[이주상]

사실 leaf-val 입력도 잘 모르겠습니다

[강동옥]

(is-leaf? (leaf 4))
> #t

(is-leaf? (node (list (leaf 'abc) (leaf 4))))
> #f

(leaf-val (leaf 4))
> 4
(leaf-val (leaf 'ab))
> ab

(define tr (node (list (leaf 'abc) (leaf 4))))
(nth-child tr 0)
> 나름대로 정의한 (leaf 'abc) 결과

[이주상]

(node (list (node (list (leaf 1))) (leaf 2)))

(define tr (node (list (node (list (leaf 1) (leaf 2))) (leaf 3))))
(nth-child tr 0)

의 경우 어떻게 출력해야하나요

[최민아]

leaf나 node를 나름대로의 방식으로 정의했을 것입니다.

(define tr (node (list (node (list (leaf 1) (leaf 2))) (leaf 3))))
(nth-child tr 0)

의 경우 (node (list (leaf 1) (leaf 2)))을 각자 정의한대로 리턴하면 됩니다.