Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!udel!rochester!kodak!ektools!randolph
From: randolph@ektools.UUCP (Gary L. Randolph)
Newsgroups: comp.lang.c++
Subject: Re: private to a class or to an object?
Message-ID: <2125@ektools.UUCP>
Date: 20 Sep 89 17:04:33 GMT
References: <517@wizard.UUCP>
Sender: randolph@ektools (Gary L. Randolph)
Reply-To: randolph@ektools.UUCP (Gary L. Randolph)
Organization: Eastman Kodak, Dept. 47, Rochester NY
Lines: 46

In article <517@wizard.UUCP> john@wizard.UUCP (John Danner) writes:
=Why is the following piece of code acceptable to cfront 1.2?
=class flug
={
=  private:
=  void printit()
=    {
=      printf("xy are %d %d\n",x,y);
=    }  
=  int x,y;
= public:
=  flug* z;
=  flug()
=    {
=    };
=  void setxy(int a, int b)
=    {
=      x = a;
=      y = b;
=    }
=  void printz()
=    {
=      z->printit();//no syntax error
=      z->x = 6;//no syntax error
=      z->y = 7;//no syntax error
=      z->printit();
=    }
=  
=};
=  main()
={
=  flug a,b;
=  a.z = &b;
=  b.setxy(1,0);
=  a.printz();
=//  printf("a.z->x = %s, a.z->y = %s\n",a.z->x,a.z->y);//syntax error private
=}
=
=Shouldn't private data be private to a single object and not accessible
=to any object of that class?  Is this something that is safe to take
=advantage of as far as compatibility with future versions of cfront?

No, C++ is type based.  This was brought up several months ago but is 
well worth mentioning periodically.  The example in Stroustrup that points
this out is on page 175.  Tiny is a class that has operator=() overloaded
so that it accesses the private variable, v, of another Tiny object.