From f8856dc7183b1cf9ea19c53c52ef80b21d8fd1df Mon Sep 17 00:00:00 2001
From: Rich Hickey <richhickey@gmail.com>
Date: Fri, 4 May 2012 20:49:08 -0400
Subject: [PATCH] better vector iterators

---
 src/jvm/clojure/lang/APersistentVector.java |  2 ++
 src/jvm/clojure/lang/PersistentVector.java  | 27 +++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/src/jvm/clojure/lang/APersistentVector.java b/src/jvm/clojure/lang/APersistentVector.java
index 2b373790ae..995789ed91 100644
--- a/src/jvm/clojure/lang/APersistentVector.java
+++ b/src/jvm/clojure/lang/APersistentVector.java
@@ -520,6 +520,8 @@ public SubVector(IPersistentMap meta, IPersistentVector v, int start, int end){
 		this.end = end;
 	}
 
+	public Iterator iterator(){return ((PersistentVector)v).rangedIterator(start,end);}
+
 	public Object nth(int i){
 		if(start + i >= end)
 			throw new IndexOutOfBoundsException();
diff --git a/src/jvm/clojure/lang/PersistentVector.java b/src/jvm/clojure/lang/PersistentVector.java
index 22dc890a9f..eb56d0f90a 100644
--- a/src/jvm/clojure/lang/PersistentVector.java
+++ b/src/jvm/clojure/lang/PersistentVector.java
@@ -13,6 +13,7 @@
 package clojure.lang;
 
 import java.io.Serializable;
+import java.util.Iterator;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -232,6 +233,32 @@ public ISeq seq(){
 	return chunkedSeq();
 }
 
+Iterator rangedIterator(final int start, final int end){
+	return new Iterator(){
+		int i = start;
+		int base = i - (i%32);
+		Object[] array = (start < count())?arrayFor(i):null;
+
+		public boolean hasNext(){
+			return i < end;
+			}
+
+		public Object next(){
+			if(i-base == 32){
+				array = arrayFor(i);
+				base += 32;
+				}
+			return array[i++ & 0x01f];
+			}
+
+		public void remove(){
+			throw new UnsupportedOperationException();
+		}
+	};
+}
+
+public Iterator iterator(){return rangedIterator(0,count());}
+
 public Object kvreduce(IFn f, Object init){
     int step = 0;
     for(int i=0;i<cnt;i+=step){