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>
template<bool Const>
class elements_view<V, N>::iterator {
using Base = conditional_t<Const, const V, V>;
iterator_t<Base> current_ = iterator_t<Base>();
public:
using iterator_category = typename iterator_traits<iterator_t<Base>>::iterator_category;
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<N>(*current_); }
constexpr iterator& operator++();
constexpr void operator++(int) requires (!forward_range<Base>);
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<N>(*(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& y, 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 random_access_range<Base>;
};
}
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) requires (!forward_range<Base>);
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;
constexpr iterator operator-(const iterator& x, difference_type y)
requires random_access_range<Base>;
Effects:
Equivalent to: return iterator{x} -= y;
constexpr difference_type operator-(const iterator& x, const iterator& y)
requires random_access_range<Base>;
Effects:
Equivalent to: return x.current_ - y.current_;