product method

Iterable<List<E>> product({ int repeat = 1, })

Returns an iterable over the cross product of this Iterable.

The resulting iterable is equivalent to nested for-loops. The rightmost elements advance on every iteration. This pattern creates a lexicographic ordering so that if the input’s iterables are sorted, the product is sorted as well.

For example, the product of ['x', 'y'] and [1, 2, 3] is created with

[['x', 'y'], [1, 2, 3]].product();

and results in an iterable with the following elements:

['x', 1]
['x', 2]
['x', 3]
['y', 1]
['y', 2]
['y', 3]

Implementation

Iterable<List<E>> product({int repeat = 1}) {
  checkNonZeroPositive(repeat, 'repeat');
  if (isEmpty || any((iterable) => iterable.isEmpty)) {
    return const [];
  } else {
    return productNotEmpty(
        map((iterable) => iterable.toList(growable: false))
            .toList(growable: false),
        repeat);
  }
}