anchor.diff:    (declare (ignore sender)))
   
   (defclass stream-sender-mixin (basic-sender)
  -  ((output-stream :reader output-stream)
  -   (close-stream? :reader close-stream?)
  +  ((output-stream :reader output-stream :initform nil)
  +   (close-stream? :reader close-stream? :initform nil)
      (location :initarg :location :reader location)))
   
   
  
positive.code: 	     `(princ ,(output-form output) stream)))
  	(t
  	 (error "don't know how to handle ~a" output))))
  
  (defmethod initialize-instance :after ((object stream-sender-mixin) 
  				       &key location)
  
negative.code:   `((stream (make-string-output-stream))))
  
  (defmethod start-handling ((sender stream-sender-mixin)) 
    `((ensure-stream-open sender)))
  
  (defmethod finish-handling ((sender stream-sender-mixin))
    `((let ((output (output-stream sender)))
  