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RE: user data types

From: Billings, Paul
Subject: RE: user data types
Date: Wed, 10 Aug 2005 10:25:02 -1000


Thank you very much for your thoughts.  I had envisioned a linear hierarchy,
however you described a design using aggregation.  Is this required due to
the way octave interfaces or simply a design preference?  A class hierarchy
(left to right):

My thinking:
octave_base_value <- Data3d <- SequenceData
                            <- Custom1Data

My understanding of your thinking:
octave_base_value <- OctaveData3d (has a Data3d* member)
Data3d <- SequenceData
       <- Custom1Data

Is 1) my understanding of your suggestion correct, and 2) do you see
advantages to either approach?  Your design would allow switching of data
types, while I would have to declare another instance.  Am I missing
something important?


> -----Original Message-----
> From: Stefan van der Walt [mailto:address@hidden
> Sent: Tuesday, August 09, 2005 11:32 PM
> To: Paul Billings
> Subject: Re: user data types
> Hi Paul
> Another simple example is at
> (the result of the thread you refer to below).
> What you want to do sounds reasonable easy to implement (although more
> complex than the example above, since you want to involve multiple
> formats).
> Still, don't think it should be a problem.  Create an Octave class,
> say OctaveFormat that is a wrapper around a base class "Format".
> OctaveFormat contains a pointer to an instance of Format (which could
> be SequenceFormat or CustomOneFormat or whatever).  Octave interacts
> with OctaveFormat, which in return interacts with the contained format
> class.
> Or something along those lines...
> Regards
> Stéfan
> On Tue, Aug 09, 2005 at 12:50:50PM -1000, Paul Billings wrote:
> > It still appears that I am on the right track.  Further
> research has turned
> > up a similar thread:
> >
> My desire for a simple example is at:
> I know I need to define the subsref function (matlab), but I'm sure
> something similar for octave.
> Is there anything tricky to having a hierarchy of these types?  I want a
> base class with most of the functionality (e.g., subsref(), size(), etc.).
> Subsref() would call a virtual function load_data() to get the specific
> data.  This virtual function would be defined in various subclasses (each
> derived from the base class), where each subclass is specific to a
> particular format (e.g., sequence of image files, custom format #1, custom
> format #2, etc.)
> Paul

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