anchor.diff:  
   ;; Event queues
   
  +(defstruct schedule-entry
  +  time event)
  +
   (defclass schedule-mixin ()
     ((schedule-time
  -         :initform nil
  -         :accessor event-schedule-time
  -         :documentation "The next time an event should be scheduled.")
  +    :initform nil
  +    :accessor event-schedule-time
  +    :documentation "The next time an event should be scheduled.")
      (schedule
  -         :initform nil
  -         :accessor event-queue-schedule
  -         :documentation "Time ordered queue of events to schedule."))
  +    :initform nil
  +    :accessor event-queue-schedule
  +    :documentation "Time ordered queue of events to schedule."))
     (:documentation "Experimental timer event extension."))
   
   (defun now ()
  
positive.code:   (do-port-force-output queue)
    ;; Slurp as many elements as available.
    (loop until (null (process-next-event (event-queue-port queue) :timeout 0)))
    ;; Check-schedule may prepend scheduled event in a queue.
    (check-schedule queue)
    (find-if predicate (event-queue-head queue)))
  
  
negative.code:                             ((null timeout) (- schedule-time (now)))
                              (T (min timeout (- schedule-time (now))))))
               (port (event-queue-port queue)))
          (when timeout (maxf timeout 0))
          (process-next-event port :wait-function wait-function :timeout timeout)
          (%event-queue-read queue))))
  
  