On 4/13/2010 10:43 AM, David Mertens wrote:
>
> PDLs have the hdr() function that returns a plain ol' Perl hash. It's
> supposed to be for FITS headers, but it's good for anything. I've used
> it for all kinds of things as a way to teach PDL how to do new tricks
> (and remember associated data) and I've been thinking about writing up
> guidelines for general OO machinations using PDL and in particular
> storing extra data in the hdr hash, just as you would store a normal
> Perl object's data in a (blessed) hash. I don't think that you need to
> subclass PDL to do that, you can simply extend it.

Yes, but there might be problems with namespace collisions.
For example, what if one had a key that matched on of the
default FITS keys, then one could get erroneous results
because of the conflict in usage.

> As for storage, a first cut could be to use Data::Dumper and put that
> directly into the header files for the data. You could then simply eval
> that part of the header file and put the resulting hash into the hdr of
> the piddle you're loading.
>
> I have no idea what kind of metadata you need to store, but I would be
> surprised if using the built-in hdr wouldn't be adequate.

I think that the built-in header might have an advantage
in performance.

--Chris

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