Function span

span<T>(
pred: (t: T) => boolean,
): (list: List.List<T>) => [List.List<T>, List.List<T>]

Splits the list into a tuple of the longest prefix satisfies pred and the rest. It is equivalent to [takeWhile(pred)(list), dropWhile(pred)(list)].

Type Parameters

Parameters

pred: (t: T) => boolean
The condition to split.

Returns (list: List.List<T>) => [List.List<T>, List.List<T>]

The tuple of split of the list.

Examples

Example

{
    const [left, right] = span((x: number) => x < 3)(
        fromArray([1, 2, 3, 4, 1, 2, 3, 4]),
    );
    expect(toArray(left)).toStrictEqual([1, 2]);
    expect(toArray(right)).toStrictEqual([3, 4, 1, 2, 3, 4]);
}
{
    const [left, right] = span((x: number) => x < 9)(fromArray([1, 2, 3]));
    expect(toArray(left)).toStrictEqual([1, 2, 3]);
    expect(toArray(right)).toStrictEqual([]);
}
{
    const [left, right] = span((x: number) => x < 0)(fromArray([1, 2, 3]));
    expect(toArray(left)).toStrictEqual([]);
    expect(toArray(right)).toStrictEqual([1, 2, 3]);
}