Reading .txt file

[iA5S216C]

I want to read a .txt file with multiple lines, like this example and output them
in the program (format: Name/Amount of numbers/Numbers):

Don     2   2 1
Julia   1   8
Robert  0
Maria   5   2 3 9 8 1
James   3   4 5 7

This is an example of my output using my code below:

Don     2   2 1
Julia   1   8
Robert  0
Maria   5   2 3 9 8 1
James   3   4 5 7
James   7   7 7 7 7 7 7 7

As you see it makes an extra line, using the last voornaam and cijfer, but why?
(Hopefully you can read through the dutch names)

void toon_teken_voor_teken ( ifstream& infilevar, ofstream& outfilevar )
{
    while ( infilevar )
    {
        char voornaam[7];
        infilevar >> voornaam;
        if ( voornaam )
        {
            cout << voornaam << "\t";
            outfilevar << voornaam << "\t";
            int cijfer, aantal_cijfers;
            infilevar >> cijfer;
            if ( cijfer == 0 )
            {
                cout << cijfer << endl;
            }
            else
            {
                if ( cijfer )
                {
                    aantal_cijfers = cijfer;
                    cout << aantal_cijfers << "\t";
                    outfilevar << aantal_cijfers << "\t";
                }
                for ( int teller = 0 ; teller <= (aantal_cijfers-1) ; teller++ )
                {
                    infilevar >> cijfer;
                    if ( cijfer )
                    {
                        cout << cijfer << " ";
                    }
                }
                cout << endl;
            }
        }
    }
}

int main ()
{
    cout << "Naam\tAantal\tGemiddeld" << endl;
    ifstream leesbestandsvar ("uitslagen.txt");
    ofstream nieuwbestandsvar ("nieuwuitslagen.txt");
    if ( leesbestandsvar )
    {
        toon_teken_voor_teken(leesbestandsvar, nieuwbestandsvar);
    }
    else
    {
        cout << "Leesbestand niet gevonden." << endl;
    }
    return 0;
}

[QWERTYman]

Put an empty line at the end of the .txt file. I haven't screwed around with C++ in a while, but I do remember that working at least.

[iA5S216C]

Well since this is for homework, I can't change the file. And it should be universal.

[QWERTYman]

Are you allowed to screw with the file through the program, like with input?

If so, you can just open an ifstream into the file with the ios_base::app option, and add a newline.

[iA5S216C]

No, probably not. Just to read it. But why doesnt my program work/does it make an extra line?

[Bazzy]

Move the while checking after getting input:

while ( true ) // condition moved
{
    char voornaam[7];

    if ( infilevar >> voornaam ) // here
        break; // exit the loop 

Otherwise the last execution of the loop will have an invalid infilevar

[iA5S216C]

Erm if I do that it will only run for the first line [Don 2 2 1].

[Bazzy]

Sorry, I forgot negation...
if ( !(infilevar >> voornaam) )

[iA5S216C]

Thanks mate, it works now.
But could you explain to me why?

[Bazzy]

Here is explained what the program does with a simplified version of your code:

1 2 3 4 5

while ( infilevar ) { infilevar >> voornaam; // ... }

while the stream infilevar is good execute the next block read input - it may fail do stuff - if input failed it gets executed anyway with odd results go back to 1

1 2 3 4 5 6

while ( true ) { if ( !(infilevar >> voornaam) ) break; // ... }

always execute the next block read input and check for failure - infilevar >> voornaam returns true if after input infilevar is good if checking failed exit from the while block do stuff go back to 1

The only difference between the two version is when you check the file state

[Duthomhas]

The problem is that you execute the entire contents of the loop without regard to the success or failure of attempting to read a voornaam from the file.

while (infilevar)  // Always true until after an attempt was made to read past EOF
{
  char firstname[7];
  infilevar >> firstname;  // Success or failure happens here

  // Now execute the rest of the loop even though the last input may have failed
  ...
}

The solution is to check for failure after reading but before the rest of the loop.

while (true)  // It doesn't matter here whether file is good or bad
{
  char firstname[7];

  // Try to get something from the file
  infilevar >> firstname;

  // Now it matters.
  // Check to see if the last attempt to read the file worked or not.
  // If not, then quit the loop.
  if (!infilevar) break;

  // Otherwise we continue with the rest of the loop
  ...
}

Bazzy's code just combined lines 6 and 11 into a single line:

  // Try to get something from the file. On failure, quit the loop.
  if (!(infilevar >> firstname)) break;

Hope this helps.

[edit] Oops! Sorry Bazzy. I'll go away. :-\

[iA5S216C]

Ah now I understand, thank you so much guys !