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