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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Proposed change to BC iterator parameters
Date: Sun, 21 Dec 2003 14:58:35 +0100
Organization: At home
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Date: 2003-12-21T14:58:35+01:00
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Robert I. Eachus wrote:

> Currently I often provide tools in my data structures packages to
> provide everything viewed as an array.  This allows me to do what Bob
> wants, but it would be really nice to extend the language so that
> iterators are first class objects known to the language so that the
> above pseudo code (for E in ...) would be supported if the
> Some_Structure package provided an iterator.  You should also be able to
> say
> 
> if E in My_Structures.Some_Iterator then ...
> 
> (This would require another signature in the template for iterators to
> make it efficient.)
> 
> Do I think this will make it into Ada 0Y?  No.  Ada 1Z? Possibly.
> 
> But the trick of having data structure packages return an array view of
> a collection, or actually an array of access values, is very, very
> useful.  (Notice that the difference between such an iterator and normal
> iterators is that it provides a snapshot.  Changes to the actual data
> structure while iterating through the array won't be visible in the
> loop.  Often this is what you want.  Sometimes it isn't, then it gets
> painful...)

But if interfaces are being added to Ada, why not to allow abstract array
interface? Then just make My_Structure an implementation of the abstract
array and here you are! 

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