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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Ranges and (non)static constraints
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Date: Mon, 20 Nov 2006 16:48:57 +0100
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Date: 2006-11-20T16:48:57+01:00
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On Mon, 20 Nov 2006 14:12:49 -0000, Stuart wrote:

> "Stuart" <stuart@0.0> wrote in message 
> news:4561b3d2$1_1@glkas0286.greenlnk.net...
> 
>>> You mean:
>>>   type T is mod N;
>>>   subtype S is T range 1..N;
>>
>> Well, almost
>>    subtype S is T range 1..N-1;
> 
> double Doh!
> 
>     type T is mod System.Max_Binary_Modulus;
>     subtype S is T range 1..N-1;

> (many apologies; again)

Unfortunately S is not a true integer type. For example, you will get no
overflow upon wrapping. For example, when System.Max_Binary_Modulus = N,
then S'Last+2 would result in 1. For the same reason, the subtype
declaration should be rather:

   subtype S is T range 1..T(N-1);

Otherwise it won't compile when N is not in T'Range, but N-1 is.

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