filefunc.cpp

// filefunc.cpp -- function with ostream & parameter
#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
void file_it(ostream & os, double fo, const double fe[], int n);
const int LIMIT=5;
int main(){
  ofstream fout;
  const char* fn="ep-data.txt";
  fout.open(fn);
  if(!fout.is_open()){
    cout<<"Can't open "<<fn<<". Bye\n";
    exit(EXIT_FAILURE);
  }
  double objective;
  cout<<"Enter the focal length of your "
      <<"telescope objective in mm: ";
  cin>>objective;
  double eps[LIMIT];
  cout<<"Enter the focal length, in mm, of "<<LIMIT<<" eyepieces:\n";
  for(int i=0; i<LIMIT; i++){
    cout<<"Eyepiece #"<<i+1<<": ";
    cin>>eps[i];
  }
  file_it(fout,objective,eps,LIMIT);
  file_it(cout,objective,eps,LIMIT);
  cout<<"Done\n";
  return 0;
}
void file_it(ostream & os, double fo, const double fe[], int n){
  ios_base::fmtflags initial;
  initial=os.setf(ios_base::fixed);
  os.precision(0);
  os<<"Focal length of objective: "<<fo<<" mm\n";
  os.setf(ios_base::showpoint);
  os.precision(1);
  os.width(12);
  os<<"f.1. eyepiece";
  os.width(15);
  os<<"magnification"<<endl;
  for(int i=0; i<n; i++){
    os.width(12);
    os<<fe[i];
    os.width(15);
    os<<int(fo/fe[i]+0.5)<<endl;
  }
  os.setf(initial);
}