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From: George Haddad <george.haddad@lmco.com>
Subject: Re: Valid Attribute and Unchecked Conversion
Date: 1996/10/02
Message-ID: <3252ED6B.1B74@lmco.com>#1/1
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references: <DyCF97.7zp@world.std.com> <1996Sep26.191257.1@eisner>
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organization: Lockheed Martin M & S, Sunnyvale, CA
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Date: 1996-10-02T00:00:00+00:00
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Robert I. Eachus wrote:
>     Change to:
> 
>      declare
>          type T is range 1 .. 10;
>          for T'SIZE use Integer'SIZE;
>          function To_T is new Unchecked_Conversion (Integer, T'Base);
>          O : T;
>       begin
>         begin
>           O := To_T (0);
>         exception when others => null;
>         end;
> 
>         if O'Valid then
>           ...
>       end;
> 
>       ...and you still don't get what you want.  In this case the
> O'Valid check may or may not succeed, depending on the initial junk in
> that stack location.

   So, what about:

      declare
        type T is range 1 .. 10;
        function To_T is new Unchecked_Conversion (Integer, T);
        X : T;
      begin
        if To_T(0)'Valid then
           X := To_T(0);
           ...
      end;

   I realize that this involves calling the same function twice (which 
is probably not a problem given that the function is an instance of 
Unchecked_Conversion), but is the fragment above erroneous?
-- 
I found these opinions on my doorstep, would you please give them a good 
home?