c++ - 命名一个文本文件并让它显示使用函数的平均值

Question

我正在开发一个名为 Online GDB 的 C++ 编译器。我需要编写一个程序，要求用户输入文件名，然后读取该数据以计算平均值，然后显示数据。

#include <iostream>
#include <fstream>
#include <stdio.h>
#include <cstdlib>
#include <string>
#include <iomanip>
#include <fstream>
using namespace std;
// functions 
string getFileInfo();
double calculateMean (string fileName);

// main    
int main ()
{
string filename = getFileInfo(); // getting file name 
double mean = calculateMean( filename); // avg
cout << "The mean was" << endl;
return 0;
}
// function for getting file 
string getFileInfo() {
    string filename;
    ifstream inputFile; // varibles
    // asking user for the name
    cout << "Please enter a file name to read from: ";
    cin >> filename;

   inputFile.open(filename);
   // opening name and checking if its good.
   if (inputFile)
   {
       inputFile.close();
   }
   // if the file is not good 
   else
   {
    cout << "Error: Please enter a file name to read from: ";
    cin >> filename;
   }
    return 0;
}

// funtion for mean 
double calculateMean(string fileName) 
{
    ifstream infile;
    float num=0;
    float total = 0.0;
    int count = 0;
    infile.open(fileName);
    // While infile successfully extracted numbers from the stream
    while(infile >> num) {
        total += num;
        ++count;
    }
    // don't need the file anymore, close it
    infile.close();

    // give the average
   return total/count;
}

我找到平均值的部分工作正常，但我在文件命名方面遇到了问题。

它运行并询问我的名字，当我输入时它直接进入错误并再次输入然后它显示这个:

terminate called after throwing an instance of 'std::logic_error'
what(): basic_string::_S_construct null not valid 
Aborted. 

我以前从未见过这个，我已经尝试创建一个文件，如果我不这样做，那么什么也不会显示。

Answer 1

此代码完全有效

    #include <iostream>
    #include <fstream>
    #include <stdio.h>
    #include <cstdlib>
    #include <string>
    #include <iomanip>
    #include <fstream>
    using namespace std;
    //int calculatorMin(string fileName);
    //void displayInfo(double mean, int main);
    string getFileInfo();
    double calculateMean (string fileName);

    // main    
    int main ()
    {
    string filename = getFileInfo(); // getting file name 
    double mean = calculateMean( filename); // avg
    return 0;
    }
    // function for getting file 
    string getFileInfo() {
        string filename;
        ifstream inputFile;

        cout << "Please enter a file name to read from: ";
        cin >> filename;

       inputFile.open(filename);

       if (inputFile)
       {
           inputFile.close();
       }

       else
       {
        cout << "Error: Please enter a file name to read from: ";
        cin >> filename;
       }
        //if it opens then name is good and close file then return name
        //if it didn't open, ask for a new name.
        return filename;
    }

    // funtion for mean 
    double calculateMean(string fileName) 
    {
        ifstream infile;
        float num=0;
        float total = 0.0;
        int count = 0;
        infile.open(fileName);
        // While infile successfully extracted numbers from the stream
        while(infile >> num) {
            total += num;
            ++count;
        }
        // don't need the file anymore, close it
        infile.close();
           cout << "The mean was " << total/count << endl;
        // give the average
       return total/count;

    }