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From: Marius Amado-Alves <marius@amado-alves.info>
Subject: Re: How do you bitwise operations in Ada '83 and '95
Date: Thu, 20 Jul 2006 10:38:49 +0100
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Date: 2006-07-20T11:50:13+02:00

>> 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.

But clearly the only advantage of Interfaces over core language  
arithmetic would be speed.
And I doubt the compiler does not optimize a multiplication or  
division by a constant power of 2 by representing it as a shift  
instructions if this is the speediest method anyway.