import edu.neu.ccs.demeter.dj.*; Container = "(" List(Item) Capacity ")". Item : Container | Simple. List(S) ~ {S}. Simple = ItemName Weight . ItemName = Ident. Capacity = int. Weight = int. SummingVisitorDJ = int extends Visitor. CountingVisitorDJ = int extends Visitor. AverageVisitorDJ = CountingVisitorDJ SummingVisitorDJ float extends Visitor. ResultVisitorDJ = AverageVisitorDJ extends Visitor. Main = .