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i have to write a code that prompts user to enter a file name (containing 2 columns of integer). The program then reads that file, prints out the numbers set.

My txt file looks like this (the numbers are separated by space):

2 3

5 6

7 8

8 9

5 7

I thought it would be easy, but now i stuck. When i run the program, this line appeared

"There're no number in the file."

I set number to "int", so why can't the compiler read the number? But when i change the type to "string", the numbers did appear O_O , since i later need to calculate the average of those num also, i cannot use string.

Here is my code, I appreciate any help TT___TT

#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>

using namespace std;

int main()
{
    ifstream in_file;
    string filename;
    int number;
    int number1;
    cout << "In order to process, please enter the file name: ";
    cin >> filename;
    in_file.open(filename.c_str());
    if (!in_file.is_open())
    {
        cout << "Cannot open file" << endl;
    }
    else
    {
        in_file >> number;
        if (in_file.fail())
        {
            cout << "There're no number in the file." << endl;
        }
        while (in_file >> number >> number1)
        {
            cout  << number << " " << number1;
        }
    }

system("pause");
return 0;
}
Onion
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2 Answers2

1

Error in your logic:

    in_file >> number;   // Assigns 2 from first line to number
    if (in_file.fail())
    {
        cout << "There're no number in the file." << endl;
    }

    while (in_file >> number >> number1) // Assigns 3 to number from first line
                                         // and assigns 5 to number1 from second line
    {
        cout  << number << " " << number1;
    }

You need to use just:

    while (in_file >> number >> number1)
    {
        cout  << number << " " << number1;
    }

If you must print "There're no number in the file." in the output, you can use:

    bool gotSomeNumbers = false;
    while (in_file >> number >> number1)
    {
        cout  << number << " " << number1;
        gotSomeNumbers = true;
    }

    if (!gotSomeNumbers)
    {
         cout << "There're no number in the file." << endl;
    }
R Sahu
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0

The method you are using to find to know whether file is empty is not correct in following way :: As soon as this line gets executed

in_file >> number;

The compiler will treat first line as an integer as a whole , i.e. number = "2 3" in given scenario. now this is not a standard number because of space in between 2 and 3 and

in_file.fail() will return true.

The Correct way is to use "eof" function as follows : (I also added 1-2 lines to calculate average of these numbers as you mentioned)

Correct code

Reference : When will ofstream::open fail? Checking for an empty file in C++

Community
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Nitin Kotwar
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