tmp/tmpx7d8eef7/{from.md → to.md}
RENAMED
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| 1 |
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#### Class template `common_iterator` <a id="common.iterator">[[common.iterator]]</a>
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Class template `common_iterator` is an iterator/sentinel adaptor that is
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capable of representing a non-common range of elements (where the types
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of the iterator and sentinel differ) as a common range (where they are
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the same). It does this by holding either an iterator or a sentinel, and
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implementing the equality comparison operators appropriately.
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[*Note 1*: The `common_iterator` type is useful for interfacing with
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legacy code that expects the begin and end of a range to have the same
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type. — *end note*]
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[*Example 1*:
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``` cpp
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template<class ForwardIterator>
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void fun(ForwardIterator begin, ForwardIterator end);
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list<int> s;
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// populate the list s
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using CI = common_iterator<counted_iterator<list<int>::iterator>, default_sentinel_t>;
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// call fun on a range of 10 ints
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fun(CI(counted_iterator(s.begin(), 10)), CI(default_sentinel));
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```
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— *end example*]
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``` cpp
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namespace std {
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template<input_or_output_iterator I, sentinel_for<I> S>
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requires (!same_as<I, S> && copyable<I>)
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class common_iterator {
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public:
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constexpr common_iterator() = default;
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constexpr common_iterator(I i);
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constexpr common_iterator(S s);
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template<class I2, class S2>
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requires convertible_to<const I2&, I> && convertible_to<const S2&, S>
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constexpr common_iterator(const common_iterator<I2, S2>& x);
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template<class I2, class S2>
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requires convertible_to<const I2&, I> && convertible_to<const S2&, S> &&
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assignable_from<I&, const I2&> && assignable_from<S&, const S2&>
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common_iterator& operator=(const common_iterator<I2, S2>& x);
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decltype(auto) operator*();
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decltype(auto) operator*() const
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requires dereferenceable<const I>;
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decltype(auto) operator->() const
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requires see below;
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common_iterator& operator++();
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decltype(auto) operator++(int);
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template<class I2, sentinel_for<I> S2>
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requires sentinel_for<S, I2>
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friend bool operator==(
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const common_iterator& x, const common_iterator<I2, S2>& y);
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template<class I2, sentinel_for<I> S2>
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requires sentinel_for<S, I2> && equality_comparable_with<I, I2>
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friend bool operator==(
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const common_iterator& x, const common_iterator<I2, S2>& y);
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template<sized_sentinel_for<I> I2, sized_sentinel_for<I> S2>
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requires sized_sentinel_for<S, I2>
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friend iter_difference_t<I2> operator-(
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const common_iterator& x, const common_iterator<I2, S2>& y);
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friend iter_rvalue_reference_t<I> iter_move(const common_iterator& i)
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noexcept(noexcept(ranges::iter_move(declval<const I&>())))
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requires input_iterator<I>;
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template<indirectly_swappable<I> I2, class S2>
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friend void iter_swap(const common_iterator& x, const common_iterator<I2, S2>& y)
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noexcept(noexcept(ranges::iter_swap(declval<const I&>(), declval<const I2&>())));
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private:
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variant<I, S> v_; // exposition only
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};
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template<class I, class S>
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struct incrementable_traits<common_iterator<I, S>> {
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using difference_type = iter_difference_t<I>;
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};
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template<input_iterator I, class S>
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struct iterator_traits<common_iterator<I, S>> {
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using iterator_concept = see below;
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using iterator_category = see below;
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using value_type = iter_value_t<I>;
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using difference_type = iter_difference_t<I>;
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using pointer = see below;
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using reference = iter_reference_t<I>;
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};
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}
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```
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