rlm@10: /**
rlm@10:  *   Copyright (c) Rich Hickey. All rights reserved.
rlm@10:  *   The use and distribution terms for this software are covered by the
rlm@10:  *   Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
rlm@10:  *   which can be found in the file epl-v10.html at the root of this distribution.
rlm@10:  *   By using this software in any fashion, you are agreeing to be bound by
rlm@10:  * 	 the terms of this license.
rlm@10:  *   You must not remove this notice, or any other, from this software.
rlm@10:  **/
rlm@10: 
rlm@10: /* rich Jun 28, 2007 */
rlm@10: 
rlm@10: package clojure.lang;
rlm@10: 
rlm@10: public class Delay implements IDeref{
rlm@10: Object val;
rlm@10: IFn fn;
rlm@10: 
rlm@10: public Delay(IFn fn){
rlm@10: 	this.fn = fn;
rlm@10: 	this.val = null;
rlm@10: }
rlm@10: 
rlm@10: static public Object force(Object x) throws Exception{
rlm@10: 	return (x instanceof Delay) ?
rlm@10: 	       ((Delay) x).deref()
rlm@10: 	       : x;
rlm@10: }
rlm@10: 
rlm@10: synchronized public Object deref() throws Exception{
rlm@10: 	if(fn != null)
rlm@10: 		{
rlm@10: 		val = fn.invoke();
rlm@10: 		fn = null;
rlm@10: 		}
rlm@10: 	return val;
rlm@10: }
rlm@10: }