anchor.diff:    );; LET
   
   
  -;; (enumerate-measurement-domains)
  +;; (find-measurement-domain :electrical-current)
   
  +;; (mapcar #'measurement-domain-symbol (enumerate-measurement-domains))
  +
  
positive.code: 
  (validate-class measurement-domain)
  
  (define-condition measurement-domain-not-fond (entity-not-found)
    ()
    (:report
     (lambda (c s)
  
negative.code:     (let ((s (etypecase name
  	       (symbol name)
  	       (string (intern* (read-from-string name)
  				(find-package '#:keyword))))))
        (with-lock-held (%domains-lock%)
  	(or (find s %domains%
  		  :test #'eq
  