anchor.diff:  (defdynamic handler-frame)
   
   (defclass handler-frame ()
  -  (handlers
  -   parent-frame))
  +  (.handlers
  +   .parent-frame))
   
   (defun make-handler-frame ((handlers list))
     (let ((f (make handler-frame)))
  
positive.code:                         slots)
          (class ,class-name))))
  
  (defmacro generic (name)
    #`(identifier ,name generic))
  
  (defmacro defgeneric (name &rest args)
    #`(progn
        (defvar (generic ,name) (make-generic))
  
negative.code:   (list-add list elt))
  
  (defclass list-iter () 
    (.list
     .i))
  
  (defun list-iter ((list list))
    (let ((iter (make list-iter)))
  