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From: rod.chapman@praxis-cs.co.uk (Rod Chapman)
Newsgroups: comp.lang.ada
Subject: Re: [Spark] Converting Arrays
Date: 12 Mar 2003 01:43:31 -0800
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Lutz Donnerhacke <lutz@iks-jena.de> wrote in message news:<slrnb6rfur.nq.lutz@taranis.iks-jena.de>...
> * Rod Chapman wrote:
> > A common trick in this case is to use a local,
> > hidden procedure to initialise the out parameter:
> 
> Cool idea. I read the book yesterday evening till midnight and came to the
> conclusion, that I have to replace Fullpath by a large constraint array.
> This was obviosly wrong. You can always switch off Spark checkings when
> running into trouble. :-/
> 
> But how can I write the required pre conditions?
> 

You can pass the Length of the Path parameter as an addition "in"
parameter.  e.g.

  procedure To_Fullname (S           : in     String;
                         Path        :    out Fullname;
                         Path_Length : in     Natural);
  --# derives Path from S, Path_Length;
  --# pre S'Length < Path_Length;

Then a caller simply does:

  To_Fullname (LS, P, P'Length);

or similar.
 - Rod


I