将数字转换为数字列表

Question

如何将数字转换为数字列表？

我目前在做:

;; (num->list 12345) -> '(1 2 3 4 5)
(define (num->list n)
  (local 
    ((define (num->list n)
       (map (lambda (c)
              (char->num c))
            (string->list (number->string n))))

    (define (char->num c)
      (- (char->integer c) 48)))

    (num->list n)))

但想知道是否有更好的方法.

Answer 1

以下是我在Racket中的表现:

(require srfi/1 srfi/26)
(define (digits->list num (base 10))
  (unfold-right zero? (cut remainder <> base) (cut quotient <> base) num))

这是unfold为此而设计的那种问题.:-D