1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/src/clojure/lang/Delay.java	Sat Aug 21 06:25:44 2010 -0400
     1.3 @@ -0,0 +1,38 @@
     1.4 +/**
     1.5 + *   Copyright (c) Rich Hickey. All rights reserved.
     1.6 + *   The use and distribution terms for this software are covered by the
     1.7 + *   Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
     1.8 + *   which can be found in the file epl-v10.html at the root of this distribution.
     1.9 + *   By using this software in any fashion, you are agreeing to be bound by
    1.10 + * 	 the terms of this license.
    1.11 + *   You must not remove this notice, or any other, from this software.
    1.12 + **/
    1.13 +
    1.14 +/* rich Jun 28, 2007 */
    1.15 +
    1.16 +package clojure.lang;
    1.17 +
    1.18 +public class Delay implements IDeref{
    1.19 +Object val;
    1.20 +IFn fn;
    1.21 +
    1.22 +public Delay(IFn fn){
    1.23 +	this.fn = fn;
    1.24 +	this.val = null;
    1.25 +}
    1.26 +
    1.27 +static public Object force(Object x) throws Exception{
    1.28 +	return (x instanceof Delay) ?
    1.29 +	       ((Delay) x).deref()
    1.30 +	       : x;
    1.31 +}
    1.32 +
    1.33 +synchronized public Object deref() throws Exception{
    1.34 +	if(fn != null)
    1.35 +		{
    1.36 +		val = fn.invoke();
    1.37 +		fn = null;
    1.38 +		}
    1.39 +	return val;
    1.40 +}
    1.41 +}