val (>>=) : 'a t -> ('a -> 'b t) -> 'b ttype ic = Lwt_io.input_channeltype oc = Lwt_io.output_channelval iter : ('a -> unit t) -> 'a list -> unit tval read_line : ic -> string option tval read : ic -> int -> string tval read_exactly : ic -> int -> string option tval write : oc -> string -> unit t