1 //===----------------------------------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 // UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
10
11 // <chrono>
12 // class month;
13
14 // constexpr month operator+(const month& x, const months& y) noexcept;
15 // Returns: month(int{x} + y.count()).
16 //
17 // constexpr month operator+(const months& x, const month& y) noexcept;
18 // Returns:
19 // month{modulo(static_cast<long long>(int{x}) + (y.count() - 1), 12) + 1}
20 // where modulo(n, 12) computes the remainder of n divided by 12 using Euclidean division.
21 // [Note: Given a divisor of 12, Euclidean division truncates towards negative infinity
22 // and always produces a remainder in the range of [0, 11].
23 // Assuming no overflow in the signed summation, this operation results in a month
24 // holding a value in the range [1, 12] even if !x.ok(). —end note]
25 // [Example: February + months{11} == January. —end example]
26
27
28
29 #include <chrono>
30 #include <type_traits>
31 #include <cassert>
32
33 #include "test_macros.h"
34
35 template <typename M, typename Ms>
testConstexpr()36 constexpr bool testConstexpr()
37 {
38 M m{1};
39 Ms offset{4};
40 if (m + offset != M{5}) return false;
41 if (offset + m != M{5}) return false;
42 // Check the example
43 if (M{2} + Ms{11} != M{1}) return false;
44 return true;
45 }
46
main()47 int main()
48 {
49 using month = std::chrono::month;
50 using months = std::chrono::months;
51
52 ASSERT_NOEXCEPT(std::declval<month>() + std::declval<months>());
53 ASSERT_NOEXCEPT(std::declval<months>() + std::declval<month>());
54
55 ASSERT_SAME_TYPE(month, decltype(std::declval<month>() + std::declval<months>()));
56 ASSERT_SAME_TYPE(month, decltype(std::declval<months>() + std::declval<month>() ));
57
58 static_assert(testConstexpr<month, months>(), "");
59
60 month my{2};
61 for (unsigned i = 0; i <= 15; ++i)
62 {
63 month m1 = my + months{i};
64 month m2 = months{i} + my;
65 assert(m1 == m2);
66 unsigned exp = i + 2;
67 while (exp > 12)
68 exp -= 12;
69 assert(static_cast<unsigned>(m1) == exp);
70 assert(static_cast<unsigned>(m2) == exp);
71 }
72 }
73