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