(deffacts dane
(lista -2 3 -7 9 11 -20 19 6 -1)
(suma 0)
)

(defrule sumowanie
?i<-(lista ?x $?reszta)
?ii<-(suma ?ile)
=>
(retract ?i ?ii)
(assert (lista $?reszta))
(assert (suma (+ ?ile ?x)))
)