anchor.diff:    (measurement-symbol (class-of instance)))
   
   
  -;;; define core measurement domains and base unit classes
  +;;; %% Initialize core measurement domains and base unit classes
  +
   (let ((kwd (find-package '#:keyword))
         (md-c (find-class 'measurement-domain))
         (mc-c (find-class 'measurement-class))
  
positive.code:              (entity-not-found-name c)))))
  
  
  ;;; % Measurement Class Storage and Access
  
  ;;; %% Locking (Thread Safety)
  
  (declaim (type (vector measurement-class) %measurement-classes% ))
  
  
negative.code: (defgeneric measurement-symbol (instance))
  
  
  ;;; % Measurement Class
  
  (defclass* (measurement-class 
  	    :conc-name #:measurement-)
      (standard-class pretty-printable-object)
    ((symbol symbol  :read-only t)))
  
  