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From: Christoph Grein <christoph.grein@eurocopter.de>
Newsgroups: comp.lang.ada
Subject: Re: Types, subtypes and ranges
Date: Wed, 14 Mar 2001 14:50:00 +0100 (MET)
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Date: 2001-03-14T14:50:00+01:00

Anders Wirzenius wrote:

> the 'Image attribute is inherited all the way up as long as
> you don't break the chain of subtypes:

Your wording is not quite correct. Inheritance is used in a different sense only 
for type derivation.

Here you have only subtypes, and these are no subtype-specific operations (OK, 
there are other subtype-specific attributes like 'Size). Thus e.g. 
Integer'Image, Natural'Image, Positive'Image all denote the same operation, 
there is no range check involved.

Positive'Image (-1) is absolutely OK and will return "-1" and not raise an 
exception.

The rationale behind this is that at some place you might not see the type, only 
the subtype.

(To be very precise, you never see a type name, only the first named subtype.)