internal override BitSet Lastpos(int positions)
{
if (last == null)
{
if (contentType == Type.Sequence && !right.Nullable())
{
last = right.Lastpos(positions);
}
else if (contentType == Type.Choice || contentType == Type.Sequence)
{
last = (BitSet)left.Lastpos(positions).Clone();
last.Or(right.Lastpos(positions));
}
else // Type.Qmark, Type.Star, or Type.Plus
{
last = left.Lastpos(positions);
}
}
return(last);
}