How to print void function after cout statement?

Question

I'm trying to print the output of the function after my values are sent to the function. The cout statement needs a string but I'm not sure how I can return a string from my reduce_fraction function while keeping the math correct. In my add_fraction function, you'll see that I simply want to print the added fraction then the reduced fraction right below it. The compiler returns no errors but the output just shows the "Improper Fraction" answer.

#include <iostream>
#include <string>

using namespace std;


 void reduce_fraction (int top, int bottom)
 {
    for (int i = top * bottom; i > 1; i--) {  
            if ((top % i == 0) && (bottom % i == 0)) {  
         bottom /= i;  
            top /= i;  
    }  

     }
}

void add_fraction (int numerator, int numerator2, int denominator, int              
denominator2)
{
int top;
int bottom;
top = numerator2 * denominator + denominator2 * numerator;
bottom = denominator2 * denominator;

cout << "Improper Fraction -> ";
cout << top << "/" << bottom << endl;
cout << "Simplified Fraction -> ";
reduce_fraction(top, bottom);
}


int main()
{

int numerator;
int denominator;
int numerator2;
int denominator2;
char operation;

cout << "Input the numerator: ";
cin >> numerator;

cout << "Input the denominator: ";
cin >> denominator;

cout << "Input the numerator2: ";
cin >> numerator2;

cout << "Input the denominator: ";
cin >> denominator2;

cout << "Input the operation: ";
cin >> operation;

if (operation == '+'){
    add_fraction(numerator, numerator2, denominator, denominator2);
}

return 0;   
}

Answer 1

Use reference to reflect the changes in top and bottom and print those in your add_fraction function after calling reduce_fraction

void reduce_fraction ( int & top, int & bottom)
{                         ~~~        ~~~
 //...
}

Then,

reduce_fraction(top, bottom);
cout << top << "/" << bottom << endl;