Re: accesing internal codes used for an enumeration

["Marc A. Criley" <mcqada@earthlink.net>]

Marius Amado Alves wrote:
> 
> I am trying to implement a lexicon (in the database sense) as an
> enumeration with a representation clause.
> 
> Example lexicon:
> 
>   Name <-> Code
>   -------------
>   Ping      123
>   Pong      456
> 
> Implementation:
> 
>   type Names is (Ping, Pong);
>   for Names use (Ping => 123, Pong => 456);
> 
> I found out the hardway that attribute Pos does not return the internal
> code.  The ARM says this at 13.4(11), and tells you to use
> Unchecked_Conversion instead--but does not instruct you on the types of
> the conversion.  Where might one learn that?  Thanks.

If you're using GNAT and don't mind going non-portable, GNAT provides
the 'Enum_Rep attribute to extract the specified enumeration
representation.  (See the GNAT Reference Manual.)

Marc A. Criley
Senior Staff Engineer
Quadrus Corporation
www.quadruscorp.com