Help with error?

[ccwtree11]

The file that this code uses looks like this:
1 1
6 11
3 3
10 16
7 10
8 9
1 16
For some reason, it reports the last integer pair (1 16) twice. This is the output of that file:
Integer pair: 1 and 1
Number of primes: 0
1 has 1 divisor(s)

Integer pair: 6 and 11
Number of primes: 2
10 has 4 divisor(s)

Integer pair: 3 and 3
Number of primes: 1
3 has 2 divisor(s)

Integer pair: 10 and 1
Number of primes: 2
12 has 6 divisor(s)

Integer pair: 7 and 10
Number of primes: 1
10 has 4 divisor(s)

Integer pair: 8 and 9
Number of primes: 0
8 has 4 divisor(s)

Integer pair: 1 and 16
Number of primes: 6
12 has 6 divisor(s)

Integer pair: 1 and 16
Number of primes: 6
12 has 6 divisor(s)

// checkFile.h
// Cedar Wiseman
// COSC 2030, Section 11, Spring 2014
// Project01
// January 29, 2014
// reads in pairs of integers, loops on range of integers calculating number of primes and integer with greatest number of divisors
// excessive commenting is for my future reference

#ifndef CHECK_H_
#define CHECK_H_

#include <iostream>
#include <fstream> //used by doCalculation

#include "math.h"  // used by isPrime

using namespace std;

bool isPrime ( int num )  // doCalculation calls this, sending it a number for each interation of the for loop that goes from the 
{                         // first integer in the pair to the second
    if ( num <= 1 )
	{
        return false;  // 1 isn't prime
	}
    else if ( num == 2 )
	{
        return true;  // 2 is prime
	}
    else if  ( num % 2 == 0 )
	{
        return false;  // if divisible by 2, it's not a prime
	}
    else
    {
        bool prime = true;  // innocent until proven guilty
        int divisor = 3;  // after checking 1 and 2, 3 is the next potential divisor
        double num_d = static_cast<double>( num );  // converts the passed integer into a double   
        int upperLimit = static_cast<int>( sqrt(num_d) + 1 );  // if the divisor is greater than the square root of the number, the
															   // number is prime (converted back to integer because of future integer
        while ( divisor <= upperLimit )						   // arithmetic)
        {
            if ( num % divisor == 0 )
			{
                prime = false;  // means it's divisible by something
			}

            divisor += 2;  // only need to check if potential divisors are odd
        }

        return prime;
    }
}

void doCalculation ( istream & infile )
{
	while ( true )
	{
		int a, b, c = 0, primecount = 0, most_divisors = 0;  

		if ( infile.fail() )  // check for end of file before every read
		{
			break;
		}

		infile >> a >> b;  // taking in both integers in the pair
		for ( int i = a; i <= b; i++ )  // it's assumed that a<b
		{
			int divisors = 0;  // defined here because it must reset before each iteration
		
			if ( isPrime(i) )  // callins isPrime for current iteration
			{
				primecount++;  // increments if true
			}

			if ( i > 1 )  // this if else statement is necessary for situations where one of the integers is <2 because j=2
			{             // in the following loop
				for ( int j = 2; j <= i; j++ )
				{
					if ( i % j == 0 )
					{
						divisors++;  // remainder of 0 means it's a divisor
					}
				}
			}
			else
			{
				divisors = 0;  // necessary to get the correct output for cases such as the pair (1,1)
			}

			if ( divisors >= most_divisors )  // this is used for output of the most divisors
			{
				most_divisors = divisors;
				c = i;  // stores which integer has the most divisors
			}
		}
			
		cout << endl << "Integer pair: " << a << " and " << b << endl << "Number of primes: " << primecount << endl << c 
			<< " has " << most_divisors + 1 << " divisor(s)" << endl;
	}
}

#endif 

[long double main]

The problem is (probably) that the end-of-file flag doesn't get set until you actually try to read past the end. (That is, if your last input operation happens to just reach the end of the file, the eof flag won't get set -- only when you try to read more).
So, your very last input extraction fails and the variables remain at their previous values, which is why it gets printed a second time.

So instead of

if ( infile.fail() )  // check for end of file before every read
{
    break;
}

infile >> a >> b;  // taking in both integers in the pair 

Do this:

if (!(infile >> a >> b)) // Check that we could actually read something
{
    break;
}

[ccwtree11]

Thank you so much!