anchor.diff:  			for i from initial-index to final-index by 2
   			for xp = initial-xp then x
   			for yp = initial-yp then y
  -			for x = (svref coord-seq i)
  -			for y = (svref coord-seq (1+ i))
  +			for x = (elt coord-seq i)
  +			for y = (elt coord-seq (1+ i))
   			do (setf (values xn yn)
   				 (if (eql i final-index)
   				     (values final-xn final-yn)
  -				     (values (svref coord-seq (+ i 2))
  -					     (svref coord-seq (+ i 3)))))
  +				     (values (elt coord-seq (+ i 2))
  +					     (elt coord-seq (+ i 3)))))
   			   (multiple-value-bind (ex1 ey1)
   			       (normalize-coords (- x xp) (- y yp))
   			     (multiple-value-bind (ex2 ey2)
  
positive.code: 				   final-xn final-yn
  				   initial-index final-index)
  		 (if closed
  		     (values (svref coord-seq (- len 2))
  			     (svref coord-seq (- len 1))
  			     x1 y1
  			     0 (- len 2))
  		     (values x1 y1
  			     (svref coord-seq (- len 2))
  			     (svref coord-seq (- len 1))
  			     2 (- len 4)))
  	       (ecase (line-style-joint-shape line-style)
  		 (:miter
  
negative.code: 	 (coord-seq-bounds coord-seq 0))
  	((eq (line-style-joint-shape line-style) :round)
  	 (coord-seq-bounds coord-seq border))
  	(t (let* ((x1 (elt coord-seq 0))
  		  (y1 (elt coord-seq 1))
  		  (min-x x1)
  		  (min-y y1)
  		  (max-x x1)
  