Why do we return by value while implementing cascading of cin cout?

Question

This is a code to print/input the linked list by overloading cin/cout. Why is the return type ostream& in place of just ostream?

ostream& operator<<(ostream& os, node* head)
{
    print(head);
}



// Overloading the istream operator '>>' to take continuous input into the linked
istream& operator>>(istream& is, node*& head)
{
    takeInput(head);
}

// Driver Code
int main()
{
    node* head = NULL;

    // input linked list
    cin >> head;

    // print linked list
    cout << head;
    return 0;
}

Answer 1

It's because by default, c++ returns a copy of a variable. So ostream will be a copy, while ostream& will be a reference. References are commonly used in c++ for this reason and to save performance