public static CharacterSet union(CharacterSet x,CharacterSet y)
	{
		if(x instanceof OldCharacterSet && y instanceof OldCharacterSet)
		{
			return OldCharacterSet.union((OldCharacterSet) x,(OldCharacterSet) y);
		}
		else if(x instanceof NewCharacterSet && y instanceof NewCharacterSet)
		{
			return NewCharacterSet.union((NewCharacterSet) x,(NewCharacterSet) y);
		}
		else return null;
	}