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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: design changes per Ada 2005/12?
Date: Tue, 26 Apr 2011 18:12:02 -0500
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2011-04-26T18:12:02-05:00
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"Lucretia" <Lucretia9000@yahoo.co.uk> wrote in message 
news:524ddf9b-2727-461a-b14b-e2171cf61190@dn9g2000vbb.googlegroups.com...
On Apr 23, 1:41 am, "Randy Brukardt" <ra...@rrsoftware.com> wrote:
> "Lucretia" <Lucretia9...@yahoo.co.uk> wrote in message
...
>> We tried that with the new Queue containers, and IMHO it is a disaster. 
>> You
>> have to use an extra instantiation and extra formal parameters for a 
>> feature
>> that you are not going to use on 90% of the programs. (Typically, you 
>> only
>> use one kind of queue in a program.)
>
>Things like iterators could be implemented with interfaces ok.

And indeed they are (see AI05-0139-2). But it is interesting that iterators 
were the only example where interfaces worked. We tried and discarded models 
using interfaces for both implicit dereferencing and indexing, because they 
either ended up as nothing more than a marker (which can be accomplished in 
a straightforward way without using any interfaces), or because they 
required violating visibility/overloading rules.

                                        Randy.