Homework 2

due until 11.11., 8:30

You are already familiar with the cout command to print information to the console. Using a very similar command, you can redirect output directly to a file. For this you have to include the header file fstream and use an ofstream object, as is demonstrated by the listing below.

#include <iostream>
#include <fstream>

using namespace std;

int main(void)
{
 int a,b;
  
 // open file output.dat in order to write into it,
 // if the file already exists it will be overwritten
 ofstream out("output.dat");

 // Read input from console
 cout << "a = ";  cin >> a;      
 cout << "b = ";  cin >> b;

 cout << "a = " << a
      << "\t b = " << b << endl;   // Print to console
 out  << "a = " << a
      <<  "\t b = " << b << endl;  // Print to file

 out.close();

 return(0);

The formatting command \t prints a tabulator in the respective position. After executing this program a new file output.dat has been generated which contains all the things you stuffed into out using the << operator. The final command out.close() closes the file.

Your assignment is:

Modify the program logmap.cxx (which is the solution to the problem to Lab 2) in the following way:

• Instead of iterating and printing the results (to the console) at the same time, modify your code such that first all calculations are done and only subsequently the results are written to the file.
• To keep things simple, you just have to store iteration results for one r value at a time. In the current program we carry out Nskip steps before we print values, i.e. you will need Nend - Nskip entries in your array.
• Insert an extra loop (inside the loop which modifies r) to print the values stored in the array to the file.
• Make sure your file is closed properly, i.e. if your file-handle is called out then do not forget the line out.close()