == std::strong_ordering::greater);
49 
50     ASSERT_SAME_TYPE(decltype(std::compare_three_way()(WeaklyOrdered{1}, WeaklyOrdered{2})), std::weak_ordering);
51     assert(std::compare_three_way()(WeaklyOrdered{1}, WeaklyOrdered{2}) == std::weak_ordering::less);
52     assert(std::compare_three_way()(WeaklyOrdered{1}, WeaklyOrdered{1}) == std::weak_ordering::equivalent);
53     assert(std::compare_three_way()(WeaklyOrdered{2}, WeaklyOrdered{1}) == std::weak_ordering::greater);
54 
55     ASSERT_SAME_TYPE(decltype(std::compare_three_way()(1.0, 1.0)), std::partial_ordering);
56     double nan = std::numeric_limits<double>::quiet_NaN();
57     assert(std::compare_three_way()(1.0, 2.0) == std::partial_ordering::less);
58     assert(std::compare_three_way()(1.0, 1.0) == std::partial_ordering::equivalent);
59     assert(std::compare_three_way()(2.0, 1.0) == std::partial_ordering::greater);
60     assert(std::compare_three_way()(nan, nan) == std::partial_ordering::unordered);
61 
62     // Try heterogeneous comparison.
63     ASSERT_SAME_TYPE(decltype(std::compare_three_way()(42.0, 42)), std::partial_ordering);
64     assert(std::compare_three_way()(42.0, 42) == std::partial_ordering::equivalent);
65     ASSERT_SAME_TYPE(decltype(std::compare_three_way()(42, 42.0)), std::partial_ordering);
66     assert(std::compare_three_way()(42, 42.0) == std::partial_ordering::equivalent);
67 
68     return true;
69 }
70 
71 int main(int, char**)
72 {
73     test();
74     static_assert(test());
75 
76     do_pointer_comparison_test(std::compare_three_way());
77 
78     static_assert(test_sfinae(1, 2));
79     static_assert(!test_sfinae(1, nullptr));
80     static_assert(!test_sfinae(NotThreeWayComparable(), NotThreeWayComparable()));
81 
82     return 0;
83 }
84