Scheme：合并和排序功能

Question

I'm trying to write a function that merges and then sorts a list, but now I have two different functions; one that merges it and one that sorts it. So I'm trying to write another function, that calls either functions, so it can merge and sort a list at once in that function.

This is what I have:

;; this merges the list
(define (merge l1 l2)
  (cond ((null? l1) l2)
        ((null? l2) l1)
        ((< (car l1) (car l2)) (cons (car l1) (merge (cdr l1) l2)))
        (else (cons (car l2) (merge l1 (cdr l2))))))

;; this sorts the list
(define sort
  (lambda (lst)
    (if (null? lst)
        '()
        (insert (car lst)
                (sort (cdr lst))))))

(define insert
  (lambda (elt sorted-lst)
    (if (null? sorted-lst)
        (list elt)
        (if (<= elt (car sorted-lst))
            (cons elt sorted-lst)
            (cons (car sorted-lst)
                  (insert elt (cdr sorted-lst)))))))

Answer 1

You define your merge-sort like this:

(define (merge-sort l1 l2) (sort (merge l1 l2)))

Example:

> (merge-sort (list 8 3 7 4 9 2) (list 5 1 0 6 4))
(0 1 2 3 4 4 5 6 7 8 9)

Answer 2

为什么不使用已经为您写的书 :)