cppdraft_translate/cppdraft/range/elements/iterator.md

[range.elements.iterator]

25 Ranges library [ranges]

25.7 Range adaptors [range.adaptors]

25.7.23 Elements view [range.elements]

25.7.23.3 Class template elements_view​::​iterator [range.elements.iterator]

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namespace std::ranges {template<input_range V, size_t N>requires view && has-tuple-element<range_value_t, N> &&has-tuple-element<remove_reference_t<range_reference_t>, N> &&returnable-element<range_reference_t, N>templateclass elements_view<V, N>::iterator {using Base = maybe-const<Const, V>; // exposition only iterator_t<Base> current_ = iterator_t<Base>(); // exposition onlystatic constexpr decltype(auto) get-element(const iterator_t<Base>& i); // exposition onlypublic:using iterator_concept = see below; using iterator_category = see below; // not always presentusing value_type = remove_cvref_t<tuple_element_t<N, range_value_t<Base>>>; using difference_type = range_difference_t<Base>; iterator() requires default_initializable<iterator_t<Base>> = default; constexpr explicit iterator(iterator_t<Base> current); constexpr iterator(iterator i)requires Const && convertible_to<iterator_t, iterator_t<Base>>; constexpr const iterator_t<Base>& base() const & noexcept; constexpr iterator_t<Base> base() &&; constexpr decltype(auto) operator*() const{ return get-element(current_); }constexpr iterator& operator++(); constexpr void operator++(int); constexpr iterator operator++(int) requires forward_range<Base>; constexpr iterator& operator--() requires bidirectional_range<Base>; constexpr iterator operator--(int) requires bidirectional_range<Base>; constexpr iterator& operator+=(difference_type x)requires random_access_range<Base>; constexpr iterator& operator-=(difference_type x)requires random_access_range<Base>; constexpr decltype(auto) operator[](difference_type n) constrequires random_access_range<Base>{ return get-element(current_ + n); }friend constexpr bool operator==(const iterator& x, const iterator& y)requires equality_comparable<iterator_t<Base>>; friend constexpr bool operator<(const iterator& x, const iterator& y)requires random_access_range<Base>; friend constexpr bool operator>(const iterator& x, const iterator& y)requires random_access_range<Base>; friend constexpr bool operator<=(const iterator& x, const iterator& y)requires random_access_range<Base>; friend constexpr bool operator>=(const iterator& x, const iterator& y)requires random_access_range<Base>; friend constexpr auto operator<=>(const iterator& x, const iterator& y)requires random_access_range<Base> && three_way_comparable<iterator_t<Base>>; friend constexpr iterator operator+(const iterator& x, difference_type y)requires random_access_range<Base>; friend constexpr iterator operator+(difference_type x, const iterator& y)requires random_access_range<Base>; friend constexpr iterator operator-(const iterator& x, difference_type y)requires random_access_range<Base>; friend constexpr difference_type operator-(const iterator& x, const iterator& y)requires sized_sentinel_for<iterator_t<Base>, iterator_t<Base>>; };}

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The member typedef-name iterator_concept is defined as follows:

• (1.1)

  If Base models random_access_range, then iterator_concept denotes random_access_iterator_tag.

• (1.2)

  Otherwise, if Base models bidirectional_range, then iterator_concept denotes bidirectional_iterator_tag.

• (1.3)

  Otherwise, if Base models forward_range, then iterator_concept denotes forward_iterator_tag.

• (1.4)

  Otherwise, iterator_concept denotes input_iterator_tag.

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The member typedef-name iterator_category is defined if and only if Base models forward_range.

In that case, iterator_category is defined as follows: Let C denote the typeiterator_traits<iterator_t<Base>>​::​iterator_category.

• (2.1)

  If std​::​get(**current_*) is an rvalue,iterator_category denotes input_iterator_tag.

• (2.2)

  Otherwise, if C models derived_from<random_access_iterator_tag>,iterator_category denotes random_access_iterator_tag.

• (2.3)

  Otherwise, iterator_category denotes C.

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static constexpr decltype(auto) get-element(const iterator_t<Base>& i);

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Effects: Equivalent to:if constexpr (is_reference_v<range_reference_t<Base>>) {return std::get(*i);} else {using E = remove_cv_t<tuple_element_t<N, range_reference_t<Base>>>; return static_cast(std::get(*i));}

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constexpr explicit iterator(iterator_t<Base> current);

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Effects: Initializes current_ with std​::​move(current).

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constexpr iterator(iterator<!Const> i) requires Const && [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<iterator_t<V>, iterator_t<Base>>;

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Effects: Initializes current_ with std​::​move(i.current_).

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constexpr const iterator_t<Base>& base() const & noexcept;

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Effects: Equivalent to: return current_;

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constexpr iterator_t<Base> base() &&;

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Effects: Equivalent to: return std​::​move(current_);

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constexpr iterator& operator++();

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Effects: Equivalent to:++current_;return *this;

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constexpr void operator++(int);

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Effects: Equivalent to: ++current_.

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constexpr iterator operator++(int) requires [forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")<Base>;

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Effects: Equivalent to:auto temp = *this;++current_;return temp;

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constexpr iterator& operator--() requires [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]")<Base>;

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Effects: Equivalent to:--current_;return *this;

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constexpr iterator operator--(int) requires [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]")<Base>;

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Effects: Equivalent to:auto temp = *this;--current_;return temp;

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constexpr iterator& operator+=(difference_type n) requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;

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Effects: Equivalent to:current_ += n;return *this;

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constexpr iterator& operator-=(difference_type n) requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;

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Effects: Equivalent to:current_ -= n;return *this;

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friend constexpr bool operator==(const iterator& x, const iterator& y) requires [equality_comparable](concept.equalitycomparable#concept:equality_comparable "18.5.4 Concept equality_­comparable [concept.equalitycomparable]")<Base>;

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Effects: Equivalent to: return x.current_ == y.current_;

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friend constexpr bool operator<(const iterator& x, const iterator& y) requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;

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Effects: Equivalent to: return x.current_ < y.current_;

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friend constexpr bool operator>(const iterator& x, const iterator& y) requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;

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Effects: Equivalent to: return y < x;

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friend constexpr bool operator<=(const iterator& x, const iterator& y) requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;

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Effects: Equivalent to: return !(y < x);

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friend constexpr bool operator>=(const iterator& x, const iterator& y) requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;

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Effects: Equivalent to: return !(x < y);

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friend constexpr auto operator<=>(const iterator& x, const iterator& y) requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base> && [three_way_comparable](cmp.concept#concept:three_way_comparable "17.12.4 Concept three_­way_­comparable [cmp.concept]")<iterator_t<Base>>;

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Effects: Equivalent to: return x.current_ <=> y.current_;

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friend constexpr iterator operator+(const iterator& x, difference_type y) requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;

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Effects: Equivalent to: return iterator{x} += y;

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friend constexpr iterator operator+(difference_type x, const iterator& y) requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;

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Effects: Equivalent to: return y + x;

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friend constexpr iterator operator-(const iterator& x, difference_type y) requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;

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Effects: Equivalent to: return iterator{x} -= y;

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friend constexpr difference_type operator-(const iterator& x, const iterator& y) requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<iterator_t<Base>, iterator_t<Base>>;

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Effects: Equivalent to: return x.current_ - y.current_;