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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
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 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re:
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Date: Wed, 24 Oct 2012 19:20:32 +0200
Organization: Ada @ Home
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Date: 2012-10-24T19:20:32+02:00
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Le Wed, 24 Oct 2012 18:45:27 +0200, Yannick Duch=C3=AAne (Hibou57)  =

<yannick_duchene@yahoo.fr> a =C3=A9crit:

> Le Wed, 24 Oct 2012 18:40:58 +0200, Yannick Duch=C3=AAne (Hibou57)  =

> <yannick_duchene@yahoo.fr> a =C3=A9crit:
>
>> same snippet. Obviously, this does not stand for the reliable
> Read =E2=80=9Cdoes not stand for the real thing=E2=80=9D.
>
>>            type A_Type  is mod 256;
>
> Sorry, forget to say about a second variation: replace the above with =
 =

> `type A_Type is new Positive;` and there will be no more error at  =

> runtime (the first error, that is, with the useless package body still=
  =

> there). That one is a lot weird.
>

More on that particular point. I you change `mod 256` into anything the =
 =

modulo is above 256, not necessarily a power of two, as this works with =
 =

`mod 257` two, then the bug disappears. The bug is there for any value  =

below and included, 256.

I suspected the element size, and indeed, that's not really the modulo, =
 =

but the size. Replace `type A_Type is mod 256;` with this, with an added=
  =

representation clause:

     type A_Type  is mod 256;
     for A_Type'Size use 16;

The module is still 256, but now the size changed, and the bug is not  =

exposed.


-- =

=E2=80=9CSyntactic sugar causes cancer of the semi-colons.=E2=80=9D [1]
=E2=80=9CStructured Programming supports the law of the excluded muddle.=
=E2=80=9D [1]
[1]: Epigrams on Programming =E2=80=94 Alan J. =E2=80=94 P. Yale Univers=
ity