//Uses stdlib.h:
void Rational::reduce()
{
    const int FALSE = 0;
    const int TRUE = 1;
    int negative; //Set to TRUE if calling object is negative.

    if (denominator == 0)
    {
        cout << "Division by zero detected by reduce.\n";
        exit(1);
    }

    if (numerator == 0)
    {
        denominator = 1;
        return;
    }
   
    if (numerator*denominator < 0)
        negative = TRUE;
    else
        negative = FALSE;
    numerator = abs(numerator);
    denominator = abs(denominator);
  
    for (int i = 2; i <= numerator; i++)
    {
        while (((numerator % i) == 0) && ((denominator % i) == 0)) 
        {
             numerator = numerator/i;
             denominator = denominator/i;
        }
    }

    if (negative)
        numerator = -numerator;
}

Rational operator /(const Rational& r1, const Rational& r2)
{
    Rational temp;
    temp.numerator = r1.numerator * r2.denominator; 
    temp.denominator = r1.denominator * r2.numerator;
    temp.reduce();
    return temp;
}