anchor.diff:  
   (defun pov-rope-reduce (sequence separator)
     (rope-map #'object-rope sequence :separator separator))
  -
  -(defun float-string (f)
  -  (declare (type double-float f))
  -  (format nil "~F" f))
  -
  -(defun int-string (i)
  -  (declare (type fixnum i))
  -  (format nil "~D" i))
   
   ;; Convert something to a POV-ray object
   
  
positive.code:     (rope '|#| (pov-directive-type object) '| |
            (pov-directive-name object)
            '| = |
            (object-rope (pov-directive-value object)))))
  
  (defstruct (pov-include (:constructor pov-include (file)))
    file)
  
negative.code: 
  (defmethod object-rope ((object pov-rgb))
    (rope '|rgb<|
          (pov-rgb-r object) '|, |
          (pov-rgb-g object) '|, |
          (pov-rgb-b object)
          '|>|))
  
  (defstruct (pov-rgbf (:constructor %pov-rgbf (r g b f)))
  