Re: Overlapping ranges

["AG" <ang@xtra.co.nz>]

"Richard Riehle" <richard@adaworks.com> wrote in message
news:3EFE3491.F968568D@adaworks.com...
> AG wrote:
>
> > Assuming I have a package declaration like this:
> >
> > package range is
> >   type x1 is range 0..255;
> >   type x2 is range 127..2**15-1;
> > end ranges;
> >
> > Is there a way to declare a function
> > using that package that will accept
> > values of either x1 or x2 (and nothing
> > else) restricted to the range 127..255 ?
>
> Perhaps I don't understand why this is a problem for
> you.  Why not something such as,

Because I don't want to allow an illegal
value to make it inside the function
(not even to raise an exception)

What I was after was some implementation
that won't need custom exceptions/error
codes or so.


> With this as a possible implementation of the body,
>
> package body ranges is
>
>    function Fudge (A : X1; B : X2) return Number'Base is

-- What happens here if you do something like
-- X3 := A + 1   ???

>    begin
>      if A in X1 then
>          return Number(A) + Number(B);
>       else
>          raise X1_Error;
>       end if;
>    end Fudge;