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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Imitation is the sincerest form of flattery
Date: Sun, 23 Mar 2003 10:01:04 +0100
Organization: At home
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Date: 2003-03-23T10:01:04+01:00
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AG wrote:

> "Pascal Obry" <p.obry@wanadoo.fr> wrote in message
> news:ubs03lcdz.fsf@wanadoo.fr...
>
>> You mean that the compiler must generate a call to
>> Set_Element/Get_Element
> for
>> every reference to an array item, right ?
> 
> Well, I don't know what Dmitry meant of course :)
> 
> But my case would be that of the compiler knowing
> pretty darn well what the index is - it could be just
> a simple integer or so. The whole point is not about
> hiding the info from the compiler (how could you?)
> but about hiding/decoupling it from the clients of
> the package. And keeping control of it. And being
> able to change it without breaking all the clients ...

This is a more specialized problem. And yes, of course, there has to be 
universal index types. For example:

type My_Index is private index;
   -- Have to implement 'Succ, 'Pred, 'Range etc
type My_Array is array (My_Index range <>) of Something;

Here index is private, array is public. The most general case is when 
everything: index, element, and array are private:

type Item is private;
type Key is private index;
   -- Have to implement 'Succ, 'Pred, 'Range etc
type Table is private array (Key range <>) of Item;
   -- Have to implement Get, Set, Slice etc.

-- 
Regards,
Dmitry A. Kazakov
www.dmitry-kazakov.de