cppdraft_translate/cppdraft/range/transform/iterator.md

[range.transform.iterator]

25 Ranges library [ranges]

25.7 Range adaptors [range.adaptors]

25.7.9 Transform view [range.transform]

25.7.9.3 Class template transform_view​::​iterator [range.transform.iterator]

🔗

namespace std::ranges {template<input_range V, move_constructible F>requires view && is_object_v &&regular_invocable<F&, range_reference_t> &&can-reference<invoke_result_t<F&, range_reference_t>>templateclass transform_view<V, F>::iterator {private:using Parent = maybe-const<Const, transform_view>; // exposition onlyusing Base = maybe-const<Const, V>; // exposition only iterator_t<Base> current_ = iterator_t<Base>(); // exposition onlyParent parent_ = nullptr; // exposition onlypublic:using iterator_concept = see below; using iterator_category = see below; // not always presentusing value_type = remove_cvref_t<invoke_result_t<maybe-const<Const, F>&, range_reference_t<Base>>>; using difference_type = range_difference_t<Base>; iterator() requires default_initializable<iterator_t<Base>> = default; constexpr iterator(Parent& parent, 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() constnoexcept(noexcept(invoke(**parent_->fun_, **current_))) {return invoke(**parent_->fun_, **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 n)requires random_access_range<Base>; constexpr iterator& operator-=(difference_type n)requires random_access_range<Base>; constexpr decltype(auto) operator[](difference_type n) constrequires random_access_range<Base> {return invoke(**parent_*->fun_, 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+(iterator i, difference_type n)requires random_access_range<Base>; friend constexpr iterator operator+(difference_type n, iterator i)requires random_access_range<Base>; friend constexpr iterator operator-(iterator i, difference_type n)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>>; };}

1

#

iterator​::​iterator_concept is defined as follows:

• (1.1)

  If Base models random_access_range, theniterator_concept denotes random_access_iterator_tag.

• (1.2)

  Otherwise, if Base models bidirectional_range, theniterator_concept denotes bidirectional_iterator_tag.

• (1.3)

  Otherwise, if Base models forward_range, theniterator_concept denotes forward_iterator_tag.

• (1.4)

  Otherwise, iterator_concept denotes input_iterator_tag.

2

#

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

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

• (2.1)

  If is_reference_v<invoke_result_t<maybe-const<Const, F>&, range_reference_t<Base>>> is true, then

  • (2.1.1)

if C models derived_from<contiguous_iterator_tag>,iterator_category denotes random_access_iterator_tag;

• (2.1.2)

otherwise,iterator_category denotes C.

• (2.2)

  Otherwise, iterator_category denotes input_iterator_tag.

🔗

constexpr iterator(Parent& parent, iterator_t<Base> current);

3

#

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

🔗

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>>;

4

#

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

🔗

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

5

#

Effects: Equivalent to: return current_;

🔗

constexpr iterator_t<Base> base() &&;

6

#

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

🔗

constexpr iterator& operator++();

7

#

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

🔗

constexpr void operator++(int);

8

#

Effects: Equivalent to ++current_.

🔗

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

9

#

Effects: Equivalent to:auto tmp = *this;++*this;return tmp;

🔗

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

10

#

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

🔗

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

11

#

Effects: Equivalent to:auto tmp = *this;--*this;return tmp;

🔗

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>;

12

#

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

🔗

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>;

13

#

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

🔗

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]")<iterator_t<Base>>;

14

#

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

🔗

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>;

15

#

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

🔗

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>;

16

#

Effects: Equivalent to: return y < x;

🔗

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>;

17

#

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

🔗

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>;

18

#

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

🔗

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>>;

19

#

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

🔗

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

20

#

Effects: Equivalent to: return iterator{*i.parent_, i.current_ + n};

🔗

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

21

#

Effects: Equivalent to: return iterator{*i.parent_, i.current_ - n};

🔗

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>>;

22

#

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