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 // constexpr counted_iterator& operator--()
12 //  requires bidirectional_iterator<I>;
13 // constexpr counted_iterator operator--(int)
14 //  requires bidirectional_iterator<I>;
15 
16 #include <iterator>
17 
18 #include "test_macros.h"
19 #include "test_iterators.h"
20 
21 template<class Iter>
22 concept MinusEnabled = requires(Iter& iter) {
23   iter--;
24   --iter;
25 };
26 
27 constexpr bool test() {
28   int buffer[8] = {1, 2, 3, 4, 5, 6, 7, 8};
29 
30   {
31     using Counted = std::counted_iterator<bidirectional_iterator<int*>>;
32     std::counted_iterator iter(bidirectional_iterator<int*>{buffer + 2}, 6);
33     assert(iter-- == Counted(bidirectional_iterator<int*>{buffer + 2}, 6));
34     assert(--iter == Counted(bidirectional_iterator<int*>{buffer}, 8));
35     assert(iter.count() == 8);
36 
37     ASSERT_SAME_TYPE(decltype(iter--), Counted);
38     ASSERT_SAME_TYPE(decltype(--iter), Counted&);
39   }
40   {
41     using Counted = std::counted_iterator<random_access_iterator<int*>>;
42     Counted iter(random_access_iterator<int*>{buffer + 2}, 6);
43     assert(iter-- == Counted(random_access_iterator<int*>{buffer + 2}, 6));
44     assert(--iter == Counted(random_access_iterator<int*>{buffer}, 8));
45     assert(iter.count() == 8);
46 
47     ASSERT_SAME_TYPE(decltype(iter--), Counted);
48     ASSERT_SAME_TYPE(decltype(--iter), Counted&);
49   }
50   {
51     using Counted = std::counted_iterator<contiguous_iterator<int*>>;
52     std::counted_iterator iter(contiguous_iterator<int*>{buffer + 2}, 6);
53     assert(iter-- == Counted(contiguous_iterator<int*>{buffer + 2}, 6));
54     assert(--iter == Counted(contiguous_iterator<int*>{buffer}, 8));
55     assert(iter.count() == 8);
56 
57     ASSERT_SAME_TYPE(decltype(iter--), Counted);
58     ASSERT_SAME_TYPE(decltype(--iter), Counted&);
59   }
60 
61   {
62     static_assert( MinusEnabled<std::counted_iterator<contiguous_iterator<int*>>>);
63     static_assert(!MinusEnabled<const std::counted_iterator<contiguous_iterator<int*>>>);
64     static_assert(!MinusEnabled<std::counted_iterator<forward_iterator<int*>>>);
65   }
66 
67   return true;
68 }
69 
70 int main(int, char**) {
71   test();
72   static_assert(test());
73 
74   return 0;
75 }
76