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From: Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov>
Newsgroups: comp.lang.ada
Subject: Re: Need advice: Enumerate or not
Date: 16 May 2002 09:03:25 -0400
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Preben Randhol <randhol+abuse@pvv.org> writes:

> On Wed, 15 May 2002 12:26:50 GMT, Jim Rogers wrote:
> > The Ada 95 approach is perhaps harder to read, because all the
> > decisions are performed by dispatching and not by explicit
> > branching in your code. On the other hand, the dispatching
> > approach reduces maintenance cost and explicit complexity.
> 
> The only thing I must do is:
> 
> with Some_New_pacakge; use Some_New_pacakge; 

No, the child package where the actual operation is defined does _not_
need to be visible for dispatching to happen. That is crucial to the
dispatching design; the top level Update procedure can be written with
_no_ knowledge of what procedures are actually dispatched to.

> and make sure that the pacakges supply an update fuction.

This is done by making the root operation abstract; then the compiler
ensures that each derived type supplies an update function.


I suggest you write a very simple application that does dispatching,
so you get a better feel for how it works. Model the hierarchy you are
thinking of here, but just do Text_IO, so it's easy to get it working.
Then you can decide how to proceed with the real application.

-- 
-- Stephe