Функция калькулятор

(define tc1 (list 1 '* 2.11 '/ 13 '- 3 '+ 2))
(define tc2 (list 3 '* 2.11))
(define tc3 (list 3 '/ 5))
(define tc4 (list 2 '- 33))
(define tc5 (list 2 '+ 1))
 
(define (calc sp)
;(let loop ((sp spisok) (n 0))
  (if (> (length sp) 2)
     (cond ((eq? (cadr sp) '+) (calc (cons (+ (car sp) (caddr sp)) (cdddr sp) )))
             ((eq? (cadr sp) '*) (calc (cons (* (car sp) (caddr sp)) (cdddr sp) )))
             ((eq? (cadr sp) '/) (if (zerop (caddr sp) 'DivByZero (calc (cons (/ (car sp) (caddr sp))) (cdddr sp) )))
             ((eq? (cadr sp) '-) (calc (cons (- (car sp) (caddr sp)) (cdddr sp) ))))
     sp))

(defun div (n m) #'(lambda () (/ n m)))
 
(defun try! (a b)
  (if (zerop a) 1 (funcall b)))
 
(try! 3 (div 1 2))
 
==> 1/2
 
(try! 0 (div 1 0))
 
==> 1
 
(try! 2 (div 1 0))
 
Divide: деление на нуль
==> ERRSTATE

(defun eDiv (x y &optional (r 'чушь))
  (try
      (/ x y)
   except
      r))
 
==> eDiv
 
(eDiv 6 7)
 
==> 6/7
 
(eDiv 6 0)
 
==> чушь