| // 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; |
| |
| /** Common parts of [HashSet] and [LinkedHashSet] implementations. */ |
| abstract class _HashSetBase<E> extends SetBase<E> { |
| |
| // The following two methods override the ones in SetBase. |
| // It's possible to be more efficient if we have a way to create an empty |
| // set of the correct type. |
| |
| Set<E> difference(Set<Object> other) { |
| Set<E> result = _newSet(); |
| for (var element in this) { |
| if (!other.contains(element)) result.add(element); |
| } |
| return result; |
| } |
| |
| Set<E> intersection(Set<Object> other) { |
| Set<E> result = _newSet(); |
| for (var element in this) { |
| if (other.contains(element)) result.add(element); |
| } |
| return result; |
| } |
| |
| Set<E> _newSet(); |
| |
| // Subclasses can optimize this further. |
| Set<E> toSet() => _newSet()..addAll(this); |
| } |
| |
| /** |
| * An unordered hash-table based [Set] implementation. |
| * |
| * The elements of a `HashSet` must have consistent equality |
| * and hashCode implementations. This means that the equals operation |
| * must define a stable equivalence relation on the elements (reflexive, |
| * symmetric, transitive, and consistent over time), and that the hashCode |
| * must consistent with equality, so that the same for objects that are |
| * considered equal. |
| * |
| * The set allows `null` as an element. |
| * |
| * Most simple operations on `HashSet` are done in (potentially amorteized) |
| * constant time: [add], [contains], [remove], and [length], provided the hash |
| * codes of objects are well distributed. |
| */ |
| abstract class HashSet<E> implements Set<E> { |
| /** |
| * Create a hash set using the provided [equals] as equality. |
| * |
| * The provided [equals] must define a stable equivalence relation, and |
| * [hashCode] must be consistent with [equals]. If the [equals] or [hashCode] |
| * methods won't work on all objects, but only to instances of E, the |
| * [isValidKey] predicate can be used to restrict the keys that they are |
| * applied to. Any key for which [isValidKey] returns false is automatically |
| * assumed to not be in the set. |
| * |
| * If [equals] or [hashCode] are omitted, the set uses |
| * the objects' intrinsic [Object.operator==] and [Object.hashCode]. |
| * |
| * If [isValidKey] is omitted, it defaults to testing if the object is an |
| * [E] instance. |
| * |
| * If you supply one of [equals] and [hashCode], |
| * you should generally also to supply the other. |
| * An example would be using [identical] and [identityHashCode], |
| * which is equivalent to using the shorthand [LinkedSet.identity]). |
| */ |
| external factory HashSet({bool equals(E e1, E e2), |
| int hashCode(E e), |
| bool isValidKey(potentialKey)}); |
| |
| /** |
| * Creates an unordered identity-based set. |
| * |
| * Effectively a shorthand for: |
| * |
| * new HashSet(equals: identical, hashCode: identityHashCodeOf) |
| */ |
| external factory HashSet.identity(); |
| |
| /** |
| * Create a hash set containing all [elements]. |
| * |
| * Creates a hash set as by `new HashSet<E>()` and adds each element of |
| * `elements` to this set in the order they are iterated. |
| * |
| * All the [elements] should be assignable to [E]. |
| * The `elements` iterable itself may have any element type, so this |
| * constructor can be used to down-cast a `Set`, for example as: |
| * |
| * Set<SuperType> superSet = ...; |
| * Set<SubType> subSet = |
| * new HashSet<SubType>.from(superSet.where((e) => e is SubType)); |
| */ |
| factory HashSet.from(Iterable elements) { |
| HashSet<E> result = new HashSet<E>(); |
| for (E e in elements) result.add(e); |
| return result; |
| } |
| |
| /** |
| * Provides an iterator that iterates over the elements of this set. |
| * |
| * The order of iteration is unspecified, |
| * but consistent between changes to the set. |
| */ |
| Iterator<E> get iterator; |
| } |