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 // template<common_with<I> I2>
14 //   friend constexpr iter_difference_t<I2> operator-(
15 //     const counted_iterator& x, const counted_iterator<I2>& y);
16 
17 #include <iterator>
18 
19 #include "test_macros.h"
20 #include "test_iterators.h"
21 
22 // This iterator is common_with forward_iterator but NOT comparable with it.
23 template <class It>
24 class CommonWithForwardIter
25 {
26     It it_;
27 
28 public:
29     typedef          std::input_iterator_tag                   iterator_category;
30     typedef typename std::iterator_traits<It>::value_type      value_type;
31     typedef typename std::iterator_traits<It>::difference_type difference_type;
32     typedef It                                                 pointer;
33     typedef typename std::iterator_traits<It>::reference       reference;
34 
35     constexpr It base() const {return it_;}
36 
37     CommonWithForwardIter() = default;
38     explicit constexpr CommonWithForwardIter(It it) : it_(it) {}
39     constexpr CommonWithForwardIter(const forward_iterator<It>& it) : it_(it.base()) {}
40 
41     constexpr reference operator*() const {return *it_;}
42 
43     constexpr CommonWithForwardIter& operator++() {++it_; return *this;}
44     constexpr CommonWithForwardIter operator++(int)
45         {CommonWithForwardIter tmp(*this); ++(*this); return tmp;}
46 };
47 
48 constexpr bool test() {
49   int buffer[8] = {1, 2, 3, 4, 5, 6, 7, 8};
50 
51   {
52     std::counted_iterator iter1(random_access_iterator<int*>{buffer}, 8);
53     std::counted_iterator iter2(random_access_iterator<int*>{buffer + 4}, 4);
54     assert(iter1 - iter2 == -4);
55     assert(iter2 - iter1 == 4);
56     assert(iter1.count() == 8);
57     assert(iter2.count() == 4);
58 
59     ASSERT_SAME_TYPE(decltype(iter1 - iter2), std::iter_difference_t<int*>);
60   }
61   {
62     const std::counted_iterator iter1(random_access_iterator<int*>{buffer}, 8);
63     const std::counted_iterator iter2(random_access_iterator<int*>{buffer + 4}, 4);
64     assert(iter1 - iter2 == -4);
65     assert(iter2 - iter1 == 4);
66     assert(iter1.count() == 8);
67     assert(iter2.count() == 4);
68 
69     ASSERT_SAME_TYPE(decltype(iter1 - iter2), std::iter_difference_t<int*>);
70   }
71   {
72     std::counted_iterator iter1(contiguous_iterator<int*>{buffer}, 8);
73     std::counted_iterator iter2(contiguous_iterator<int*>{buffer + 2}, 6);
74     assert(iter1 - iter2 == -2);
75     assert(iter2 - iter1 == 2);
76     assert(iter1.count() == 8);
77     assert(iter2.count() == 6);
78 
79     ASSERT_SAME_TYPE(decltype(iter1 - iter2), std::iter_difference_t<int*>);
80   }
81   {
82     const std::counted_iterator iter1(contiguous_iterator<int*>{buffer}, 8);
83     const std::counted_iterator iter2(contiguous_iterator<int*>{buffer + 2}, 6);
84     assert(iter1 - iter2 == -2);
85     assert(iter2 - iter1 == 2);
86     assert(iter1.count() == 8);
87     assert(iter2.count() == 6);
88 
89     ASSERT_SAME_TYPE(decltype(iter1 - iter2), std::iter_difference_t<int*>);
90   }
91   // The minus operator works even if Iter is not a random_access_iterator because
92   // counted_iterator is able to implement it by subtracting the counts rather than
93   // the underlying iterators.
94   {
95     std::counted_iterator iter1(CommonWithForwardIter<int*>{buffer}, 8);
96     std::counted_iterator iter2(forward_iterator<int*>{buffer + 2}, 6);
97     assert(iter1 - iter2 == -2);
98     assert(iter2 - iter1 == 2);
99     assert(iter1.count() == 8);
100     assert(iter2.count() == 6);
101 
102     ASSERT_SAME_TYPE(decltype(iter1 - iter2), std::iter_difference_t<int*>);
103   }
104   {
105     const std::counted_iterator iter1(CommonWithForwardIter<int*>{buffer}, 8);
106     const std::counted_iterator iter2(forward_iterator<int*>{buffer + 2}, 6);
107     assert(iter1 - iter2 == -2);
108     assert(iter2 - iter1 == 2);
109     assert(iter1.count() == 8);
110     assert(iter2.count() == 6);
111 
112     ASSERT_SAME_TYPE(decltype(iter1 - iter2), std::iter_difference_t<int*>);
113   }
114 
115   return true;
116 }
117 
118 int main(int, char**) {
119   test();
120   static_assert(test());
121 
122   return 0;
123 }
124