edward

 1(define-record-type Stack
 2  (%make-stack store)
 3  stack?
 4  (store stack-store stack-store-set!))
 5
 6(define (make-stack)
 7  (%make-stack '()))
 8
 9(define (stack-clear! stack)
10  (stack-store-set! stack '()))
11
12(define (stack-size stack)
13  (length (stack-store stack)))
14
15(define (stack-empty? stack)
16  (zero? (stack-size stack)))
17
18(define (stack-push stack elem)
19  (stack-store-set!
20    stack
21    (cons elem (stack-store stack))))
22
23(define (stack-pop stack)
24  (let* ((lst (stack-store stack))
25         (top (car lst)))
26    (stack-store-set! stack (cdr lst))
27    top))
28
29(define (stack-pops stack amount)
30  (if (<= amount 1)
31    (list (stack-pop stack))
32    (cons
33      (stack-pop stack)
34      (stack-pops stack (dec amount)))))