关于AI中的难度区分问题

sulfurliuz

这是一个自带战役里生产骑士的语段
(defrule
(difficulty == easy)
(unit-type-count-total knight-line < 1)
(can-train knight-line)
=>
(train knight-line)
(chat-local-to-self "knight")
)
(defrule
(difficulty <= moderate)
(unit-type-count-total knight-line < 4)
(can-train knight-line)
=>
(train knight-line)
(chat-local-to-self "knight")
)

第一段是简单（标准）的模式
第二段中等如果是小于等于的话，困难怎么办？