namespace std::ranges {
template<forward_range V, indirect_­binary_­predicate<iterator_t<V>, iterator_t<V>> Pred>
  requires view<V> && is_object_v<Pred>
class chunk_by_view : public view_interface<chunk_by_view<V, Pred>> {
  // ...

public:
  chunk_by_view() requires default_­initializable<V> && default_­initializable<Pred> = default;
  constexpr explicit chunk_by_view(V base, Pred pred);

  constexpr V base() const & requires copy_­constructible<V> { return base_; }
  constexpr V base() && { return std::move(base_); }

  constexpr const Pred& pred() const;

  constexpr iterator begin();
  constexpr auto end();

  constexpr iterator_t<V> find-next(iterator_t<V>);                 // exposition only
  constexpr iterator_t<V> find-prev(iterator_t<V>)                  // exposition only
    requires bidirectional_­range<V>;
};