module First = struct

    let next r = incr r; !r

end

module Second = struct

    let r = ref 0

    let next () = incr r; !r

end


module Third = struct


    module Counter (ANY : sig end) = struct

        let r = ref 0

        let next () = incr r; !r

    end

    let create_counter () =
        let module M = Counter(struct end) in
        M.next

    let next1 = create_counter ()

    let next2 = create_counter ()

end