anchor.diff:  
   
   ;;;
  -;;; performance measurement functions
  +;;; Performance measurement functions
   ;;;
   
   (defvar *flops-per-interaction* 20)
  
positive.code: 
  
  ;;;
  ;;; timing functions
  ;;;
  
  (let (start-event stop-event)
  
negative.code: 
  (defmethod glut:display ((w nbody-window))
    (with-slots (new-pos old-pos vel delta-time damping num-bodies p) w
      ;; update simulation
      (nbody-demo-update-simulation new-pos old-pos vel delta-time damping num-bodies p)
      (rotatef new-pos old-pos)
      ;; clear buffers
      (gl:clear :color-buffer :depth-buffer-bit)
      ;; view transform
      (gl:matrix-mode :modelview)
      (gl:load-identity)
      (gl:translate 0.0 0.0 -100.0)
      (gl:rotate 0.0 1.0 0.0 0.0)
      (gl:rotate 0.0 0.0 1.0 0.0)
      ;; display bodies
      (nbody-demo-display new-pos num-bodies)
      ;; swap buffers
      (glut:swap-buffers)
      ;; display frame rate
      (display-frame-rate num-bodies)))
  
  (defmethod glut:reshape ((w nbody-window) width height)
    ;; configure on projection mode
  