anchor.diff:                ;; would be, henceforward, "Buried" within methods
                 ;; specialized onto generic functions.
                 ;;
  -              ;; For instance, the function SCALE-FOR-SI-DEGREE should
  +              ;; For instance, the function SCALE-SI should
                 ;; be defined as to dispatch onto the measurement unit
                 ;; type for the scale. When the measurement is a
                 ;; KILOGRAM, then it must be scaled with +3 implicit
  
positive.code:   (let ((deg (measurement-degree m))
          (mag (measurement-magnitude m)))
      (multiple-value-bind (mag-adj deg-adj)
          (scale-for-si-degree mag deg)
        (let ((prefix
               (find deg-adj %prefixes%
                     :key #'prefix-degree
  
negative.code:        (values  (shift-magnitude magnitude scale deg)
                  deg)))))
  
  ;; (scale-si 1 5)
  ;; => 100, 3
  ;; (= 1E+05 100E+03)
  
  ;; (scale-si 10 5)
  ;; => 1000, 3
  ;; (= 10E+05 1000E+03)
  ;; => T
  
  ;; (scale-si 1 -5)
  ;; => 10, -6
  ;;
  ;; (= 1E-05 10E-06)
  ;; => T
  
  ;; (scale-si 10 -5)
  ;; => 100, -6
  ;;
  
  
  ;; (scale-si 1 -2)
  ;; => 1, -2
  
  ;; (scale-si 1 -2 t)
  ;; => 10, -3
  
  
  ;; (scale-si 1 2)
  ;; => 1, 2
  
  ;; (scale-si 1 2 t)
  ;; => 100, 0
  ;;
  ;; (= (* 1 (expt 10 2)) (* 100 (expt 10 0)))
  