在Scheme中找到列表的最大值和最小值

Question

I need to find the max and min of a list and then add in a new list. This is my code so far:

(define alist '(18 39 57 -4 0)

(define (nMax alist)
  (if (null? (cdr alist))
      (car alist)
      (if (> (car alist) (nMax (cdr alist)))
          (car alist)
          (nMax (cdr alist)))))

(define (nMin alist)
  (if (null? (cdr alist))
      (car alist)
      (if (< (car alist) (nMin (cdr alist)))
          (car alist)
          (nMin (cdr alist)))))

and now I'm stuck. How can i add nMin + nMax in a new list? My output should be something like this:

'(57 -4)

Answer 1

Try this:

(define alist '(18 39 57 -4 0))

(define (max-min alist)
  (list (nMax alist)
        (nMin alist)))

(max-min alist)
> '(57 -4)

Answer 2

类似于(cons (nMax alist) (cons (nMin alist) '()))