剪辑 defrule 不起作用

Question

我有包含 url 本身和整数计数器的 url 的 deftemplate：

(deftemplate url_t
(slot counter
(type INTEGER)
(default 0))
(slot url
(type STRING)
(default "")))

我正在尝试定义规则以在计数器值 >0 时打印 url 字符串

(defrule print-url
    (url_t (counter ?counter) (url ?url))
    (test (> ?counter 0))
=>
(printout t "url is " ?url crlf)
)

但是当我尝试更改 url_t 的值时： (assert url_t (counter 2) (url "hello hello")) 不执行规则。我的错误在哪里？

Answer 1

如果您描述中的断言语句正是您输入的内容，那么这就是您的问题，因为语法无效。除此之外，您的 deftemplate 或 defrule 的语法没有任何问题：

CLIPS> (clear)
CLIPS> (unwatch all)
CLIPS> 
(deftemplate url_t
   (slot counter
      (type INTEGER)
      (default 0))
   (slot url
      (type STRING)
      (default "")))
CLIPS> 
(defrule print-url
   (url_t (counter ?counter) (url ?url))
   (test (> ?counter 0))
   =>
   (printout t "url is " ?url crlf))
CLIPS> (assert (url_t (counter 2) (url "hello hello")))
<Fact-1>
CLIPS> (facts)
f-0     (initial-fact)
f-1     (url_t (counter 2) (url "hello hello"))
For a total of 2 facts.
CLIPS> (agenda)
0      print-url: f-1
For a total of 1 activation.
CLIPS> (run)
url is hello hello
CLIPS> (modify 1 (counter 3) (url "goodbye goodbye"))
<Fact-2>
CLIPS> (agenda)
0      print-url: f-2
For a total of 1 activation.
CLIPS> (run 1)
url is goodbye goodbye
CLIPS> (modify 2 (counter 0) (url "won't fire"))
<Fact-3>
CLIPS> (agenda)
CLIPS>