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From: Adam Beneschan <adam@irvine.com>
Newsgroups: comp.lang.ada
Subject: Re: Array Help?
Date: Wed, 29 Feb 2012 12:40:57 -0800 (PST)
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Date: 2012-02-29T12:40:57-08:00
List-Id: <comp.lang.ada>

On Feb 29, 8:09=A0am, Robert A Duff <bobd...@shell01.TheWorld.com>
wrote:
> Adam Beneschan <a...@irvine.com> writes:
> > =A0 type Integer_Array is array (Integer range <>) of Integer;
> > =A0 A : Integer_Array (2 .. 7);
>
> Right, and this is a rich source of bugs. =A0You usually want
> arrays to start at 1, or sometimes 0 (assuming the index type
> is a signed integer type, which is almost always the case
> for unconstrained arrays).

I think most of my array subtypes start at 0 or 1.  Occasionally I
find a good reason to start at -1.  The other thing is that if I write
a procedure with an unconstrained array parameter P, I'll often
declare a local variable like

   A : Some_Array (P'Range);

where the array may or may not be the same array type as the
parameter.  It's very useful to be able to declare an array where the
index values mean the same thing as the index values into a different
array, rather than having to deal with some blasted +/- offset when
trying to work with parallel elements in the two arrays.

                       -- Adam