stack set

(define display1 null)
(define (make-stack)
  (set! make-stack null))
(define (push n stack)
  (set! make-stack (append (list n) make-stack)))
(define (pop stack)
  (if (null? make-stack)
      "Stack empty!"
      (begin (set! display1 (car make-stack))
             (set! make-stack (cdr make-stack))
             display1)))