How to implement greatest common divisor to simplify fractions

Question

#include <iostream>
using namespace std;

int g_c_d(int n, int d);

class Fraction
{

private:
  //variables to store numerator and denominator
  int num;
  int denom;

public:
  Fraction(){}
  Fraction(int num): num(num) {}
  Fraction(int num, int denom): num(num), denom(denom) {}

  void set_num(int n){ num = n;}
  void set_denom(int d){ denom = d;}

  int get_numerator() const {return num;}
  int get_denominator() const {return denom;}
};

  int g_c_d(int n, int d){
    return d == 0? n : g_c_d(d, n % d);
 }

istream &operator>> (istream &input, Fraction &f)
{
  int n, d;
  char slash;
  input >> n;
  input >> slash;
  input >> d;

  if (d == 0) {n = 0;} //if denom is 0; fraction = 0/0
  f = Fraction(n, d);
  return input;
}

ostream &operator<<(ostream &output, const Fraction &frac)
{
  return output << frac.get_numerator() << "/" << frac.get_denominator();
}


int main()
{
   int n, d;
   Fraction frac;

   int gcd;
   n = frac.get_numerator();
   d = frac.get_denominator();
   gcd = g_c_d(frac.get_numerator() , frac.get_denominator());

   cout << "Enter a fraction" << endl;
   cin >> frac;
   frac.set_num(n/gcd);
   frac.set_denom(d/gcd);
   cout << "your fraction is: ";
   cout << frac << endl;

   return 0;
}

Hi im trying to simplify fractions entered by a user. However everytime I enter a fraction that is to be simplified the output returned is "1/0".

Can some one please help, it'll be massively appreciated!

Answer 1

The problem is that you do all your computations on frac before asking the user to input a fraction — and then you overwrite whatever the user inputs. You need to move this bit:

   cout << "Enter a fraction" << endl;
   cin >> frac;

much, much higher up.