Question

I have 2 questions:
1. How do I make it so that if a certain file isn't entered, it wont proceed?
2. My numbers wont show the decimal points and I'm not understanding why, I used setprecision

    #include <iostream>
    #include <fstream>
    #include <string>
    #include <iomanip> 
    using namespace std;
    int main()
    {
        ifstream inFile;
        ofstream outFile;
        string file;
        int Bailey , 
            Harrison, 
            Grant, 
            Peterson, 
            Hsu, 
            Bowles, 
            Anderson, 
            Nguyen, 
            Sharp, 
            Jones, 
            McMillan, 
            Gabriel;
        int m, f , cc, un;


        cout << "                  Welcome to Maggie's Student Survey!"; //Introduction
       cout << endl;
       cout << " Enter the file name you wish to open: " <<endl;// promts  the user to enter the file name they want to open
        getline(cin, file);
        inFile.open(file);
        outFile.open(file);
        cout << " The Student's Genders, Colleges, and Scores:" << endl;
        cout << "\n Bailey           M CC 68"
            "\n Harrison         F CC 71"
            "\n Grant            M UN 75"
            "\n Peterson         F UN 69"
            "\n Hsu              M UN 79"
            "\n Bowles           M CC 75"
            "\n Anderson         F UN 64"
            "\n Nguyen           F CC 68"
            "\n Sharp            F CC 75"
            "\n Jones            M UN 75"
            "\n McMillan         F UN 80"
            "\n Gabriel          F UN 62 " << endl; //the data file so the       user can see what they opened
        m = (75 + 79 + 75 + 75) / 4; // average will be 76
        f = (71 + 69 + 64 + 68 + 75 + 80 + 62) / 7; //average will be 69.85
        cc = (71 + 75 + 68 + 75) / 4; //average will be 72.25
        un = (75 + 69 + 79 + 64 + 75 + 80 + 62) / 7; // average will be 72
        cout << " Total Males Average Scores: " << std::setprecision(2) << m  << endl;
        cout << " Total Females Average Scores: " << std::setprecision(2) << f << endl;
        cout << " Total Community College Average Scores " << std::setprecision(2) << cc << endl;
        cout << " Total University Average Scores: " << std::setprecision(2) << un    << endl;

        system("pause");

Answer 1

关于你的第二个问题，我提出了一个解决方案，首先你需要声明m，f，cc，un为双打，而不是整数。然后尝试将其他数字存储为其他变量。例如对于cc：

 #include <iostream>
 #include <iomanip> 


int main()
{    
    double a, b, c, d; // or ints, here it doesn't matter
    a = 71;
    b = 75;
    c = 68;
    d = 75;
    double cc = (a + b + c + d) / 4; //average will be 72.25
    std::cout << " Total Community College Average Scores " << std::setprecision(4) << cc << '\n';
    system("pause");
}

如果你这样做，精度可以工作。我将其设置为4以显示您的号码，2是不够的。

其他解决方案（可能更容易）：

 #include <iostream>
 #include <iomanip> 


int main()
{   
    double p;
    p = 71 + 75 + 68 + 75;
    double cc = p / 4; //average will be 72.25
    std::cout << " Total Community College Average Scores " << std::setprecision(4) << cc << '\n';
    system("pause");
}

Answer 2

falco的答案解决了您需要如何将平均变量更改为doubles。另外，我将除以4.0而不是4，以使浮点除法更明确。否则，您最终可能会执行整数除法并获得预期结果。

如果文件不存在，以下示例应该让您开始使程序不继续。我假设你的意思是“如果没有输入某个文件”。

    std::cout << "Enter the file name you wish to open: " << std::endl;
    std::getline( std::cin, filename );

    std::ifstream inFile( filename, std::ios::in );
    if ( !inFile )
    {
        // return if the file couldn't be opened
        return 1;
    }

    // write some stuff to the file

Setprecision and file

2 个答案: