public override void Next()
{
iter1.Next();
if (iter1.Done())
{
iter1 = iter2;
iter2 = null;
}
}
public IterPair(Sym12TernaryTable table, Iter iter1, Iter iter2) : base(table)
{
Debug.Assert(!iter1.Done() & !iter2.Done());
this.iter1 = iter1;
this.iter2 = iter2;
}