Re: Bit operations in Ada

[Robert A Duff <bobduff@shell01.TheWorld.com>]

Dennis Hoppe <dennis.hoppe@hoppinet.de> writes:

> Hello,
>
> I'm new to Ada and bitwise operations is a new challenge in this
> realm. My objective is to manipulate some bit strings in Ada, especially:
>
> a) addition/subtraction mod 2**n,
> b) change bits directly (e.g, via array access)
> c) shift operations
> d) rotate operations
> e) and, xor, not, or

I'm curious why you want to do all these things on the same type.
You say, "My objective is...", but what's the higher-level objective?

Anyway, I would use Unchecked_Conversion between a modular type and a
packed array of Boolean, as suggested by Ludovic Brenta.
Possibly wrapped in useful functions.

Instead of pragma Pack, I would use
"for Bit_Field'Component_Size use 1;".
They both do the same thing, but conceptually, "pack" means
"I want small things, so whole-object operations are faster,
at the expense of per-component operations", whereas the
Component_Size clause means "I depend on the exact bit size
for correctness".

- Bob