read files

This is a discussion on read files within the C++ Programming forums, part of the General Programming Boards category; I'am having trouble reading files. can someone tell me whats wrong with this. Code: #include<iostream> #include<fstream> int main(void) { int ...

  1. #1
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    read files

    I'am having trouble reading files. can someone tell me whats wrong with this.

    Code:
    #include<iostream>
    #include<fstream>
                                                                                                     
    int main(void)
    {
       int i;
       int j;
       int num;
       int up[8] = {24,49,74,99,124,149,174,200};
       int low[8] = {0,25,50,75,100,125,150,175};
       int ans[8] = {0,0,0,0,0,0,0,0};
                                                                                                     
       ifstream infile;
       infile.open("scores.c");
                                                                                                     
       for(i = 0; i <= 26; i++)         // there are 26 scores to check
         infile >> num;
                                                                                                     
       for(j = 0; j < 8; j++)
         {
            if( num <= up[j] && num >= low[j])
              {
                 ans[j]++;
                 break;
              }
         }
       for(j = 0; j < 8; j++)
              cout << low[j] << " - " << up[j] << " = " << ans[j] <<endl;
                                                                                                     
       infile.close();
    }

  2. #2
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    can u say what is wrong with it, other than not accessing the std namespace for fstream, cout and endl it runs fine.

  3. #3
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    In the output I get only one file read instead of 26.

  4. #4
    Code Goddess Prelude's Avatar
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    9,796
    >ifstream infile;
    >infile.open("scores.c");
    I couldn't help but notice that you don't account for namespaces yet you still use current standard headers. This is sure to give you a slew of errors. Also, these two lines can be merged like so:
    Code:
    std::ifstream infile ( "scores.c" );
    >for(i = 0; i <= 26; i++) // there are 26 scores to check
    Then why are you looping 27 times? If you start at 0 and go until after 26, you'll go too far. Remember that the following is almost always a mistake:
    Code:
    for ( i = 0; i <= N; i++ )
    And should almost always be this:
    Code:
    for ( i = 0; i < N; i++)
    The same goes for any variation of the above two loops, if you start at 0 then you test for < N, if you start at 1 you test for <= N. But back to the loop, you read 26 scores (assuming you've fixed your loop) and throw away all but the last of them. Most likely this isn't what you wanted.

    >for(j = 0; j < 8; j++)
    I assume this loop checks some kind of score range with the number you read before. A comment here would be very nice.

    >cout << low[j] << " - " << up[j] << " = " << ans[j] <<endl;
    Both cout and endl are in the std namespace.

    >infile.close();
    Technically you don't need this as the destructor for ifstream closes the file for you.
    My best code is written with the delete key.

  5. #5
    Registered User
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    I'am using JED, a g++ complier in linux, for some reason it works without namespace.

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