今天看到一个策略，里面有个ATR的参数Atr_Length，既没有声明，也没有赋值，策略可以正常运行，请教老师这是什么意思？ 这样写有问题吗？

Defs

//基础计算

Integer Common_Data_Calculation_Display(Numeric Atr_Length)

{

Lots = Max(1, Round(Fund / (O * ContractUnit * BigPointValue * MarginRatio / Rollover), 0));

Atr = AvgTrueRange(Atr_Length);

OneTick = MinMove * PriceScale * Rollover;

Commentary("CurrentBar = "+Text(CurrentBar));

Commentary("BarsSinceToday = "+Text(BarsSinceToday()));

Commentary("Lots = "+Text(Lots));

Commentary("OneTick = "+Text(OneTick));

Return 1;

}