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From: "J-P. Rosen" <rosen@adalog.fr>
Newsgroups: comp.lang.ada
Subject: Re: Ada array contiguity.
Date: Mon, 20 Feb 2023 08:12:41 +0100
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Le 19/02/2023 à 18:54, Niklas Holsti a écrit :
> On 2023-02-19 19:10, J-P. Rosen wrote:
>> Le 19/02/2023 à 15:59, Niklas Holsti a écrit :
>>> Indeed. But it seems to me that Arr'Size = Arr'Length * Comp'Size is 
>>> the meaning usually intended for programming purposes.
>>
>> Certainly not if Comp'Size is not an integer number of bytes.
> 
> I'm not so certain. By choosing various roundings-up of the component 
> size, you can choose between "bit-contiguous", "byte-contiguous", etc.
> 
> For example, bit-contiguous with 2-bit components:
> 
>     type Comp is (A, B, C, D) with Size => 2;
> 
>     type Arr is array (1 .. 10) of Comp
>        with Pack, Size => 10 * Comp'Size;
> 
> Nybble-contiguous with Comp'Size => 4, byte- (octet-) contiguous with 
> Comp'Size => 8, etc.
> 
Of course, if you add representation clauses, the compiler will obey 
them. But the OP's question was whether it was /guaranteed/ to have 
contiguous representation, and the answer is no - for good reasons.

-- 
J-P. Rosen
Adalog
2 rue du Docteur Lombard, 92441 Issy-les-Moulineaux CEDEX
https://www.adalog.fr https://www.adacontrol.fr