how to use _addSpecial command via c++ driver

gistfile1.cpp

BSONObjBuilder b;
b.append( "query", BSONObj() ); // append original BSON object of query
b.append( "$maxScan", 1 ); // append special parameter

auto_ptr<DBClientCursor> cursor = c.query( ns, Query(b.obj()) );

while( cursor->more() ){
    BSONObj p = cursor->next();
    cout << p.toString() << endl;
}

forget to add

DBClientConnection c;
c.connect("localhost");