/**
* Takes a Seq of nested CollectionInterface, SplFixedArray, ArrayObject, ArrayIterator or array, and flattens
* it to a new Sequence
* Note: This is a slight deviation from the CollectionInterface spec, as flatten should always receive the
* the same type as itself. However this has been relaxed in this case, as we know that Seq is
* can always hold more than one value. Therefor converting single collections into a sequence is
* safe. As arrays are simply unwrapped Seq, we can also safely accept them for flattening.
* The outcome will always be the expected result, even with the relaxation of the rules:
* A de-nested Seq.
* We do not, however, know if a traversable will ever terminate, so we will not attempt to flatten those.
* If you have a nested sequence of transversable, iterate over them with ->flatMap using unary('iterator_to_array').
* @return Seq
*/
public function flatten()
{
$output = [];
foreach (I($this->hash) as $value) {
$array = __PRIVATE__::getArrayFrom($value);
$output[] = $array !== null ? $array : __CONTRACT__::contentIsA(FoldableInterface::class, $value);
}
return static::from(call_user_func_array('array_merge', $output));
}
/**
* @covers ::getArrayFrom
* @dataProvider getArrayFromProvider
*/
public function test_getArrayFrom($container, $expected)
{
self::assertSame($expected, internal::getArrayFrom($container));
}