Why friend function is preferred to member function for operator<<

Question

When you are going to print an object, a friend operator<< is used. Can we use member function for operator<< ?

class A {

public:
void operator<         


        

Answer 1

You have no choice -- it has to be a free function.

Note, however, that it need not necessarily be a friend function. It only needs to be a friend if you actually need to grant it private access. For example, I use the following in programming competitions:

template 
std::ostream& operator<<(std::ostream& os, const std::pair& p)
{
  return os << '(' << p.first << ", " << p.second << ')';
}

No need for it to be friend, as first and second are accessible publicly.