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From: Ted Dennison <dennison@telepath.com>
Subject: Re: Self-referential types
Date: 1999/10/13
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In article <3803c8bc_2@news1.prserv.net>,
  "Matthew Heaney" <matthew_heaney@acm.org> wrote:
> In article <3803B5E3.F96A6DD4@mitre.org> , "Robert I. Eachus"
> <eachus@mitre.org> wrote:
>

>   type Digital_Clock (...) is
>     limited record
>       Master_Obs : Master_Obs_Type (Digital_Clock'Access);
>       Slave_Obs  : Slave_Obs_Type (Digital_Clock'Access);
>       Control    : Control_Type (Digital_Clock'Access);
>     end record;

Ok...What does this buy you over using non-anonomous access fields and
an initilization? And how does this constitute MI?

> Some guys use public taggedness everywhere with gay abandon.  This is
> wrong.  Don't use taggedness unless you need to, and if you do, then
> hide it in the private region if you can.

Hmm. Generally I do that so that someone who wants to extend a new type
that I haven't thought of doesn't have to put it in a child package. But
admittedly, I don't myself derive new types without putting them in
child packages. So perhaps I'm allowing too much freedom?

> I will be discussing this technique this Sunday (17 Oct 99) during my
> Design Patterns tutorial, at this year's SIGAda conference.

Hmmm. It would be nice to attend that. But I don't think I could sell
enough candy bars at work in the next couple of days to pay for the
trip. :-)

--
T.E.D.


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