// Copyright (c) 2011, 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; | |

/** | |

* A collection of objects in which each object can occur only once. | |

* | |

* That is, for each object of the element type, the object is either considered | |

* to be in the set, or to _not_ be in the set. | |

* | |

* Set implementations may consider some elements indistinguishable. These | |

* elements are treated as being the same for any operation on the set. | |

* | |

* The default [Set] implementation, [LinkedHashSet], considers objects | |

* indistinguishable if they are equal with regard to | |

* operator [Object.==]. | |

* | |

* Iterating over elements of a set may be either unordered | |

* or ordered in some way. Examples: | |

* | |

* * A [HashSet] is unordered, which means that its iteration order is | |

* uspecified, | |

* * [LinkedHashSet] iterates in the insertion order of its elements, and | |

* * a sorted set like [SplayTreeSet] iterates the elements in sorted order. | |

* | |

* It is generally not allowed to modify the set (add or remove elements) while | |

* an operation on the set is being performed, for example during a call to | |

* [forEach] or [containsAll]. Nor is it allowed to modify the set while | |

* iterating either the set itself or any [Iterable] that is backed by the set, | |

* such as the ones returned by methods like [where] and [map]. | |

*/ | |

abstract class Set<E> extends Iterable<E> implements EfficientLength { | |

/** | |

* Creates an empty [Set]. | |

* | |

* The created [Set] is a plain [LinkedHashSet]. | |

* As such, it considers elements that are equal (using [==]) to be | |

* indistinguishable, and requires them to have a compatible | |

* [Object.hashCode] implementation. | |

* | |

* The set is equivalent to one created by `new LinkedHashSet<E>()`. | |

*/ | |

factory Set() = LinkedHashSet<E>; | |

/** | |

* Creates an empty identity [Set]. | |

* | |

* The created [Set] is a [LinkedHashSet] that uses identity as equality | |

* relation. | |

* | |

* The set is equivalent to one created by `new LinkedHashSet<E>.identity()`. | |

*/ | |

factory Set.identity() = LinkedHashSet<E>.identity; | |

/** | |

* Creates a [Set] that contains all [elements]. | |

* | |

* All the [elements] should be assignable to [E]. | |

* The `elements` iterable itself can have any type, | |

* so this constructor can be used to down-cast a `Set`, for example as: | |

* | |

* Set<SuperType> superSet = ...; | |

* Set<SubType> subSet = | |

* new Set<SubType>.from(superSet.where((e) => e is SubType)); | |

* | |

* The created [Set] is a [LinkedHashSet]. As such, it considers elements that | |

* are equal (using [==]) to be indistinguishable, and requires them to | |

* have a compatible [Object.hashCode] implementation. | |

* | |

* The set is equivalent to one created by | |

* `new LinkedHashSet<E>.from(elements)`. | |

*/ | |

factory Set.from(Iterable elements) = LinkedHashSet<E>.from; | |

/** | |

* Provides an iterator that iterates over the elements of this set. | |

* | |

* The order of iteration is defined by the individual `Set` implementation, | |

* but must be consistent between changes to the set. | |

*/ | |

Iterator<E> get iterator; | |

/** | |

* Returns true if [value] is in the set. | |

*/ | |

bool contains(Object value); | |

/** | |

* Adds [value] into the set. Returns `true` if [value] was added to the set. | |

* | |

* If [value] already exists, the set is not changed and `false` is returned. | |

*/ | |

bool add(E value); | |

/** | |

* Adds all [elements] to this Set. | |

* | |

* Equivalent to adding each element in [elements] using [add], | |

* but some collections may be able to optimize it. | |

*/ | |

void addAll(Iterable<E> elements); | |

/** | |

* Removes [value] from the set. Returns true if [value] was | |

* in the set. Returns false otherwise. The method has no effect | |

* if [value] value was not in the set. | |

*/ | |

bool remove(Object value); | |

/** | |

* If an object equal to [object] is in the set, return it. | |

* | |

* Checks if there is an object in the set that is equal to [object]. | |

* If so, that object is returned, otherwise returns null. | |

*/ | |

E lookup(Object object); | |

/** | |

* Removes each element of [elements] from this set. | |

*/ | |

void removeAll(Iterable<Object> elements); | |

/** | |

* Removes all elements of this set that are not elements in [elements]. | |

* | |

* Checks for each element of [elements] whether there is an element in this | |

* set that is equal to it (according to `this.contains`), and if so, the | |

* equal element in this set is retained, and elements that are not equal | |

* to any element in `elements` are removed. | |

*/ | |

void retainAll(Iterable<Object> elements); | |

/** | |

* Removes all elements of this set that satisfy [test]. | |

*/ | |

void removeWhere(bool test(E element)); | |

/** | |

* Removes all elements of this set that fail to satisfy [test]. | |

*/ | |

void retainWhere(bool test(E element)); | |

/** | |

* Returns whether this Set contains all the elements of [other]. | |

*/ | |

bool containsAll(Iterable<Object> other); | |

/** | |

* Returns a new set which is the intersection between this set and [other]. | |

* | |

* That is, the returned set contains all the elements of this [Set] that | |

* are also elements of [other] according to `other.contains`. | |

*/ | |

Set<E> intersection(Set<Object> other); | |

/** | |

* Returns a new set which contains all the elements of this set and [other]. | |

* | |

* That is, the returned set contains all the elements of this [Set] and | |

* all the elements of [other]. | |

*/ | |

Set<E> union(Set<E> other); | |

/** | |

* Returns a new set with the the elements of this that are not in [other]. | |

* | |

* That is, the returned set contains all the elements of this [Set] that | |

* are not elements of [other] according to `other.contains`. | |

*/ | |

Set<E> difference(Set<E> other); | |

/** | |

* Removes all elements in the set. | |

*/ | |

void clear(); | |

/* Creates a [Set] with the same elements and behavior as this `Set`. | |

* | |

* The returned set behaves the same as this set | |

* with regard to adding and removing elements. | |

* It initially contains the same elements. | |

* If this set specifies an ordering of the elements, | |

* the returned set will have the same order. | |

*/ | |

Set<E> toSet(); | |

} |