这是我到目前为止所拥有的,但是由于有错误,我无法运行它,所以我不知道它是否有效,我试图创建自己的堆栈对象使用drracket中面向对象的编程,我使用调度方法调用了我的不同过程,如果它们被正确调用。例如,首先我会创建一个堆栈,然后我将弹出并弹出堆栈,也可以打印它。
(define (make-stack)
(define my-stack '())
(define (pop)
(define (pop-helper my-stack)
(let ((result (car my-stack))))
(set! my-stack (cdr my-stack))
result)
(pop-helper my-stack))
(define (push)
(define (push-helper x my-stack)
(set! my-stack (cons x my-stack)))
(push-helper x my-stack))
(define (empty?)
(define (empty-helper my-stack)
(if (null? my-stack) #t
#f))
(empty-helper my-stack))
(define (print)
(define (print-helper my-stack)
(if (empty?) '()
(print (cdr my-stack))))
(print-helper my-stack))
(define (dispatch method)
(cond
((eq? method 'pop) pop)
((eq? method 'push) push)
((eq? method 'print) print)
(else (lambda() (display "Unknown Request: ")(display method)(newline)))))
dispatch)
预先感谢!
您在两个过程中有几个语法错误,并且不得将堆栈作为参数传递,它会遮蔽my-stack
全局变量。这是解决方案:
(define (pop)
(let ((result (car my-stack))) ; `let` brackets were off
(set! my-stack (cdr my-stack))
result))
(define (push x) ; `x` parameter was missing
(set! my-stack (cons x my-stack)))