anchor.diff:  	  (values t t)
   	  (values nil nil)))))
   
  +(defun default-describe-presentation-type (description stream plural-count)
  +  (if (symbolp description)
  +      (setq description (make-default-description (symbol-name description))))
  +  (cond ((numberp plural-count)
  +	 (format stream "~D ~A~P" plural-count description plural-count))
  +	(plural-count
  +	 (format stream "~As" description))
  +	(t (format stream "~:[a~;an~] ~A"
  +		   (find (char description 0) "aeiouAEIOU")
  +		   description))))
  +
  +(define-presentation-generic-function %describe-presentation-type
  +    describe-presentation-type
  +  (type-key parameters options type stream plural-count ))
  +
  +(define-default-presentation-method describe-presentation-type
  +    (type stream plural-count)
  +  (with-presentation-type-decoded (name parameters options)
  +    type
  +    (declare (ignore name parameters))
  +    (let ((description (or (getf options :description)
  +			   (description (class-of type-key)))))
  +      (default-describe-presentation-type description
  +	                                  stream
  +	                                  plural-count))))
  +
  +(defun describe-presentation-type (type
  +				   &optional
  +				   (stream *standard-output*)
  +				   (plural-count 1))
  +  (flet ((describe (stream)
  +	   (funcall-presentation-generic-function describe-presentation-type
  +						  type
  +						  stream
  +						  plural-count)))
  +    (if stream
  +	(describe stream)
  +	(with-output-to-string (s)
  +	  (describe s)))))
  +
   ;;; The presentation types
   
   (define-presentation-type t ())
  
positive.code: 	       (t nil)))))
  
  (defmacro define-presentation-type (name parameters
                                           &key options inherit-from
                                           description (history t)
                                           parameters-are-types)
    (let* ((params-ll (transform-parameters-lambda-list parameters))
  	 (options-ll (transform-options-lambda-list options))
  	 (inherit-from-func (make-inherit-from-lambda params-ll
  
negative.code:   (let ((meta (find-class name nil)))
      (and meta
  	 (typep meta 'standard-class))))
  
  (defun make-default-description (name)
    "Create a description string from the type name"
    (let ((downcase-name (string-downcase name)))
      (setq downcase-name (nsubstitute-if-not #\Space
  					    #'alphanumericp
  					    downcase-name))
      (string-trim " " downcase-name)))
  
  (defun record-presentation-type (name parameters params-ll options options-ll
  				 inherit-from-func description history
  