Re: Queue implementation in Ada

[Simon Wright <simon@pushface.org>]

Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org> writes:

> 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.

Good point.

I've been put off Doubly_Linked_Lists because I would usually have been
quite happy with singly linked lists. But really, what difference does
it make if all you're doing is implementing a Queue!