// average5A.cpp
// Averages a sequence of integers input from a
// text file specified by the user.
// The numbers are read to end of file.
// Error state of file input stream is checked
// after file is opened and after all file inputs.
// This program uses a break statement in the loop,
// eliminating some repetition of code.

#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;

int main()
{
   // Announce purpose of program:
   cout << "This program averages a sequence of integers "
             << "in a file specified by you." << endl << endl;

   // Obtain filename from user input, as a C-string:
   char filename[21];   // C-string with up to 20 characters
   cout << "Enter filename: ";
   cin.getline(filename, 20);

   // Prepare to read from file:
   ifstream inputFile;
   inputFile.open(filename);

   // Check whether file exists and is readable:
   if ( !inputFile )
   {
      cout << "Can't read file "
               << filename << "." << endl;
      return 1;
   }  // if

   // Announce input:
   cout << "Now reading numbers from file "
         << filename << ":" << endl << endl;

   // Cumulative sum:
   int sum = 0;
   int count = 0;

   // Input the numbers to be averaged,
   // echo them, and add them all to
   // cumulative sum, until end of file:
   while ( true )
   {
      // Input a number:
      int number;
      inputFile >> number;

      // Exit loop when end of file is reached.
      // Avoid processing the non-number.
      if ( !inputFile )
         break;

      // Echo the most recently read number:
      cout << setw(15) << number << endl;

      // Add current number to cumulative sum:
      sum += number;

      // Increment count of numbers entered so far:
      count++;
   }  // while

   // Prevent division by zero:
   if ( count == 0 )
   {
      cout << "You didn't enter any numbers." << endl;
      return 1;
   }  // if

   // Compute the average and output the result:
   float average = (float) sum / count;
   cout << endl << "The average is: "
                << average << "." << endl;

   return 0;
}  // function main