| 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 | /**
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| 11 | * Create an iterator of evenly spaced values.
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| 12 | *
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| 13 | * @param start - The starting value for the range, inclusive.
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| 14 | *
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| 15 | * @param stop - The stopping value for the range, exclusive.
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| 16 | *
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| 17 | * @param step - The distance between each value.
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| 18 | *
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| 19 | * @returns An iterator which produces evenly spaced values.
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| 20 | *
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| 21 | * #### Notes
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| 22 | * In the single argument form of `range(stop)`, `start` defaults to
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| 23 | * `0` and `step` defaults to `1`.
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| 24 | *
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| 25 | * In the two argument form of `range(start, stop)`, `step` defaults
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| 26 | * to `1`.
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| 27 | *
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| 28 | * #### Example
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| 29 | * ```typescript
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| 30 | * import { range } from '@lumino/algorithm';
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| 31 | *
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| 32 | * let stream = range(2, 4);
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| 33 | *
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| 34 | * Array.from(stream); // [2, 3]
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| 35 | * ```
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| 36 | */
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| 37 | export function* range(
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| 38 | start: number,
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| 39 | stop?: number,
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| 40 | step?: number
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| 41 | ): IterableIterator<number> {
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| 42 | if (stop === undefined) {
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| 43 | stop = start;
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| 44 | start = 0;
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| 45 | step = 1;
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| 46 | } else if (step === undefined) {
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| 47 | step = 1;
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| 48 | }
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| 49 | const length = Private.rangeLength(start, stop, step);
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| 50 | for (let index = 0; index < length; index++) {
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| 51 | yield start + step * index;
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| 52 | }
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| 53 | }
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| 54 |
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| 55 | /**
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| 56 | * The namespace for the module implementation details.
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| 57 | */
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| 58 | namespace Private {
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| 59 | /**
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| 60 | * Compute the effective length of a range.
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| 61 | *
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| 62 | * @param start - The starting value for the range, inclusive.
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| 63 | *
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| 64 | * @param stop - The stopping value for the range, exclusive.
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| 65 | *
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| 66 | * @param step - The distance between each value.
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| 67 | *
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| 68 | * @returns The number of steps need to traverse the range.
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| 69 | */
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| 70 | export function rangeLength(
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| 71 | start: number,
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| 72 | stop: number,
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| 73 | step: number
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| 74 | ): number {
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| 75 | if (step === 0) {
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| 76 | return Infinity;
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| 77 | }
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| 78 | if (start > stop && step > 0) {
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| 79 | return 0;
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| 80 | }
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| 81 | if (start < stop && step < 0) {
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| 82 | return 0;
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| 83 | }
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| 84 | return Math.ceil((stop - start) / step);
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| 85 | }
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| 86 | }
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