anchor.diff:  
   (defgeneric stream-element-type (stream))
   (defgeneric close (stream &key abort))
  +(defgeneric open-stream-p (stream))
  +(defgeneric input-stream-p (stream))
  +(defgeneric output-stream-p (stream))
   (defgeneric stream-file-position (stream &optional position-spec))
   (defgeneric stream-file-length (stream))
   (defgeneric stream-clear-input (stream))
  
positive.code: ;;; Gray Streams classes.
  
  (defclass fundamental-stream (stream standard-object)
    ()
    (:documentation "The base class for all Gray streams."))
  
  (defclass fundamental-input-stream (fundamental-stream)
  
negative.code:    :close
     :stream-file-position
     :stream-file-length
     :open-stream-p
     :input-stream-p
     :output-stream-p
     ;; Input stream methods.
     :stream-clear-input
     :stream-read-sequence
  