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| 1 // Copyright 2014 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 Iterable generate(initial(), next(o)) => new GeneratingIterable(initial, next); | |
| 18 | |
| 19 /// An Iterable who's first value is [object] and who's subsequent values are | |
| 20 /// generated by passing the current value to the [next] function. | |
| 21 /// | |
| 22 /// The class is useful for creating lazy iterables from object hierarchies and | |
| 23 /// graphs. | |
| 24 /// | |
| 25 /// It's important that for the given initial value and next function that the | |
| 26 /// sequence of items eventually terminates. Otherwise calling methods that | |
| 27 /// expect a finite sequence, like `length` or `last`, will cause an infinite | |
| 28 /// loop. | |
| 29 /// | |
| 30 /// Example: | |
| 31 /// | |
| 32 /// class Node { | |
| 33 /// Node parent; | |
| 34 /// | |
| 35 /// /// An iterable of node and all ancestors up to the root. | |
| 36 /// Iterable<Node> ancestors = | |
| 37 /// new GeneratingIterable<Node>(() => this, (n) => n.parent); | |
| 38 /// | |
| 39 /// /// An iterable of the root and the path of nodes to this. The | |
| 40 /// /// reverse of ancestors. | |
| 41 /// Iterable<Node> path = ancestors.toList().reversed(); | |
| 42 /// } | |
| 43 /// | |
| 44 class GeneratingIterable<T> extends IterableBase<T> { | |
| 45 final initial; | |
| 46 final next; | |
| 47 | |
| 48 GeneratingIterable(T this.initial(), T this.next(T o)); | |
| 49 | |
| 50 @override | |
| 51 Iterator<T> get iterator => new _GeneratingIterator(initial(), next); | |
| 52 } | |
| 53 | |
| 54 class _GeneratingIterator<T> implements Iterator<T> { | |
| 55 final next; | |
| 56 T object; | |
| 57 bool started = false; | |
| 58 | |
| 59 _GeneratingIterator(T this.object, T this.next(T o)); | |
| 60 | |
| 61 @override | |
| 62 T get current => started ? object : null; | |
| 63 | |
| 64 @override | |
| 65 bool moveNext() { | |
| 66 if (object == null) return false; | |
| 67 if (started) { | |
| 68 object = next(object); | |
| 69 } else { | |
| 70 started = true; | |
| 71 } | |
| 72 return object != null; | |
| 73 } | |
| 74 } | |
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Chromium Code Reviews
Issue 2989763002:
Update charted to 0.4.8 and roll (Closed)
