anchor.diff:  	       #'< :key #'time-of)))
   
   
  -
   (defmethod evolve ((obj object))
     (funcall (fn-of (imminent-event obj)) obj))
  
positive.code:     nil))
  
  
  (defclass with-id ()
    ((id
      :initarg :id
      :initform (error ":id missing")
  
negative.code:   (:documentation "Reverse the effect of i/o-connect."))
  
  
  
  ;; TYPES
  
  (deftype id-type ()
    '(integer 0))
  
  