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From: thh@hpindda.HP.COM (Tom Harper)
Newsgroups: comp.lang.c++
Subject: Member Name Visibility Question
Message-ID: <6170007@hpindda.HP.COM>
Date: 6 Mar 89 19:55:40 GMT
Organization: HP Information Networks, Cupertino, CA
Lines: 64

I have a question concerning the visibility of member names.  I cannot get
an example to work as I expect based on the information found on page 
281 of Stroustrup's "The C++ Programming Language".  Hopefully someone can
point out the error of my ways to me.

The following code works as I expect:

#include <stream.h>

class baseclass    {    
    int a;
    public: 
        baseclass();  
        int c;    
    };
    
baseclass::baseclass()  {    c = 13;    }
    
class derived : public baseclass     {    
    public:   
        derived();   
    };

derived::derived()  { ; }

void ef (derived& a)    {    cout << "a.c: " << a.c << "\n";    }

main()    {    derived a;        ef(a);    }

The external function ef has visibility of baseclass member c.
Running the executable produces the output "a.c: 13".  No surprises for me
here.

Example two restricts the base class in the derived class definition:

#include <stream.h>

class baseclass    {    
    int a;
    public: 
        baseclass();  
        int c;    
    };
    
baseclass::baseclass()  {    c = 13;    }
    
class derived : private baseclass     {    
    public:   
        derived();   
        baseclass::c;    // Hopefully make c visible to derived class objects.
    };

derived::derived()  {     ;     }

void ef (derived& a)    {    cout << "a.c: " << a.c << "\n";    }

main()    {    derived a;    ef(a);    }

This results in a compiler error telling me that c is a private member.  The
message is: "ef() cannot access c: baseclass is a private base class.".  I 
expected that c would be visible to objects of class derived, since it is
declared in the public member list.  What am I not correctly understanding?

Tom Harper thh@hpindda.HP.COM