Re: Bit manipulation

[Sandro Binetti <sandrobinetti@my-deja.com>]

In article <2WTH$pdrCfOd@eisner.decus.org>,
  Kilgallen@eisner.decus.org.nospam (Larry Kilgallen) wrote:

> Quite often when someone wants to do something like that, they had
> formerly programmed in some other language whose ability to define
> data types is not so robust as Ada.

Ok! I'm a C programmer too. Why do you say "robust"? You can write
a "robust" source code even by using other languages than ADA. The
matter is not that. In this case I'd say "flexible", instead of "not
robust".

I always discriminate a data structure in two indipendent points of
wiew:
1) the semantic one (the type, of course)
2) the sintactic one (the way the type is stored and internally
represented)
In some occasion, expecially when you work at low-level device
handling, you need to approach the problem by a semantic (logic) way,
without forgetting that your "idea" has a peculiar way to be treated on
the target hardware (and, so, it can't be completely divided from the
sintactic approach). That's to say that, in such an occasion like
these, there no need (and no meaning) to split the type from its
internal representation: it's only a conceptual overhead!

>
> Except for the particular situation of changing case of an ASCII
> Roman letter (for which Ada95 has built-in capabilities), flipping
> a bit in a character is totally meaningless.

Are you sure? Can you say there'no situation at all in witch you need
to manipulate a seven-bit character, regardless of its ASCII semantic?
Have you ever thougth of some encryption-encoding algorithm, based on
some perverse actions on a character bit?

>
> If you really meant to blip a bit in a data cell that happens to
> be 8 bits wide, then please study record and array declarations
> in an introductory Ada text

Done, when I was 18!

Thanks a lot for your interest in my "stupid" problem.
--
Ciao, Sandro


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