c++ - 如何在 C++ 中打印 double

Question

我正在做一个 C++ 练习。它需要我打印一个 double，但我已经尝试了几次以下代码，但没有用。如何在以下代码中将 GPA 打印为 double ？

#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;
}

它的结果是 "Student:783-92-4716 Units:100 GradePts:345 GPA:3"

但我期望的是 "Student:783-92-4716 Units:100 GradePts:345 GPA:3.45"

除了在 GPA 中获得整数，我怎样才能获得双倍？

Answer 1

Instead of getting a integer in the GPA, how can I get a double?

当你使用

    int gpa;
    gpa = double(gradepts)/units;

您正在截断 double。

如果你想保留至少两位小数，你可以使用:

double gpa(){
    int gpa = 100*gradepts/units;
    return gpa/100.0;
}