//assume the following declarations

ifstream inStr;

inStr.open("myfile");

int howMany = 0;
int dataValue;

// code to read data values from a file and count howmany there are

// METHOD 1  -- using a pre-test loop with an priming read

    inStr >> dataValue;
    while (!inStr.eof()) {
       howMany++;
       inStr >> dataValue;
    }


// METHOD 2   -- using a post-test loop and an if statement
 
    do {
       inStr >> dataValue;
       if (!inStr.eof() howMany++;
    } while (!inStr.eof());


// METHOD 3   -- using an infinite loop and break

    while (true) {
       inStr >> dataValue;
       if (inStr.eof()) break; // exit on end of file
       howMany++;
    }

   
// METHOD 4   -- using the value returned by >>
//               this one is not exactly the same as the other three since
//               it will stop if invalid data is read not just on end of file

    while (inStr >> dataValue) howMany++;





//****************************************************************************
// function to ask user for a file name and attach to an ifstream
//
//  parameter usage : inStr -- exports the stream attached
//
//  Post-conditions -- inStr is attached to a file and is ready for extractions
//                  -- the cin stream is cleared of data 
//****************************************************************************
void openIn(ifstream& inStr) {

    string filename;
  
    cout << "Enter the name of the file -- ";

    while (true) {
        cin >> filename;
        inStr.open(filename.c_str());
        if (inStr) break;       // successful attachment
     
        // not successful
        clrStream();            // clear all characters from the cin stream
        cout << "Unable to open file " << filename << " Reenter filename -- ";
    }
    clrStream();            // clear to the end of the line
}