ROOT::Math::RhoEtaPhiPointD is a typedef to ROOT::Math::PositionVector3D<ROOT::Math::CylindricalEta3D<double>,ROOT::Math::DefaultCoordinateSystemTag>

typedef ROOT::Math::PositionVector3D<ROOT::Math::CylindricalEta3D<double>,ROOT::Math::DefaultCoordinateSystemTag> | ROOT::Math::RhoEtaPhiPointD |