anchor.diff:    (:documentation "TODO"))
   
   
  -(defgeneric i/o-connect (output input)
  -  (:documentation "Connect output to input."))
  -
  -
  -(defgeneric i/o-connected-p (output input)
  -  (:documentation "Return t if output is connected to input, nil
  +(defgeneric i/o-connect (src dest)
  +  (: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 (output input)
  +(defgeneric i/o-disconnect (src dst)
     (:documentation "Reverse the effect of i/o-connect."))
   
   
  
positive.code: 
  (defmethod schedule ((act actor) (fn function)
  		     &key (at 0) (relative-p t) (id 0 id-p))
    (let ((abs-time (+ at (if relative-p
  			    (gettime)
  			    0))))
  
negative.code:   nil)
  
  
  (defclass in-port (with-id)
    nil)
  
  
  (defclass out-port (with-id)
    nil)
  
  
  (defclass actor (object)
    ((in-ports
      :initarg :in-ports
      :initform (list)
      :accessor in-ports-of
      :type list)
     (out-ports
      :initarg :out-ports
      :initform (list)
      :accessor out-ports-of
      :type list)
     (events
      :accessor events-of
      :initform (list)
      :type list)))
  
  
  