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From: brandis@inf.ethz.ch (Marc Brandis)
Newsgroups: comp.object
Subject: Re: Examples of Multiple Inheritance?
Summary: Programming languages are not the real world !
Keywords: multiple inheritance
Message-ID: <17562@neptune.inf.ethz.ch>
Date: 6 Dec 90 10:34:55 GMT
References: <60700005@inmet> <980@culhua.prg.ox.ac.uk>
Sender: news@neptune.inf.ethz.ch
Reply-To: brandis@inf.ethz.ch (Marc Brandis)
Organization: Departement Informatik, ETH, Zurich
Lines: 35

In article <980@culhua.prg.ox.ac.uk> ajs@prg.ox.ac.uk (Adolfo Socorro) writes:
>There are lots. How about
>
>        Person
>        /    \
>    Student  Teacher
>       \       /
>   Teaching Assistant
>
>or perhaps
>
>       Account
>       /     \
>   Savings  Checking 
>   Account   Account
>      \       /
>     NOW Account
>
Sorry, but I think you are missing the point. The fact that there
are examples in the real world where a thing has properties of several other
things does not imply that you need multiple inheritance in a programming
language. Very often, the kind of situations that you are describing can be
solved by using references to other objects and just deriving from one class.
You may argue that this is not a direct projection of the real world into
the program, but this is not needed at all.

What would be interesting are some examples where multiple inheritance was
useful in writing a large program, which would have been much harder to 
implement without it.


Marc-Michael Brandis
Computer Systems Laboratory, Swiss Federal Institute of Technology
CH-8092 Zurich, Switzerland
email: brandis@inf.ethz.ch


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