scheme - 根据Scheme对列表进行分区

Question

我将如何创建一个分区函数，该函数需要一个数字和一个列表来将列表分区为较小的列表列表，其大小由数字给出这样

Partition 3 '(a b c d e f g h) -> '((a b c) (d e f) (g h)) and etc. using take and drop?

Answer 1

我会给你一些提示，这样你就可以自己找到答案。填空:

(define (partition n lst)
  (cond (<???>                      ; if the list is empty
         <???>)                     ; then return the empty list
        ((< <???> n)                ; if the lists' length is less than n
         <???>)                     ; return a list with lst as its only element
        (else                       ; otherwise
         (cons                      ; cons a list with the result of
          (<???> lst n)             ; grabbing the first n elements of lst with
          (<???> n                  ; the result of advancing the recursion and
                 (<???> lst n)))))) ; removing the first n elements of lst

显然，您必须按照问题描述中的要求在解决方案中的某个位置使用 take 和 drop。像这样测试您的解决方案:

(partition 3 '(a b c d e f g h))
=> '((a b c) (d e f) (g h))

(partition 3 '(a b c d e f g h i))
=>'((a b c) (d e f) (g h i))