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From: mheaney@ni.net (Matthew Heaney)
Subject: Re: Ada Enumerations
Date: 1997/12/04
Message-ID: <mheaney-ya023680000412970252290001@news.ni.net>#1/1
X-Deja-AN: 295200271
References: <662cs9$b34$1@newman.pcisys.net>
 <663j9f$e1l@mtinsc02.worldnet.att.net> <dewar.881162762@merv>
 <3485D2AE.3F54@hso.link.com>
Organization: Estormza Software
Newsgroups: comp.lang.ada
Date: 1997-12-04T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <3485D2AE.3F54@hso.link.com>, "Stanley R. Allen"
<s_allen@hso.link.com> wrote:

>> If you are using GNAT, you can use the 'Enum_Rep attribute to get the
>> representation value for an enumeration literal. This seems a generally
>> useful attribute, it would be nice if other Ada 95 compilers would
>> implement it.
>> 
>
>Hear, Hear!  I was surprised that Ada95 didn't correct this obvious
>deficiency in Ada83.

Personally, I feel that if you're always looking at the rep of the
enumerands, then you probably don't want an enumeration type anyway.  That
being said, why don't you just perform an instantiation of UC at the point
of declaration of the type?

with Unchecked_Conversion, Interfaces;
package Color_Types is

   type Color is (Red, Green, Blue);
   
   for Color use (Red => 2, Green => 5, Blue => 8);

   for Color'Size use 8;

   function To_Rep is
      new Unchecked_Conversion (Color, Interfaces.Unsigned_8);

end Color_Types;

What's the big deal?  It's only 1 extra declaration (the instantiation of UC).

--------------------------------------------------------------------
Matthew Heaney
Software Development Consultant
<mailto:matthew_heaney@acm.org>
(818) 985-1271