References

summary
private	F * _product(pools: Array<Iterable>, i: number, n: number): IterableIterator Algorithm used by product to compute the product of one or more iterables from pools of symbols.
public	F * diagonal(A: Iterable, B: Iterable): IterableIterator Computes the product of two iterables in a way that allows for one or both of them to be infinite (in contrast with product).
public	F product(iterables: Iterable<Iterable>, repeat: number): IterableIterator Computes the product of the iterables given as first parameter.