From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00
	autolearn=unavailable autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail
From: Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Queue implementation in Ada
Date: Tue, 28 Oct 2014 11:29:28 -0700
Organization: Also freenews.netfront.net; news.tornevall.net;
 news.eternal-september.org
Message-ID: <m2ona2$tv6$2@dont-email.me>
References: <8456b674-a10d-411f-bcf6-90d9638b7fc9@googlegroups.com>
	<m2n2jl$d70$1@dont-email.me> <lyk33k7btz.fsf@pushface.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
Injection-Date: Tue, 28 Oct 2014 18:29:23 +0000 (UTC)
Injection-Info: mx02.eternal-september.org;
 posting-host="206f88a41f45fc94d25d07d064d738e2";
	logging-data="30694"; mail-complaints-to="abuse@eternal-september.org";
	posting-account="U2FsdGVkX1/HJlpeRD1tOfNH6dwtZvP9GfvSx5jqhO8="
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
 rv:31.0) Gecko/20100101 Thunderbird/31.2.0
In-Reply-To: <lyk33k7btz.fsf@pushface.org>
Cancel-Lock: sha1:44w1vejA35pvgFEk1dwjas7c62U=
Xref: news.eternal-september.org comp.lang.ada:22860
Date: 2014-10-28T11:29:28-07:00
List-Id: <comp.lang.ada>

On 10/28/2014 03:00 AM, Simon Wright wrote:
> Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org> writes:
> 
>> If you want unsynchronized queues, you could build your own, possibly
>> using Ada.Containers.Doubly_Linked_Lists (ARM A.18.3).
> 
> I used Vectors, ARM A.18.2. Not sure why one would choose one over the
> other?

In the sense that both are random-access sequences, with essentially the same
interface, there is none. One could build either as a wrapper around the other.

Clearly any difference must be in the implementation. Given that one is named
Doubly_Linked_Lists and the other adds index-based access, it's reasonable to
think that the former is expected to be implemented as a linked list and the
latter as an array. Since a queue experiences frequent additions to the tail and
frequent deletions from the head, the linked list seems appropriate.

-- 
Jeff Carter
"My mind is a raging torrent, flooded with rivulets of
thought, cascading into a waterfall of creative alternatives."
Blazing Saddles
89