#include <fstream>
#include <iostream>
#include <cstdlib>
#include <cctype>
using namespace std;
 
void open_file(ifstream& fin);
//Precondition: The File Written.dat must exist
//Postcondition: opens that file
 
double calc_average(ifstream& fin);
//Precondition, file must be opened and linked
//Takes the average of a list of numbers
 
 
int main()
{
    double average;
    ifstream file_in;
 
    open_file(file_in);
    average=calc_average(file_in);
 
}
 
 
 
 
void open_file(ifstream& fin)
{
    fin.open("written.dat");
    if (fin.fail())
    {   
        cout<<"fin failed line 26";
        exit(1);
    }   
}
 
 
 
 
double calc_average(fin)
{
    double next, sum;
    int count=0;
 
    while (fin>>next)
    {   
        sum=next+sum;
        count++;
    }   
 
    return (sum/count);
}

int main()
{
		.
		.
		.
		.
		.
		.
 
		return 0;
}

double calc_average(fin)