| 1 | import { AsyncIterableX } from './asynciterablex';
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| 2 | export class ScanAsyncIterable extends AsyncIterableX {
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| 3 | constructor(source, fn, seed) {
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| 4 | super();
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| 5 | this._source = source;
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| 6 | this._fn = fn;
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| 7 | this._hasSeed = seed.length === 1;
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| 8 | this._seed = seed[0];
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| 9 | }
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| 10 | async *[Symbol.asyncIterator]() {
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| 11 | let i = 0, hasValue = false, acc = this._seed;
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| 12 | for await (let item of this._source) {
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| 13 | if (hasValue || (hasValue = this._hasSeed)) {
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| 14 | acc = await this._fn(acc, item, i++);
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| 15 | yield acc;
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| 16 | }
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| 17 | else {
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| 18 | acc = item;
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| 19 | hasValue = true;
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| 20 | i++;
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| 21 | }
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| 22 | }
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| 23 | if (i === 1 && !this._hasSeed) {
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| 24 | yield acc;
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| 25 | }
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| 26 | }
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| 27 | }
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| 28 | export function scan(source, accumulator, ...seed) {
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| 29 | return new ScanAsyncIterable(source, accumulator, seed);
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| 30 | }
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| 31 |
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| 32 |
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