anchor.diff:  
   (defgeneric (setf stored-account) (account account-id storage))
   
  -;;; Application
  -
  -(defclass account ()
  -  ((balance :initarg :balance :accessor balance)))
  -
  -(defmethod withdraw ((account account) amount)
  -  (decf (balance account) amount))
  +;;; Inner Hexagon - Application
   
   (defclass bank ()
     ((storage :initarg :storage :reader storage)))
  
positive.code:   (let ((account (stored-account account-id (storage bank))))
      (withdraw account amount)))
  
  ;;; Storage Adaptor Implementation
  
  (defmethod stored-account (account-id (storage hash-table))
    (gethash account-id storage))
  
negative.code: (defmethod (setf stored-account) (account account-id (storage hash-table))
    (setf (gethash account-id storage) account))
  
  ;;; Outer Hexagon - Test Adapter
  
  (setf lisp-unit:*print-failures* t)
  
  