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Help with File Reading loop

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Join Date: Feb 2005

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maizen

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Help with File Reading loop

Feb 28th, 2005

Okay, I'm trying to do my homework, but my code isn't doing what I want it to. What I'm trying to do is have the user enter a file name and then the program will output the number of words in the file. It works fine the first time through the loop, but when prompted again, the file never opens correctly. Here is my code:

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#include <iostream>
#include <fstream>
#include <cassert>
 
using namespace std;
 
int main()
{
    int      numberOfWords;
    string   fileName;
    string   wordString;
    ifstream infile;
 
    cout << "File to process (type quit to exit): ";
    cin  >> fileName;
 
    while(fileName != "quit")
    {
        infile.open(fileName.c_str());
 
        assert(infile);
 
        infile >> wordString;
 
        for(numberOfWords = 0; infile; numberOfWords++)
        {
            infile >> wordString;
        }
 
        infile.close();
 
        cout << fileName << " has " << numberOfWords
             << " words." << endl << endl;
 
        cout << "File to process (type quit to exit): ";
        cin  >> fileName;
    }
}
#include <iostream>
#include <fstream>
#include <cassert>

using namespace std;

int main()
{
    int      numberOfWords;
    string   fileName;
    string   wordString;
    ifstream infile;

    cout << "File to process (type quit to exit): ";
    cin  >> fileName;

    while(fileName != "quit")
    {
        infile.open(fileName.c_str());

        assert(infile);

        infile >> wordString;

        for(numberOfWords = 0; infile; numberOfWords++)
        {
            infile >> wordString;
        }

        infile.close();

        cout << fileName << " has " << numberOfWords
             << " words." << endl << endl;

        cout << "File to process (type quit to exit): ";
        cin  >> fileName;
    }
}

Last edited by alc6379; Mar 1st, 2005 at 11:22 am.

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Join Date: Feb 2005

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maizen

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Re: Help with File Reading loop

Feb 28th, 2005

I have six different files that all work the first time through the loop. I've tried re-ordering the loop stuff, but nothing seems to work. I then tried infile.close() but that didn't do anything. Please don't write the code for me... maybe a suggestion on what to do would be best. I really like this class. This is the first time I've run into something I cannot fix myself.
Thanks.

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maizen

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Re: Help with File Reading loop

Feb 28th, 2005

I tried inFile.clear(), too but that also did nothing to help my problem.

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Tight_Coder_Ex Tight_Coder_Ex is offline

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Re: Help with File Reading loop

Feb 28th, 2005

DISREGUARD, You are using iostream and I'm not sure how that works with strings.

You can't compare strings the way you do.

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while (strcmp (filename, "quit") != 0)
while (strcmp (filename, "quit") != 0)

I think that should solve your problem.

Last edited by Tight_Coder_Ex; Feb 28th, 2005 at 9:57 pm. Reason: Failed to notice you are using iostream

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Join Date: Feb 2005

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maizen

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Re: Help with File Reading loop

Feb 28th, 2005

what do you mean by "You can't compare strings the way you do."? I enter the loop just fine. I also got a couple errors when I tried replacing my code with yours. BTW, I haven't learned about comparing strings yet... I gues I have to figure out a different way.

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Narue

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Re: Help with File Reading loop

Feb 28th, 2005

>You can't compare strings the way you do.
Sure you can. The string class overloads the relational operators. Though <string> needs to be included.

>the file never opens correctly
Try this:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream>
#include <fstream>
#include <cassert>
#include <string>
 
using namespace std;
 
int main()
{
  int numberOfWords;
  string fileName;
  string wordString;
 
  cout << "File to process (type quit to exit): ";
  cin >> fileName;
 
  while(fileName != "quit")
  {
    ifstream infile(fileName.c_str());
 
    assert(infile);
 
    infile >> wordString;
 
    for(numberOfWords = 0; infile; numberOfWords++)
    {
      infile >> wordString;
    }
 
    cout << fileName << " has " << numberOfWords
      << " words." << endl << endl;
 
    cout << "File to process (type quit to exit): ";
    cin >> fileName;
  }
}
#include <iostream>
#include <fstream>
#include <cassert>
#include <string>

using namespace std;

int main()
{
  int numberOfWords;
  string fileName;
  string wordString;

  cout << "File to process (type quit to exit): ";
  cin >> fileName;

  while(fileName != "quit")
  {
    ifstream infile(fileName.c_str());

    assert(infile);

    infile >> wordString;

    for(numberOfWords = 0; infile; numberOfWords++)
    {
      infile >> wordString;
    }

    cout << fileName << " has " << numberOfWords
      << " words." << endl << endl;

    cout << "File to process (type quit to exit): ";
    cin >> fileName;
  }
}

>assert(infile);
No. assert is designed as a debugging tool, not as a run-time error handling mechanism. Failure to open a file is not considered a programming error, it's an input error in this case. So you should be using a conditional statement:

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if (!in) {
  cerr<<"Failure to open file"<<endl;
  // Terminate here or handle the error
}
if (!in) {
  cerr<<"Failure to open file"<<endl;
  // Terminate here or handle the error
}

I know it's subtle, but a program error and a programming error are two completely different things and need to be dealt with in different ways.

I'm here to prove you wrong.

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maizen

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Re: Help with File Reading loop

Feb 28th, 2005

I just read (http://www.eg.bucknell.edu/~cs204/Fa...++-strings.pdf) that you can use the comparisson opperators to compare strings and it returns a boolean value.

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maizen

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Re: Help with File Reading loop

Feb 28th, 2005

I treid putting #include <string> but it didn't change anything. The assert thing comes from my teacher. He wanted us to use that instead of an if statement. Don't ask me why. I think an if statement is more clear during the run time phase of a program, though an assert statement may look cleaner in the actual code. Any more suggestions?

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Narue

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Re: Help with File Reading loop

Feb 28th, 2005

>He wanted us to use that instead of an if statement.
Tell him I said he's a bad teacher.

>Any more suggestions?
...Well, if you bothered to read the code I gave you, you'll find that I changed more than just adding "#include <string>". :rolleyes: Try running the code.

I'm here to prove you wrong.