public XIterator<E> row(int rowNum, XIterator<E> resum) {
		Link cur = head.next;
		int index = -1;
		if (resum != null && (resum instanceof LinkedRowMatrix.innerXiterator)) {
			innerXiterator xi = (innerXiterator) resum;
			cur = xi.cur;
			index = xi.index;
		}
		while ((cur != null) && (cur.val.row != rowNum)) {
			++index;
			cur = cur.next;
		}
		return new innerXiterator(cur, index, rowNum);
	}