C++ File Question

This is a discussion on C++ File Question within the C++ Programming forums, part of the General Programming Boards category; In this program I have to write a program that has to take the inputs of a file and output ...

  1. #1
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    C++ File Question

    In this program I have to write a program that has to take the inputs of a file and output the average of the sum of numbers. My question is regarding how to average the numbers by adding the total numbers in the file. Would I have to do a count?

    Code:
    #include <fstream>#include <iostream>
    
    
    int main()
    {
        using namespace std;
        ifstream in_stream;
    
    
        cout << "I am going to take the numbers from the input file and average them." << endl;
    
    
        in_stream.open ( "input.dat" );
        if ( in_stream.fail( ) )
        {
            cout << "Please check if the file is saved properly. It could not open." << endl;
        }
    
    
        double first_number, next_number, total_numbers;
        int count = 0;
    
    
        in_stream >> first_number >> next_number >> total_numbers;
    
    
        first_number = 0;
        next_number = first_number + next_number;
    
    
        cout << "The average of the numbers is ";
    
    
        cout << ( first_number + next_number ) / total_numbers << endl;
        in_stream.close ();
    
    
        cout << "The program will now close." << endl;
    
    
    }

  2. #2
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    Not sure what you mean? Do you mean how to calculate the average? Then the answer is to add up all numbers and devide it by the number of numbers. F.ex.: The average og 4,5,6 = (4+5+6)/3.

    Other than that, it'd depend on how the file is formatted.

  3. #3
    Programming Wraith GReaper's Avatar
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    You need a loop to keep reading numbers until there's nothing else to read. Since for the average you need the sum and the amount, in each iteration add the retrieved number to a sum buffer and increment a counter. When the loop ends, you know what to do.
    Just a sample:
    Code:
    double temp, sum = 0;
    int i = 0;
    
    while (inputFile >> temp)
    {
        sum += temp;
        ++i;
    }
    Devoted my life to programming...

  4. #4
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    Ok, That makes sense, I was once again making it harder than it should have been. When dealing with files do you suggest I only declare one variable rather than declaring many as I did before.

  5. #5
    C++まいる!Cをこわせ! Elysia's Avatar
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    Many variables make a program needlessly hard to understand. Don't declare more than needed.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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