C++ cout输出小数位数

方法一：使用setiosflags

#include 
#include
#include 
#include


int main()
{
    std::cout << std::setiosflags(std::ios::fixed);
    double pi = 3.1415926535;
    std::cout << std::setprecision(10) << "pi = " << pi << " pi = " << pi 
        << " pi = " << std::setprecision(5) << pi < 
控制台输出：
 
pi = 3.1415926535 pi = 3.1415926535 pi = 3.14159