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From: Georg Bauhaus <bauhaus@futureapps.invalid>
Newsgroups: comp.lang.ada
Subject: Re: What is the purpose of Vector.Query_Element?
Date: Mon, 27 Jul 2015 01:02:45 +0200
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On 27.07.15 00:09, EGarrulo wrote:
> The package that defines Vector provides this procedure:
>
> procedure Query_Element
>    (Container : in Vector;
>     Index : in Index_Type;
>     Process : not null access procedure (Element : in Element_Type));
>
> Why is this procedure provided?

To avoid copying.
"These procedures provide in situ access to an element."
  -- Ada Rationale 2005 Ch 8.2.
http://www.adaic.org/resources/add_content/standards/05rat/html/Rat-8-2.html

>  Isn't `Query_Element (Vector, Index, Process'Access)` the same as `Process (Element (Vector, Index))`?

Maybe the difference is a little more apparent when
considering Update_Element.