在C ++中使用重载的I / O运算符输出方程式

Question

今天，我刚刚学习了有关在C ++中重载运算符的知识。特别是I / O运算符和算术运算符。我试图通过编写这样的代码将两者结合起来

cout << a + b; // both a and b are 2 objects belonging to the same class called Fraction.

但是，我无法使其达到预期的效果。您可以在下面的代码中看到它。

#include <iostream>
using namespace std;

class Fraction
{
    public:
        int numerator, denominator;
        friend istream& operator >> (istream&, Fraction&);
        friend ostream& operator << (ostream&, Fraction&);
        Fraction operator + (Fraction x)
        {
            Fraction tmp;
            tmp.denominator = denominator * x.denominator;
            tmp.numerator = numerator * x.denominator + x.numerator*denominator;
            return tmp;
        }
};
istream& operator >> (istream& is, Fraction &x)
{
    is >> x.numerator >> x.denominator;
    return is;
}
ostream& operator << (ostream& os,  Fraction &x)
{
    os << x.numerator << "/" << x.denominator << " ";
    return os;
}

int main()
{
    Fraction a, b;
    cin >> a >> b;
    Fraction c = a + b;
    cout << c; // This code worked but required an extra object to be declared.
    // cout << a + b; Compiler error. How to make the "<<" operator to print the result as intended
    return 0;
}