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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Generic-Package Elaboration Question / Possible GNAT Bug.
Date: Wed, 23 Nov 2011 11:30:59 +0100
Organization: cbb software GmbH
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Date: 2011-11-23T11:30:59+01:00
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On Wed, 23 Nov 2011 10:54:18 +0100, Georg Bauhaus wrote:

> On 23.11.11 09:44, Dmitry A. Kazakov wrote:
> 
>> The proper one is:
>>
>>     procedure ...
>>        raise Contraint_Error; -- I don't tell you when and how
> 
> So I won't know what my client code has done wrong.

The client code cannot do anything illegal. Constraint_Error is a valid
behavior.

[In terms of preconditions, in a properly designed program all dynamic
preconditions are trivially true.]

> How am I to learn how to do it right?

To do what? Program semantics is your business. How do you learn to call
sine instead of sqrt?

> Trial and error?

Understanding the problem domain, consulting the customer, reading design
manual, drinking coffee with sugar...

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de