What’s wrong with the following attempts at establishing friends?
a. class snap {
friend clasp;
...
};
class clasp { ... };
b. class cuff {
public:
void snip(muff &) { ... }
...

};
class muff {
friend void cuff::snip(muff &);
...
};
c. class muff {
friend void cuff::snip(muff &);
...
};
class cuff {
public:
void snip(muff &) { ... }
...
};