24 Ranges library [ranges]

24.7 Range adaptors [range.adaptors]

24.7.16 Elements view [range.elements]

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

namespace std::ranges { template<input_­range V, size_t N> requires view<V> && has-tuple-element<range_value_t<V>, N> && has-tuple-element<remove_reference_t<range_reference_t<V>>, N> && returnable-element<range_reference_t<V>, N> template<bool Const> class elements_view<V, N>::iterator { // exposition only using Base = maybe-const<Const, V>; // exposition only iterator_t<Base> current_ = iterator_t<Base>(); // exposition only static constexpr decltype(auto) get-element(const iterator_t<Base>& i); // exposition only public: using iterator_concept = see below; using iterator_category = see below; // not always present using value_type = remove_cvref_t<tuple_element_t<N, range_value_t<Base>>>; using difference_type = range_difference_t<Base>; iterator() = default; constexpr explicit iterator(iterator_t<Base> current); constexpr iterator(iterator<!Const> i) requires Const && convertible_­to<iterator_t<V>, iterator_t<Base>>; constexpr iterator_t<Base> base() const& requires copyable<iterator_t<Base>>; 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) const requires 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>>; }; }
The member typedef-name iterator_­concept is defined as follows:
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 type iterator_­traits<iterator_­t<Base>>​::​iterator_­category.
  • If get<N>(*current_­) is an rvalue, iterator_­category denotes input_­iterator_­tag.
  • Otherwise, if C models derived_­from<random_­access_­iterator_­tag>, iterator_­category denotes random_­access_­iterator_­tag.
  • Otherwise, iterator_­category denotes C.
static constexpr decltype(auto) get-element(const iterator_t<Base>& i); // exposition only
Effects: Equivalent to: if constexpr (is_reference_v<range_reference_t<Base>>) { return get<N>(*i); } else { using E = remove_cv_t<tuple_element_t<N, range_reference_t<Base>>>; return static_cast<E>(get<N>(*i)); }
constexpr explicit iterator(iterator_t<Base> current);
Effects: Initializes current_­ with std​::​move(current).
constexpr iterator(iterator<!Const> i) requires Const && convertible_­to<iterator_t<V>, iterator_t<Base>>;
Effects: Initializes current_­ with std​::​move(i.current_­).
constexpr iterator_t<Base> base() const& requires copyable<iterator_t<Base>>;
Effects: Equivalent to: return current_­;
constexpr iterator_t<Base> base() &&;
Effects: Equivalent to: return std​::​move(current_­);
constexpr iterator& operator++();
Effects: Equivalent to: ++current_; return *this;
constexpr void operator++(int);
Effects: Equivalent to: ++current_­.
constexpr iterator operator++(int) requires forward_­range<Base>;
Effects: Equivalent to: auto temp = *this; ++current_; return temp;
constexpr iterator& operator--() requires bidirectional_­range<Base>;
Effects: Equivalent to: --current_; return *this;
constexpr iterator operator--(int) requires bidirectional_­range<Base>;
Effects: Equivalent to: auto temp = *this; --current_; return temp;
constexpr iterator& operator+=(difference_type n); requires random_­access_­range<Base>;
Effects: Equivalent to: current_ += n; return *this;
constexpr iterator& operator-=(difference_type n) requires random_­access_­range<Base>;
Effects: Equivalent to: current_ -= n; return *this;
friend constexpr bool operator==(const iterator& x, const iterator& y) requires equality_­comparable<Base>;
Effects: Equivalent to: return x.current_­ == y.current_­;
friend constexpr bool operator<(const iterator& x, const iterator& y) requires random_­access_­range<Base>;
Effects: Equivalent to: return x.current_­ < y.current_­;
friend constexpr bool operator>(const iterator& x, const iterator& y) requires random_­access_­range<Base>;
Effects: Equivalent to: return y < x;
friend constexpr bool operator<=(const iterator& x, const iterator& y) requires random_­access_­range<Base>;
Effects: Equivalent to: return !(y < x);
friend constexpr bool operator>=(const iterator& x, const iterator& y) requires random_­access_­range<Base>;
Effects: Equivalent to: return !(x < y);
friend constexpr auto operator<=>(const iterator& x, const iterator& y) requires random_­access_­range<Base> && three_­way_­comparable<iterator_t<Base>>;
Effects: Equivalent to: return x.current_­ <=> y.current_­;
friend constexpr iterator operator+(const iterator& x, difference_type y) requires random_­access_­range<Base>;
Effects: Equivalent to: return iterator{x} += y;
friend constexpr iterator operator+(difference_type x, const iterator& y) requires random_­access_­range<Base>;
Effects: Equivalent to: return y + x;
friend constexpr iterator operator-(const iterator& x, difference_type y) requires random_­access_­range<Base>;
Effects: Equivalent to: return iterator{x} -= y;
friend constexpr difference_type operator-(const iterator& x, const iterator& y) requires sized_­sentinel_­for<iterator_t<Base>, iterator_t<Base>>;
Effects: Equivalent to: return x.current_­ - y.current_­;