比较剪辑中的nil

Question

如何在剪辑中与nil进行比较？
我试过了

(defrule update-time                                                        
    ?cur-time <- (current-time ?time)                                           
    (order (event-time ?new-time-o&:(neq ?new-time-o nil)))     

我也试过

(neq ?new-time-o "nil")

似乎没有任何效果，我没有激活。

Answer 1

您没有提供足够的信息来回答您的问题。给定适当的数据，此规则将激活：

CLIPS> (deftemplate order (slot event-time))
CLIPS> 
(defrule update-time                                                        
   ?cur-time <- (current-time ?time)                                           
   (order (event-time ?new-time-o&:(neq ?new-time-o nil)))    
   =>)
CLIPS> (assert (order (event-time (time))))
<Fact-1>
CLIPS> (assert (current-time (time)))
<Fact-2>
CLIPS> (agenda)
0      update-time: f-2,f-1
For a total of 1 activation.
CLIPS>