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1 // Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file | 1 // Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file |
2 // for details. All rights reserved. Use of this source code is governed by a | 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. | 3 // BSD-style license that can be found in the LICENSE file. |
4 | 4 |
5 /** | 5 /** |
6 * The [Collection] interface is the public interface of all | 6 * The common interface of all collections. |
7 * collections. | 7 * |
| 8 * The [Collection] class contains a skeleton implementation of |
| 9 * an iterator based collection. |
8 */ | 10 */ |
9 abstract class Collection<E> extends Iterable<E> { | 11 abstract class Collection<E> extends Iterable<E> { |
10 /** | 12 /** |
11 * Applies the function [f] to each element of this collection. | |
12 */ | |
13 void forEach(void f(E element)); | |
14 | |
15 /** | |
16 * Returns a new collection with the elements [: f(e) :] | 13 * Returns a new collection with the elements [: f(e) :] |
17 * for each element [:e:] of this collection. | 14 * for each element [:e:] of this collection. |
18 * | 15 * |
19 * Note on typing: the return type of f() could be an arbitrary | 16 * Subclasses of [Collection] should implement the [map] method |
20 * type and consequently the returned collection's | 17 * to return a collection of the same general type as themselves. |
21 * typeis Collection. | 18 * E.g., [List.map] should return a [List]. |
22 */ | 19 */ |
23 Collection map(f(E element)); | 20 Collection map(f(E element)); |
24 | 21 |
25 /** | 22 /** |
| 23 * Returns a collection with the elements of this collection |
| 24 * that satisfy the predicate [f]. |
| 25 * |
| 26 * The returned collection should be of the same type as the collection |
| 27 * creating it. |
| 28 * |
| 29 * An element satisfies the predicate [f] if [:f(element):] |
| 30 * returns true. |
| 31 */ |
| 32 Collection<E> filter(bool f(E element)); |
| 33 |
| 34 /** |
| 35 * Returns the number of elements in this collection. |
| 36 */ |
| 37 int get length; |
| 38 |
| 39 /** |
| 40 * Check whether the collection contains an element equal to [element]. |
| 41 */ |
| 42 bool contains(E element) { |
| 43 for (E e in this) { |
| 44 if (e == element) return true; |
| 45 } |
| 46 return false; |
| 47 } |
| 48 |
| 49 /** |
| 50 * Applies the function [f] to each element of this collection. |
| 51 */ |
| 52 void forEach(void f(E element)) { |
| 53 for (E element in this) f(element); |
| 54 } |
| 55 |
| 56 /** |
26 * Reduce a collection to a single value by iteratively combining each element | 57 * Reduce a collection to a single value by iteratively combining each element |
27 * of the collection with an existing value using the provided function. | 58 * of the collection with an existing value using the provided function. |
28 * Use [initialValue] as the initial value, and the function [combine] to | 59 * Use [initialValue] as the initial value, and the function [combine] to |
29 * create a new value from the previous one and an element. | 60 * create a new value from the previous one and an element. |
30 * | 61 * |
31 * Example of calculating the sum of a collection: | 62 * Example of calculating the sum of a collection: |
32 * | 63 * |
33 * collection.reduce(0, (prev, element) => prev + element); | 64 * collection.reduce(0, (prev, element) => prev + element); |
34 */ | 65 */ |
35 Dynamic reduce(Dynamic initialValue, | 66 Dynamic reduce(var initialValue, |
36 Dynamic combine(Dynamic previousValue, E element)); | 67 Dynamic combine(var previousValue, E element)) { |
37 | 68 var value = initialValue; |
38 /** | 69 for (E element in this) value = combine(value, element); |
39 * Returns a new collection with the elements of this collection | 70 return value; |
40 * that satisfy the predicate [f]. | 71 } |
41 * | |
42 * An element satisfies the predicate [f] if [:f(element):] | |
43 * returns true. | |
44 */ | |
45 Collection<E> filter(bool f(E element)); | |
46 | 72 |
47 /** | 73 /** |
48 * Returns true if every elements of this collection satisify the | 74 * Returns true if every elements of this collection satisify the |
49 * predicate [f]. Returns false otherwise. | 75 * predicate [f]. Returns false otherwise. |
50 */ | 76 */ |
51 bool every(bool f(E element)); | 77 bool every(bool f(E element)) { |
| 78 for (E element in this) { |
| 79 if (!f(element)) return false; |
| 80 } |
| 81 return true; |
| 82 } |
52 | 83 |
53 /** | 84 /** |
54 * Returns true if one element of this collection satisfies the | 85 * Returns true if one element of this collection satisfies the |
55 * predicate [f]. Returns false otherwise. | 86 * predicate [f]. Returns false otherwise. |
56 */ | 87 */ |
57 bool some(bool f(E element)); | 88 bool some(bool f(E element)) { |
| 89 for (E element in this) { |
| 90 if (f(element)) return true; |
| 91 } |
| 92 return false; |
| 93 } |
58 | 94 |
59 /** | 95 /** |
60 * Returns true if there is no element in this collection. | 96 * Returns true if there is no element in this collection. |
61 */ | 97 */ |
62 bool isEmpty(); | 98 bool isEmpty() => !iterator().hasNext(); |
63 | |
64 /** | |
65 * Returns the number of elements in this collection. | |
66 */ | |
67 int get length; | |
68 } | 99 } |
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