无法看到streamreader的问题 [英] Can't see the problem with streamreader

问题描述

我有一个流阅读器。它从包含两列的文件一次读取一行。第一个是整数值，第二个是double。我需要将它们分成二维阵列的单独侧面。 [int] [double]但是为了让事情变得更容易，2D数组保持为双倍 - 我只需要将数字分开以供日后使用。这就是我所拥有的：

I have a stream reader. It reads a line at a time from a file that contains two columns. The first is an integer value and the second is double. I need to seperate these into seperate sides of a 2 dimensional array. [ int ] [ double ] but to make things easier the 2D array is kept as double - I just need the numbers seperate for later on. This is what I have:

String^ File = "C:\\Users\\**** :) secret ****\\Documents\\Error.txt";
 StreamReader^ sr = File::OpenText(File);
 String^ str;
 bool Flip = true;
 int index = 0;

while ((str = sr->ReadLine()) != nullptr)
{
      // initiates a stringbuilder of 50 characters
      StringBuilder^ sb = gcnew StringBuilder("", 50); 
      for(int i=0; i < str->Length; i++)
    {// for each char in line of string str if it is a digit or decimal place then...
              if(Char::IsDigit( str[i]) || str[i] == '.')  
                      sb->Append( str[i] ); //  append to stringbuilder
              else  {
                    // otherwise convert the stringbuilder to a double number
                      double Num = Convert::ToDouble( sb ); 

                      Flip = !Flip; // decides which 'side' of 2d array to place in
                      if(!Flip) 2dArray[index, 0] = Num; // column 1 
                      else      2dArray[index, 1] = Num; // column 2
                       // remove all elements of string clear for rest of line read.
                      sb->Remove(0, sb->Length-1); 

                     
                    }
       }
       index++; // increments for array index
}

为了测试这个，我把数字放在for循环中以找到最大值和最小值。然后将它们发送到文本框以供显示。数据完全不变......表示此代码存在问题。这封装在try {} catch {}中。省略这个告诉我



Num =转换:: ToDouble（sb）;



isn'不允许。那么我还有什么选择呢？编译器没问题:(



非常感谢

To test this I''ve put the numbers through a for loop to find the max and minimum. These are then sent to textboxes for display. The data is completely unchanged...indicating there is a problem with this code. This was encapsulated inside a try {} catch{}. Omitting this showed me that the

Num = Convert::ToDouble( sb );

isn''t allowed. So what alternative do I have? No problem came up with the compiler :(

Many thanks

推荐答案

它不是很很好的代码，正如谢尔盖（SA）所说，但它是可以解决的。虽然SA是正确的，它是一个解决问题的坏方法，并且使用string.Split将是一个更整洁，更易读的解决方案，你遇到的问题是没有Convert.ToDouble重载，它接受一个StringBuilder，因此它作为一个Object传递，这可能会导致问题。使用ToString转换StringBuilder将解决这个问题。



但你应该使用Double.Parse，因为它只需要一个字符串，问题从一开始就更加明显！



还有另外一个问题但是你的方法是：除非你的行以非数字值结尾，否则你每次只能提取一个数字......：笑：

It''s not very nice code, as Sergey (SA) says, but it is fixable. While SA is right that it is a bad solution to the problem, and using string.Split would be a neater and more readable solution, the problem you have met is that there is no Convert.ToDouble overload that takes a StringBuilder so it is passed as a Object and that probably causes the problem. Using ToString to convert the StringBuilder would solve that problem.

But you should use Double.Parse instead, as it only takes a string and the problem would have been more obvious right from the start!

There is another problem with your approach though: unless your line ends with a non digit value, you will only extract one number each time...:laugh:

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