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(void)
{
	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 lengths, in mm, of " << LIMIT << " eyepieces:\n";
	for (int i = 0; i < LIMIT; i++) {
		cout << "Eyepieces #" << i + i << ": ";
		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);		// save initial formatting state
	os.precision(0);
	os << "Focal length of objective: " << fo << " mm\n";
	os.setf(ios::showpoint);
	os.precision(1);
	os.width(12);
	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);
	}
}