(define (new-instance class . parameters)
 (let ((instance (apply class parameters)))
   (virtual-operations instance)
   instance))

(define (send message object . args)
  (let ((method (method-lookup object message)))
    (cond ((procedure? method) (apply method args))
          ((null? method) (error "Message not understood: " message))
          (else (error "Inappropriate result of method lookup: " method)))))