C++ double类型转string类型后,怎么实现小数点后只显示一个数字

#include <iostream>

#include <sstream>

#include <iomanip>

  

template <class T>

std::string fmt(T in, int width = 0, int prec = 0) {

    std::ostringstream s;

    s << std::setw(width) << std::setprecision(prec) << in;

    return s.str();

}

  

int main(){

    std::string s = fmt(66.0 / 30.0, 2, 2);

    std::cout << s << "\n";

}