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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 | 1x 1x 1x 1x 3x 1x 3x 12x 4x 4x 12x 12x 3x 9x | import { Tuple } from "@benneq/object";
import { generate } from "@benneq/array";
/**
* Creates a {@link Function} that returns a {@link Tuple} of {@link Iterable}s
* with the given `length`, where each {@link Iterable} yields the same values
* as the source {@link Iterable}, in the same order.
*
* @example
* ```ts
* const iterable = [1, 2, 3];
* const [iterable1, iterable2] = tee(2)(iterable);
* console.log(iterable1); // 1, 2, 3
* console.log(iterable2); // 1, 2, 3
* ```
*
* @param length - the length of the {@link Tuple}
* @returns the tuple of {@link Iterable}s
*/
export const tee =
<N extends number>(length: N) =>
<T>(
iterable: Iterable<T>,
buffers = generate<IteratorResult<T>[]>(length, () => []),
iterator = iterable[Symbol.iterator]()
): Tuple<IterableIterator<T>, N> => {
return buffers.map(function* (buffer) {
while (true) {
// if the buffer is empty, fetch a new value from the source iterable
if (!buffer.length) {
const result = iterator.next();
for (const buffer of buffers) {
buffer.push(result);
}
}
// source iterable is done, no more values to come
if ((buffer[0] as IteratorResult<T>).done) {
return;
}
yield (buffer.shift() as IteratorResult<T>).value;
}
}) as Tuple<IterableIterator<T>, N>;
};
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