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From: beard@ux1.lbl.gov (Patrick C Beard)
Newsgroups: comp.lang.c++
Subject: Re: Private base class
Summary: whoops, correction.
Message-ID: <4606@helios.ee.lbl.gov>
Date: 11 Jan 90 03:25:21 GMT
References: <1533@castle.ed.ac.uk> <4604@helios.ee.lbl.gov>
Sender: usenet@helios.ee.lbl.gov
Reply-To: beard@ux1.lbl.gov (Patrick C Beard)
Organization: Lawrence Berkeley Laboratory, Berkeley
Lines: 47
X-Local-Date: 10 Jan 90 19:25:21 PST

In article <4604@helios.ee.lbl.gov> I write:
[code example deleted]
##Compiling this with CC (cfront version 1.2.1) gives the following
##errors:
##CC  test.c:
##
##"test.c", line 18: error:  a is from private base class
##"test.c", line 19: error:  f is from private base class
##2 errors
#
#As it should, you have inherited the base class privately.  In other
#words, all members, public, protected, or private, are inaccessible
#to the derived class.
#
#derived : public base {...};
#
#Redeclaring the members a and f can only make the visibility MORE strict,
#not less.  From the AT&T C++ reference manual (pp. 70-71):  "If a class
#is declared to be a base class for another class using the private access
#specifier, the public and protected members of the base class are private
#members of the derived class."  By not specifying the access in the declaration
#of the derived class, base is by default private.

And, on the next page of the manual (sorry I didn't see this at the time of
my last posting):

class B {
public: int a;
private: int b;
protected: int c;
};

class D : private B {
public:
	B::a;	// make 'a' a public member of D.
	B::b;	// make 'b' a public member of D (which is an error).
protected:
	B::c;	// make 'c' a protected member of D (ok).
	B::a;	// make 'a' a protected member of D (error, reducing access).
};

These are called "access declarations."  Sorry for my confusion.

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-  Patrick Beard, Macintosh Programmer                        (beard@lbl.gov) -
-  Berkeley Systems, Inc.  ".......<dead air>.......Good day!" - Paul Harvey  -
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