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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: discriminant questions
Date: Wed, 21 Sep 2011 21:52:47 -0500
Organization: Jacob Sparre Andersen Research & Innovation
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Xref: news1.google.com comp.lang.ada:18072
Date: 2011-09-21T21:52:47-05:00
List-Id: <comp.lang.ada>

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:1tpl2pc36ptr4$.txv4v3wmkjlm.dlg@40tude.net...
...
>> Nobody is forcing referential semantics, although it might be the most
>> natural and efficient solution for iterators.
>
> Of course it does, because the iterator refers to the container and to an
> element in that container. Which is evidently fragile as any reference 
> when
> the container and its element mutate.

Fragile perhaps, but it is definitely possible to be safe (which is more 
important, IMHO). Ada.Containers are safe in this aspect, as any attempt to 
mutate the container ("tampering") is required to raise Program_Error. 
That's true as long as the iterator or reference exist. (Note that 
"tampering" only is an issue if the container is changed; it's not a problem 
for the individual element contents to be changed, which some exceptions 
having to do with discriminants or tags.)

                                          Randy.