Use iterator, moveNext(), current.

sdk/lib/core/sequences.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * An indexed sequence of elements of the same type.
  *
  * This is a primitive interface that any finite integer-indexable
  * sequence can implement.
  * It is intended for data structures where access by index is
@@ skipping 15 matching lines @@
    */
   T operator[](int index);
 }
 
 /**
  * A skeleton class for a [Collection] that is also a [Sequence].
  */
 abstract class SequenceCollection<E> implements Collection<E>, Sequence<E> {
   // The class is intended for use as a mixin as well.
 
-  Iterator<E> iterator() => new SequenceIterator(sequence);
+  Iterator<E> get iterator => new SequenceIterator(sequence);
 
   void forEach(f(E element)) {
     for (int i = 0; i < this.length; i++) f(this[i]);
   }
 
   Collection mappedBy(f(E element)) {
     List result = new List();
     for (int i = 0; i < this.length; i++) {
       result.add(f(this[i]));
     }
@@ skipping 140 matching lines @@
         "Cannot insert range in an unmodifiable list");
   }
 }
 
 /**
  * Iterates over a [Sequence] in growing index order.
  */
 class SequenceIterator<E> implements Iterator<E> {
   Sequence<E> _sequence;
   int _position;
-  SequenceIterator(this._sequence) : _position = 0;
-  bool get hasNext => _position < _sequence.length;
-  E next() {
-    if (hasNext) return _sequence[_position++];
+  SequenceIterator(this._sequence) : _position = -1;
+  bool moveNext() {
+    _position++;
+    if (_position < _sequence.length) return true;
+    _position = _sequence.length;
+    return false;
+  }
+  E get current {
+    if (0 <= _position && _position < _sequence.length) {
+      return _sequence[_position];
+    }
+    // TODO(floitsch): adapt error-message.
     throw new StateError("No more elements");
   }
 }