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// This module is browser compatible.
/** * Yields `r` length `Arrays` from the input `iterable`. Order of selection does * not matter and elements are chosen without replacement. * * ```ts * import { assertEquals } from "https://deno.land/std/testing/asserts.ts"; * import { combinations } from "https://deno.land/x/combinatorics/mod.ts"; * * const sequences = [...combinations([1, 2, 3, 4], 2)]; * * assertEquals(sequences, [ *   [1, 2], *   [1, 3], *   [1, 4], *   [2, 3], *   [2, 4], *   [3, 4], * ]); * ``` */export function* combinations<T>(  iterable: Iterable<T>,  r: number,): Generator<T[]> {  if (!Number.isInteger(r) || r < 0) {    throw RangeError("r must be a non-negative integer");  }  const pool = [...iterable];  const n = pool.length;  if (r > n) {    return;  }  const indices = new Uint32Array(r).map((_, index) => index);  yield pool.slice(0, r);  while (true) {    let i: number;    loop: {      for (i = r - 1; i >= 0; i--) {        if (indices[i] !== i + n - r) {          break loop;        }      }      return;    }    const result: T[] = Array(r);    for (let j = 0; j < i; j++) {      result[j] = pool[indices[j]];    }    let index = indices[i] += 1;    result[i] = pool[index];    for (let j = i + 1; j < r; j++) {      indices[j] = index += 1;      result[j] = pool[index];    }    yield result;  }}