anchor.diff:  (defclass restart (condition)
     (.associated-condition))
   
  -;; Specific restarts
  +;;; Specific restarts
   (defclass abort (restart))
   (defclass continue (restart))
   (defclass use-value (restart)
  
positive.code:       (restart-bind ((use-value (lambda (r)
                                    (return-from return (prompt "Use value")))
                         c))
          (signal c)))))
  
  ;;;; Debugger
  
  
negative.code: (defclass error (serious-condition))
  (defclass warning (condition))
  
  ;;; Specific errors
  (defclass unbound-variable (error))
  (defclass simple-error (error))
  (defmethod show-object ((s simple-error))
  