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Ublas : |
Subject: Re: [ublas] fixed size vector in boost::numeric::ublas?
From: Vardan Akopian (vakopian_at_[hidden])
Date: 2010-07-23 15:00:09
On Fri, Jul 23, 2010 at 5:23 AM, Nasos Iliopoulos <nasos_i_at_[hidden]> wrote:
>
> If I remember well from my implelentation the major decision that has to be made relates to the resize(..) member function. Since the fixed types cannot resize it would seem obvious that those functions should not be implemented at all, but I think uBlas is using it in some algorithms, so either the algorithms need to be specialized, or the the fixed type resize function needs to be implements as an empty function. I think the first option is the best.
>
The idea of a fixed size vector has been discussed multiple times on
this list over the years. Typically it has been rejected because the
Vector Concept (as per
http://www.boost.org/doc/libs/1_43_0/libs/numeric/ublas/doc/container_concept.htm#vector
), defines the resize() method. Moreover it has a post condition
v.size () == n. So not having an implementation would break the
concept, having an empty implementation would break the concept's post
condition. A third option is to throw an exception (saying that it
cannot be resized). I'm not sure if throwing an exception technically
breaks the concept. If it does not, then we're fine. Otherwise, we
should either consider changing the concept, or agree that
fixed_vector does not implement the Vector concept (in which case
naming it a "..._vector" is somewhat misleading).
-Vardan