From: Ole-Hjalmar Kristensen <ohk@clustra.com>
Subject: Re: Ada OO Mechanism
Date: 1999/05/26
Date: 1999-05-26T00:00:00+00:00 [thread overview]
Message-ID: <umq675fhalz.fsf@maestro.clustra.com> (raw)
In-Reply-To: t7g14lrlag.fsf@calumny.jyacc.com
Hyman Rosen <hymie@prolifics.com> writes:
> Samuel Mize <smize@imagin.net> writes:
> > THE QUESTION: how does one do "mix-in" classes in C++? I'd bet a
> > nickel that you can, but I don't know the specific mechanism. The
> > "mix-in" metaphor is described in the Ada 95 Rationale, 4.6.2.
>
> I believe this Ada --
>
> generic
> type S is abstract tagged private;
> package P is
> type T is abstract new S with private;
> -- operations on T
> private
> type T is abstract new S with
> record
> -- additional components
> end record;
> end P;
>
> corrsponds to this C++ --
>
> template <typename S>
> class P
> {
> public:
> class T : public S
> {
> private:
> // additional components
> }
> };
>
> and given some type A, one could declare objects of type P<A>::T.
> These objects are derived from A and also implement the extra
> operations of T. I haven't bothered to duplicate the 'abstract',
> but that's easily done by giving T an abstract destructor, ~T() = 0.
>
In C++, you don't even need templates to do mix-in's. The following
method will work:
class a {
public:
virtual void f() = 0;
};
class b: virtual public a {
public:
void g(){
....
f();
....
}
};
class a_impl_1: virtual public a {
public:
void f(){
do_something();
}
};
class a_impl_2: virtual public a {
public:
void f(){
do_something_else();
}
};
class mixed1: public b, public a_impl_1{
};
class mixed2: public b, public a_impl_2{
};
Now, in mixed1, g will call a_impl_1::g(), and in mixed2, g will call
a_impl_2::g().
Any function which is virtual in class a is accessible to any derived
class, but the actual function which is called is determined at run
time. The classes which are derived from a has to declare a as a
virtual base class, or we would get multiple a's in mixed1 and mixed2,
and the mechanism would not work.
<stuff deleted>
--
E pluribus Unix
next prev parent reply other threads:[~1999-05-26 0:00 UTC|newest]
Thread overview: 116+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-05-20 0:00 Ada OO Mechanism Shawn M. Root
1999-05-20 0:00 ` Samuel Mize
1999-05-20 0:00 ` David Botton
1999-05-20 0:00 ` Samuel Mize
1999-05-20 0:00 ` David Botton
1999-05-24 0:00 ` Hyman Rosen
1999-05-24 0:00 ` Robert Dewar
1999-05-24 0:00 ` Hyman Rosen
1999-05-24 0:00 ` Mike
1999-05-25 0:00 ` Robert Dewar
1999-05-24 0:00 ` David Starner
1999-05-24 0:00 ` bob
1999-05-24 0:00 ` David Starner
1999-05-25 0:00 ` Ole-Hjalmar Kristensen
1999-05-25 0:00 ` Florian Weimer
1999-05-25 0:00 ` Mark A Biggar
1999-05-25 0:00 ` Hyman Rosen
1999-05-25 0:00 ` Richard D Riehle
1999-05-25 0:00 ` David Botton
1999-05-26 0:00 ` Tom Moran
1999-05-27 0:00 ` Aidan Skinner
1999-05-25 0:00 ` Samuel Mize
1999-05-25 0:00 ` Hyman Rosen
1999-05-25 0:00 ` Samuel Mize
1999-05-25 0:00 ` Chris
1999-05-25 0:00 ` David Botton
1999-05-27 0:00 ` Aidan Skinner
1999-05-27 0:00 ` Gautier
1999-05-27 0:00 ` Samuel Mize
