/**
* Returns a new Collection containing a - b.
* The cardinality of each
* element e in the returned Collection will be the cardinality of e
* in a minus the cardinality of e in b, or zero, whichever is greater.
*
* @param \AppserverIo\Collections\CollectionInterface $a The Collection to subtract from, must not be null
* @param \AppserverIo\Collections\CollectionInterface $b The Collection to subtract, must not be null
*
* @return void
*/
public static function subtract(CollectionInterface $a, CollectionInterface $b)
{
// initialize the array with the value to return that should be returned
$return = array();
// iterate over the Collection and check if the object exists in
// the second Collection
foreach ($a as $key => $element) {
// if the object does not exist in the second Collection add
// it to the return array
if ($b->exists($key)) {
$return[$key] = $element;
}
}
// clear all elements and add the subtracted
$a->clear();
$a->addAll($return);
}
