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// Copyright (c) 2016, 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.
/// @assertion abstract class SetBase<E>
/// Base implementation of Set.
/// This class provides a base implementation of a [Set] that depends only on the
/// abstract members: [add], [contains], [lookup], [remove], [iterator], [length]
/// and [toSet].
/// @description Implementation of [add], [contains], [lookup], [remove],
/// [iterator], [length] and [toSet]
/// @author
library set_base_lib;
import "dart:collection";
class SetBaseImpl<E> extends SetBase<E> {
LinkedHashSet<E> _set;
SetBaseImpl(): _set = new LinkedHashSet<E>();
SetBaseImpl.from(Iterable content): _set = new LinkedHashSet<E>.from(content);
bool add(E element) => _set.add(element);
bool contains(Object? element) => _set.contains(element);
E? lookup(Object? element) => _set.lookup(element);
bool remove(Object? element) => _set.remove(element);
Iterator<E> get iterator => _set.iterator;
int get length => _set.length;
Set<E> toSet() => _set.toSet();
SetBase create([Iterable? content]) {
if (content == null) {
return new SetBaseImpl();
} else {
return new SetBaseImpl.from(content);