anchor.diff:    ;; NB. This function implements a numeric conversion on
     ;; a basis of of prefix magnitude. Conversions per ratios of derived
     ;; units must be implemneted seperately.
  +  
  +  ;; FIXME: This was designed specifically around base units, and as
  +  ;; such, assumes that M is already factored to a base unit
     (declare (type measurement m)
              (values real))
  -  (let ((deg (measurement-degree m)))
  +  (let* ((deg (measurement-degree m))
  +	 (unit (class-of m))
  +	 (expt-base (measurement-factor-base unit))
  +	 (base-factor (measurement-base-factor unit))
  +	 (base-factor-degree (measurement-base-factor-exponent unit))
  +	 (base-mag (* (measurement-magnitude m)
  +		      base-factor
  +		      (expt expt-base base-factor-degree))))
  +    
       (cond 
  -      ((zerop deg) (values (measurement-magnitude m)))
  -      (t (values (* (measurement-magnitude m)
  -                    (expt (measurement-factor-base m) 
  -                          deg)))))))
  -
  -;; (base-magnitude (make-measurement 1 :m 3))
  +      ((zerop deg) (values base-mag))
  +      (t (values (* base-mag
  +                    (expt expt-base deg)))))))
  +
  +
  +;; (base-magnitude (make-measurement 1 :|m| 3))
   ;; => 1000
   
  -;; (base-magnitude (make-measurement 1 :m -3))
  +;; (base-magnitude (make-measurement 1 :|m| -3))
   ;; => 1/1000
   
  -;; (base-magnitude (make-measurement 1/5 :m))
  +;; (base-magnitude (make-measurement 1/5 :|m|))
   ;; => 1/5
   
  -;; (base-magnitude (make-measurement 1/5 :m -3))
  +;; (base-magnitude (make-measurement 1/5 :|m| -3))
   ;; => 1/5000
   
   
  
positive.code: (defgeneric measurement-symbol (instance))
  
  
  ;;; % Measurement Class
  
  (defclass* (measurement-class 
  	    :conc-name #:measurement-)
      (pretty-printable-object standard-class)
    ((symbol symbol  :read-only t)))
  
  (validate-class measurement-class)
  
  
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)  
  