// Fraction structure, using typedef

#include <iostream>
using namespace std;

struct Fraction
{
  int num;
  int denom;

};

// some useful functions

void PrintFraction(Fraction f);		// pass by value
void InputFraction(Fraction& fptr);	// pass by address

Fraction AddByRef(const Fraction& f1, const Fraction& f2);
Fraction AddByAddress(const Fraction* p1, const Fraction* p2);

// Test routine (main)

int main()
{
   Fraction f1 = {0,1}, f2 = {3,4}, f3 = {1,2};
   Fraction r1, r2;
 
   cout << "f1 = ";  
   PrintFraction(f1);  
   cout << "\tf2 = ";  
   PrintFraction(f2);  
   cout << "\tf3 = ";  
   PrintFraction(f3);  

   // Test out the InputFraction funtion
   cout << "\n\nInput new fraction for f1: ";
   InputFraction(f1);
   cout << "\nInput new fraction for f2: ";
   InputFraction(f2);
   cout << "\nInput new fraction for f3: ";
   InputFraction(f3);

   cout << "\nNew values:\n";
   cout << "\nf1 = ";  
   PrintFraction(f1);  
   cout << "\tf2 = ";  
   PrintFraction(f2);  
   cout << "\tf3 = ";  
   PrintFraction(f3);  

   // Test out the add functions
   r1 = AddByRef(f1, f2);
   r2 = AddByAddress(&f1, &f3);
   cout << "\n\nf1 + f2 = ";
   PrintFraction(r1);

   cout << "\nf1 + f3 = ";
   PrintFraction(r2);

   cout << "\nf2 + f3 = ";
   PrintFraction(AddByRef(f2, f3));

   cout << "\n";
   return 0;
}


void PrintFraction(Fraction f)
{
   cout << f.num << '/' << f.denom;
}

void InputFraction(Fraction& f)
{
   char divsign;			// to consume the '/'
   cin >> f.num >> divsign >> f.denom;
}

Fraction AddByRef(const Fraction& f1, const Fraction& f2)
// pass by const reference.  f1 and f2 are nicknames for the incoming data
{
   Fraction r;			// to store the result
   r.num = f1.num * f2.denom + f2.num * f1.denom;
   r.denom = f1.denom * f2.denom;

   return r;			// returned by value
				//  why should we NOT return by reference?
}

Fraction AddByAddress(const Fraction* p1, const Fraction* p2)
{
   Fraction r;
   r.num = p1->num * p2->denom + p2->num * p1->denom;
   r.denom = p1->denom * p2->denom;

   return r;			// returned by value
}