libcxx/test/std/iterators/predef.iterators/counted.iterator/minus.iter.pass.cpp

   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 }