设置精度C

Question

所以，我试图在代码中设置输入值的精度。我希望这些值以后以两个小数点的精度打印，尽管我不确定如何。

这是我的代码。

#include <iostream>
#include <iomanip>
float uphill, wellD, waterLvl, buckVol;
float buckAscRate, downHill, volume;
float last;
float timeReq;
int scene = 1;


void timeRequired()
{
    std::setw(2);
    std::setprecision(2);
    std::cout << "Scenario " << scene << ":" << std::endl;
    std::cout << "up hill" << "          " << uphill << " sec" << std::endl;
    std::cout << "well diamter" << "          " << wellD << " in" << std::endl;
    std::cout << "water level" << "          " << waterLvl << " in" << std::endl;
    std::cout << "bucket volume" << "          " << buckVol << " cu ft" << std::endl;
    std::cout << "bucket ascent rate" << "          " << buckAscRate << " in/sec" << std::endl;
    std::cout << "down hill" << "          " << downHill << " sec" << std::endl;
    std::cout << "required volume" << "          " << volume << " cu ft" << std::endl;
    timeReq = (uphill + downHill);
    std::cout << "TIME REQUIRED" << "          " << timeReq << " sec" << std::endl;
    std::cout << " " << std::endl;

}
void scenarioCONT()
{
    do
    {
        std::cin >> wellD;
        std::cin >> waterLvl;
        std::cin >> buckVol;
        std::cin >> buckAscRate;
        std::cin >> downHill;
        std::cin >> volume;
        std::cin >> last;
        if (uphill <= 1) uphill = 2;
        if (wellD <= 0) wellD = 1;
        if (waterLvl <= 0) waterLvl = 1;
        if (buckVol <= 0) buckVol = 1;
        if (buckAscRate <= 0) buckAscRate = 1;
        if (downHill <= 0) buckAscRate = 1;
        if (volume <= 0) volume = 1;
        if (last > 1)
        {
            uphill = last;
            scenarioCONT();
        }

    } while (last != 0);

}
void scenario()
{
    do
    {
        std::cin >> uphill;
        std::cin >> wellD;
        std::cin >> waterLvl;
        std::cin >> buckVol;
        std::cin >> buckAscRate;
        std::cin >> downHill;
        std::cin >> volume;
        std::cin >> last;
        if (uphill <= 1) uphill = 2;
        if (wellD <= 0) wellD = 1;
        if (waterLvl <= 0) waterLvl = 1;
        if (buckVol <= 0) buckVol = 1;
        if (buckAscRate <= 0) buckAscRate = 1;
        if (downHill <= 0) buckAscRate = 1;
        if (volume <= 0) volume = 1;
        if (last > 1)
        {
            timeRequired();
            uphill = last;
            scenarioCONT();
        }
            scene++;
            timeRequired();

    } while (last != 0);

}


int main()
{
    scenario();
    system("pause");
}

我被告知要使用ionmanip设置精度，尽管我不是100％的方法。有任何建议吗？

Answer 1

您可以使用std::setprecision函数。以下示例直接从http://www.cplusplus.com/reference/iomanip/setprecision/

取

  double f =3.14159;
  std::cout << std::setprecision(5) << f << 'n';
  std::cout << std::setprecision(9) << f << 'n';

Answer 2

如果要输出2个小数位数，则应将std::fixed与std::setprecision()一起使用。

。

在这里看看。

为了更轻松地理解，这是一个示例： cout << setprecision(2)<< 3.1415;输出3.1（总计2位数字）和

cout << setprecision(2)<<fixed<< 3.1415;输出3.14（浮点后2位数字）