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Re: Interesting Filled Contour Problem [message #79897 is a reply to message #79893]

Tue, 17 April 2012 04:54

Carsten Lechte
Messages: 124
Registered: August 2006

Senior Member

On 17/04/12 05:21, Craig Markwardt wrote:
> NAN OP X
> will always result in a value of NAN, for all operations OP and for all operands X

Unless that OP is a comparison operator; then the result is always
false, i.e. NAN eq NAN is false etc.

> Strangely,
> NAN< 0
> produces NAN, so apparently NAN is a negative number (!!!).

You jest, but what is happening is this:

IDL> print, asdf, asdf GT 0, asdf LT 0, asdf < 0, asdf > 0
-1.0000000 -NaN NaN 1.0000000
0 0 0 1
1 0 0 0
-1.0000000 -NaN NaN 0.0000000
0.0000000 0.0000000 0.0000000 1.0000000

It seems like "asdf < 0" zeros those elements WHERE( asdf gt 0), i.e.
element 3, while "asdf > 0" uses the COMPLEMENT of WHERE( asdf gt 0),
i.e. [0,1,2], instead of zeroing WHERE( asdf LT 0), i.e. [0].

Unexpected, inconsistent, yet conforming to IEEE.

chl

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[Message index]

		Re: Interesting Filled Contour Problem By: Kenneth P. Bowman on Tue, 17 April 2012 09:00
		Re: Interesting Filled Contour Problem By: Carsten Lechte on Tue, 17 April 2012 04:54
		Re: Interesting Filled Contour Problem By: David Fanning on Mon, 16 April 2012 20:51
		Re: Interesting Filled Contour Problem By: Craig Markwardt on Mon, 16 April 2012 20:21
		Re: Interesting Filled Contour Problem By: David Fanning on Mon, 16 April 2012 13:57
		Re: Interesting Filled Contour Problem By: David Fanning on Mon, 16 April 2012 12:28

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