anchor.diff:                         (dif/4 start2)
                          (dif/4 start3)))
                      defs))
  -                 ((> n 8)
  +                 ((> n *fwd-base-case*)
                     (gen (truncate n 2))
                     (let* ((n/2 (truncate n 2))
                            (n/4 (truncate n 4))
  
positive.code:              (gen (n)
                 (cond
                   ((= n 16)
                    (push
                     `(dif/16 (start)
                       (declare (type index start))
  
negative.code: (defvar *fwd-base-case* 8)
  
  (defun gen-base-difs ()
    (list `(dif/1 (start)
            (declare (ignore start))
  