如何将此代码转换为 Racket/Scheme [英] How can I transform this code into Racket/ Scheme

问题描述

这是我想翻译成 Racket 的代码:

This is the code I want translated into Racket:

public static ArrayList<Integer> convert(int k, int n) {
        ArrayList<Integer> lst = new ArrayList<>();
        while (k / n != 0) {
            lst.add(k % n); 
            k = k/n;
        }
        lst.add(k % n);
        return lst; 
    }   

例如在 Racket 中，(convert 23 2) 应该返回十进制 23 的二进制，即 (list 1 0 1 1 1).

e.g. in Racket the (convert 23 2) should return the binary of the decimal 23, which is (list 1 0 1 1 1).

这是我目前得到的:

(define (convert k n)
  (cond 
    [(> (/ k n) 0) (list(modulo k n))]
    [else  0] 
))

它适用于列表的第一个元素.

It works for the first element of the list.

感谢您的帮助！

推荐答案

请注意 Java 中的 / 运算符执行整数除法，因此在 Racket 中您必须使用 quotient 以获得相同的效果.

Be aware that the / operator in Java performs integer division, so in Racket you'd have to use quotient to obtain the same effect.

这是一个使用命名的let来实现循环的好机会，因为结果列表需要反向累加.除此之外，解决方案非常简单:

This is a good opportunity to use a named let to implement the loop, as the result list needs to be accumulated in reverse. Other than that, the solution is pretty straightforward:

(define (convert k n)
  (let loop ((k k) (acc '()))
    (if (zero? (quotient k n))
        (cons (modulo k n) acc)
        (loop (quotient k n) (cons (modulo k n) acc)))))

例如:

(convert 23 2)
=> '(1 0 1 1 1)

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