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 } from './iter';
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11 |
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12 | /**
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13 | * Create an iterator which repeats a value a number of times.
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14 | *
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15 | * @param value - The value to repeat.
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16 | *
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17 | * @param count - The number of times to repeat the value.
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18 | *
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19 | * @returns A new iterator which repeats the specified value.
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20 | *
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21 | * #### Example
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22 | * ```typescript
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23 | * import { repeat, toArray } from '@lumino/algorithm';
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24 | *
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25 | * let stream = repeat(7, 3);
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26 | *
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27 | * toArray(stream); // [7, 7, 7]
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28 | * ```
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29 | */
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30 | export function repeat<T>(value: T, count: number): IIterator<T> {
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31 | return new RepeatIterator<T>(value, count);
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32 | }
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33 |
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34 | /**
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35 | * Create an iterator which yields a value a single time.
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36 | *
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37 | * @param value - The value to wrap in an iterator.
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38 | *
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39 | * @returns A new iterator which yields the value a single time.
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40 | *
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41 | * #### Example
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42 | * ```typescript
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43 | * import { once, toArray } from '@lumino/algorithm';
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44 | *
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45 | * let stream = once(7);
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46 | *
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47 | * toArray(stream); // [7]
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48 | * ```
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49 | */
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50 | export function once<T>(value: T): IIterator<T> {
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51 | return new RepeatIterator<T>(value, 1);
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52 | }
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53 |
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54 | /**
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55 | * An iterator which repeats a value a specified number of times.
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56 | */
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57 | export class RepeatIterator<T> implements IIterator<T> {
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58 | /**
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59 | * Construct a new repeat iterator.
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60 | *
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61 | * @param value - The value to repeat.
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62 | *
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63 | * @param count - The number of times to repeat the value.
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64 | */
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65 | constructor(value: T, count: number) {
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66 | this._value = value;
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67 | this._count = count;
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68 | }
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69 |
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70 | /**
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71 | * Get an iterator over the object's values.
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72 | *
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73 | * @returns An iterator which yields the object's values.
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74 | */
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75 | iter(): IIterator<T> {
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76 | return this;
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77 | }
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78 |
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79 | /**
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80 | * Create an independent clone of the iterator.
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81 | *
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82 | * @returns A new independent clone of the iterator.
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83 | */
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84 | clone(): IIterator<T> {
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85 | return new RepeatIterator<T>(this._value, this._count);
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86 | }
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87 |
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88 | /**
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89 | * Get the next value from the iterator.
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90 | *
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91 | * @returns The next value from the iterator, or `undefined`.
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92 | */
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93 | next(): T | undefined {
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94 | if (this._count <= 0) {
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95 | return undefined;
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96 | }
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97 | this._count--;
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98 | return this._value;
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99 | }
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100 |
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101 | private _value: T;
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102 | private _count: number;
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103 | }
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