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Side by Side Diff: packages/polymer_expressions/lib/src/globals.dart

Issue 2312183003: Removed Polymer from Observatory deps (Closed)
Patch Set: Created 4 years, 3 months ago
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1 // Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
2 // for details. All rights reserved. Use of this source code is governed by a
3 // BSD-style license that can be found in the LICENSE file.
4
5 /**
6 * Contains functions that are included by default in [PolymerExpressions].
7 *
8 * - [enumerate]: a convenient way to iterate over items and the indexes.
9 */
10 // Code from https://github.com/google/quiver-dart/commit/52edc4baf37e99ff6a8f99 c648b29b135fc0b880
11 library polymer_expressions.src.globals;
12
13 import 'dart:collection';
14 import 'package:observe/observe.dart' show reflectable;
15
16 /**
17 * Returns an [Iterable] of [IndexedValue]s where the nth value holds the nth
18 * element of [iterable] and its index.
19 */
20 Iterable<IndexedValue> enumerate(Iterable iterable) =>
21 new EnumerateIterable(iterable);
22
23 @reflectable class IndexedValue<V> {
24 final int index;
25 final V value;
26
27 operator==(o) => o is IndexedValue && o.index == index && o.value == value;
28 int get hashCode => value.hashCode;
29 String toString() => '($index, $value)';
30
31 IndexedValue(this.index, this.value);
32 }
33
34 /**
35 * An [Iterable] of [IndexedValue]s where the nth value holds the nth
36 * element of [iterable] and its index. See [enumerate].
37 */
38 // This was inspired by MappedIterable internal to Dart collections.
39 class EnumerateIterable<V> extends IterableBase<IndexedValue<V>> {
40 final Iterable<V> _iterable;
41
42 EnumerateIterable(this._iterable);
43
44 Iterator<IndexedValue<V>> get iterator =>
45 new EnumerateIterator<V>(_iterable.iterator);
46
47 // Length related functions are independent of the mapping.
48 int get length => _iterable.length;
49 bool get isEmpty => _iterable.isEmpty;
50
51 // Index based lookup can be done before transforming.
52 IndexedValue<V> get first => new IndexedValue<V>(0, _iterable.first);
53 IndexedValue<V> get last => new IndexedValue<V>(length - 1, _iterable.last);
54 IndexedValue<V> get single => new IndexedValue<V>(0, _iterable.single);
55 IndexedValue<V> elementAt(int index) =>
56 new IndexedValue<V>(index, _iterable.elementAt(index));
57 }
58
59 /** The [Iterator] returned by [EnumerateIterable.iterator]. */
60 class EnumerateIterator<V> extends Iterator<IndexedValue<V>> {
61 final Iterator<V> _iterator;
62 int _index = 0;
63 IndexedValue<V> _current;
64
65 EnumerateIterator(this._iterator);
66
67 IndexedValue<V> get current => _current;
68
69 bool moveNext() {
70 if (_iterator.moveNext()) {
71 _current = new IndexedValue(_index++, _iterator.current);
72 return true;
73 }
74 _current = null;
75 return false;
76 }
77 }
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