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set.dart
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set.dart
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// Copyright (c) 2014, 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.
/// Base implementations of [Set].
part of dart.collection;
/// Mixin 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].
///
/// Some of the methods assume that `toSet` creates a modifiable set.
/// If using this mixin for an unmodifiable set,
/// where `toSet` should return an unmodifiable set,
/// it's necessary to reimplement
/// [retainAll], [union], [intersection] and [difference].
///
/// Implementations of `Set` using this mixin should consider also implementing
/// `clear` in constant time. The default implementation works by removing every
/// element.
abstract class SetMixin<E> implements Set<E> {
// This class reimplements all of [IterableMixin].
// If/when Dart mixins get more powerful, we should just create a single
// Mixin class from IterableMixin and the new methods of this class.
bool add(E value);
bool contains(Object? element);
E? lookup(Object? element);
bool remove(Object? value);
Iterator<E> get iterator;
Set<E> toSet();
int get length;
bool get isEmpty => length == 0;
bool get isNotEmpty => length != 0;
Set<R> cast<R>() => Set.castFrom<E, R>(this);
Iterable<E> followedBy(Iterable<E> other) =>
FollowedByIterable<E>.firstEfficient(this, other);
Iterable<T> whereType<T>() => WhereTypeIterable<T>(this);
void clear() {
removeAll(toList());
}
void addAll(Iterable<E> elements) {
for (E element in elements) add(element);
}
void removeAll(Iterable<Object?> elements) {
for (Object? element in elements) remove(element);
}
void retainAll(Iterable<Object?> elements) {
// Create a copy of the set, remove all of elements from the copy,
// then remove all remaining elements in copy from this.
Set<E> toRemove = toSet();
for (Object? o in elements) {
toRemove.remove(o);
}
removeAll(toRemove);
}
void removeWhere(bool test(E element)) {
List<Object?> toRemove = [];
for (E element in this) {
if (test(element)) toRemove.add(element);
}
removeAll(toRemove);
}
void retainWhere(bool test(E element)) {
List<Object?> toRemove = [];
for (E element in this) {
if (!test(element)) toRemove.add(element);
}
removeAll(toRemove);
}
bool containsAll(Iterable<Object?> other) {
for (var o in other) {
if (!contains(o)) return false;
}
return true;
}
Set<E> union(Set<E> other) {
return toSet()..addAll(other);
}
Set<E> intersection(Set<Object?> other) {
Set<E> result = toSet();
for (E element in this) {
if (!other.contains(element)) result.remove(element);
}
return result;
}
Set<E> difference(Set<Object?> other) {
Set<E> result = toSet();
for (E element in this) {
if (other.contains(element)) result.remove(element);
}
return result;
}
List<E> toList({bool growable = true}) =>
List<E>.of(this, growable: growable);
Iterable<T> map<T>(T f(E element)) =>
EfficientLengthMappedIterable<E, T>(this, f);
E get single {
if (length > 1) throw IterableElementError.tooMany();
Iterator<E> it = iterator;
if (!it.moveNext()) throw IterableElementError.noElement();
E result = it.current;
return result;
}
String toString() => IterableBase.iterableToFullString(this, '{', '}');
// Copied from IterableMixin.
// Should be inherited if we had multi-level mixins.
Iterable<E> where(bool f(E element)) => WhereIterable<E>(this, f);
Iterable<T> expand<T>(Iterable<T> f(E element)) =>
ExpandIterable<E, T>(this, f);
void forEach(void f(E element)) {
for (E element in this) f(element);
}
E reduce(E combine(E value, E element)) {
Iterator<E> iterator = this.iterator;
if (!iterator.moveNext()) {
throw IterableElementError.noElement();
}
E value = iterator.current;
while (iterator.moveNext()) {
value = combine(value, iterator.current);
}
return value;
}
T fold<T>(T initialValue, T combine(T previousValue, E element)) {
var value = initialValue;
for (E element in this) value = combine(value, element);
return value;
}
bool every(bool f(E element)) {
for (E element in this) {
if (!f(element)) return false;
}
return true;
}
String join([String separator = ""]) {
Iterator<E> iterator = this.iterator;
if (!iterator.moveNext()) return "";
StringBuffer buffer = StringBuffer();
if (separator == null || separator == "") {
do {
buffer.write(iterator.current);
} while (iterator.moveNext());
} else {
buffer.write(iterator.current);
while (iterator.moveNext()) {
buffer.write(separator);
buffer.write(iterator.current);
}
}
return buffer.toString();
}
bool any(bool test(E element)) {
for (E element in this) {
if (test(element)) return true;
}
return false;
}
Iterable<E> take(int n) {
return TakeIterable<E>(this, n);
}
Iterable<E> takeWhile(bool test(E value)) {
return TakeWhileIterable<E>(this, test);
}
Iterable<E> skip(int n) {
return SkipIterable<E>(this, n);
}
Iterable<E> skipWhile(bool test(E value)) {
return SkipWhileIterable<E>(this, test);
}
E get first {
Iterator<E> it = iterator;
if (!it.moveNext()) {
throw IterableElementError.noElement();
}
return it.current;
}
E get last {
Iterator<E> it = iterator;
if (!it.moveNext()) {
throw IterableElementError.noElement();
}
E result;
do {
result = it.current;
} while (it.moveNext());
return result;
}
E firstWhere(bool test(E value), {E Function()? orElse}) {
for (E element in this) {
if (test(element)) return element;
}
if (orElse != null) return orElse();
throw IterableElementError.noElement();
}
E lastWhere(bool test(E value), {E Function()? orElse}) {
late E result;
bool foundMatching = false;
for (E element in this) {
if (test(element)) {
result = element;
foundMatching = true;
}
}
if (foundMatching) return result;
if (orElse != null) return orElse();
throw IterableElementError.noElement();
}
E singleWhere(bool test(E value), {E Function()? orElse}) {
late E result;
bool foundMatching = false;
for (E element in this) {
if (test(element)) {
if (foundMatching) {
throw IterableElementError.tooMany();
}
result = element;
foundMatching = true;
}
}
if (foundMatching) return result;
if (orElse != null) return orElse();
throw IterableElementError.noElement();
}
E elementAt(int index) {
checkNotNullable(index, "index");
RangeError.checkNotNegative(index, "index");
int elementIndex = 0;
for (E element in this) {
if (index == elementIndex) return element;
elementIndex++;
}
throw RangeError.index(index, this, "index", null, elementIndex);
}
}
/// 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].
