(deftemplate stage
(slot value ))

(deftemplate mains_light_on
(slot value))

(deftemplate boots
(slot value))

(deftemplate crashes
(slot value))

(defrule start
=>
(assert (stage (value 1)))
(printout t "Is the mains light on?")
(assert (mains_light_on (value (readline))))
(printout t "Does it boot?")
(assert (boots (value (readline))))
(printout t "Does it crash later?")
(assert (crashes (value (readline))))
)

(defrule idiot_check
(stage (value 1))
(mains_light_on (value "no"))
=>
(printout t "Your problem is that your computer isn't plugged in!" crlf)
)

(defrule try_reinstalling
(boots (value "yes"))
?cr <- (crashes (value "yes"))
?st <- (stage (value 1))
=>
(printout t "Try reinstalling the operating system" crlf)
(printout t "Now does it crash?")
(retract ?st ?cr)
(assert (crashes (value (readline))))
(assert (stage (value 2)))
)

(defrule dunno
(stage (value 2))
(crashes (value "yes"))
=>
(printout t "Take it to a specialist service centre" crlf))

(defrule watch_it
(stage (value 2))
(crashes (value "no"))
=>
(printout t "Let's hope you've fixed it. Keep an eye on it." crlf))

(reset)
(run)