c++ - 如何在C++中打印 double

我正在从事C++练习。它要求我打印一个双，但是我尝试了以下代码几次，但是没有用。如何在以下代码中将GPA打印为双份？

#include <iostream>
#include <string>
using namespace std;
class gradeRecord{
private:
    string studentID;
    int units,gradepts;

public:
    gradeRecord(string stuID, int unts, int gpts){
        studentID = stuID;
        units = unts;
        gradepts = gpts;
    }

    double gpa(){
        int gpa;
        gpa = double(gradepts)/units;
        return gpa;
    }

    void updateGradeInfo(int unts,int gpts){
        units = unts;
        gradepts = gpts;
    }

    void writeGradeInfo(){
        cout << "Student:" << studentID << "\t"
            << "Unit:" << units << "\t"
            << "GradePts:" << gradepts << "\t"
            << "GPA:" << gpa();
    }

};

int main(){
    gradeRecord studObj("783-29-4716", 100, 345);
    studObj.writeGradeInfo();
    return 0;
}

结果出来的
“学生:783-92-4716单位:100级分数:345 GPA:3”

但是我期望的是
“学生:783-92-4716单位:100级分数:345 GPA:3.45”

如何获得GPA中的整数而不是GPA中的整数？

最佳答案

您可以通过包含一个操纵器轻松地完成操作。该操纵器在头<iomanip>中声明。并直接在std::cout上设置精度，并使用std::fixed格式说明符。

#include <iomanip>      // std::setprecision

  double gpa(){
  int gpa = 100*gradepts/units;
  std::cout << std::setprecision(3) << gpa/100.0 << '\n'; // you can set your precission to a value you plan to use
  std::cout << std::fixed;
    return gpa/100.0;
}

这应该使您的更正工作为:

#include <iostream>
#include <iomanip>      // std::setprecision


using namespace std;
class gradeRecord{
private:
    string studentID;
    int units,gradepts;

public:
    gradeRecord(string stuID, int unts, int gpts){
        studentID = stuID;
        units = unts;
        gradepts = gpts;
    }

      double gpa(){
      int gpa = 100*gradepts/units;
      std::cout << std::setprecision(3) << gpa/100.0 << '\n'; // you can set your precission to a value you plan to use
      std::cout << std::fixed;
        return gpa/100.0;
    }

    void updateGradeInfo(int unts,int gpts){
        units = unts;
        gradepts = gpts;
    }

    void writeGradeInfo(){
        cout << "Student:" << studentID << "\t"
            << "Unit:" << units << "\t"
            << "GradePts:" << gradepts << "\t"
            << "GPA:" << gpa();
    }

};

int main(){
    gradeRecord studObj("783-29-4716", 100, 345);
    studObj.writeGradeInfo();
    return 0;
}

我希望这能解决您的问题。

关于c++ - 如何在C++中打印 double ，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/48859063/