anchor.diff:  #||
   (progn
     (defparameter *re-graph*
  -    (make-graph '((0.0 0.0 :id node-1) (0.0 1.0 :id node-2) (1.0 1.0 :id node-3))
  -                '((node-1 node-2) (node-2 node-3))))
  +    (make-graph '((0.0 0.0 :id node-1)
  +                  (0.0 1.0 :id node-2)
  +                  (1.0 1.0 :id node-3)
  +                  (1.0 0.0 :id node-4))
  +                '((node-1 node-2) (node-1 node-4) (node-2 node-3) (node-4 node-1))))
   
     (defparameter *rs*
       (let ((node-1 (find-node *re-graph* 'node-1))
  
positive.code:    (home-node :accessor home-node :initarg :home-node
                :initform (required-initarg :home-node))
     (max-damage :accessor max-damage :initarg :max-damage
                 :initform nil)))
  
  
  (defmethod initialize-instance :after ((self <rescue-env>) &key)
  
negative.code:             (node-id self)
              (mapcar #'edge-id (node-edges self)))))
  
  (defun node-neighbors (node)
    (mapcar #'edge-to (node-edges node)))
  
  (defun node-distance (node-1 node-2)
    (let* ((x1 (node-x node-1))
           (x2 (node-x node-2))
  