anchor.diff:  (defgeneric measurement-symbol (instance))
   
   
  +(defgeneric measurement-base-factor (measurement)) ;; NEW
  +(defgeneric measurement-base-factor-exponent (measurement)) ;; NEW
  +
  +
   ;;; % Measurement Class
   
   (defclass* (measurement-class 
   	    :conc-name #:measurement-)
       (pretty-printable-object standard-class)
  -  ((symbol symbol  :read-only t)))
  +  ((symbol symbol  :read-only t)
  +   (base-factor 
  +    real 
  +    :read-only t
  +    :initform 1)
  +   (base-factor-exponent 
  +    fixnum 
  +    :read-only t
  +    :initform 0)
  +   ))
   
   (validate-class measurement-class)
   
  
positive.code: 
  ;;; % DERIVED MEASUREMENT UNITS
  
  #+NIL
  (defclass derived-measurement (measurement)
    ;; ???
    ())
  
  
  
  
negative.code: See also: 
  * `measurement-degree'
  * `measurement-magnitude'")
    (:method ((instance measurement-class))
      (values 10))
    (:method ((instance measurement))
      (measurement-factor-base (class-of instance))))
  
  
  (defun base-magnitude (m)  
  