Returns a subset of the current
ImmSet starting from a given key up to,
but not including, the element at the provided length from the starting
public function slice( int $start, int $len, ): ImmSet<Tv>;
$start is 0-based.
$len is 1-based. So
slice(0, 2) would return the
elements at key 0 and 1.
$start- The starting value in the current
ImmSetfor the returned
$len- The length of the returned
ImmSetthat is a proper subset of the current
$startup to but not including the element
$start + $len.
Set::slice for usage examples.