FengLi666

4.9

1

while 的实现你没有写完，一次就停了： ``` scheme (define (expand-predicate predicate i body) (if (predicate i) (cons 'begin body))) (define (while->combination exp) (expand-predicate (while-predicate exp) (while-variable exp) (while-body exp))) ``` 此外，for的实现我有疑问： ``` scheme (define...