# Module Std.String_zipper

    module String_zipper: String_zipper

    type t

    val contents : t -> string

    val left_contents : t -> string

    val right_contents : t -> string

    val insert_before : t -> char -> t

    val insert_after : t -> char -> t

    val drop_before : t -> (char * t) option

    val drop_after : t -> (char * t) option

    val drop_all_before : t -> (char list * t) option

    val drop_all_after : t -> (char list * t) option

    val previous : t -> t option

    val next : t -> t option

    val first : t -> t

    val last : t -> t

    val replace_left : t -> string -> t

    val replace_right : t -> string -> t

    val create : string -> string -> t