- Examples

// templateClassTemplateGeneralFriendship.cpp
#include <iostream>
template <typename T> void myFriendFunction(T);
template <typename U> class MyFriend;
class GrantingFriendshipAsClass{
  template <typename U> friend void myFriendFunction(U);
  template <typename U> friend class MyFriend;
private:
  std::string secret{"My secret from GrantingFriendshipAsClass."};
};
template <typename T>
class GrantingFriendshipAsClassTemplate{
  template <typename U> friend void myFriendFunction(U);
  template <typename U> friend class MyFriend;
private:
  std::string secret{"My secret from GrantingFriendshipAsClassTemplate."};
};
template <typename T>
void myFriendFunction(T){
  GrantingFriendshipAsClass myFriend;
  std::cout << myFriend.secret << std::endl;
  GrantingFriendshipAsClassTemplate<double> myFriend1;
  std::cout << myFriend1.secret << std::endl;
}
template <typename T>
class MyFriend{
public:
  MyFriend(){
    GrantingFriendshipAsClass myFriend;
    std::cout << myFriend.secret << std::endl;
    GrantingFriendshipAsClassTemplate<T> myFriend1;
    std::cout << myFriend1.secret << std::endl;
  }
};
int main(){
  std::cout << std::endl;
  int a{2011};
  myFriendFunction(a);
  MyFriend<double> myFriend;
  std::cout << std::endl;
}