anchor.diff:  (define-presentation-method present (object (type complex) stream
   				     (view textual-view)
   				     &key acceptably for-context-type)
  -  (declare (ignore view acceptably for-context-type))
  +  (declare (ignore acceptably for-context-type))
     (present (realpart object) (presentation-type-of (realpart object))
   	   :stream stream :view view :sensitive nil)
     (write-char #\Space stream)
  
positive.code: (defgeneric presentation-type-of (object))
  
  (defmethod presentation-type-of (object)
    'expression)
  
  (defmethod presentation-type-of ((object standard-object))
  
negative.code: (define-presentation-method present (object (type boolean) stream
  				     (view textual-view)
  				     &key acceptably for-context-type)
    (declare (ignore acceptably for-context-type))
    (if object
        (write-string "Yes" stream)
        (write-string "No" stream)))
  