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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: How do you bitwise operations in Ada '83 and '95
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Date: Sat, 22 Jul 2006 15:31:51 +0200
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Date: 2006-07-22T15:31:51+02:00
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On Sat, 22 Jul 2006 12:52:29 +0200, Georg Bauhaus wrote:

> On Sat, 2006-07-22 at 10:32 +0200, Dmitry A. Kazakov wrote:
> 
>>  Does ANSI C standard require (x<<1) == (x*2)?
>> 
>> As for Ada 95, ARM certainly does not. This is why Shift_* is not portable.
> 
> type Unsigned_n is mod 2**n;  -- Annex B.2
> 
> won't be portable for the same reason?

Why? Semantics of modular arithmetic is defined in a portable way. As long
as you deal with *numbers* everything is OK.

> As for the bit representation of these intrinsic modular values,
> wouldn't shift_left etc. have to provide a result that does
> make sense, as per the AS-IF rule?

I am not a language lawyer. To me shifts aren't numeric operations, but
ones on arrays of bits. Mixing both is asking for trouble.

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