"Warp" <war### [at] tagpovrayorg> wrote in message
news:40363b1e@news.povray.org...
> Dan P <dan### [at] yahoocom> wrote:
> > I have to disagree with this: If X derives Y, X is still X, but inherits
the
> > methods and members of Y. Also, Y is not an X -- for example, if Y was a
> > Stream and X was a RandomAccessStream, A RandomAccessStream contains
methods
> > and members of a Stream, but it is still a RandomAccess Stream. A Stream
is
> > not a RandomAccessStream from the other way around as well so X cannot
> > actually be Y.
>
>   Then perhaps you should read some book about OO programming.
>
>   The "is-a" relation between inherited classes is one of the fundamental
> properties of object-oriented programming. If you don't understand that
> then you still have much to study.

Let's think of it in more familiar terms because computer-science is
confusing. When mom squirted you out, you became an object derived from
attributes of your mom and your dad. Are you your mom or your dad? If you
were to clone yourself, is that clone a clone of your mom or your dad? If
you have a child, is that child you? No, although the child may inherit some
of your traits, like your eye color and sunny disposition, that child is not
you, it just inherits some attribute from you. Now, let's say the world sees
your son and asks, "Is he a Warp?" They would be asking, "Is he your child,"
or, "Is he in Warp's family?" That is the sense in which a person talks
about an object "being" another object.

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