@SuppressWarnings("unchecked") void addBox(ValueBox vb){
  if (boxes instanceof List) {
    List<ValueBox> list=(List<ValueBox>)boxes;
    list.add(vb);
  }
 else   if (boxes instanceof ValueBox) {
    ValueBox ovb=(ValueBox)boxes;
    List<ValueBox> list=new ArrayList<ValueBox>();
    list.add(ovb);
    list.add(vb);
    boxes=list;
  }
 else {
    boxes=vb;
  }
}

@ SuppressWarnings ( "unchecked" ) void addBox ( ValueBox vb ) { if ( boxes instanceof List ) { List < ValueBox > list = ( List < ValueBox > ) boxes ; list . add ( vb ) ; } else if ( boxes instanceof ValueBox ) { ValueBox ovb = ( ValueBox ) boxes ; List < ValueBox > list = new ArrayList < ValueBox > ( ) ; list . add ( ovb ) ; list . add ( vb ) ; boxes = list ; } else { boxes = vb ; } }
adds a value box to this operand .
