我为一个插槽定义了一个限制选项的类:
(defclass TARGET (is-a USER)
(slot uuid
(type STRING))
(slot function
(type SYMBOL)
(allowed-symbols a1 a2 b c d e f g))
)
(make-instance target of TARGET
(uuid "a123")
(function zzz)
)
我预计CLIPS会抱怨“zzz”(不允许),但事实并非如此。为什么呢?
祝你好运。 尼古拉
答案 0 :(得分:2)
约束检查是静态地(在解析期间)和动态地(在执行期间)完成的。默认情况下,仅启用静态约束检查。实例的插槽分配是在调用消息时动态完成的,因为在执行消息处理程序期间,非法值可能会被替换为合法值。
在下面的情况中,definstances在定义时不会生成错误,因为无效值可以在运行时替换,但是defrule确实会生成错误,因为对象模式直接获取槽的值而不使用消息合格。
CLIPS> (clear)
CLIPS>
(defclass TARGET (is-a USER)
(slot uuid
(type STRING))
(slot function
(type SYMBOL)
(allowed-symbols a1 a2 b c d e f g)))
CLIPS>
(definstances static
(target1 of TARGET (uuid "a123") (function zzz)))
CLIPS>
(defrule static
(object (is-a TARGET) (function zzz))
=>)
[CSTRNCHK1] A literal restriction value found in CE #1
does not match the allowed values for slot function.
ERROR:
(defrule MAIN::static
(object (is-a TARGET)
(function zzz))
=>)
CLIPS> (reset)
CLIPS>
(make-instance target2 of TARGET
(uuid "b456")
(function zzz))
[target2]
CLIPS>
如果启用动态约束检查,则在实际创建实例时,您会在执行期间看到错误:
CLIPS> (set-dynamic-constraint-checking TRUE)
FALSE
CLIPS>
(make-instance target3 of TARGET
(uuid "c789")
(function zzz))
[CSTRNCHK1] zzz for slot function of instance [target3] found in put-function primary in class TARGET
does not match the allowed values.
[PRCCODE4] Execution halted during the actions of message-handler put-function primary in class TARGET
FALSE
CLIPS> (reset)
[CSTRNCHK1] zzz for slot function of instance [target1] found in put-function primary in class TARGET
does not match the allowed values.
[PRCCODE4] Execution halted during the actions of message-handler put-function primary in class TARGET
CLIPS>