Re: [boost] Re: Container Adaptors

From: David A. Greene (greened_at_[hidden])
Date: 2002-10-28 16:00:38

Roland Richter wrote:
>
> + Yes, it might be valueable to have a container adaptor or "views"
>   library (I like the later term better) which follows closely the
>   paths of the iterator adaptor library.

That's the general idea, yes.

> + If given some further thought, such an container adaptor library
>   appears as a straight-forward extension to the iterator adaptor
>   library. As much as the iterator adaptor lib is designed to
>   make "smart iterators" out of dumb one's, a container adaptor
>   library would wrap STL containers and add functionality to them.

Precisely.  It's not really an extension of iterator adaptor, but
rather it follows the same model.

> + Another way to think of views is that these mimic STL containers
>   (i.e., provide a common subset of methods, such as begin(), end(),
>    size(), etc.), but do return adapted iterators instead of ordinary ones.
>   Simply put: filter_view::iterator = filter_iterator_type etc.

"View" sounds a little too static to me.  The idea I have is not to
take existing data and provide different perspective on it.  Rather
it is to take a entity that organizes data and provide a different
interface to it, which may result in a different organization of the
data.  Views may be a subset of this goal.

> + I do not know your exact requirements; however, I doubt that views
>   are what you really need to design a "fixed-sized vector", since,
>   as Martin Weiser already pointed out, such container adaptors provide
>   "immutable 'views' onto existing data".

Right, that was exactly my comment.

>  > We raised this topic some time ago, but got only a limited response. Not
>  > much discussion evolved.
> 
> I guess the reason for this is that STL supports a style of programming
> where iterators are used in preference over containers. Thus, to adapt
> iterators seems to be more important than to adapt containers.

Unless the container is modeling some real-world item.  As I've
mentioned before, I've found it useful in simulation.

> As a final point, let me add that I hacked an own version of a views
> library (completely relying on Boost.IteratorAdapor, which makes things
> much easier compared to VTL) some time ago (not guaranteed to even
> compile with any compiler different than gcc).
> 
> If there actually is some interest in it [is there?], I'd be happy
> to contribute it to the Boost community.

How does it differ from the VTL?

                      -Dave

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