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From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: Processing array subsections, a newbie question.
Date: Sat, 12 Jun 2010 22:54:38 +0200
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Date: 2010-06-12T22:54:38+02:00
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"Peter C. Chapin" <pcc482719@gmail.com> writes:
> Ok        : Boolean := True;
> Index_Fst : Natural := Buffer'First;
> Index_Lst : Natural;
> ...
>
> while Ok and Index_Fst <= Buffer'Last loop
>   Do_Something(Buffer, Index_Fst, Index_Lst, Ok);
>   Index_Fst := Index_Lst + 1;
> end loop;
>
> The problem with this code is that the assignment to Index_Fst inside the loop
> might raise Constraint_Error if Index_Lst = Buffer'Last after Do_Something
> finishes. I can work around this problem but my solutions tend to be rather
> ungainly looking. Surely there must be an easy way to handle this.

How about:

Ok        : Boolean := True;
Index_Fst : Natural := Buffer'First;
Index_Lst : Natural;
...
loop
   Do_Something(Buffer, Index_Fst, Index_Lst, Ok);
   exit when not Ok;
   exit when Index_Fst = Buffer'Last;
   Index_Fst := Index_Lst + 1;
end loop;

-- 
Ludovic Brenta;