anchor.diff:  
   (defmethod object-rope ((object pov-rgb))
     (rope '|rgb<|
  -        (float-string (pov-rgb-r object)) '|, |
  -        (float-string (pov-rgb-g object)) '|, |
  -        (float-string (pov-rgb-b object))
  +        (pov-rgb-r object) '|, |
  +        (pov-rgb-g object) '|, |
  +        (pov-rgb-b object)
           '|>|))
   
   (defstruct (pov-rgbf (:constructor %pov-rgbf (r g b f)))
  
positive.code:   (pov-print object stream))
  
  (defmethod object-rope ((object pov-float))
    (float-string (pov-float-value object)))
  
  (defmethod object-rope  ((object pov-float))
    (rope (float-string (pov-float-value object))))
  
  (defstruct (pov-float-vector (:constructor %pov-float-vector (x y z)))
    "Type for a povray vector."
  
negative.code:     (rope '|#| (pov-directive-type object) '| |
            (pov-directive-name object)
            '| = |
            (pov-directive-value object))))
  
  (defstruct (pov-include (:constructor pov-include (file)))
    file)
  