factored out delayed eval to Delay class

2 files changed, 50 insertions, 22 deletions

diff --git a/src/jvm/clojure/lang/Delay.java b/src/jvm/clojure/lang/Delay.java
new file mode 100644
index 00000000..fb1278fc
--- /dev/null
+++ b/src/jvm/clojure/lang/Delay.java
@@ -0,0 +1,38 @@
+/**
+ *   Copyright (c) Rich Hickey. All rights reserved.
+ *   The use and distribution terms for this software are covered by the
+ *   Common Public License 1.0 (http://opensource.org/licenses/cpl.php)
+ *   which can be found in the file CPL.TXT at the root of this distribution.
+ *   By using this software in any fashion, you are agreeing to be bound by
+ * 	 the terms of this license.
+ *   You must not remove this notice, or any other, from this software.
+ **/
+
+/* rich Jun 28, 2007 */
+
+package clojure.lang;
+
+public class Delay{
+volatile Object val;
+IFn fn;
+
+
+public Delay(IFn fn){
+	this.fn = fn;
+}
+
+public Object force() throws Exception{
+	if(val == this)
+		{
+		synchronized(this)
+			{
+			if(val == this)
+				{
+				val = fn.invoke();
+				fn = null;
+				}
+			}
+		}
+	return val;
+}
+}
diff --git a/src/jvm/clojure/lang/FnSeq.java b/src/jvm/clojure/lang/FnSeq.java
index 476145c0..236448db 100644
--- a/src/jvm/clojure/lang/FnSeq.java
+++ b/src/jvm/clojure/lang/FnSeq.java
@@ -12,14 +12,12 @@ package clojure.lang;
 

 public class FnSeq extends ASeq{

 

-Object _first;

-IFn restFn;

-volatile ISeq _rest;

+final Object _first;

+final Delay _rest;

 

-public FnSeq(Object first, IFn restFn) {

+public FnSeq(Object first, Delay rest) {

     this._first = first;

-    this.restFn = restFn;

-    this._rest = this;

+    this._rest = rest;

 }

 

 public Object first() {

@@ -27,21 +25,13 @@ public Object first() {
 }

 

 public ISeq rest() {

-    if(_rest != this)

-        return _rest;

-    synchronized(this){

-        if(_rest == this)

-            {

-            try{

-                _rest = (ISeq) restFn.invoke();

-            }

-            catch(Exception ex)

-                {

-                throw new Error(ex.toString());

-                }

-            restFn = null;

-            }

-        return _rest;

-    }

+	try

+		{

+		return (ISeq) _rest.force();

+		}

+	catch(Exception e)

+		{

+		throw new Error(e.toString());

+		}

 }

 }