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Date: Wed, 18 Aug 2010 14:51:28 +0200
From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
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Subject: Re: S-expression I/O in Ada
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Date: 2010-08-18T14:51:28+02:00
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On 18.08.10 13:59, Natasha Kerensikova wrote:

> Then I don't really understand the point of having both Vectors and
> Doubly_Linked_Lists. The interface of Vectors is a strict superset of
> the interface of Doubly_Linked_Lists, and the only difference in
> complexity (which is advice anyway, so non-guaranteed) is on Prepend.

The difference in complexity, in both time and space, is likely
present in other operations. The Implementation Advice in the
LRM stipulates that Vector is likely an array, internally. It is
in GNAT's Vectors, last time I checked.  In addition to Cursor based
operations, Vectors have Index based operations, like
arrays. Lists don't have them; I trust that Vectors have the
lowest overhead for directly accessing specific elements of any
container, e.g.  "the elements at index 5 and 5 plus offset".
If you wanted the same for a list then this could mean linear
traversal. (At least when there are no auxiliary tables internal
to the list implementation, which might in turn be implemented
using a vector kind of thing, exposing a need for a vector
abstraction...)


Georg