import edu.neu.ccs.demeter.dj.*;
Container = "(" <contents> List(Item) <capacity> Capacity ")".
Item : Container | Simple. 
List(S) ~ {S}.
Simple = <name> ItemName <w> Weight .
ItemName = <i> Ident.
Capacity = <i> int.
Weight = <i> int.


SummingVisitorDJ = <total> int extends Visitor.
CountingVisitorDJ = <total> int extends Visitor.
AverageVisitorDJ = 
<cV> CountingVisitorDJ
<sV> SummingVisitorDJ
<current> float extends Visitor.
ResultVisitorDJ = <aV> AverageVisitorDJ extends Visitor.

Main = .