PracticeDev/study_cpp/cpp_primer_source_code/Chapter 8/filefunct.cpp

62 lines
1.6 KiB
C++

//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 lengths, 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";
// cin.get();
// cin.get();
return 0;
}
void file_it(ostream & os, double fo, const double fe[],int n)
{
// save initial formatting state
ios_base::fmtflags initial;
initial = os.setf(ios_base::fixed, ios_base::floatfield);
std::streamsize sz = os.precision(0);
os << "Focal length of objective: " << fo << " mm\n";
os.precision(1);
os.width(12);
os << "f.l. 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;
}
// restore initial formatting state
os.setf(initial, ios_base::floatfield);
os.precision(sz);
}