(defun qsort (li &optional (compare #'>))
  (cond
    ((endp list) nil)
    (t (let*
	 ((pivot (first li))
	  (comp (lambda (x) (funcall compare pivot x)))
	  (left (remove-if comp (rest li)))
	  (right (remove-if-not comp (rest li))))
	 (append (qsort left compare) (cons pivot (qsort right compare)))))))