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1 // Copyright 2013 Google Inc. All Rights Reserved. | |
2 // | |
3 // Licensed under the Apache License, Version 2.0 (the "License"); | |
4 // you may not use this file except in compliance with the License. | |
5 // You may obtain a copy of the License at | |
6 // | |
7 // http://www.apache.org/licenses/LICENSE-2.0 | |
8 // | |
9 // Unless required by applicable law or agreed to in writing, software | |
10 // distributed under the License is distributed on an "AS IS" BASIS, | |
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
12 // See the License for the specific language governing permissions and | |
13 // limitations under the License. | |
14 | |
15 part of quiver.iterables; | |
16 | |
17 /// Returns an [Iterable] that infinitely cycles through the elements of | |
18 /// [iterable]. If [iterable] is empty, the returned Iterable will also be empty
. | |
19 Iterable cycle(Iterable iterable) => new _Cycle(iterable); | |
20 | |
21 class _Cycle<T> extends InfiniteIterable<T> { | |
22 final Iterable<T> _iterable; | |
23 | |
24 _Cycle(this._iterable); | |
25 | |
26 Iterator<T> get iterator => new _CycleIterator(_iterable); | |
27 | |
28 bool get isEmpty => _iterable.isEmpty; | |
29 | |
30 bool get isNotEmpty => _iterable.isNotEmpty; | |
31 | |
32 // TODO(justin): add methods that can be answered by the wrapped iterable | |
33 } | |
34 | |
35 class _CycleIterator<T> implements Iterator<T> { | |
36 final Iterable<T> _iterable; | |
37 Iterator<T> _iterator; | |
38 | |
39 _CycleIterator(_iterable) | |
40 : _iterable = _iterable, | |
41 _iterator = _iterable.iterator; | |
42 | |
43 T get current => _iterator.current; | |
44 | |
45 bool moveNext() { | |
46 if (!_iterator.moveNext()) { | |
47 _iterator = _iterable.iterator; | |
48 return _iterator.moveNext(); | |
49 } | |
50 return true; | |
51 } | |
52 } | |
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