anchor.diff:    (:print-name . "radian")
     (:print-label . "rad")
     (:symbol . :|rad|))
  -
   
   (register-measurement-class (find-class 'radian))
   
  
positive.code: (register-measurement-class (find-class 'mile))
  
  
  (defclass angular-measure (measurement-class)
    ()
    (:metaclass measurement-domain)
  
negative.code: ;;     :initarg :base-scale
  
  
  ;;; %% Derived Measures of Length
  
  ;; referencing [NIST SP811]
  
  (defclass foot (measurement)
  