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 // UNSUPPORTED: gcc-10
12 
13 // constexpr counted_iterator& operator--()
14 //  requires bidirectional_iterator<I>;
15 // constexpr counted_iterator operator--(int)
16 //  requires bidirectional_iterator<I>;
17 
18 #include <iterator>
19 
20 #include "test_macros.h"
21 #include "test_iterators.h"
22 
23 template<class Iter>
24 concept MinusEnabled = requires(Iter& iter) {
25   iter--;
26   --iter;
27 };
28 
29 constexpr bool test() {
30   int buffer[8] = {1, 2, 3, 4, 5, 6, 7, 8};
31 
32   {
33     using Counted = std::counted_iterator<bidirectional_iterator<int*>>;
34     std::counted_iterator iter(bidirectional_iterator<int*>{buffer + 2}, 6);
35     assert(iter-- == Counted(bidirectional_iterator<int*>{buffer + 2}, 6));
36     assert(--iter == Counted(bidirectional_iterator<int*>{buffer}, 8));
37     assert(iter.count() == 8);
38 
39     ASSERT_SAME_TYPE(decltype(iter--), Counted);
40     ASSERT_SAME_TYPE(decltype(--iter), Counted&);
41   }
42   {
43     using Counted = std::counted_iterator<random_access_iterator<int*>>;
44     Counted iter(random_access_iterator<int*>{buffer + 2}, 6);
45     assert(iter-- == Counted(random_access_iterator<int*>{buffer + 2}, 6));
46     assert(--iter == Counted(random_access_iterator<int*>{buffer}, 8));
47     assert(iter.count() == 8);
48 
49     ASSERT_SAME_TYPE(decltype(iter--), Counted);
50     ASSERT_SAME_TYPE(decltype(--iter), Counted&);
51   }
52   {
53     using Counted = std::counted_iterator<contiguous_iterator<int*>>;
54     std::counted_iterator iter(contiguous_iterator<int*>{buffer + 2}, 6);
55     assert(iter-- == Counted(contiguous_iterator<int*>{buffer + 2}, 6));
56     assert(--iter == Counted(contiguous_iterator<int*>{buffer}, 8));
57     assert(iter.count() == 8);
58 
59     ASSERT_SAME_TYPE(decltype(iter--), Counted);
60     ASSERT_SAME_TYPE(decltype(--iter), Counted&);
61   }
62 
63   {
64     static_assert( MinusEnabled<std::counted_iterator<contiguous_iterator<int*>>>);
65     static_assert(!MinusEnabled<const std::counted_iterator<contiguous_iterator<int*>>>);
66     static_assert(!MinusEnabled<std::counted_iterator<forward_iterator<int*>>>);
67   }
68 
69   return true;
70 }
71 
72 int main(int, char**) {
73   test();
74   static_assert(test());
75 
76   return 0;
77 }
78