Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!mit-eddie!mit-amt!peter
From: peter@mit-amt.MEDIA.MIT.EDU (Peter Schroeder)
Newsgroups: comp.lang.c++
Subject: wanting to be a `friend' of a derived class
Keywords: derivation,friend,private
Message-ID: <714@mit-amt.MEDIA.MIT.EDU>
Date: 18 Sep 89 20:41:09 GMT
Organization: MIT Media Lab, Cambridge, MA
Lines: 62


// I want `another' to have access to the private part of `derived'
// which, under cfront 1.2, I can apparently only get by making `another' friend
// to the base class.

// this program produces:

// make test
//    CC  -O  -n -o test test.C
// CC  test.C:
// "test.C", line 32: error:  a is protected 
// 1 error
// *** Error code 1

// Stop.


#include	<stream.h>

class base{
protected:
   int a;
public:
   base() : a( 1 ) {}
   // friend class another;        this is what it takes to work. Why?
};

class derived : private base{
public:
   // friend int another::mult();  this is really what I want
   friend class another;           // but I'd settle for this
   derived() : () {}
};

class another{
   int b;
public:
   another() : b( 1 ) {}
   int mult( derived& d )
      { return b * d.a; }          // I need it here
};

main()
{
   another a;
   derived d;

   cout << a.mult( d ) << "\n";
}

// Notice that this is simplified considerably from the actual problem where I
// really need the friend mechanism, rather then a function such as
//    int derived::geta() { return a; }
// which obviously would also solve my problem.

// What am I overlooking?

// Thanks for your help!

// Peter
// peter@media-lab.media.mit.edu
*/