//
// sumfile2.cpp
// CSC 215
// John Rogers
//
// This program reads a list of integers from a 
// file and outputs their sum.  Unlike sumfile.cpp,
// this program verifies that it has actually opened
// the file.
//

//
// iostream.h is needed to allow input from cin and output to cout.
//
#include <iostream.h>
//
// fstream.h is needed to allow the use of file stream objects, ie,
// objects from the classes ifstream and ofstream.
//
#include <fstream.h>
//
// stdlib.h is needed to allow the use of the exit() function.
//
#include <stdlib.h>

int main()
{
  int sum = 0, number;
  ifstream inputfile;
  
// 
// Connect the input file stream object inputfile
// to the file numbers.dat.  Exit the program if
// the open failed.
//
  inputfile.open("numbers.dat");
  if (inputfile.fail()) {
  	cout << "Unable to open the input file." << endl;
  	exit(1);
  }
  
// 
// Read the integers in inputfile, adding each
// to sum.
//
  while (inputfile >> number) {
  	sum += number;
  }
  
  cout << "The sum is " << sum << endl;

  inputfile.close();

  return 0;
}