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

   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 }