(define a 10)
(define b 1)
;; setvar nolonger works on undefined variables.
;; so setvar cannot be used in the loop.
(defun f (n)
(if (= n 0) 0
(progn
(define b 10)
(undefine 'b)
(f (- n 1)))))
(f 10000)
(define b 75)
(check (and (= a 10)
(= b 75)))
