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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.
import 'union_set.dart';
/// A controller that exposes a view of the union of a collection of sets.
/// This is a convenience class for creating a [UnionSet] whose contents change
/// over the lifetime of a class. For example:
/// ```dart
/// class Engine {
/// Set<Test> get activeTests => _activeTestsGroup.set;
/// final _activeTestsGroup = UnionSetController<Test>();
/// void addSuite(Suite suite) {
/// _activeTestsGroup.add(suite.tests);
/// _runSuite(suite);
/// _activeTestsGroup.remove(suite.tests);
/// }
/// }
/// ```
class UnionSetController<E> {
/// The [UnionSet] that provides a view of the union of sets in [this].
UnionSet<E> get set => _set;
UnionSet<E> _set;
/// The sets whose union is exposed through [set].
final _sets = <Set<E>>{};
/// Creates a set of sets that provides a view of the union of those sets.
/// If [disjoint] is `true`, this assumes that all component sets are
/// disjoint—that is, that they contain no elements in common. This makes
/// many operations including [length] more efficient.
UnionSetController({bool disjoint = false}) {
_set = UnionSet<E>(_sets, disjoint: disjoint);
/// Adds the contents of [component] to [set].
/// If the contents of [component] change over time, [set] will change
/// accordingly.
void add(Set<E> component) {
/// Removes the contents of [component] to [set].
/// If another set in [this] has overlapping elements with [component], those
/// elements will remain in [set].
bool remove(Set<E> component) => _sets.remove(component);