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 
23 template<class T, class U>
24 constexpr auto test_sfinae(T t, U u)
25     -> decltype(std::compare_three_way()(t, u), std::true_type{})
26     { return std::true_type{}; }
27 
28 constexpr auto test_sfinae(...)
29     { return std::false_type{}; }
30 
31 struct NotThreeWayComparable {
32     std::strong_ordering operator<=>(const NotThreeWayComparable&) const;
33 };
34 ASSERT_SAME_TYPE(std::compare_three_way_result_t<NotThreeWayComparable>, std::strong_ordering);
35 static_assert(!std::three_way_comparable<NotThreeWayComparable>);  // it lacks operator==
36 
37 struct WeaklyOrdered {
38     int i;
39     friend constexpr std::weak_ordering operator<=>(const WeaklyOrdered&, const WeaklyOrdered&) = default;
40 };
41 
42 constexpr 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 
70 int 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