type 'a t = | List_zip of 'a list * 'a * 'a listThis type aims to implement a zipper for lists. The context is the first parameter. It represents the list of the elements in reverse order that has been traversed to reach the focused element (the second parameter). The last element is the remaining elements of the list.
*)val init : 'a list -> 'a tinit l inits a focused list. It raises an exception
Empty_list if l is empty, hence has no element to focus on.
forward z returns a the new focused_list where the focuses element is the next one in the initial list. It raises End_of_list if no such element is available
backward z returns a the new focused_list where the focuses element is the previous one in the initial list. It raises End_of_list if no such element is available
val fold : ('b -> ('a list * 'a * 'a list) -> 'b) -> 'b -> 'a t -> 'bfold f a z returns f (... (f (f a z1) z2) ...) z_n where z_1=z and z_{i+1}=forward z_i and forward z_n would raise an exception End_of_list.