open MutableList (** Creation and manipulation of counter functions *) let make_counter () = let r = ref 0 in let f () = incr r; !r in f (** Definition of the ignore function used in the example *) let ignore x = () (** Iterating over a mutable list of counter functions *) let step_all_imper (l : (unit->int) mlist) = miter (fun (f:unit->int) -> ignore (f())) l |