how to get the min & max of a file

Quick question, so I need to get the min and max of a file. The numbers in the file are:
3
5
8
4

and this is my code:

Code:

/* Write a program that will search a file of numbers
of type int and write the largest and the smallest numbers
to the screen. The file contains nothing but numbers of
type int separated by blanks or line breaks. If this is being
done as a class assignment, obtain the file name from your
instructor. */

#include <iostream>
#include <fstream>
#include <cstdlib>
#include <iomanip>
#include <stdlib.h>
using namespace std;

void make_neat(ifstream& messy_file, ofstream& neat_file,
int number_after_decimalpoint, int field_width);

int main ()
{
        using namespace std;
        ifstream in_stream;
        ofstream out_stream;

        in_stream.open("infile.txt");
        out_stream.open("outfile.txt");

        if (in_stream.fail( ))
        {
                cout << "Input file opening failed.\n";
                exit(1);
        }
        if (out_stream.fail( ))
        {
                cout << "Output file opening failed.\n";
                exit(1);
        }

        make_neat(in_stream, out_stream, 5, 1);

        int largest, smallest;
        in_stream >> largest >> smallest;
        out_stream << "largest = " 
                   << largest << endl;
        out_stream << "smallest = "
                   << smallest << endl;

        in_stream.close( );
        out_stream.close( );

        return 0;
}

void make_neat(ifstream& messy_file, ofstream& neat_file,
              int number_after_decimalpoint, int field_width)
{
        neat_file.precision(number_after_decimalpoint);

        cout.precision(number_after_decimalpoint);

        double next;
        while (messy_file >> next)
        {
                cout << setw(field_width) << next << endl;
                neat_file << setw(field_width) << next << endl;
        }
}

Right now it is just displaying all of the numbers from the file and I'm really kind of stuck... any help is MUCH appreciated!

You need a variable to remember the current max, and then as you read in each number check to see if it is higher. Do something similar with the min.