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From: rich@kappa.Rice.EDU (Richard Murphey)
Newsgroups: comp.lang.c++
Subject: Re: Use of inheritance for classification? (iostream)
Keywords: MI, iostream
Message-ID: <3297@kalliope.rice.edu>
Date: 19 May 89 19:58:46 GMT
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> Here is an example that I think satisfies the above request. It isn't
> contrived, its simple, and its a familiar "problem domain".
> 
> The iostream library that is scheduled to be part of 2.0 uses
> 
> class ios { ... }
> 
> class istream : virtual public ios { ... } ;
> 
> class ostream : virtual public ios { ... } ;
> 
> class iostream : public istream, public ostream { ... } ;
> 
> Input operations are allowed on istreams.  Output operations on
> ostreams.  iostreams allow both operations (as when updating disk
> files)
> 
[picture omitted]
> 
> Jerry Schwarz
> AT&T Bell Labs, Murray Hill

For the novice C++ programmer iostreams seems like one of the
most attractive features of C++.  Your example works fine with
g++-1.35.0!

#include <stream.h>
#define nl <<"\n"
#define sp <<" "<<

class iostream : public istream, public ostream
{
  iostream();
};

iostream::iostream() 
:istream(stdin), ostream(stdout)
{ 
}

int
main(int argc, char *argv[])
{
  char a[80];

  iostream h;
  h << "test" nl;
  h >> a;
  h << "got" sp a nl;
  return 0;
}

Script started on Fri May 19 14:56:23 1989
rich@kappa /usr1/rich/pub/135/t> make t
g++ -g -Wall  t.C -o t -lm
rich@kappa /usr1/rich/pub/135/t> t
test
stuff
got stuff
rich@kappa /usr1/rich/pub/135/t> exit
rich@kappa /usr1/rich/pub/135/t> 
script done on Fri May 19 14:56:58 1989


I don't claim to understand Multiple inheritance well, but this
instance of it does seem useful as you suggest.

Regards,
Rich Murphey
Electrical Engineering
Rice University
rich@rice.edu