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