anchor.diff:  			 :source-unit source-unit
   			 :destination-unit dest-unit
   			 :magnitude factor-magnitude
  -			 :exponent facor-exponent)))
  +			 :exponent factor-exponent)))
   
   
   (defgeneric find-conversion-factor (source-unit dest-unit domain)
  
positive.code:   ;; FIXME: #I18N
    (:print-name . "angular measure")
    (:print-label . "angular measure")
    (:base-measure . radian))
    
  
  (defclass radian (measurement)
    ()
  
negative.code: 
  ;; (scalar-magnitude (convert-measurement (make-measurement (rational pi) :|rad|) :|deg|))
  ;; => 180
  
  ;;; %% Dimensionless Measure
  
  (defclass dimensionless-measure (measurement-class)
    ()
    (:documentation "Informal domain for dimensionless measures")
    (:metaclass measurement-domain)
    ;; FIXME: #I18N
    (:print-name . "dimensionless measure")
    (:print-label . "dimensionless measure")
    (:symbol . :dimensionless-measure)
    (:base-measure . unity))
  
  (register-measurement-domain (find-class 'dimensionless-measure))
  
  (defclass unity (measurement)
    ()
    (:documentation "Informal base measure of dimensionless measures")
    (:metaclass angular-measure)
    (:print-name . "unity")
    (:print-label . "u")
    (:symbol . :|u|))
  
  (register-measurement-class (find-class 'unity))
  
  
  
  #| Topic: Measurement Formulas
  
  