anchor.diff:  	   (let ((low (decode-unit* state read-func)))
   	     (declare (type (unsigned-byte 16) low))
   	     (unless (<= #xDC00 low #xDFFF)
  -	       (error 'scsu-decode-error
  +	       (error 'scsu-error
   		      :format-control "High surrogate appeared alone"))
   	     (decode-from-surrogate-pair code-point low)))
   	  ((<= #xDC00 code-point #xDFFF) ; low surrogate
  -	   (error 'scsu-decode-error
  +	   (error 'scsu-error
   		  :format-control "Low surrogate appeared alone"))
   	  (t
   	   code-point))))
  
positive.code: 	   (setf (scsu-state-mode state) :single-byte-mode)
  	   (decode-unit* state read-func))
  	  (#xF2
  	   (error 'scsu-decode-error
  		  :format-control "reserved byte ~A is used"
  		  :format-arguments (list byte)))))))
  
  
negative.code: 	      (decode-define-window-extended state read-func)
  	      (decode-unit* state read-func))
  	     (#xC
  	      (error 'scsu-error
  		     :format-control "reserved byte ~A is used"
  		     :format-arguments (list byte)))
  	     (#.+SQU+			; Quote Unicode
  