anchor.diff:  ;; simple-error is defined in JS
   (set-superclass (class simple-error) (class error))
   (defmethod show ((s simple-error))
  -  (show-unreadable #'simple-error
  -                   (string-concat (simple-error-message s) (simple-error-arg s))))
  +  (string-concat (simple-error-message s) (simple-error-arg s)))
   
   (defclass control-error (error))
   
  
positive.code: 
  (defgeneric show (object))
  
  (eval-when-compile
    (defun show-unreadable (class-name &optional (more ""))
      (string-concat "#(" (symbol-name class-name) more ")")))
  
  (defmacro define-stupid-show (class-name)
    #`(defmethod show ((a ,class-name))
        ,(string-to-form (show-unreadable class-name))))
  
  (defmethod show ((a object))
    #{ JSON.stringify(~a) #})
  
  
negative.code:         ,@(compound-map (lambda (slot)
                            #`(defslot ,slot ,class-name))
                          slots)
          (class ,class-name))))
  
  (defmacro defgeneric (name &rest args)
  