Simple ifstream function not reading full file?

[bryan177mcsc]

Hi :)
I am trying to make a program that reads inputs from different days, saves the dates and other info in a text file and then has the option of reading if needed. Everything is working okay so far, except for the fact that it only reads the first line, and then it stops. I don't know why.

  void reader()
  {
  ifstream comboReader("combo.txt");
  string line, num,temp ;
  stringstream td ;
  float dLine;
  float total = 0.0;
  int iter = 0,iter0 = 0;
  std::vector <float> hours(0);
  while(!comboReader.eof())
  {
    getline(comboReader,line); //take a line from file
    comboReader >> temp ; //split the line into two
    comboReader >> num ; 

    td << num ;  //load the second value into stringstream td
    td >> dLine ; //extract a float

    hours.push_back(dLine); //add the double to a vector
    iter++ ; //count iterations to make sure program is not overlooping
    td.clear(); //empty bit flags
    td.str(""); //empty contents of td stringstream object
    cout << line << endl; //print line? but it only prints the first line
  }
  comboReader.close();
  cout << "total items in vector: " << hours.size() << endl ; //check
  cout << "Iterations: " << iter << endl ; //check
  cout << "Test Item 3 Value: " << hours.at(2) << endl ; //check

}

Everything is working properly except for the last line in my while loop which is supposed to simply print out the file as it is.

[LB]

After line 12, you should never touch comboReader again, yet you do on the next two lines.

Never loop on eof() - it does not work as expected. Specifically, the eof flag is only set when you try to read after getting to the end of the file. Instead, loop on the input operation:

while(std::getline(comboReader, line))
{
    std::istringstream td (line);
    if(td >> temp >> num)
    {

[bryan177mcsc]

std::istringstream td (line);
    if(td >> temp >> num)
    {

I'm a bit confused about this, is istringstream supposed to replace stringstream?
Will I still be able to use 'num' as a float, because I need to add the values later.

[LB]

I intended for you to delete line 5 when I wrote that, but forgot to mention it.

And yes, all stream classes support all primitive data types.

[bryan177mcsc]

Okay, I deleted line 5 but now I seem to have a problem.

I tried doing hours.push_back(num);
and it's giving me an error because it thinks I'm trying to push a string. How would I be able to make num into a float to push it into the vector if I'm deleting line 5.

[bryan177mcsc]

This is my new edited code, but the Item 3 Test is failing, it should be giving me a value of 3.2

void reader()
{
  ifstream comboReader("combo.txt");
  string line, num,temp ;
  float dLine;
  float total = 0.0;
  int iter = 0,iter0 = 0;
  std::vector <float> hours(0);
  while(getline(comboReader,line))
  {
    cout << line << endl ;
    std::istringstream td (line);
    if(td >> temp >> num)
    {
    hours.push_back(num); //what to do here...
    iter++ ;
    }
  }
  comboReader.close();
  cout << "total items in vector: " << hours.size() << endl ;
  cout << "Iterations: " << iter << endl ;
  cout << "Test Item 3 Value: " << hours.at(2) << endl ;

}

[LB]

Line 4:

string line;
float num, temp;

What is dLine for? You never assign anything to it so when you use it on line 15 it has random garbage value.

[bryan177mcsc]

Thanks LB,

dLine was what I was using previously to change the second string into a float, I had no idea I could use istringstream instead. It works great now. :)

I have a question if you can, does istringstream automatically read out every word in a string? Because if not why does the if statement work?

[LB]

std::istringstream is a derived class of std::istream, and std::cin is also a derived class instance of std::istream. Anything you can do with std::cin, you can do with std::istringstream. The difference is that std::cin reads from standard input (e.g. the console) and std::istringstream reads from a string you supply it.

The same relationship exists for std::ostringstream and std::cout - they are both derived classes of std::ostream.

[bryan177mcsc]

Thanks for the explanation LB, don't understand much of it but I recently started, have yet to learn more about C++.

[LB]

The learning curve is steep, but after a certain point things start rapidly clicking into place ;)