Another approach: use a persistent data structure ala clojure's: http://blog.higher-order.net/2009/02/01/understanding-clojures-persistentvector-implementation

Another approach: use a persistent data structure ala clojure's: http://blog.higher-order.net/2009/02/01/understanding-clojures-persistentvector-implementation http://blog.higher-order.net/2009/02/01/understanding-clojur...