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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: A few questions
Date: Thu, 12 Nov 2015 21:56:26 +0100
Organization: cbb software GmbH
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Date: 2015-11-12T21:56:26+01:00
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On Thu, 12 Nov 2015 12:28:46 -0600, Randy Brukardt wrote:

> Personally, I find the "of" form unnecessary; we've iterated arrays for 
> decades without direct access to the element (using the "cursor", that is 
> the array index), so why are containers different?

Of course it is different. Index does not iterate array, it does the
array's index range. That is the difference.

You can iterate elements of a container or indices of a container. It is
not same.

> Especially as the 
> indexing form works on all of the language-defined containers (you never 
> need to explicitly call Reference or Element). So an "in" iterator looks 
> just like the array iteration that we've been using from the beginning of 
> time. What's so hard about that?

There could be cases when a container does not have any natural index. E.g.
a bag, a set, a files directory etc. You could iterate elements of without
inventing indices. Especially when the index is volatile. Consider an
implementation that gets a result set of a DB query and then iterates the
result.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de