How to pass data file as an argument into a function in c++?

Question

With this code I can read a data file and put it in an array. But now I want to convert this code in a function having the file as an argument. Someone know how I can do that?

int main(int argc, char const *argv[]){

if (argc < 2)
{   
     cerr << "input the name of file\n"<< endl;
}   

string program_name = argv[0];
ifstream input(argv[1]);
vector<vector<double> > v;

if (input)
{
    string line; 
    int i = 0;
    while (getline(input, line))
    {
        if (line[0] != '#')
        {
            v.push_back(vector<double>());
            stringstream split(line);
            double value;
            while (split >> value)
            {
                v.back().push_back(value);
            }           
        }
    }
}

for (int i = 0; i < v.size(); i++) 
{    
         for (int j = 0; j < v[i].size(); j++) 
         cout << v[i][j] << '\t';    
         cout << endl;
}

Thomas Matthews · Accepted Answer · 2016-03-17 16:56:44Z

2

Something like this?

void my_function(const std::string& filename,
                 vector< vector<double> >& v)
{
 //...
}

Per your question, the function is receiving the name of the file as a string and the vector is passed as well.

Another alternative is to pass the file as a stream:

void somebody_function(std::istream& input_file,
                       vector< vector< double > >& v)
{
 //...
}

answered Mar 17, 2016 at 16:56

Thomas Matthews

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3 Comments

Thomas Matthews Over a year ago

@Fredifqh: If my answer is helpful, please click on the check mark. BTW, I'm not Louen.

Fredifqh Over a year ago

Hi Thomas, I modified the code. But the code is not working. Is the first time that I use this link. I want to show you the new code, but I don't know where I should put it.

Thomas Matthews Over a year ago

If the issue is different than the one you posted, post a new question. Before you post new code, use a debugger to find out where the code is not executing properly.

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