为什么输出不同于我预期的代码？ [英] why output is different from the code I expected?

问题描述

我运行此代码，但输出与我预期的不同。
输出：

  c = 1324 
v = 1324.99 
  

我预计输出应该是 v 的1324.987。为什么 v 中的数据与输出不同？

我在windows 8 32上使用代码lite

  #include< iostream> 
 using namespace std; 
 int main（）
 {
 double v = 1324.987; 
 int n; 
 n = int（v）; 
 cout<< c =<< n<< endl; 
 cout<< v =<< v<< endl; 
 return 0; 
} 
  

解决方案

cout 为6，因此只显示6个小数位。数字四舍五入到最接近的值，这就是为什么你看到1324.99。您需要设置更高的精度才能查看更正确的值

但是，设置精度太高可能会打印出大量的垃圾数字，因为二进制浮点类型不能精确存储所有十进制浮点值。 p>

I run this code but the output was different from what I expected. The output:

c = 1324
v = 1324.99

I expected that the output should be 1324.987 for v. Why is the data in v different from output?

I'm using code lite on windows 8 32.

#include <iostream>
using namespace std;
int main()
{
    double v = 1324.987;
    int n;
    n = int (v);
    cout << "c = " << n << endl;
    cout << "v = " << v << endl;
    return 0;
}

解决方案

The default precision when printing with cout is 6, so only 6 decimal places will be displayed. The number is rounded to the nearest value, that's why you saw 1324.99. You need to set a higher precision to see the more "correct" value

However, setting the precision too high may print out a lot of garbage digits behind, because binary floating-point types cannot store all decimal floating-point values exactly.

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