The pair l, r represents the list List.rev_append l r, but with the focus on r

Empty zipper.

Empty zipper? Returns true iff the two lists are empty.

Convert the zipper back to a list. to_list (l,r) is List.rev_append l r.

Convert the zipper back to a reversed list. In other words, to_list (l,r) is List.rev_append r l.

Create a zipper pointing at the first element of the list.

Go to the left, or do nothing if the zipper is already at leftmost pos.

Go to the left, or

• raises Invalid_argument

  if the zipper is already at leftmost pos.

Go to the right, or do nothing if the zipper is already at rightmost pos.

Go to the right, or

• raises Invalid_argument

  if the zipper is already at rightmost pos.

Modify the current element, if any, by returning a new element, or returning None if the element is to be deleted.

Insert an element at the current position. If an element was focused, insert x l adds x just before it, and focuses on x.

remove l removes the current element, if any.

Is the zipper focused on some element? That is, will focused return a Some v?

Return the focused element, if any. focused zip = Some _ iff empty zip = false.

Return the focused element, or

• raises Not_found

  if the zipper is at an end.

Drop every element on the "left" (calling left then will do nothing).

Drop every element on the "right" (calling right then will do nothing), keeping the focused element, if any.

Drop every element on the "right" (calling right then will do nothing), including the focused element if it is present.