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From: stefan-lucks@see-the.signature
Newsgroups: comp.lang.ada
Subject: Re: Efficient Sequential Access to Arrays
Date: Thu, 26 Jul 2012 21:37:48 +0200
Organization: Bauhaus-Universitaet Weimar
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Date: 2012-07-26T21:37:48+02:00
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On Thu, 26 Jul 2012, Georg Bauhaus wrote:

> On 26.07.12 10:38, Keean Schupke wrote:
> > What is the literal for 'invalid', IE:
> > 
> > X : Index := #INVALID -- we should be able to initialise to invalid.
> 
> A good approximation should be
> 
>   X : Index := To_Index (Index'Last + 1);
> 
> where To_Index is an instance of Unchecked_Conversion.

If To_Index is defined as

  function To_Index is new Unchecked_Conversion(Integer, Index);

this will fail if Index'Last = Integer'Last. 

Better use pragma Normalize_Scalars -- that cannot surprise you with a 
Constraint_Error at initialization time.  

-- 
---- Stefan.Lucks (at) uni-weimar.de, University of Weimar, Germany  ----
    <http://www.uni-weimar.de/cms/medien/mediensicherheit/home.html>
------  I  love  the  taste  of  Cryptanalysis  in  the  morning!  ------