Reapply "New implementation of {,Linked}Hash{Set,Map}."

sdk/lib/collection/set.dart

-// Copyright (c) 2013, 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.collection;
-
-
-
-class HashSet<E> extends Collection<E> implements Set<E> {
-  // The map backing this set. The associations in this map are all
-  // of the form element -> element. If a value is not in the map,
-  // then it is not in the set.
-  final _HashMapImpl<E, E> _backingMap;
-
-  HashSet() : _backingMap = new _HashMapImpl<E, E>();
-
-  /**
-   * Creates a [Set] that contains all elements of [other].
-   */
-  factory HashSet.from(Iterable<E> other) {
-    Set<E> set = new HashSet<E>();
-    for (final e in other) {
-      set.add(e);
-    }
-    return set;
-  }
-
-  void clear() {
-    _backingMap.clear();
-  }
-
-  void add(E value) {
-    _backingMap[value] = value;
-  }
-
-  bool remove(Object value) {
-    if (!_backingMap.containsKey(value)) return false;
-    _backingMap.remove(value);
-    return true;
-  }
-
-  bool contains(E value) {
-    return _backingMap.containsKey(value);
-  }
-
-  Set<E> intersection(Collection<E> collection) {
-    Set<E> result = new Set<E>();
-    collection.forEach((E value) {
-      if (contains(value)) result.add(value);
-    });
-    return result;
-  }
-
-  bool isSubsetOf(Collection<E> other) {
-    return new Set<E>.from(other).containsAll(this);
-  }
-
-  bool containsAll(Collection<E> collection) {
-    return collection.every((E value) {
-      return contains(value);
-    });
-  }
-
-  void forEach(void f(E element)) {
-    _backingMap.forEach((E key, E value) {
-      f(key);
-    });
-  }
-
-  bool get isEmpty {
-    return _backingMap.isEmpty;
-  }
-
-  int get length {
-    return _backingMap.length;
-  }
-
-  Iterator<E> get iterator => new _HashSetIterator<E>(this);
-
-  String toString() {
-    return Collections.collectionToString(this);
-  }
-}
-
-class _HashSetIterator<E> implements Iterator<E> {
-
-  _HashSetIterator(HashSet<E> set)
-    : _keysIterator = set._backingMap._keys.iterator;
-
-  E get current {
-    var result = _keysIterator.current;
-    if (identical(result, _HashMapImpl._DELETED_KEY)) {
-      // TODO(floitsch): improve the error reporting.
-      throw new StateError("Concurrent modification.");
-    }
-    return result;
-  }
-
-  bool moveNext() {
-    bool result;
-    do {
-      result = _keysIterator.moveNext();
-    } while (result &&
-             (_keysIterator.current == null ||
-              identical(_keysIterator.current, _HashMapImpl._DELETED_KEY)));
-    return result;
-  }
-
-  Iterator _keysIterator;
-}