anchor.diff:      :type list)))
   
   
  +(defclass port (with-id)
  +  ((owner
  +    :initarg :owner
  +    :initform (error ":owner missing")
  +    :accessor owner-of
  +    :type actor)))
  +
  +
  +(defclass in-port (port)
  +  nil)
  +
  +
  +(defclass out-port (port)
  +  nil)
  +
  +
   
   ;; PARAMETERS
   
  
positive.code:   (:documentation "Connect src to dest."))
  
  
  (defgeneric i/o-connected-p (src dst)
    (:documentation "Return t if src is connected to dst, nil
    otherwise."))
  
  
  (defgeneric i/o-disconnect (src dst)
    (:documentation "Reverse the effect of i/o-connect."))
  
  
  
  
negative.code:   nil)
  
  
  (defclass actor (object)
    ((in-ports
      :initarg :in-ports
  