Float的問題

Question

所以，我遇到了使用float的問題。當我去編譯時，有一些特定的區域會告訴我一個錯誤：「不能顯式地將類型'double'轉換爲'float'。存在明確的轉換（你是否錯過了一隻貓？）問題是它只是在做它的三行代碼（涉及remainingChange％0.25，remainingChange％0.10和remainingChange％0.05）我假設這與小數和精度有關，但我似乎無法弄清楚。解決它的任何指向我的方向是正確的建議，將不勝感激謝謝

這裏是適用的代碼：

private void button1_Click(object sender, RoutedEventArgs e) 
    { 
     //Set up try catch for errors 
     try 
     { 
      //declare variables 
      float changeDue = 0; 
      float remainingChange = 0; 
      float purchaseAmount = 0; 
      float paymentAmount = 0; 

      //if statement to verify that the purchase amount is not empty 
      if (string.IsNullOrWhiteSpace(PurchaseAmount.Text)) 
      { 
       Error.Text = "The purhcase amount is empty"; 
       return; 
      } 

      //else-if statement to verify that the payment amount is not empty 
      else if (string.IsNullOrWhiteSpace(PaymentAmount.Text)) 
      { 
       Error.Text = "The submitted amount is empty"; 
       return; 
      } 

      //else-if statement to verify that the purchase and payment amounts are numeric 
      else if (!float.TryParse(PurchaseAmount.Text, out purchaseAmount)) 
      { 
       Error.Text = "The purchase amount will only take numbers"; 
       return; 
      } 

      else if (!float.TryParse(PaymentAmount.Text, out paymentAmount)) 
      { 
       Error.Text = "The submitted amount can only accept numbers"; 
       return; 
      } 

      //else-if statement to verify that the payment amount is greater than the purhcase amount 
      else if (purchaseAmount > paymentAmount) 
      { 
       Error.Text = "Submitted value can't be less than purchased value"; 
       return; 
      } 

      Error.Text = ""; 

      //Determine the change due and how it will be paid out, then write the values to the window 
      changeDue = paymentAmount - purchaseAmount; 

      remainingChange = changeDue % 100; 
      Hundreds.Text = ((changeDue/100) - (remainingChange/100)).ToString(); 

      Fifties.Text = ((remainingChange/50) - ((remainingChange % 50)/50)).ToString(); 
      remainingChange = remainingChange % 50; 

      Twenties.Text = ((remainingChange/20) - ((remainingChange % 20)/20)).ToString(); 
      remainingChange = remainingChange % 20; 

      Tens.Text = ((remainingChange/10) - ((remainingChange % 10)/10)).ToString(); 
      remainingChange = remainingChange % 10; 

      Fives.Text = ((remainingChange/5) - ((remainingChange % 5)/5)).ToString(); 
      remainingChange = remainingChange % 5; 

      Ones.Text = ((remainingChange/1) - ((remainingChange % 1)/1)).ToString(); 
      remainingChange = remainingChange % 1; 

      Quarters.Text = ((remainingChange/0.25) - ((remainingChange % 0.25)/0.25)).ToString(); 
      remainingChange = remainingChange % 0.25; 

      Dimes.Text = ((remainingChange/0.10) - ((remainingChange % 0.10)/0.10)).ToString(); 
      remainingChange = remainingChange % 0.10; 

      Nickels.Text = ((remainingChange/0.05) - ((remainingChange % 0.05)/0.05)).ToString(); 
      remainingChange = remainingChange % 0.05; 

      Pennies.Text = ((remainingChange/0.01) - ((remainingChange % 0.01)/0.01)).ToString(); 
     } 
     catch (Exception ex) 
     { 
      MessageBox.Show("An error has occurred. The error was: " + ex.Message, "Error sample", MessageBoxButton.OK, MessageBoxImage.Warning); 
     } 
    } 

Answer 1

當使用逐字數字，像0.05編譯器默認爲雙Ť YPE。由於％運算符的一個操作數是雙精度型，所以結果將作爲double來處理。 您可以使用f後綴對這些浮點數進行註釋，以便編譯器知道您希望將這些數字用作浮點數（System.Single）而不是缺省雙精度數。

試試這個：

remainingChange = remainingChange % 0.10f; //note the f suffix after the number 

不用通過這樣做，你失去了一些精確的說，但我收集這不是你的情況的問題。

Answer 2

如果其中一種浮點類型是double，則表達式的計算結果爲雙倍，這就是爲什麼您需要明確地轉換爲float。

remainingChange = (float)(remainingChange % 0.05);