Question

当我这样做时（访问医生超时）：

(define (visit-doctor name)
  (if (equal? name 'suppertime) (end-session)
  ((write-line (list 'hello name))
  (write-line '(what seems to be the trouble?))
  (doctor-driver-loop name initial-earlier-response))))

(define (end-session) (write-line '(the doctor is done seeing patients today)))

它给了我这个错误：

申请：不是程序; 期望一个可以应用于参数的过程给出：＃参数...：＃＃

Answer 1

您的问题是您尝试使用括号分组代码块 Scheme不会这样做。

您的else分支

((write-line (list 'hello name))
 (write-line '(what seems to be the trouble?))
 (doctor-driver-loop name initial-earlier-response))

这是三个元素的列表。

该列表的第一个元素应该是一个过程，然后应用于其他两个元素，但是当您评估(write-line (list 'hello name))时没有得到过程时，您会得到#<void>。

修复方法是使用begin对其进行排序：

(begin (write-line (list 'hello name))
       (write-line '(what seems to be the trouble?))
       (doctor-driver-loop name initial-earlier-response))

以下代码出错

1 个答案: