anchor.diff:  
   (defun abbreviate-record (stream record width abbreviator)
     "Attempts to abbreviate the text contained in an output RECORD on STREAM to fit within WIDTH, using the function ABBREVIATOR to produce a shortened string."
  -  (declare (optimize (debug 3)))
     (multiple-value-bind (text-record text-style)
         (find-text-record record)
       (when text-record
  
positive.code: 
  (defun find-text-record (record)
    "If RECORD contains exactly one text-displayed-output-record, we can abbreviate it. Otherwise, give up. Returns a string containing the contents of the record, and a text style."
    (declare (optimize (debug 3) (speed 1) (safety 3)))
    (let ((count 0)
          text-style
          result)
  
negative.code:                   (setf text-style (text-output-record-style record))
                    (incf count)))))
        (walk record)
        (when (= count 1)
          (values result text-style)))))
  
  (defun abbrev-guess-pos (medium string text-style desired-width start end)
    "Makes a guess where to split STRING between START and END in order to fit within WIDTH. Returns the ending character index."
  