IScriptExpression n_expr, FilterPassController filterPassController  )
IScriptExpression n_expr, FilterPassController filterPassController, IExecutorHelper helper  )
	public static NEvaluator newInstance( int operator, IScriptExpression op_expr, 			IScriptExpression n_expr, FilterPassController filterPassController  )	 	throws DataException	{		NEvaluator instance = null;		switch ( operator )		{			case IConditionalExpression.OP_TOP_N :				instance = new TopNEvaluator();				instance.n_percent = false;				break;			case IConditionalExpression.OP_TOP_PERCENT:				instance = new TopNEvaluator( );				instance.n_percent = true;				break;			case IConditionalExpression.OP_BOTTOM_N:				instance = new BottomNEvaluator( );				instance.n_percent = false;				break;			case IConditionalExpression.OP_BOTTOM_PERCENT:				instance = new BottomNEvaluator( );				instance.n_percent = true;				break;			default:				assert false;		// shouldn't get here				return null;		}				instance.op_expr = op_expr;		instance.n_expr = n_expr;		instance.filterPassController = filterPassController;		return instance;	}