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Subject: Re: Style Question: normal record vs discriminated null-record.
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Date: 2014-06-03T00:20:04-06:00
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On 02-Jun-14 22:38, J-P. Rosen wrote:
> Depends how you perceive your data. Discriminants are intended to define
> some kind of subclasses of your type, and can be used to parameterized
> inner components. Some criteria for you to chose:
>
> 1 - You can define subtypes according to certain values of discriminants.
>
> 2 - Discriminants are always initialized.
>
> 3 - Discriminants cannot be changed after the declaration.

Right -- the particular situation [alerts] seems like a good fit because 
of these qualities:
(1) Subtypes for critical failures can be defines and quick/clear 
disambiguation/determination in handling [an unconstrained type] via 'in'.
(2) Which means, ideally that the point that generates the alert always 
generates correctly.
(3) That they cannot be altered means that to 'change' the message is to 
handle it and generate a new one -- kind of like "renaming"/re-raising 
exceptions.

This is what makes it seem like a good fit, but I was still wondering 
what "normal Ada programmers" thought about it.