CLIPS 编程需要解释

Question

1) 如果用户输入不是是/否，我需要一种方法来重复问题？

2) 我需要一种方法让 CLIPS 接受大小写字母。

我通过谷歌搜索找到了这个示例，但我不太确定它在某些行上是如何工作的。谁能向我解释这是如何工作的？或者有更好的方法来做我需要的两件事。

(deffunction ask-question (?question $?allowed-values)
   (printout t ?question)
   (bind ?answer (read))
   (if (lexemep ?answer) 
       then (bind ?answer (lowcase ?answer)))
   (while (not (member ?answer ?allowed-values)) do
      (printout t ?question)
      (bind ?answer (read))
      (if (lexemep ?answer) 
          then (bind ?answer (lowcase ?answer))))
   ?answer)

(deffunction yes-or-no-p (?question)
   (bind ?response (ask-question ?question yes no y n))
   (if (or (eq ?response yes) (eq ?response y))
       then yes 
       else no))

Answer 1

ask-question 函数的伪代码：

Print the question.
Get the answer.

If 
  The answer is a symbol or string
Then 
  Convert the answer to lower case.
End if

While the answer is not one of the allowed values

   Print the question.
   Get the answer.

   If 
     The answer is a symbol or string
   Then 
     Convert the answer to lower case.
   End if

End while

Return the answer.