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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: If not Ada, what else...
Date: Thu, 30 Jul 2015 08:34:55 +0200
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Xref: number.nntp.giganews.com comp.lang.ada:194477
Date: 2015-07-30T08:34:55+02:00
List-Id: <comp.lang.ada>

On Wed, 29 Jul 2015 21:54:58 -0700, Paul Rubin wrote:

> Consider a multi-threaded program whose threads communicate through
> async queues.  So a work request comes into one thread, it gets decoded
> into a dictionary (container instance), and then the dictionary is
> dropped onto a queue.  Another thread later picks it up and processes
> it, sending the results through yet another queue.

Since queues marshal data there is no place for GC here. You put a *copy*
into the queue on one side and get another *copy* on the other. Queues,
messages, mailboxes etc are all by-value.

One of the advantages of Ada's tasking was the rendezvous allowing
by-reference passing, since rendezvous is a synchronous call.

Queueing references (I do it all the time implementing drivers and
protocols) is a great pain and GC is no help, because of canceling requests
and other sorts of stuff requiring deterministic time and order of
execution such actions. GC (at least a built-in one) has no place in
systems programming.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de