(define (driver-loop)
  (display "Please divide two numbers as an s-exp")
  (newline)
  (let ((x (read)))
    (try (throw "cannot divide by zero")
     catch
     (lambda (exn)
       (if (= 0 (caddr x))
           (display exn)
           (eval x)))))
  (newline)
  (driver-loop))

(driver-loop)