anchor.diff:    (symbol-macrolet ((designator named-readtable-designator))
       (cond ((find-readtable designator))
   	  ((not default-p)
  -	   (error "The name ~S does not designate any readtable." designator))
  +	   (error 'readtable-does-not-exist :readtable-name designator))
   	  (t (setf (find-readtable designator) (ensure-readtable default))))))
   
   
positive.code:                    Not acceptable as a user-specified readtable name." name))
  	  ((let ((rt (find-readtable name)))
  	     (and rt (cerror "Overwrite existing readtable." 
  			     'readtable-does-already-exist :readtable rt))))
  	  (t (let ((result (apply #'merge-readtables-into
  				  ;; The first readtable specified in the :merge list is
  				  ;; taken as the basis for all subsequent (destructive!)
  
negative.code:   (cond ((eq reserved-name nil)       *standard-readtable*)
  	((eq reserved-name :standard) *standard-readtable*)
  	((eq reserved-name :current)  *readtable*)
  	(t (error "Bug: no such reserved readtable: ~S" reserved-name))))
  
  (defun find-readtable (named-readtable-designator)
    "Looks for the readtable specified by NAMED-READTABLE-DESIGNATOR and 
  