请教一个假参数的问题

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; }