Question

Ok so basically I have this text file with numbers and letters that’s supposed to represent the vertices of a polygon. This part isn’t important because I’m having trouble parsing from the file into an int. So far the function looks like:

    void parseModel(void)
{
    int num_vertices, num_faces;
    char data[255];
    ifstream ifs("rect-skinny.d");
    ifs.getline(data, 255);
    istrstream ins(data);
    ins >> num_vertices;
    cout << num_vertices << endl;
    ifs.close();
}

I’ve tried many different methods that all gave me different but incorrect answers. This one outputs the number -858993460 for some reason. Other times it would just output closed brackets when I would try to print data separately. I can’t figure out what I’m doing wrong since this seems like it should work. The input file is:

 data    8    6
 -0.5   1.0   0.3
 0.5   1.0   0.3
 0.5   -1.0   0.3
 -0.5   -1.0   0.3
 -0.5   1.0   -0.3
 0.5   1.0   -0.3
 0.5   -1.0   -0.3
 -0.5   -1.0   -0.3
   4   1   2   3   4
   4   1   5   6   2
   4   2   6   7   3
   4   5   8   7   6
   4   1   4   8   5
   4   3   7   8   4

Basically all I’m trying to do right now is get the first line and put those numbers int it into num_vertices and num_faces, respectively.

Answer 1

After you read the text string “data” it will contain “data 8 6“.

The line ins >> num_vertices; will try to read an integer, but will find “data 8 6” and so will fail. Try something like this:

void parseModel(void)
{
    int num_vertices, num_faces;
    char data[255];
    std::ifstream ifs("rect-skinny.d");
    ifs.getline(data, 255);       // data contains "data    8    6"
    std::istrstream ins(data);    // ins  contains "data    8    6"
    ins.ignore(4, ' ');           // ins  contains "    8    6"
    ins >> num_vertices;
    std::cout << num_vertices << endl;
    ifs.close();
}