zipper ocaml
type 'a zipper = { left: 'a list; right: 'a list; }
let of_list l =
{ left = []; right = l }
let move_right z = match z.right with
| [] -> invalid_arg "move_right"
| x :: r -> { left = x :: z.left; right = r }
let move_left z = match z.left with
| [] -> invalid_arg "move_left"
| x :: l -> { left = l; right = x :: z.right }
let to_list z =
List.rev_append z.left z.right
let insert z x =
{ z with left = x :: z.left }
let delete_left z = match z.left with
| [] -> invalid_arg "delete_left"
| _ :: l -> { z with left = l }
let delete_right z = match z.right with
| [] -> invalid_arg "delete_right"
| _ :: r -> { z with right = r }