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From: dmitry6243@my-deja.com
Subject: Re: Disallowing Pre-Defined Operations
Date: 2000/03/13
Message-ID: <8aibjl$egt$1@nnrp1.deja.com>#1/1
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References: <8a9eeg$qtv$1@newpoisson.nosc.mil> <8ababr$c3u$1@wanadoo.fr>
 <38CA05AF.7E77790D@online.no>
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Date: 2000-03-13T00:00:00+00:00
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In article <38CA05AF.7E77790D@online.no>,
  "Tarjei Tj�stheim Jensen" <tarjei@online.no> wrote:
>
>
> That is really a workaround. I think both he and I would have
preferred
> something like
>
> pragma disallow_predefined(operator => "/", a_type, a_type);
> pragma disallow_predefined(operator => all, all, a_type);
> pragma allow_predefined(operator => "+", a_type, a_type);
> pragma map_predefined_result(result_type => integer, operator => "/",
a_type,
> a_type);
>
> I think that would be more readable and a lot less work. It will of
course not
> work very well with a nonconforming compiler.

I do not think that using pragmas (there are already too many of them)
is a right way. Anyway a more general solution is required. Some time
ago I proposed explicit operation hiding, something like:

package Unordered_Numbers is
   type Unordered is new Integer;

   function ">"  (Left, Right : Unordered) return Boolean is null;
   function ">=" (Left, Right : Unordered) return Boolean is null;
   function "<"  (Left, Right : Unordered) return Boolean is null;
   function "<=" (Left, Right : Unordered) return Boolean is null;
end Unordered_Numbers;

It was considered too complex to implement.

Regards,
Dmitry


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