1 files changed, 10 insertions, 6 deletions
diff --git a/src/de/lmu/ifi/dbs/elki/utilities/datastructures/iterator/ArrayListIter.java b/src/de/lmu/ifi/dbs/elki/utilities/datastructures/iterator/ArrayListIter.java
index 820217ec..68cd0448 100644
--- a/src/de/lmu/ifi/dbs/elki/utilities/datastructures/iterator/ArrayListIter.java
+++ b/src/de/lmu/ifi/dbs/elki/utilities/datastructures/iterator/ArrayListIter.java
@@ -4,7 +4,7 @@ package de.lmu.ifi.dbs.elki.utilities.datastructures.iterator;
  This file is part of ELKI:
  Environment for Developing KDD-Applications Supported by Index-Structures
 
- Copyright (C) 2013
+ Copyright (C) 2014
  Ludwig-Maximilians-Universität München
  Lehr- und Forschungseinheit für Datenbanksysteme
  ELKI Development Team
@@ -60,12 +60,13 @@ public class ArrayListIter<O> implements ArrayIter {
 
   @Override
   public boolean valid() {
-    return pos < data.size();
+    return pos < data.size() && pos >= 0;
   }
 
   @Override
-  public void advance() {
+  public ArrayIter advance() {
     pos++;
+    return this;
   }
 
   @Override
@@ -74,18 +75,21 @@ public class ArrayListIter<O> implements ArrayIter {
   }
 
   @Override
-  public void advance(int count) {
+  public ArrayIter advance(int count) {
     pos += count;
+    return this;
   }
 
   @Override
-  public void retract() {
+  public ArrayIter retract() {
     pos--;
+    return this;
   }
 
   @Override
-  public void seek(int off) {
+  public ArrayIter seek(int off) {
     pos = off;
+    return this;
   }
 
   /**