Wrote functions to convert collections and maps to strings and invoked

corelib/src/implementation/queue.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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 entry in a doubly linked list. It contains a pointer to the next
  * entry, the previous entry, and the boxed element.
  */
 class DoubleLinkedQueueEntry<E> {
   DoubleLinkedQueueEntry<E> _previous;
@@ skipping 212 matching lines @@
       DoubleLinkedQueueEntry<E> nextEntry = entry._next;
       if (f(entry._element)) other.addLast(entry._element);
       entry = nextEntry;
     }
     return other;
   }
 
   _DoubleLinkedQueueIterator<E> iterator() {
     return new _DoubleLinkedQueueIterator<E>(_sentinel);
   }
+
+  String toString() {
+    return Collections.collectionToString(this);
+  }
 }
 
 class _DoubleLinkedQueueIterator<E> implements Iterator<E> {
   final _DoubleLinkedQueueEntrySentinel<E> _sentinel;
   DoubleLinkedQueueEntry<E> _currentEntry;
 
   _DoubleLinkedQueueIterator(_DoubleLinkedQueueEntrySentinel this._sentinel) {
     _currentEntry = _sentinel;
   }
 
   bool hasNext() {
     return _currentEntry._next !== _sentinel;
   }
 
   E next() {
     if (!hasNext()) {
       throw const NoMoreElementsException();
     }
     _currentEntry = _currentEntry._next;
     return _currentEntry.element;
   }
 }