| 1 | // Copyright (c) Jupyter Development Team.
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| 2 | // Distributed under the terms of the Modified BSD License.
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| 3 | /*-----------------------------------------------------------------------------
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| 4 | | Copyright (c) 2014-2017, PhosphorJS Contributors
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| 5 | |
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| 6 | | Distributed under the terms of the BSD 3-Clause License.
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| 7 | |
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| 8 | | The full license is in the file LICENSE, distributed with this software.
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| 9 | |----------------------------------------------------------------------------*/
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| 10 | import { IIterator, iter, IterableOrArrayLike } from './iter';
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| 11 |
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| 12 | /**
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| 13 | * Chain together several iterables.
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| 14 | *
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| 15 | * @param objects - The iterable or array-like objects of interest.
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| 16 | *
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| 17 | * @returns An iterator which yields the values of the iterables
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| 18 | * in the order in which they are supplied.
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| 19 | *
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| 20 | * #### Example
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| 21 | * ```typescript
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| 22 | * import { chain, toArray } from '@lumino/algorithm';
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| 23 | *
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| 24 | * let data1 = [1, 2, 3];
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| 25 | * let data2 = [4, 5, 6];
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| 26 | *
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| 27 | * let stream = chain(data1, data2);
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| 28 | *
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| 29 | * toArray(stream); // [1, 2, 3, 4, 5, 6]
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| 30 | * ```
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| 31 | */
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| 32 | export function chain<T>(...objects: IterableOrArrayLike<T>[]): IIterator<T> {
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| 33 | return new ChainIterator<T>(iter(objects.map(iter)));
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| 34 | }
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| 35 |
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| 36 | /**
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| 37 | * An iterator which chains together several iterators.
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| 38 | */
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| 39 | export class ChainIterator<T> implements IIterator<T> {
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| 40 | /**
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| 41 | * Construct a new chain iterator.
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| 42 | *
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| 43 | * @param source - The iterator of iterators of interest.
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| 44 | */
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| 45 | constructor(source: IIterator<IIterator<T>>) {
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| 46 | this._source = source;
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| 47 | this._active = undefined;
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| 48 | }
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| 49 |
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| 50 | /**
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| 51 | * Get an iterator over the object's values.
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| 52 | *
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| 53 | * @returns An iterator which yields the object's values.
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| 54 | */
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| 55 | iter(): IIterator<T> {
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| 56 | return this;
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| 57 | }
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| 58 |
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| 59 | /**
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| 60 | * Create an independent clone of the iterator.
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| 61 | *
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| 62 | * @returns A new independent clone of the iterator.
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| 63 | */
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| 64 | clone(): IIterator<T> {
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| 65 | let result = new ChainIterator<T>(this._source.clone());
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| 66 | result._active = this._active && this._active.clone();
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| 67 | result._cloned = true;
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| 68 | this._cloned = true;
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| 69 | return result;
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| 70 | }
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| 71 |
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| 72 | /**
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| 73 | * Get the next value from the iterator.
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| 74 | *
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| 75 | * @returns The next value from the iterator, or `undefined`.
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| 76 | */
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| 77 | next(): T | undefined {
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| 78 | if (this._active === undefined) {
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| 79 | let active = this._source.next();
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| 80 | if (active === undefined) {
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| 81 | return undefined;
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| 82 | }
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| 83 | this._active = this._cloned ? active.clone() : active;
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| 84 | }
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| 85 | let value = this._active.next();
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| 86 | if (value !== undefined) {
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| 87 | return value;
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| 88 | }
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| 89 | this._active = undefined;
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| 90 | return this.next();
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| 91 | }
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| 92 |
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| 93 | private _source: IIterator<IIterator<T>>;
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| 94 | private _active: IIterator<T> | undefined;
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| 95 | private _cloned = false;
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| 96 | }
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