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From: "Ehud Lamm" <mslamm@mscc.huji.ac.il>
Newsgroups: comp.lang.ada
Subject: Re: Container reqs
Date: Tue, 23 Oct 2001 16:23:01 +0200
Organization: The Hebrew University of Jerusalem
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Date: 2001-10-23T16:23:01+02:00
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<je@brighton.ac.uk> wrote in message
news:3BD527A8.93C1F68B@brighton.ac.uk...
> Yes; but if you *want* to avoid inheritance, the STL is an existence
> proof for a possible solution... :-)
>
> OTOH, if you do want to use inheritance here, some trickery is probably
> needed to avoid the library-level problem (since you'll presumably want
> generic packages but don't want to force library-level instantiation).
>

Life isn't simple, is it?

I outlined a basic approach that works for me, a few days a go (the abstract
types package is parametreized by item. Inheritance, providing
implementation, is done in child units).

Others presented their apporaches.

Let me say a few words concerning my point of view, from a teaching
perspective. Since you teach too, I'd be happy to hear your views on these
issues.

- I want to teach the concept of ADTs, without talking about inheritance,
tagged types etc.

- I want to be able to show how ADTs can help reuse, by utilizing the
container library.

- Following the above, I want to be able to explore the concept of
"interfaces" in the most general sense: what is sometimes called interface
oriented programming. I want to show how a Set ADT defines an interface, and
how this interface can have multiple implementations. This, in Ada, means
inheritance, and tagged types. However, the situation right now, means you
can only directly support one interface (MI idioms are going to be too
confusing, I'm afraid).

- Interface leads us to class-wide programming, or to the use of signature
packages.

- The interface relations are best explored using inheritance, and that's
fine. Inheritance however can easily be used for other purposes, and I want
to minimize the possbility for confusion.

- I want to utilize Ada's strong typing, and detest access to Object'class
solutions.

And all this, before getting into issues of guarded, bounded and other
design dimensions. These are also worth considering...

Ehud