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From: Jacob Sparre Andersen <sparre@nbi.dk>
Newsgroups: comp.lang.ada
Subject: Re: Zero length Objects
Date: 30 Jun 2004 22:32:26 +0200
Organization: Munin
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Date: 2004-06-30T22:32:26+02:00
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Robert C. Leif wrote:

> I am trying to create a means to report the value of experimental
> parameters.  I would like to store only those parameters that I have
> selected.  Since thanks to Robert I. Eachus, I am using a variant
> record, I can set the parameter to null, which is presently stored
> as 16 bits.  I created an empty type; please see the small main
> procedure below. I have not been able to have the size attribute
> work directly on null.
> 
> with Ada.Text_Io;
> procedure Empty_Pkg is 
>    package T_Io renames Ada.Text_Io;
>    type Empty_Type is 
>          (Empty); 
>    for Empty_Type'Size use 0;
>    Empty_Var : Empty_Type;  
> begin
>    T_Io.Put_Line("The size of empty is " & Integer'Image(Empty_Var'Size));
> 
> end Empty_Pkg;
> 
> This produced: The size of empty is 8

I thought:

   type Even_Emptier_Type is null record;
   for Even_Emptier_Type'Size use 0;
   Even_Emptier_Var : Even_Emptier_Type;

might be more effective, but no, also the size of Even_Emptier_Var is 8. :(

Jacob
-- 
"Banning open source would have immediate, broad, and
 strongly negative impacts on the ability of many sensitive
 and security-focused DOD groups to protect themselves
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