(VAR x y z )
(RULES 
        top(left(car(x,y),car(old,z))) -> top(right(y,car(old,z)))
        top(left(car(x,car(old,y)),z)) -> top(right(car(old,y),z))
        top(right(x,car(y,car(old,z)))) -> top(left(x,car(old,z)))
        top(right(car(old,x),car(y,z))) -> top(left(car(old,x),z))
        top(left(bot,car(old,x))) -> top(right(bot,car(old,x)))
        top(right(car(old,x),bot)) -> top(left(car(old,x),bot))
        top(left(car(x,y),z)) ->= top(left(y,z))
        top(right(x,car(y,z))) ->= top(right(x,z))
        bot ->= car(new,bot)
)