8:27am ccbsd3:friend/> g++ friend.cpp
friend.cpp: In function `void modifyme(int, int)':
friend.cpp:8: error: `int MySomething::kk' is private
friend.cpp:26: error: within this context
friend.cpp: In function `int main()':
friend.cpp:8: error: `int MySomething::kk' is private
friend.cpp:42: error: within this context
friend.cpp:42: error: expected `;' before ':' token
wcpeng has logged off ttypo from 140.113.24.231.
8:27am ccbsd3:friend/> cat -n friend.cpp 
     1	//friend.cpp -- by tsaiwn@csie.nctu.edu.tw
     2	//friend id the only one who can touch your private
     3	#include <iostream>
     4	using namespace std;
     5	//          ? FRIEND function
     6	//          ? OVERLOADed function  (function name overloaded)
     7	   class MySomething {
     8	      int kk;
     9	     public:
    10	      float x,y;
    11	      void talk(int);
    12	     private:
    13	      float z;
    14	      friend void modifyme(int);
    15	      friend void modifyme(float);
    16	   };
    17	
    18	   void modifyme(int m){
    19	      MySomething you;
    20	      you.kk = m*10;
    21	      cout << "in First me\n";
    22	      // ...
    23	   }
    24	   void modifyme(int m,int n){   // not my friend
    25	      MySomething you;
    26	      you.kk = m+n;    // ERROR !
    27	      cout << "in Second me\n";
    28	      // ...
    29	   }
    30	   void modifyme(float m){
    31	      MySomething you;
    32	      you.z = m;
    33	      you.x = m;
    34	      cout << "in Third me\n";
    35	      // ...
    36	   }
    37	int main()
    38	{   MySomething him;
    39	    modifyme(10);
    40	    modifyme(1,2);
    41	    modifyme((float)10.0);
    42	    him.kk := 123;    // ERROR !
    43	    return 0;
    44	}
8:28am ccbsd3:friend/> vim friend.cpp

    26   //   you.kk = m+n;    // ERROR !
    42   //   him.kk := 123;    // ERROR !

8:30am ccbsd3:friend/> g++ friend.cpp
8:30am ccbsd3:friend/> ./a.out
in First me
in Second me
in Third me
8:30am ccbsd3:friend/>