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Re: Difference between NaN and NA?


From: Jaroslav Hajek
Subject: Re: Difference between NaN and NA?
Date: Fri, 9 Apr 2010 07:20:03 +0200

On Fri, Apr 9, 2010 at 7:03 AM, Søren Hauberg <address@hidden> wrote:
> tor, 08 04 2010 kl. 13:31 +0200, skrev Jaroslav Hajek:
>> But why make it built-in? I think that even with the current limited
>> OOP capabilities, it is possible to build a class that maintains the
>> NA's as a separate mask, making even the elementary operations
>> NA-aware (i.e. so that x + NA is NA and never NaN). Overloading the
>> statistics functions like mean etc. would also be quite simple.
>
> The problem with the current OOP programming is that you can't really
> inherit from base classes. If we created a 'NA_Friendly_Matrix' (NAFM?)
> class, but didn't (as an example) provide an implementation of the 'sin'
> function, the user would experience an error when calling 'sin'. The
> user would be forced to manually convert to an ordinary matrix whenever
> calling a function that does not have a NAFM implementation (the OOP
> stuff doesn't seem to provide a mechanism for automatically converting
> to a built-in type). This would IMHO just be a pain to use.
>
> So, if we were to have such a class, I fear it would have to be
> implemented in C++ and be part of Octave core. But perhaps I'm just
> missing the obvious here...
>

No, you're not, I agree this is a downside. Still, I think it would be
better than what we currently have.
Besides, it would be rather easy to overload all known mappers for the
class, using some sort of auto-generated m-files.


-- 
RNDr. Jaroslav Hajek, PhD
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz



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