Declaring who our friend is

class body {

friend class antibody;

friend void massage (body &);

public:

// stuff deleted

};

Here we declare the (fictitious) class “antibody” to be a friend of our class “body”, so any member function of the antibody class has access to our private and protected stuff.

Also, the (again fictitious) non-member function “massage” can access all of our body class. A non-member function is not a member function of any class (just as any function in F77 or C used to be).

#include "body.h"

class cube : public body {

friend ostream& operator<< (ostream&, cube &);

public:

cube (const float);

cube (const float, const Color &c);

cube (const cube &);

// stuff deleted...

};

Here we define the “non-member operator” operator<< (which is a function just like the “massage” from above) to be a friend of our class cube. This function has now access to all of our protected and private stuff. By the way, the cout object is of class “ostream”.

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