Returning multiple variables in 1 function to main()

[noobie09]

I am trying to return 2 numbers from my function to main(). They are both read in from an input file but it is not working out.

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

ofstream outfile;
void heading(int);
int stuid(int,int);

int main()
{
    
    int x,y,h;
    
    
    heading(h);
    stuid(x,y);
    cout << x << endl;
    
    
    system("PAUSE");
    return 0;
}
void heading(int) // Table Heading
{
     outfile.open("Table");
     
     outfile << "\t\t\t\t\tStudent Information" << endl << endl;
     outfile << "Student ID\t\tGrade\t\tAverage\t\tLetter Grade" << endl<< endl;



}
int stuid(int a, int b) // Student ID
{

    int x,y;
  
    ifstream infile("grades.txt");
  
 
    infile >> x;
    infile >> y;
    return x,y;
    
}

[vivekkrs]

Only one value can be returned using "return".

[JLBorges]

Option one: pass parameters by reference
Option two: return a std::pair of integers

#include <iostream>
#include <utility>

// pass by reference
void foo( int& a, int& b )
{
    a = 100 ;
    b = 234 ;
}

// return pair by value
std::pair<int,int> bar()
{
    int a = 500 ;
    int b = 678 ;
    return std::make_pair( a, b ) ;
}

int main()
{
    int i, j ;
    foo(i,j) ;
    std::cout << i << ' ' << j << '\n' ;

    std::pair<int,int> result = bar() ;
    const int k = result.first ;
    const int l = result.second ;
    std::cout << k << ' ' << l << '\n' ;
}

[onur]

Create a custom struct with meaningful members and return this struct. This is similar to returning a std::pair but imho more readable.

[Duthomhas]

Returning multiple values are what tuples are for:

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


void heading(int) // Table Heading
{
     ofstream outfile("Table.txt");
     
     outfile << "\t\t\t\t\tStudent Information" << endl << endl;
     outfile << "Student ID\t\tGrade\t\tAverage\t\tLetter Grade" << endl<< endl;
}

tuple<int,int> stuid() // Student ID
{

    int x,y;
  
    ifstream infile("grades.txt");
 
    infile >> x;
    infile >> y;

    return make_tuple(x,y);
}

int main()
{
    
    int x,y,h;
    
    
    heading(h);
    tie(x,y) = stuid();
    cout << x << endl;
    
    
    system("PAUSE");
    return 0;
}

The more traditional method is via references:

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


void heading(int) // Table Heading
{
     ofstream outfile("Table.txt");
     
     outfile << "\t\t\t\t\tStudent Information" << endl << endl;
     outfile << "Student ID\t\tGrade\t\tAverage\t\tLetter Grade" << endl<< endl;
}


void stuid(int& a, int& b) // Student ID
{
    ifstream infile("grades.txt");
 
    infile >> a;
    infile >> b;
}

int main()
{
    
    int x,y,h;
    
    
    heading(h);

    stuid(x,y);
    cout << x << endl;
    
    
    system("PAUSE");
    return 0;
}

I am still amazed that people are taught to put main() at the beginning of the file instead of at the end, where it belongs (IMNSHO), so I swapped things around a little. Much less confusing that way.

Notice also that you don't need that global variable.

Lastly, your variable names are not helpful. Try to come up with something that tells you what they are for.

Hope this helps.