将自然数转换为特定的基数并将其作为列表返回 [英] Transform a natural number to a specific base and return it as a list

问题描述

我想将函数的结果显示为列表而不是数字.我的结果是:

I want to show the result of my function as a list not as a number. My result is:

(define lst (list ))
(define (num->base n b)
  (if (zero? n)
     (append lst (list 0))
     (append lst (list (+ (* 10 (num->base (quotient n b) b)) (modulo n b))))))

出现下一个错误:

expected: number?
given: '(0)
argument position: 2nd
other arguments...:
10

推荐答案

我认为你必须重新考虑这个问题.将结果附加到全局变量绝对不是要走的路，让我们通过尾递归尝试不同的方法:

I think you have to rethink this problem. Appending results to a global variable is definitely not the way to go, let's try a different approach via tail recursion:

(define (num->base n b)
  (let loop ((n n) (acc '()))
    (if (< n b)
        (cons n acc)
        (loop (quotient n b)
              (cons (modulo n b) acc)))))

它按预期工作:

(num->base 12345 10)
=> '(1 2 3 4 5)

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