anchor.diff:      (setf (buffer-mark-p buffer) nil)
       (setf (buffer-mark-overlay buffer) nil)
       (setf (buffer-mark-marker buffer) nil)
  +    (setf (buffer-keep-binfo buffer) nil)
       (setf (buffer-nlines buffer) 1)
  -    (setf (buffer-undo-size buffer) 0)
  -    (setf (buffer-undo-stack buffer) nil)
  -    (setf (buffer-redo-stack buffer) nil)
  -    (setf (buffer-undo-node buffer) 0)
  -    (setf (buffer-saved-node buffer) 0)
  -    (setf (buffer-overlays buffer) nil)
  -    (setf (buffer-markers buffer) nil)
  -    (setf (buffer-truncate-lines buffer) t)
  -    (setf (buffer-variables buffer) (make-hash-table :test 'equal))
  -    (unless (ghost-buffer-p buffer)
  -      (push buffer *buffer-list*))
  -    buffer))
  +    (setf (buffer-overlays buffer) nil)))
   
   (defun buffer-p (x)
     (typep x 'buffer))
  
positive.code:                                :filename filename
                                 :read-only-p read-only-p
                                 :enable-undo-p enable-undo-p
                                 :major-mode 'fundamental-mode))
          (line (make-line nil nil "")))
      (setf (buffer-head-line buffer) line)
      (setf (buffer-tail-line buffer) line)
      (setf (buffer-cache-line buffer) line)
  
negative.code: 
  (defun buffer-erase (buffer)
    (buffer-delete-char buffer 1 0 t)
    (buffer-reset buffer)
    (dolist (marker (buffer-markers buffer))
      (setf (marker-point marker) (make-point 1 0))))
  
  (defun buffer-check-marked (buffer)
    (cond ((buffer-mark-marker buffer) t)
  