anchor.diff:      (glu:tess-end-contour tobj)
       (glu:tess-end-polygon tobj)
       (gl:end-list)
  -
  +    
     ;;;; smooth shaded, self-intersecting star
  -  (gl:new-list (1+ *start-list*) :compile)
  -  (gl:shade-model :smooth)
  -  (glu:tess-property tobj :tess-winding-rule glu:+tess-winding-positive+)
  -  (glu:tess-begin-polygon tobj nil)
  -  (glu:tess-begin-contour tobj)
  -  (loop for coords in star
  +    (setf tobj (make-instance 'star-tessellator))
  +    (gl:new-list (1+ *start-list*) :compile)
  +    (gl:shade-model :smooth)
  +    (glu:tess-property tobj :tess-winding-rule glu:+tess-winding-positive+)
  +    (glu:tess-begin-polygon tobj nil)
  +    (glu:tess-begin-contour tobj)
  +    (loop for coords in star
          do (glu:tess-vertex tobj coords))                           
  -  (glu:tess-end-contour tobj)
  -  (glu:tess-end-polygon tobj)
  -  (gl:end-list)))
  +    (glu:tess-end-contour tobj)
  +    (glu:tess-end-polygon tobj)
  +    (gl:end-list)))
   
   (defun rb-tess ()
     (setf glut:*run-main-loop-after-display* nil)
  
positive.code: 
  (in-package #:cl-glut-examples)
  
  ;;;GLuint startList;
  (defparameter *start-list* nil)
  
  (defclass tess-window (glut:window)
  
negative.code:                      :mode '(:single :rgb)))
  
  (defclass example-tessellator (glu:tessellator)
    ())
  
  (defclass star-tessellator (glu:tessellator)
    ())
  
  (defmethod glut:display ((w tess-window))
  