Input from file & FOR loop

[evangogh]

I am a newbie working on a problem that will perform various mathematical functions. My problem is I would like to know how to read in values from a file using FOR loops. I need to read in the number of values followed by the sequence of values. (I've been playing around with this for over a week and just need some help to get the ball rolling.) Thanks in advance!

[cup]

Could you give an example of what your datafile looks like.

[jfaust]

Roughly (may be problems, but here's an idea)

#include <fstream>
using namespace std;

void processFile(string filename)
{
     ifstream f(filename);

     vector<double> values;

     int count;
     f >> count;
     for( int i = 0; i < count; ++i )
     {
          double val;
          f >> val;
          values.push_back(val);
     }
}

Jeff

[zdf]

Just an idea

#include <fstream>

using namespace std;

int main()
{
  ifstream is("input");

  if ( ! is )
    return 1; // error opening
  
  while ( is.good() )
  {
    int count;
    for ( is >> count; is.good() && count; count-- )
    {
      double d;
      is >> d;
      // do something creative here
    }
    if ( count )
      return 2; // error too few values
  }

	return 0;
}

The input file may look like this:

4 1.2 3.4 5.6 6.7
2
1.2
1.3

Regards,