Move some core classes to collection library.

sdk/lib/core/iterator.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.
 
 part of dart.core;
 
 /**
  * The [Iterator] class provides methods to iterate over an object. It
  * is transparently used by the for-in construct to test for the end
  * of the iteration, and to get the elements.
  *
  * If the object iterated over is changed during the iteration, the
  * behavior is unspecified.
  *
  * The [Iterator] is initially positioned before the first element. Before
  * accessing the first element the iterator must thus be advanced ([moveNext])
  * to point to the first element. If there is no element left, then [moveNext]
  * returns false.
+ *
+ * A typical usage of an [Iterator] looks as follows:
+ *
+ *     var it = obj.iterator;
+ *     while (it.moveNext()) {
+ *       use(it.current);
+ *     }
  */
 abstract class Iterator<E> {
   /**
    * Moves to the next element. Returns true if [current] contains the next
    * element. Returns false, if no element was left.
    *
    * It is safe to invoke [moveNext] even when the iterator is already
    * positioned after the last element. In this case [moveNext] has no effect.
    */
   bool moveNext();
 
   /**
    * Returns the current element.
    *
    * Return [:null:] if the iterator has not yet been moved to the first
    * element, or if the iterator has been moved after the last element of the
    * [Iterable].
    */
   E get current;
 }
-
-class HasNextIterator<E> {
-  static const int _HAS_NEXT_AND_NEXT_IN_CURRENT = 0;
-  static const int _NO_NEXT = 1;
-  static const int _NOT_MOVED_YET = 2;
-
-  Iterator _iterator;
-  int _state = _NOT_MOVED_YET;
-
-  HasNextIterator(this._iterator);
-
-  bool get hasNext {
-    if (_state == _NOT_MOVED_YET) _move();
-    return _state == _HAS_NEXT_AND_NEXT_IN_CURRENT;
-  }
-
-  E next() {
-    // Call to hasNext is necessary to make sure we are positioned at the first
-    // element when we start iterating.
-    if (!hasNext) throw new StateError("No more elements");
-    assert(_state == _HAS_NEXT_AND_NEXT_IN_CURRENT);
-    E result = _iterator.current;
-    _move();
-    return result;
-  }
-
-  void _move() {
-    if (_iterator.moveNext()) {
-      _state = _HAS_NEXT_AND_NEXT_IN_CURRENT;
-    } else {
-      _state = _NO_NEXT;
-    }
-  }
-}