如何在一个 defrule 中定义一个全局变量并在 CLIPS 的另一个 defrule 中使用它？答案

【问题标题】：How can I define a global variable in a defrule and use it in another defrule in CLIPS?如何在一个 defrule 中定义一个全局变量并在 CLIPS 的另一个 defrule 中使用它？
【发布时间】：2018-06-02 06:06:00
【问题描述】：

我在 CLIPS 中编写了这些代码，但它不起作用。它说“局部变量不能被 deffact 访问。”我还想在其他 defrules 中使用 number1 和 number2 的值。如何在规则中将这些变量定义为全局变量？

(deffunction calculation1
(?x ?y)
(+ ?x ?y))
(defrule rule1
=>
(printout t "What is the first number?")
(bind ?number1 (read))
(assert (number-1 ?number1))
(printout t "What is the second number?")
(bind ?number2 (read))
(assert (number-2 ?number2))
(bind ?theirsum (calculation1 ?number1 ?number2))
(printout t "The sum is " ?theirsum crlf))
(deffacts data
(first num1 ?number1
second num2 ?number2))

【问题讨论】：

标签： global-variables clips

【解决方案1】：

错误消息准确地说明了问题所在。我只能猜测，你想要完成什么。问题是，deffacts 仅在 (reset) 之后才被断言。因此，在（重置）之后，所有事实都将被删除，并且 deffacts 被断言。因此，在评估 deffacts 语句的那一刻，仍然不存在局部变量（另外：局部变量仅在它们定义的范围内可见：deffunction，defrule）。全局变量也不起作用，因为它们将在您调用（重置）的那一刻被设置回来。我想到的一个解决方案是 hack：见 Clips hack

您也可以使用 CLIPS 的 build 表达式：

         CLIPS (6.30 3/17/15)
CLIPS> (defrule rule1
=>
    (printout t "What is the first number?")
    (bind ?number1 (read))
    (assert (number-1 ?number1))
    (printout t "What is the second number?")
    (bind ?number2 (read))
    (assert (number-2 ?number2))
    (bind ?theirsum (+ ?number1 ?number2))
    (printout t "The sum is " ?theirsum crlf)
    (build (str-cat
        "(deffacts data (first num1 " ?number1 " second num2 " ?number2     "))"
        )
    )
)
CLIPS> (run)
What is the first number?1
What is the second number?2
The sum is 3
CLIPS> (get-deffacts-list)
(initial-fact data)
CLIPS> (reset)
CLIPS> (facts)
f-0     (initial-fact)
f-1     (first num1 1 second num2 2)
For a total of 2 facts.

或者您可以使用文件：

         CLIPS (6.30 3/17/15)

CLIPS> (defrule rule1   
=>
    (printout t "What is the first number?")
    (bind ?number1 (read))
    (assert (number-1 ?number1))
    (printout t "What is the second number?")
    (bind ?number2 (read))
    (assert (number-2 ?number2))
    (bind ?theirsum (+ ?number1 ?number2))
    (printout t "The sum is " ?theirsum crlf)
    (printout data
        "(deffacts data (first num1 " ?number1 " second num2 " ?number2 "))"
    crlf)
    (close data)    
)
CLIPS> (run)
What is the first number?1
What is the second number?2
The sum is 3
CLIPS> (load data.dat)
Defining deffacts: data
TRUE
CLIPS> (get-deffacts-list)
(initial-fact data)

【讨论】：

我建议，你打开另一个问题，因为它在概念上与你原来的问题无关。