anchor.diff:     (delta-time :initform 0)
      (damping :initform 0)
      (num-bodies :initform 0)
  -   (p :initform 0)
  -   (start-event :initform nil)
  -   (stop-event :initform nil))
  +   (p :initform 0))
     (:default-initargs :width 640 :height 480 :pos-x 100 :pos-y 100
                        :mode '(:double :rgb) :title "nbody"))
   
  
positive.code: (defun update (new-pos old-pos vel delta-time damping num-bodies p)
    (integrate-nbody-system new-pos old-pos vel delta-time damping num-bodies p))
  
  #|
  (defun run-benchmark (new-pos old-pos vel delta-time damping num-bodies p iterations)
    (update new-pos old-pos vel delta-time damping num-bodies p)
    ;; create-timer
    ;; start-timer
    (loop repeat iterations
       do (update new-pos old-pos vel delta-time damping new-pos p))
    ;; stop-timer
    ;; get elapsed time
    ;; delete-timer
    ;; compute-perf-stats
    ;; show-log
    )
  |#
  
  (defclass nbody-window (glut:window)
    ((new-pos :initform nil)
     (old-pos :initform nil)
  
negative.code:   (gl:clear-color 0 0 0 0))
  
  (defmethod glut:display ((w nbody-window))
    ;; clear buffers
    (gl:clear :color-buffer :depth-buffer-bit)
    ;; view transform
    (gl:matrix-mode :modelview)
  