anchor.diff:  ;; (object-print-label (find-prefix= 9))
   ;; => "G"
   
  -(defmethod print-label ((object measurement) stream)
  +(defmethod print-label ((object measurement) (stream stream))
     (multiple-value-bind (mag boundp)
         (slot-value* object 'magnitude)
       (cond 
  
positive.code:   (princ (object-print-label (class-of object))
  	 stream))
  
  (defmethod print-label ((object kilogram) stream)
    "Print a KILOGRAM measurement in units of grams"
    (multiple-value-bind (mag boundp)
        (slot-value* object 'magnitude)
  
negative.code: 
  
  
  ;; (prefix-of (make-measurement 1 :|m| 24))
  ;; => #<PREFIX yotta (Y)>, 1
  ;;
  ;; (prefix-of (make-measurement 1 :|m| 23))
  ;; => #<PREFIX zetta (Z)>, 100
  ;;
  ;; (prefix-of (make-measurement 1 :|m| 22))
  ;; => #<PREFIX zetta (Z)>, 10
  ;;
  ;; (prefix-of (make-measurement 1 :|m| 21))
  ;; => #<PREFIX zetta (Z)>, 1
  ;;
  ;; (prefix-of (make-measurement 1 :|m| 3))
  ;; => #<PREFIX kilo (k)>, 1
  ;;
  ;; (prefix-of (make-measurement 1 :|m| -16))
  ;; => #<PREFIX atto (a)>, 100
  
  ;; Trivial decimal exponential mathematics, ad hoc syntax:
  