anchor.diff:  
      (labels
   
  -	((draw-tree
  -	  (x y length angle transparency depth )
  -
  -	  (multiple-value-bind
  -	   (nx ny) (to-cart length angle)
  -
  -	   (cl-cairo2:set-source-rgba 0 1.0 0 transparency)
  -	   (cl-cairo2:set-line-width (+ 1 (* 1.25 depth)))
  -	   (cl-cairo2:move-to x y)
  -	   (cl-cairo2:line-to (+ x nx) (+ y ny))
  -	   (cl-cairo2:stroke)
  +    ((draw-tree
  +      (x y length angle transparency depth )
  +
  +      (multiple-value-bind
  +       (nx ny) (to-cart length angle)
  +
  +       (cl-cairo2:set-source-rgba 0 1.0 0 transparency)
  +       (cl-cairo2:set-line-width (+ 1 (* 1.25 depth)))
  +       (cl-cairo2:move-to x y)
  +       (cl-cairo2:line-to (+ x nx) (+ y ny))
  +       (cl-cairo2:stroke)
   
          (if (> depth 0)
              (dotimes (i limbs)
  
positive.code:   (declare (iterations (unsigned-byte 32)))
  
    (let* ((ip (/ iter iterations 1.0d0))
  		 (r (* ip 255))
  		 (g (* ip 255))
  		 (b (- 255 (* ip 255) )))
  	(set-pixel img x y (truncate r) (truncate g) (truncate b))))
  
  (defun make-mandelbrot (&key (file-name)
  							 (width 100) (height 100)
  							 (xmin -2.5) (xmax 1.0)
  							 (ymin -1.0) (ymax 1.0)
  							 (iterations 100))
    "Generate a Mandelbrot Set fractal and save to the file name given.  The portion of the set drawn is given by xmin,xmax and ymin,ymax."
    (declare (width (unsigned-byte 32)))
    (declare (height (unsigned-byte 32)))
  
negative.code: (defun increment-pixel (img x y)
    "Increment each color component of the pixel in img at location x,y by 1"
    (if (< (aref img y x 0) 255)
        (progn 
          (incf (aref img y x 0))
          (incf (aref img y x 1))
          (incf (aref img y x 2)))))
  
  (defun assign-pixel (img x y iter iterations)
    "Color the pixel of img at location x,y depending on the number of iterations and the max iterations"
  