private function make_static_stream() { return Stream::make(10, 20, 30); }
public static function range($low = null, $high = null) { if ($low === null) { $low = 1; } if ($low == $high) { return Stream::make($low); } return new Stream($low, function () use($low, $high) { return Stream::range($low + 1, $high); }); }