Re: Thinking of using Ada for a job at home. Couple of questions first.

["Jeffrey R. Carter" <spam.jrcarter.not@spam.acm.org>]

John McCabe wrote:
> 
> The second question is related to the implementation of the System
> Exclusive messages. Basically this is part of the reason I thought Ada
> would be good for this task. The SysEx messages basically consist of a
> smallish header and a variety of different structures that are
> differentiated by the "Function" type in the header. Now I seem to
> remember from when I did use Ada that it's possible to define the
> record representation of a variant record such that the discriminant
> is held within the body of the record. This would mean (I think) that
> I could read a block of data from the synthesizer straight in to a
> buffer that overlaid the variant record and essentially automatically
> created a record that could be read as the particular variant related
> to the incoming data. However I also seem to remember that's not quite
> a 'recommended' way of doing that sort of thing. The other thing that
> guided me in Ada's direction is that the structure of the SysEx
> messages requires a lot of bit-fields and I'm well aware that Ada's
> representation clauses are fantastic for that sort of thing.
> 
> So, in principle, would that be the way to do this, or would you be
> able to suggest a better mechanism?

That is the way I would approach this, though I might keep the buffer and record 
separate and use Unchecked_Conversion.

I can't tell you whether the tagged approach would work, because programming by 
extension is a bad idea, and I avoid it whenever possible.

-- 
Jeff Carter
"Clear? Why, a 4-yr-old child could understand this
report. Run out and find me a 4-yr-old child. I can't
make head or tail out of it."
Duck Soup
94