Add SetBase/SetMixin.

sdk/lib/collection/set.dart

+// 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].
+ *
+ * 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 thisclass.
+
+  bool add(E element);
+
+  bool contains(Object element);
+
+  E lookup(E element);
+
+  bool remove(Object element);
+
+  Iterable<E> get iterator;
+
+  Set<E> toSet();
+
+  int get length;
+
+  bool get isEmpty => length == 0;
+
+  bool get isNotEmpty => length != 0;
+
+  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 toRemove = [];
+    for (E element in this) {
+      if (test(element)) toRemove.add(element);
+    }
+    removeAll(toRemove);
+  }
+
+  void retainWhere(bool test(E element)) {
+    List toRemove = [];
+    for (E element in this) {
+      if (!test(element)) toRemove.add(element);
+    }
+    removeAll(toRemove);
+  }
+
+  bool containsAll(Iterable<Object> other) {
+    for (Object 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> result = growable ? (new List<E>()..length = length)
+                              : new List<E>(length);
+    int i = 0;
+    for (E element in this) result[i++] = element;
+    return result;
+  }
+
+  Iterable map(f(E element)) =>
+      new EfficientLengthMappedIterable<E, dynamic>(this, f);
+
+  E get single {
+    if (length > 1) throw IterableElementError.tooMany();
+    Iterator it = iterator;
+    if (!it.moveNext()) throw IterableElementError.noElement();
+    E result = it.current;
+    return result;
+  }
+
+  String toString() => IterableMixinWorkaround.toStringIterable(this, '{', '}');
+
+  // Copied from IterableMixin.

[Søren Gjesse, 2014/05/22 09:25:52]

Is there a comment in IterableMixin to make sure to update this copy?

[Lasse Reichstein Nielsen, 2014/05/22 09:41:37]

Is now.

+  // Should be inherited if we had multi-level mixins.
+
+  Iterable<E> where(bool f(E element)) => new WhereIterable<E>(this, f);
+
+  Iterable expand(Iterable f(E element)) =>
+      new ExpandIterable<E, dynamic>(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;
+  }
+
+  dynamic fold(var initialValue,
+               dynamic combine(var 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 = new 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 new TakeIterable<E>(this, n);
+  }
+
+  Iterable<E> takeWhile(bool test(E value)) {
+    return new TakeWhileIterable<E>(this, test);
+  }
+
+  Iterable<E> skip(int n) {
+    return new SkipIterable<E>(this, n);
+  }
+
+  Iterable<E> skipWhile(bool test(E value)) {
+    return new SkipWhileIterable<E>(this, test);
+  }
+
+  E get first {
+    Iterator it = iterator;
+    if (!it.moveNext()) {
+      throw IterableElementError.noElement();
+    }
+    return it.current;
+  }
+
+  E get last {
+    Iterator it = iterator;
+    if (!it.moveNext()) {
+      throw IterableElementError.noElement();
+    }
+    E result;
+    do {
+      result = it.current;
+    } while(it.moveNext());
+    return result;
+  }
+
+  dynamic firstWhere(bool test(E value), { Object orElse() }) {
+    for (E element in this) {
+      if (test(element)) return element;
+    }
+    if (orElse != null) return orElse();
+    throw IterableElementError.noElement();
+  }
+
+  dynamic lastWhere(bool test(E value), { Object orElse() }) {
+    E result = null;
+    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 result = null;
+    bool foundMatching = false;
+    for (E element in this) {
+      if (test(element)) {
+        if (foundMatching) {
+          throw IterableElementError.tooMany();
+        }
+        result = element;
+        foundMatching = true;
+      }
+    }
+    if (foundMatching) return result;
+    throw IterableElementError.noElement();
+  }
+
+  E elementAt(int index) {
+    if (index is! int || index < 0) throw new RangeError.value(index);
+    int remaining = index;
+    for (E element in this) {
+      if (remaining == 0) return element;
+      remaining--;
+    }
+    throw new RangeError.value(index);
+  }
+}
+
+/**
+ * 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].
+ *
+ * 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> = Object with SetMixin<E>;