25 Ranges library [ranges]

25.7 Range adaptors [range.adaptors]

25.7.8 Filter view [range.filter]

25.7.8.3 Class filter_view​::​iterator [range.filter.iterator]

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namespace std::ranges { template<input_range V, indirect_unary_predicate<iterator_t<V>> Pred> requires view<V> && is_object_v<Pred> class filter_view<V, Pred>::iterator { private: iterator_t<V> current_ = iterator_t<V>(); // exposition only filter_view* parent_ = nullptr; // exposition only public: using iterator_concept = see below; using iterator_category = see below; // not always present using value_type = range_value_t<V>; using difference_type = range_difference_t<V>; iterator() requires default_initializable<iterator_t<V>> = default; constexpr iterator(filter_view& parent, iterator_t<V> current); constexpr const iterator_t<V>& base() const & noexcept; constexpr iterator_t<V> base() &&; constexpr range_reference_t<V> operator*() const; constexpr iterator_t<V> operator->() const requires has-arrow<iterator_t<V>> && copyable<iterator_t<V>>; constexpr iterator& operator++(); constexpr void operator++(int); constexpr iterator operator++(int) requires forward_range<V>; constexpr iterator& operator--() requires bidirectional_range<V>; constexpr iterator operator--(int) requires bidirectional_range<V>; friend constexpr bool operator==(const iterator& x, const iterator& y) requires equality_comparable<iterator_t<V>>; friend constexpr range_rvalue_reference_t<V> iter_move(const iterator& i) noexcept(noexcept(ranges::iter_move(i.current_))); friend constexpr void iter_swap(const iterator& x, const iterator& y) noexcept(noexcept(ranges::iter_swap(x.current_, y.current_))) requires indirectly_swappable<iterator_t<V>>; }; }
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Modification of the element a filter_view​::​iterator denotes is permitted, but results in undefined behavior if the resulting value does not satisfy the filter predicate.
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iterator​::​iterator_concept is defined as follows:
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The member typedef-name iterator_category is defined if and only if V models forward_range.
In that case, iterator​::​iterator_category is defined as follows:
  • (3.1)
    Let C denote the type iterator_traits<iterator_t<V>>​::​iterator_category.
  • (3.2)
    If C models derived_from<bidirectional_iterator_tag>, then iterator_category denotes bidirectional_iterator_tag.
  • (3.3)
    Otherwise, if C models derived_from<forward_iterator_tag>, then iterator_category denotes forward_iterator_tag.
  • (3.4)
    Otherwise, iterator_category denotes C.
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constexpr iterator(filter_view& parent, iterator_t<V> current);
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Effects: Initializes current_ with std​::​move(current) and parent_ with addressof(parent).
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constexpr const iterator_t<V>& base() const & noexcept;
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Effects: Equivalent to: return current_;
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constexpr iterator_t<V> base() &&;
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Effects: Equivalent to: return std​::​move(current_);
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constexpr range_reference_t<V> operator*() const;
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Effects: Equivalent to: return *current_;
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constexpr iterator_t<V> operator->() const requires has-arrow<iterator_t<V>> && copyable<iterator_t<V>>;
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Effects: Equivalent to: return current_;
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constexpr iterator& operator++();
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Effects: Equivalent to: current_ = ranges::find_if(std::move(++current_), ranges::end(parent_->base_), ref(*parent_->pred_)); return *this;
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constexpr void operator++(int);
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Effects: Equivalent to ++*this.
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constexpr iterator operator++(int) requires forward_range<V>;
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Effects: Equivalent to: auto tmp = *this; ++*this; return tmp;
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constexpr iterator& operator--() requires bidirectional_range<V>;
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Effects: Equivalent to: do --current_; while (!invoke(*parent_->pred_, *current_)); return *this;
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constexpr iterator operator--(int) requires bidirectional_range<V>;
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Effects: Equivalent to: auto tmp = *this; --*this; return tmp;
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friend constexpr bool operator==(const iterator& x, const iterator& y) requires equality_comparable<iterator_t<V>>;
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Effects: Equivalent to: return x.current_ == y.current_;
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friend constexpr range_rvalue_reference_t<V> iter_move(const iterator& i) noexcept(noexcept(ranges::iter_move(i.current_)));
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Effects: Equivalent to: return ranges​::​iter_move(i.current_);
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friend constexpr void iter_swap(const iterator& x, const iterator& y) noexcept(noexcept(ranges::iter_swap(x.current_, y.current_))) requires indirectly_swappable<iterator_t<V>>;
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Effects: Equivalent to ranges​::​iter_swap(x.current_, y.current_).