Function permutations

permutations<TElement>(
source: Iterable<TElement>,
size?: number,
): IEnumerable<IEnumerable<TElement>>
Generates permutations from the distinct elements of the source iterable.
Type Parameters
- TElement
  Type of elements within the source iterable.
Parameters
- source: Iterable<TElement>
  The source iterable.
- Optionalsize: number
  Optional target length for each permutation. When omitted, permutations use all distinct elements of the source.
Returns IEnumerable<IEnumerable<TElement>>
A lazy sequence of permutations, each materialised as an enumerable.
Throws
Thrown when size is less than 1 or greater than the number of distinct elements.

Remarks
source is enumerated to collect distinct elements before permutations are produced. Expect combinatorial growth in the number of permutations.
Example
```
const numbers = [1, 2, 3];
const perms = permutations(numbers, 2);
console.log(perms.select(p => p.toArray()).toArray()); // [[1, 2], [1, 3], [2, 1], [2, 3], [3, 1], [3, 2]]
```
- Defined in src/enumerator/functions/permutations.ts:19