anchor.diff:                                   (funcall sep-fun (aref sequence j))))))
               (rope-array-cat tmp))))))
   
  -(defun rope-parenthesize (a)
  +(defun rope-parenthesize (rope)
  +  "Return the parenthesized ROPE."
     (rope #\( a #\)))
  
positive.code: 
  (declaim (ftype (function (rope) non-negative-fixnum) rope-height))
  (defun rope-height (rope)
    (etypecase rope
      ((or string symbol character) 0)
      (rope-node (rope-node-height rope))))
  
negative.code: 
  (declaim (ftype (function (rope) rope-length-type) rope-length))
  (defun rope-length (rope)
    "Return the number of characters in rope"
    (etypecase rope
      (rope-node (rope-node-length rope))
      (simple-string (length rope))
  