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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Efficient Sequential Access to Arrays
Date: Thu, 26 Jul 2012 20:56:49 +0200
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Date: 2012-07-26T20:56:49+02:00
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On Thu, 26 Jul 2012 10:40:32 -0700 (PDT), Shark8 wrote:

> On Thursday, July 26, 2012 7:46:04 AM UTC-6, Dmitry A. Kazakov wrote:
>>
>> Some would disagree, but IMO in a well-written Ada program you should never
>> ever need 'Valid. Don't do Unchecked_Conversion with doubtful outcome.
>> Don't use stream attributes for constrained types.
> 
> It might not be avoidable though; the presence of 'Valid however does let
> you ensure that your [sub]typing assumptions are met.

These assumptions must be upheld per value construction.

> This might be especially true if you're importing data from some
> third-party where the input-format doesn't specifically conform to your
> expected-inputs. (This happens with disturbing frequency in handling
> electronic medical records; usually because whoever started the record was
> using a spreadsheet.)

Since this stuff is my primary occupation, a word of caution: don't do it
this way. Always implement the protocol layers as defined, right from the
representation data types (e.g. octet), up to Ada native ones. Never ever
use representation clauses to cut corners.

>> Don't use for X'Address
>> use Z'Address for the purpose of conversion etc.
> 
> What do you mean here? Overlaying?

Yes.

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