anchor.diff:               (gen (n)
                  (cond
                    ((= n 16)
  -                  (gen 4)
                     (gen 8)
                     (push
                      `(dif/16 (start)
  
positive.code:                   (aref vec (+ start 2)) (- s0-s2 s1-s3)
                    (aref vec (+ start 3)) (+ s0-s2 s1-s3)))
            nil)
          `(dif/8 (start)
            (declare (type index start))
            (let* ((s0 (aref vec start))
  
negative.code:                `(for (,n (i start)
                           ,@(and window `((j window-start))))
                    (setf (aref vec i) (%scale
                                        (%window (aref vec i)
                                                 ,window
                                                 ,(if window 'j 0))
                                        ,scale))))
  