Re: Common sense...

["chris.danx" <spamoff.danx@ntlworld.com>]

"Wes Groleau" <wesgroleau@despammed.com> wrote in message
news:3D25D743.9F10D353@despammed.com...
> I'd say the iterators should be coded to prevent
> more than one being on a particular node at any time.
>
> But then you'd have hassles with concurrency.

There are hassles with concurrency in allowing more than one iterator to use
the same node.  What if the only iterator holding a node releases it at the
same time as another aquires that node, and the node was marked for
deletion?  It could happen that the aquiring code is stopped a split second
before completion, the node released, and the aquisition code resumed
leading to a nutty situation.

The point of these data structures isn't to be task safe, it's for
non-concurrent use (Ada doesn't have tagged protected object yet, otherwise
I'd code them to be task safe).  Whenever concurrency is used, the
programmer should probably run a protected object over the list and code
their own iterators (which is feasible given the structure of the
collection).

> Maybe deletion should be delayed until such time
> as no other iterator is at that node.

Maybe.