reading a file and finding high and low number

[JB2005]

It reads numbers from a file and then it is supposed to tell the user the highest and lowest number. Seems like all the info I can find is having the user type in numbers not read them from a file and I can't seem to figure out how to make it work for my use.
I did get it to find the highest number but the lowest seems to always be 0 or if I make the lowest number start as a '1' then the lowest turns into 48.
Any ideas?

 #include<iostream>
#include<fstream>
#include<cstdlib>

using namespace std;
/*
 the vareables
 */

 double highest, lowest, current, number;
 char s;

 int main() {

    ifstream instream;

    string s;       // makes a string named s
    cout << "Enter a file name: \n";    // takes in file name
    cin >> s;       // name of file
    instream.open(s.data());     // tells it what file to open and read off of
      if (instream.fail()) {
        cout << "Failed to open file! \n";
        exit(1);
    }

    while (instream >> current) {
        number = current;
        lowest = (number <= lowest)?number:lowest; // this doesn't seem to work
        highest = (number >= highest)?number:highest; /* This seems to work for
the highest number but when I convert it for the lowest it doesn't */

    }



    cout << "The lowest number is " << lowest << endl;
    cout << "The highest number is " << highest << endl;


    instream.close();
return 0;
 }

[JLBorges]

#include<iostream>
#include<fstream>

int main()
{
    std::string file_name ;
    std::cout << "Enter a file name: " ;
    std::cin >> file_name ;

    std::ifstream instream( file_name.c_str() ) ;
    if( instream.fail() )
    {
        std::cout << "Failed to open file! \n";
        return 1 ;
    }

    double current ;
    if( instream >> current ) // read the first number in the file
    {
         double lowest = current ;
         double highest = current ;

         while( instream >> current )
         {
             if( current < lowest ) lowest = current ;
             else if( current > highest ) highest = current ;
         }

         std::cout << "The lowest number is " << lowest << '\n'
                   << "The highest number is " << highest << '\n' ;
    }

    else // could not read the first number
    {
        std::cout << "Failed to read any number from file! \n";
        return 1 ;
    }
}

[JB2005]

Thank you very much!
So it needs to pull a number to give the lowest and highest a number to start with?

[JLBorges]

> So it needs to pull a number to give the lowest and highest a number to start with?

Any variable has to be initialized before it can be used.

An alternative would be to intialize lowest with the largest value that a number can have,
and highest with the smallest value that a number can have.

double lowest = std::numeric_limits<double>::max() ; 
double highest = std::numeric_limits<double>::min() ; 

And then for every number in the file:

while( instream >> current )
{
    if( current < lowest ) lowest = current ;
    else if( current > highest ) highest = current ;
}