val length : string -> int
val elem_eq : Stdlib.Char.t -> Stdlib.Char.t -> bool
val fold_left : ('a -> char -> 'a) -> 'a -> string -> 'a
val fold_right : (char -> 'a -> 'a) -> string -> 'a -> 'a
val int_of_elem : char -> int
val elem_of_int : int -> char