How to use private struct inside of friend function?

Question

I have a function which prints entries of a "Polynomial" class:

void Polynomial::print()
{
    Term* pos = first;

    while(pos != NULL){
        std::cout << "y=" << pos->coeff << "x^" << pos->power;

        if(pos->next != NULL){
            std::cout << "+";
        }
            pos = pos->next;
        }
    std::cout<<endl;
}

and I would like to translate it so that I can use it with cout instead. I made the following friend function:

std::ostream & operator << (std::ostream &out, const Polynomial &Poly)
{
   Term* pos = Poly.first;

   while(pos != NULL){
       out << "y=" << pos->coeff << "x^" << pos->power;

      if(pos->next != NULL){
         out << "+";
      }
      pos = pos->next;
   }
   out<<endl;
}

Which told me 'Term' was not declared in this scope . Term is a private struct defined inside the class Polynomial , how do can I use it as a type inside the friend function?

Answer 1

Term是在Polynomial内部定义的，因此在Polinomial类范围之外使用时，需要使用其全名Polynomial::Term来引用它。

Polynomial::Term* pos = Poly.first;