(let* ((vector (sset-vector set))
(new-vector (make-array (if (zerop (length vector))
2
- (* (length vector) 2)))))
+ (* (length vector) 2))
+ :initial-element 0)))
(setf (sset-vector set) new-vector
(sset-free set) (length new-vector)
(sset-count set) 0)