| Re: Philosophical Question about NAN [message #63718 is a reply to message #63705] |
Tue, 18 November 2008 05:05   |
Jeremy Bailin
Messages: 618
Registered: April 2008
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Senior Member |
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On Nov 17, 9:58 am, David Fanning <n...@dfanning.com> wrote:
> Folks,
>
> I've had a couple of run-ins lately with NANs and I wonder
> why routines like TOTAL and MEAN don't have the NAN keyword
> set to 1 by default. Why does the user have to set it?
>
> I understand the argument that the NAN capability was
> added as an afterthought (or more likely when someone
> standardized the NAN bit pattern), and so the functionality
> was added as an optional addition that enhanced the function
> rather than changed it. But really...is there a reason
> why it is not the default now?
>
> One could argue, I suppose, that having a program stumble
> over a NAN alerts you to its presence in your data. That
> is useful, certainly. But, typically, once I add a NAN
> keyword to my code, I don't know (nor do I or care) if the
> argument has NANs. Is this lazy programming on my part?
>
> I am just wondering whether not setting the default value
> of the NAN keyword to 1 on routines like TOTAL, MEAN,
> et. al is the functional equivalent of not setting the
> default values of the COLOR and BITS_PER_PIXEL keywords
> to the PostScript device to something useful by default.
> That is, an act of negligence on the part of the
> manufacturer.
>
> What say you?
>
> Cheers,
>
> David
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming:http://www.dfanning.com/
> Sepore ma de ni thui. ("Perhaps thou speakest truth.")
My 2 cents... is that about 75% of the time that my data ends up
having NaNs in it, it's not intentional and is a sign of something
screwy. So by not enabling /NAN by default, debugging becomes much
simpler - it's immediately obvious if the result is NaN that
something's gone wrong, while it's not obvious if it gives me some
real but incorrect number.
-Jeremy.
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