为什么变量总是零

本文关键字：变量 为什么 | 更新日期: 2023-09-27 18:05:50

我发现了一件很奇怪的事情:

var PerformanceSingleList = TradePositionList//Compute the data for each stock everyday
            .SelectMany((o, idx) => o.Select(p =>
            {
                //default variable
                double CloseYesterday = TradePositionList.ElementAt(0).Where(q => q.Stock.Symbol == p.Stock.Symbol).Select(q => (double)q.Stock.Close).First();
                int PositionYesterday = TradePositionList.ElementAt(0).Where(q => q.Stock.Symbol == p.Stock.Symbol).Select(q => q.Position).First();
                int TradePositionToday = 0;
                if (idx != 0) //idx cann't be 0 otherwise, idx - 1 throw a error
                {
                    PositionYesterday = TradePositionList.ElementAt(idx - 1).Where(q => q.Stock.Symbol == p.Stock.Symbol).Select(q => q.Position).First(); 
                    CloseYesterday = TradePositionList.ElementAt(idx - 1).Where(q => q.Stock.Symbol == p.Stock.Symbol).Select(q => (double)q.Stock.Close).First();
                    TradePositionToday = TradePositionList.ElementAt(idx - 1).Where(q => q.Stock.Symbol == p.Stock.Symbol).Select(q => q.RealDesignTradeShare).First();                        
                }
                double Commission = Math.Abs(TradePositionToday) * (double)p.Stock.Close * C;

                return new
                {
                    p.Stock,
                    p.Position,
                    p.RealDesignPosition,
                    p.RealDesignTradeShare,
                    TradePositionToday,
                    Commission,
                    PLN = ((double)p.Stock.Close - CloseYesterday) * PositionYesterday + TradePositionToday * (double)p.Stock.Close - Math.Abs(TradePositionToday) * (double)p.Stock.Close * SA,
                    NAV = (double)p.Stock.Close * p.Position - Math.Abs(p.Position) * (double)p.Stock.Close * SA - Commission
                };
            }
               ).ToList()
            ).ToList();

但是，即使TradePositionToday不为零，PerformanceSingleList中所有的commission也为零。而且，当我使用我的小样本数据时，没有这个问题，只有当我使用真正的大数据时才会出现这个问题。

 [61]   { Stock = {{ Symbol = 1088 HK, Close = 12.860000000, Date = 3/7/2016 12:00:00 AM, Vol = 0.0490939300240106 }}, Position = -562, RealDesignPosition = 67, RealDesignTradeShare = 629, TradePositionToday = -562, Commission = 0, PLN = -7227.32, NAV = -7227.32 }    <Anonymous Type>
    Commission  0   double
    NAV -7227.32    double
    PLN -7227.32    double
    Position    -562    int
    RealDesignPosition  67  int
    RealDesignTradeShare    629 int
    Stock   { Symbol = "1088 HK", Close = 12.860000000, Date = {3/7/2016 12:00:00 AM}, Vol = 0.049093930024010565 } <Anonymous Type>
    TradePositionToday  -562    int

为什么变量总是零

不幸的是，const double C = 10/10000确实是0。10和10000都是整数，除法完成后，结果存储为int(普通类型)，然后转换为C类型的double。

如果您希望C不为零，则需要显式地告诉其中一个值为float/double类型，只需使用以下语句:

const double C = 10.0/10000;

或

const double C = ((double)10)/10000;
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