Re: Enumeration representation clause surprise.

[Adam Beneschan <adam@irvine.com>]

On Jun 13, 1:27 am, christoph.gr...@eurocopter.com wrote:
> > > With the proposed patch, it gives:
>
> > > GNAT 4.4.0 20080611 (experimental)
> > >     26.         X1 at 0 range 0 .. -1;                   -- Minus 1 !!
> > >                    |
> > >         >>> warning: component representation will be biased
>
> > So what would the value of the bias be?
>
>   type X_Type is ( X );
>   for x_type use (x => 16#7FFF_FFFF#);
>
> 16#7FFF_FFFF# of course
>
> Since this is the only value, nothing need be stored to know which
> value it is. This is like a constant in ROM, I gather.

My point is that the "bias" is the difference between the (conceptual)
value being represented, and the number actually stored in memory.  So
what number is stored in a 0-bit data item?  I suppose you could
arbitrarily decide it's zero (which would make some sense
mathematically) but it seems more commonsensical to say that nothing
is stored there because there ain't no bits to store anything in.

                              -- Adam