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From: Wojtek Narczynski <wojtek@power.com.pl>
Newsgroups: comp.lang.ada
Subject: Re: Enumeration representation enhancement proposal
Date: Wed, 20 Oct 2004 10:41:46 +0200
Organization: tp.internet - http://www.tpi.pl/
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Date: 2004-10-20T10:41:46+02:00
List-Id: <comp.lang.ada>

Hello,

>> I don't follow, could you provide a sample Ada code which would be
>> problematic?
> 
>   for Colours use (Red => 1, Green => 2, Blue => 4, Muddy => others);
> 
>   if Muddy < Blue then
>      --  Do we ever get here?  Both 3 and 5 represents Muddy.  The one
>      --  is smaller than 4 (which represents Blue), the other one
>      --  isn't.  end if;
>   end if;

(I may be repeating myself, my previous reply somehow didn't make it to
the server...)

Clearly, representation has no impact on comparison. So we do not get
there, granted that such is the order of declaration in Ada.

The above code is not harder to compile than:

for Colours use (Red => 1, Green => 3, Blue => 2, Muddy => 4);

A, B : Colors;

if A < B then null; end if;

Here the result is also rather unrelated to the underlying rep values
order.

Also, a simple "cannonicalization" {take the least possible 'others'
value to the register (not memory)} makes the case with 'others' identical
to current situation.

Regards,
Wojtek