+content and cursor position fields of the node.
+
+If the hash table `elpher-seen-nodes' contains a key equal to ADDRESS,
+the node contained as its value will be returned instead."
+ (let ((existing-node (gethash address elpher-seen-nodes)))
+ (if existing-node
+ existing-node
+ (let ((new-node (list parent address getter content pos)))
+ (puthash address new-node elpher-seen-nodes)
+ new-node))))