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