C++ 如何使用cin读取double的整个值？
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How to read the entire value of a double using cin?
提问by freinn
long double m;
cout << "enter double: "; cin >> m;
cout << "m = " << m <<endl;
Input:
输入：
enter double: 1.546640625
输入双：1.546640625
Output:
输出：
m = 1.54664
米 = 1.54664
I have to convert into a binary with point, and when I read numbers like 2.359375000
我必须转换成带点的二进制，当我读到像 2.359375000 这样的数字时
Output:
输出：
m = 2.35938
米 = 2.35938
And it works, but I think the problem is the zero in 1.546640625
它有效，但我认为问题是 1.546640625 中的零
回答by Ivaylo Strandjev
You have read the whole value of the double. The problem is with the cout. It by default rounds the value to 6 digits after the decimal point.
您已经阅读了 double 的全部价值。问题出在 cout 上。默认情况下，它会将值四舍五入到小数点后的 6 位数字。
To set the precision cout uses, use setprecisionfrom <iomanip>:
要设置精度 cout 使用，请使用setprecisionfrom <iomanip>：
#include <iostream>
#include <iomanip>
using namespace std;
int main() {
long double d;
cin >> d;
cout << setprecision(10) << d << endl;
return 0;
}
