Add "contains" method to Collection.

lib/core/sequences.dart

Index: lib/core/sequences.dart
diff --git a/lib/core/sequences.dart b/lib/core/sequences.dart
new file mode 100644
index 0000000000000000000000000000000000000000..5ed4366aa2e91f58330897c94e713d0d814d0c27
--- /dev/null
+++ b/lib/core/sequences.dart
@@ -0,0 +1,204 @@
+// Copyright (c) 2012, 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.
+
+/**
+ * An indexed sequence of elements of the same type.
+ *
+ * This is a primitive interface that any finite integer-indexable
+ * sequence can implement.
+ * It is intended for data structures where access by index is
+ * the most efficient way to access the data.
+ */
+abstract class Sequence<T> {
+  /**
+   * The limit of valid indices of the sequence.
+   *
+   * The length getter should be efficient.
+   */
+  int get length;
+
+  /**
+   * Returns the value at the given [index].
+   *
+   * Valid indices must be in the range [:0..length - 1:].
+   * The lookup operator should be efficient.
+   */
+  T operator[](int index);
+}
+
+/**
+ * A skeleton class for a [Collection] that is also a [Sequence].
+ */
+abstract class SequenceCollection<E> implements Collection<E>, Sequence<E> {
+  // The class is intended for use as a mixin as well.
+
+  Iterator<E> iterator() => new SequenceIterator(sequence);
+
+  void forEach(f(E element)) {
+    for (int i = 0; i < this.length; i++) f(this[i]);
+  }
+
+  Collection map(f(E element)) {
+    List result = new List();
+    for (int i = 0; i < this.length; i++) {
+      result.add(f(this[i]));
+    }
+    return result;
+  }
+
+  bool contains(E value) {
+    for (int i = 0; i < sequence.length; i++) {
+      if (sequence[i] == value) return true;
+    }
+    return false;
+  }
+
+  reduce(initialValue, combine(previousValue, E element)) {
+    var value = initialValue;
+    for (int i = 0; i < this.length; i++) {
+      value = combine(value, this[i]);
+    }
+    return value;
+  }
+
+  Collection<E> filter(bool f(E element)) {
+    List<E> result = <E>[];
+    for (int i = 0; i < this.length; i++) {
+      E element = this[i];
+      if (f(element)) result.add(element);
+    }
+    return result;
+  }
+
+  bool every(bool f(E element)) {
+    for (int i = 0; i < this.length; i++) {
+      if (!f(this[i])) return false;
+    }
+    return true;
+  }
+
+  bool some(bool f(E element)) {
+    for (int i = 0; i < this.length; i++) {
+      if (f(this[i])) return true;
+    }
+    return false;
+  }
+
+  bool isEmpty() {
+    return this.length == 0;
+  }
+}
+
+
+/**
+ * An unmodifiable [List] backed by a [Sequence].
+ */
+class SequenceList<E> extends SequenceCollection<E> implements List<E> {
+  Sequence<E> sequence;
+  SequenceList(this.sequence);
+
+  int get length => sequence.length;
+
+  T operator[](int index) => sequence[index];
+
+  int indexOf(E value, [int start = 0]) {
+    for (int i = start; i < sequence.length; i++) {
+      if (sequence[i] == value) return i;
+    }
+    return -1;
+  }
+
+  int lastIndexOf(E value, [int start]) {
+    if (start == null) start = sequence.length - 1;
+    for (int i = start; i >= 0; i--) {
+      if (sequence[i] == value) return i;
+    }
+    return -1;
+  }
+
+  E last() => sequence[sequence.length - 1];
+
+  List<E> getRange(int start, int length) {
+    List<E> result = <E>[];
+    for (int i = 0; i < length; i++) {
+      result.add(sequence[start + i]);
+    }
+    return result;
+  }
+
+  void operator []=(int index, E value) {
+    throw new UnsupportedOperationException(
+        "Cannot modify an unmodifiable list");
+  }
+
+  void set length(int newLength) {
+    throw new UnsupportedOperationException(
+        "Cannot change the length of an unmodifiable list");
+  }
+
+  void add(E value) {
+    throw new UnsupportedOperationException(
+        "Cannot add to an unmodifiable list");
+  }
+
+  void addLast(E value) {
+    throw new UnsupportedOperationException(
+        "Cannot add to an unmodifiable list");
+  }
+
+  void addAll(Collection<E> collection) {
+    throw new UnsupportedOperationException(
+        "Cannot add to an unmodifiable list");
+  }
+
+  void sort([Comparator<E> compare]) {
+    throw new UnsupportedOperationException(
+        "Cannot modify an unmodifiable list");
+  }
+
+  void clear() {
+    throw new UnsupportedOperationException(
+        "Cannot clear an unmodifiable list");
+  }
+
+  E removeAt(int index) {
+    throw new UnsupportedOperationException(
+        "Cannot remove in an unmodifiable list");
+  }
+
+  E removeLast() {
+    throw new UnsupportedOperationException(
+        "Cannot remove in an unmodifiable list");
+  }
+
+  void setRange(int start, int length, List<E> from, [int startFrom]) {
+    throw new UnsupportedOperationException(
+        "Cannot modify an unmodifiable list");
+  }
+
+  void removeRange(int start, int length) {
+    throw new UnsupportedOperationException(
+        "Cannot remove in an unmodifiable list");
+  }
+
+  void insertRange(int start, int length, [E initialValue]) {
+    throw new UnsupportedOperationException(
+        "Cannot insert range in an unmodifiable list");
+  }
+}
+
+/**
+ * Iterates over a [Sequence] in growing index order.
+ */
+class SequenceIterator<E> implements Iterator<E> {
+  Sequence<E> _sequence;
+  int _position;
+  SequenceIterator(this._sequence) : _position = 0;
+  bool hasNext() => _position < _sequence.length;
+  E next() {
+    if (hasNext()) return _sequence[_position++];
+    throw new NoMoreElementsException();
+  }
+}
+