1999-05-25 0:00 ` Brian Rogoff
1999-05-25 0:00 ` Jim
1999-05-26 0:00 ` Robert Dewar
1999-05-26 0:00 ` Brian Rogoff
1999-05-25 0:00 ` Richard D Riehle
1999-05-25 0:00 ` Hyman Rosen
1999-05-26 0:00 ` Ray Blaak
1999-05-26 0:00 ` Hyman Rosen
1999-05-26 0:00 ` Richard D Riehle
1999-05-26 0:00 ` Hyman Rosen
1999-05-27 0:00 ` Richard D Riehle
1999-06-05 0:00 ` Matthew Heaney
1999-06-07 0:00 ` Hyman Rosen
1999-05-28 0:00 ` Laurent Guerby
1999-06-05 0:00 ` Matthew Heaney
1999-06-07 0:00 ` Hyman Rosen
1999-06-08 0:00 ` Matthew Heaney
1999-06-08 0:00 ` Hyman Rosen
1999-06-08 0:00 ` Samuel Mize
1999-06-08 0:00 ` Hyman Rosen
1999-06-08 0:00 ` Robert Dewar
1999-06-08 0:00 ` Stanley R. Allen
1999-06-08 0:00 ` Markus Kuhn
1999-06-08 0:00 ` Stanley R. Allen
[not found] ` <t7zp2sr6yf.fsf@calumny.jyacc.c <t7emjmmx8w.fsf@calumny.jyacc.com>
1999-06-08 0:00 ` Larry Kilgallen
1999-06-08 0:00 ` Hyman Rosen
1999-06-08 0:00 ` Tucker Taft
1999-06-08 0:00 ` Brian Rogoff
1999-06-09 0:00 ` Tucker Taft
1999-06-09 0:00 ` Robert Dewar
[not found] ` < <375E92CB.27850620@averstar.com>
1999-06-09 0:00 ` Brian Rogoff
1999-06-14 0:00 ` Robert A Duff
1999-06-09 0:00 ` Matthew Heaney
1999-06-09 0:00 ` Samuel Mize
[not found] ` <t7zp2sr6yf.fsf@calumny.jyacc.c <t7r9nmz8ou.fsf@calumny.jyacc.com>
1999-06-08 0:00 ` Larry Kilgallen
1999-06-08 0:00 ` Hyman Rosen
1999-06-14 0:00 ` Robert A Duff
[not found] ` <t7zp2sr6yf.fsf@calumny.jyacc.c <375d9a3d.e1cccc63@averstar.com>
1999-06-09 0:00 ` Larry Kilgallen
1999-06-09 0:00 ` Tucker Taft
1999-05-27 0:00 ` Samuel Mize
1999-05-27 0:00 ` Hyman Rosen
1999-05-28 0:00 ` Laurent Guerby
1999-05-28 0:00 ` Richard D Riehle
1999-05-28 0:00 ` Tom Moran
1999-05-28 0:00 ` Samuel Mize
1999-05-27 0:00 ` Samuel Mize
1999-05-27 0:00 ` Jon S Anthony
1999-05-28 0:00 ` Robert I. Eachus
1999-05-28 0:00 ` Brian Rogoff
1999-05-29 0:00 ` Ehud Lamm
1999-05-30 0:00 ` chris
1999-05-30 0:00 ` Robert Dewar
1999-05-30 0:00 ` Harry George
1999-05-30 0:00 ` Vladimir Olensky
1999-05-31 0:00 ` Robert Dewar
1999-05-31 0:00 ` Vladimir Olensky
1999-06-03 0:00 ` Dale Stanbrough
1999-06-02 0:00 ` mike
1999-06-03 0:00 ` Robert Dewar
1999-06-06 0:00 ` David Botton
1999-06-07 0:00 ` Robert Dewar
1999-06-01 0:00 ` Richard D Riehle
1999-06-03 0:00 ` Matthew Heaney
1999-06-03 0:00 ` Matthew Heaney
1999-05-25 0:00 ` Samuel Mize
1999-05-25 0:00 ` Hyman Rosen
1999-05-25 0:00 ` David Starner
1999-05-26 0:00 ` Ole-Hjalmar Kristensen [this message]
1999-05-26 0:00 ` Laurent Guerby
1999-05-26 0:00 ` Hyman Rosen
1999-05-28 0:00 ` Laurent Guerby
1999-06-01 0:00 ` Hyman Rosen
1999-06-03 0:00 ` Fraser Wilson
1999-06-03 0:00 ` Matthew Heaney
1999-06-03 0:00 ` Hyman Rosen
1999-05-21 0:00 ` Dale Stanbrough
1999-05-20 0:00 ` bob
1999-05-21 0:00 ` Dale Stanbrough
1999-05-21 0:00 ` Richard D Riehle
1999-05-21 0:00 ` Shawn M. Root
1999-05-21 0:00 ` Richard D Riehle
1999-05-25 0:00 ` Shawn M. Root
1999-05-21 0:00 ` Marin David Condic
1999-05-21 0:00 ` Steve
1999-05-21 0:00 ` Dan Nagle
1999-05-24 0:00 ` Marin David Condic
1999-05-25 0:00 ` Don Overheu
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