///
/// Some of the methods assume that `toSet` creates a modifiable set.
/// If using this base class for an unmodifiable set,
/// where `toSet` should return an unmodifiable set,
/// it's necessary to reimplement
/// [retainAll], [union], [intersection] and [difference].
///
/// Implementations of `Set` using this base should consider also implementing
/// `clear` in constant time. The default implementation works by removing every
/// element.
abstract class SetBase<E> with SetMixin<E> {
/// Converts a [Set] to a [String].
///
/// Converts [set] to a string by converting each element to a string (by
/// calling [Object.toString]), joining them with ", ", and wrapping the
/// result in "{" and "}".
///
/// Handles circular references where converting one of the elements
/// to a string ends up converting [set] to a string again.
static String setToString(Set set) =>
IterableBase.iterableToFullString(set, '{', '}');
}
/// Common internal implementation of some [Set] methods.
abstract class _SetBase<E> with SetMixin<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.
const _SetBase();
Set<E> _newSet();
Set<R> _newSimilarSet<R>();
Set<R> cast<R>() => Set.castFrom<E, R>(this, newSet: _newSimilarSet);
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;
}
// Subclasses can optimize this further.
Set<E> toSet() => _newSet()..addAll(this);
}
abstract class _UnmodifiableSetMixin<E> implements Set<E> {
static Never _throwUnmodifiable() {
throw UnsupportedError("Cannot change an unmodifiable set");
}
/// This operation is not supported by an unmodifiable set.
bool add(E value) => _throwUnmodifiable();
/// This operation is not supported by an unmodifiable set.
void clear() => _throwUnmodifiable();
/// This operation is not supported by an unmodifiable set.
void addAll(Iterable<E> elements) => _throwUnmodifiable();
/// This operation is not supported by an unmodifiable set.
void removeAll(Iterable<Object?> elements) => _throwUnmodifiable();
/// This operation is not supported by an unmodifiable set.
void retainAll(Iterable<Object?> elements) => _throwUnmodifiable();
/// This operation is not supported by an unmodifiable set.
void removeWhere(bool test(E element)) => _throwUnmodifiable();
/// This operation is not supported by an unmodifiable set.
void retainWhere(bool test(E element)) => _throwUnmodifiable();
/// This operation is not supported by an unmodifiable set.
bool remove(Object? value) => _throwUnmodifiable();
}
/// Class used to implement const sets.
class _UnmodifiableSet<E> extends _SetBase<E> with _UnmodifiableSetMixin<E> {
final Map<E, Null> _map;
const _UnmodifiableSet(this._map);
Set<E> _newSet() => LinkedHashSet<E>();
Set<R> _newSimilarSet<R>() => LinkedHashSet<R>();
// Lookups use map methods.
bool contains(Object? element) => _map.containsKey(element);
Iterator<E> get iterator => _map.keys.iterator;
int get length => _map.length;
E? lookup(Object? element) {
for (var key in _map.keys) {
if (key == element) return key;
}
return null;
}
}
/// An unmodifiable [Set] view of another [Set].
///
/// Methods that could change the set, such as [add] and [remove],
/// must not be called.
@Since("2.12")
class UnmodifiableSetView<E> extends SetBase<E> with _UnmodifiableSetMixin<E> {
final Set<E> _source;
/// Creates an [UnmodifiableSetView] of [source].
UnmodifiableSetView(Set<E> source) : _source = source;
bool contains(Object? element) => _source.contains(element);
E? lookup(Object? element) => _source.lookup(element);
int get length => _source.length;
Iterator<E> get iterator => _source.iterator;
Set<E> toSet() => _source.toSet();
}