             case column_type::upper_bound:                 delta = m_r_solver.m_upper_bounds[j] - x;                 x = m_r_solver.m_upper_bounds[j];                 break;             case column_type::lower_bound:                 delta = m_r_solver.m_lower_bounds[j] - x;                 x = m_r_solver.m_lower_bounds[j];                 break;             case column_type::boxed:                 