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Newsgroups: comp.lang.ada
Subject: Re: How do you bitwise operations in Ada '83 and '95
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From: Stephen Leake <stephen_leake@acm.org>
Date: Fri, 21 Jul 2006 05:53:26 -0400
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Date: 2006-07-21T05:53:26-04:00
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Marius Amado-Alves <marius@amado-alves.info> writes:

>>> Note that I don't do bit shifting. Instead I multiply or divide by a
>>> magnitude. I don't think bit shifting is portable.
>>
>> See LRM B.2, Interfaces.Shift_Left, Shift_Right, Rotate_Left,
>> Rotate_Right.
>
> Ok, two voices by now, so it is probably portable.

As Colin has pointed out, Interfaces.Unsigned_n is not required on all
machines; a machine with a 36 bit word won't have
Interfaces.Unsigned_32.

So you need to be precise about what you mean by "portable". We
usually take that to mean "code works without change on a reasonable
set of CPUs and operating system", where "reasonable" means "the ones
I care about" :).

> But clearly the only advantage of Interfaces over core language
> arithmetic would be speed.

There's no reason to think one would be faster than the other. It
depends on the CPU and compiler.

-- 
-- Stephe