UnionOp(int type,
    int size) 
{
            super(type);
            this.branches = new Vector(size);
}

  void addElement(Op op) 
{
            this.branches.addElement(op);
}

 Op elementAt(int index) 
{
            return (Op)this.branches.elementAt(index);
}

 int size() 
{
            return this.branches.size();
}