anchor.diff:            split-sequence:split-sequence-if
             split-sequence:split-sequence-if-not))
   
  -(defun make-sequence-like (seq len &rest args &key initial-element (initial-contents nil ic?))
  +(defun make-sequence-like (seq len &rest args &key initial-element
  +                                                   (initial-contents nil ic?))
     (seq-dispatch seq
       (if ic?
           (map 'list #'identity initial-contents)
  
positive.code: 
  (defun shortest (seqs)
    "Return the shortest seq in SEQS."
    (flet ((shorter (x y)
             (select (longer x y)
               (x y)
               (y x))))
      (reduce #'shorter seqs)))
  
  (defun slice-bounds (seq start end)
    "Normalize START and END, which may be negative, to offsets
  
negative.code: (assert (equal (intersperse/list 'y '(x z)) '(x y z)))
  
  (defun intersperse/seq (new-elt seq)
    (if (< (length seq) 2)
        (copy-seq seq)
        (let* ((len1 (length seq))
               (len2 (1- (* 2 len1)))
  