Re: Not sure how this program compiles without any error.

From:

Paul Bibbings <paul.bibbings@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Mon, 12 Apr 2010 09:06:01 +0100

Message-ID:

<87bpdp14eu.fsf@gmail.com>

Suresh V <vsuresh.cs@gmail.com> writes:

#include <iostream.h>

class A {
    protected:
        int a;
};

class B : protected A
{
};

class C: private B
{
   public:
       void assign() {
           a = 1;
       }
};

int main(){
    C* a = new C();
    a->assign();
    return 0;
}

How can class 'C' has access to Class 'A' data members if class 'C' is
derived as private from class 'B' which intern derives class 'A' as
protected ? please help

Why do you think that it would not be able to? If you follow it
through: a is protected in class A; class B derives from A by protected
inheritance meaning that a is available to B (being protected in A), and
that it remains protected in B; class C derives from B by private
inheritance, meaning that a (which is protected in B) is available to
class C and is now private in that class. The call a->assign() in main
then behaves no differently (from its point of view) than if you had
written:

class C {
private:
   int a;
public:
   void assign() {
      a = 1;
   }
}

int main() {
   C *a = new C();
   a->assign();
   return 0;
}

Regards

Paul Bibbings