return function(rule)
    return {
        messages = {},
        apply = function(context)
            local child_context = context:new_child(rule)
            if child_context.mode == "affirmative" then
                child_context.mode = "negative"
            elseif child_context.mode == "negative" then
                child_context.mode = "affirmative"
            else
                child_context.mode = "negative"
            end
            child_context:apply_rule()
            child_context.result = (child_context.result == false)

            context.result = child_context.result
        end
    }
end