anchor.diff:  
   (defmethod trivial-gray-streams:stream-write-char ((stream buffer-output-stream) char)
     (prog1 char
  -    (insert-char/marker (buffer-output-stream-marker stream)
  +    (insert-char/marker (buffer-stream-marker stream)
                           char)))
   
   (defun %write-string-to-buffer-stream (stream string start end &key)
  -  (insert-string/marker (buffer-output-stream-marker stream)
  +  (insert-string/marker (buffer-stream-marker stream)
                           (subseq string start end))
     string)
   
  
positive.code:           editor-io-stream
            make-editor-io-stream))
  
  (defclass buffer-output-stream (trivial-gray-streams:fundamental-output-stream)
    ((marker
      :initarg :marker
      :accessor buffer-output-stream-marker)
     (interactive-update-p
      :initarg :interactive-update-p
      :accessor buffer-output-stream-interactive-update-p)))
  
  
negative.code:   nil)
  
  (defmethod trivial-gray-streams:stream-fresh-line ((stream buffer-output-stream))
    (unless (zerop (marker-charpos (buffer-stream-marker stream)))
      (trivial-gray-streams:stream-terpri stream)))
  
  (defmethod trivial-gray-streams:stream-write-byte ((stream buffer-output-stream) byte)
  