SB>    typedef boost::variant< boost::shared_ptr<ControlA>, boost::shared_ptr<ControlB> > Type;
SB>    std::vector< Type > contrl_vec;
SB>    contrl_vec.push_back( boost::shared_ptr< ControlA >( new ControlA() ) );
SB>    contrl_vec.push_back( boost::shared_ptr< ControlB >( new ControlB() ) );
SB>