anchor.diff:                  (incf j))))
           ret)))
   
  +(-> intersperse (t sequence) sequence)
   (defsubst intersperse (new-elt seq)
     "Return a sequence like SEQ, but with NEW-ELT inserted between each
   element."
  
positive.code: 
  If N is negative, then |N| elements are taken (in their original
  order) from the end of SEQ."
    (check-type n signed-array-index)
    (seq-dispatch seq
      (if (minusp n)
          (last seq (abs n))
  
negative.code:                   (+ len end)
                    end))))
  
  (-> slice
      (sequence signed-array-index &optional (or null signed-array-length))
      sequence)
  (defun slice (seq start &optional (end (length seq)))
    "Like `subseq', but allows negative bounds to specify offsets.
  Both START and END accept negative bounds.
  