anchor.diff:            reschedule-cb))
     (ev_periodic_init (watcher watcher) 'ev_callback offset interval (if reschedule-cb
                                                                          'ev_reschedule_callback
  -                                                                       (cffi:null-pointer)))
  -  (ev_periodic_start (event-loop loop) (watcher watcher)))
  +                                                                       (cffi:null-pointer))))
   
   (defcallback ev_reschedule_callback ev_tstamp ((watcher :pointer) (now ev_tstamp))
     (let ((w (gethash (pointer-address watcher) *watchers*)))
  
positive.code: 
  (defmethod event-dispatch ((loop ev-loop))
    (ev_run (event-loop loop) 0))
  
negative.code: (defmethod set-io-watcher ((loop ev-loop) (watcher ev-io-watcher) fd event-type function)
    (setf (gethash (callback-key watcher) *callbacks*)
          function)
    (ev_io_init (watcher watcher) 'ev_callback fd event-type))
  
  (defmethod set-timer ((loop ev-loop) (watcher ev-timer) function timeout &key (repeat 0.0d0))
    (setf (gethash (callback-key watcher) *callbacks*)
          function)
    (ev_timer_init (watcher watcher) 'ev_callback timeout repeat))
  
  (defmethod set-perodic ((loop ev-loop) (watcher ev-periodic) cb offset interval reschedule-cb)
    (setf (gethash (callback-key watcher) *callbacks*)
  