Enumerations and rep-clauses?

Enumerations and rep-clauses?

[Steve Folly]

Hi,

Given the following Ada95 situation...

  type enum is ( a, b, c, d );

  for enum use ( a => 12, b => 24, c => 36, d => 48 );

  subtype half_enum is enum range a .. b;


Is it guaranteed anywhere that half_enum has the same representation attributes
as enum? (ie. half_enum(a) => 12 and half_enum(b) => 24)

I would hope it did, but I'm having trouble finding the particular LRM
paragraph.


Thanks for your help.

-- 
Regards,
Steve Folly.
mailto:Steve.Folly@rdel.co.uk

Re: Enumerations and rep-clauses?

[Tucker Taft]

Steve Folly wrote:
> 
> Hi,
> 
> Given the following Ada95 situation...
> 
>   type enum is ( a, b, c, d );
> 
>   for enum use ( a => 12, b => 24, c => 36, d => 48 );
> 
>   subtype half_enum is enum range a .. b;
> 
> Is it guaranteed anywhere that half_enum has the same representation attributes
> as enum? (ie. half_enum(a) => 12 and half_enum(b) => 24)

Yes.

> 
> I would hope it did, but I'm having trouble finding the particular LRM
> paragraph.

An enumeration representation clause specifies a "type-related" aspect
of representation, so it is shared by all subtypes.  See RM95 13.1(8) which
indicates that all rep clauses other than Size and Alignment clauses
are type-related.  (Size and Alignment are subtype-specific.)
> 
> Thanks for your help.
> 
> --
> Regards,
> Steve Folly.
> mailto:Steve.Folly@rdel.co.uk

-- 
-Tucker Taft   stt@averstar.com   http://www.averstar.com/~stt/
Technical Director, Distributed IT Solutions  (www.averstar.com/tools)
AverStar (formerly Intermetrics, Inc.)   Burlington, MA  USA

Re: Enumerations and rep-clauses?

[Steve Folly]

"Tucker Taft" <stt@averstar.com> wrote, amongst other things, in message
news:38BABF5D.A278EF9A@averstar.com...

> An enumeration representation clause specifies a "type-related" aspect
> of representation, so it is shared by all subtypes.  See RM95 13.1(8)
which
> indicates that all rep clauses other than Size and Alignment clauses
> are type-related.  (Size and Alignment are subtype-specific.)
> --
> -Tucker Taft   stt@averstar.com   http://www.averstar.com/~stt/
> Technical Director, Distributed IT Solutions  (www.averstar.com/tools)
> AverStar (formerly Intermetrics, Inc.)   Burlington, MA  USA

Got it!

Thanks very much for your help.


--
Regards,
Steve Folly.
http://www.follysplace.demon.co.uk
donationsto:myaccount@mybank.co.uk