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Re: NaN problems [message #43725 is a reply to message #43584]

Fri, 22 April 2005 20:38

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Y.T. writes:

> I don't have access to IDL on a win-box, but I have a (potentially
> stupid) question: On that page of yours where you write
>
> IDL> print, array ne array
> 0 0 0 0 0
>
> have you tried the converse, i.e.
>
> IDL> print, array eq array
>
> ?
>
> I am asking since, while it is true that a NaN is not equal to a NaN it
> does not seem to follow (to my wrinkled brain) that a NaN is
> necessarily UNequal to a NaN.
>
> In your version you test for the latter, and I'm kinda curious what
> would happen if you tried the former...

Well, looks like some things have changed since that
article was written. Here is what I get in IDL 6.1 on Windows:

IDL> a = [ 1.0, 2.0, !Values.F_NAN, 4.0, !Values.F_NAN ]
IDL> print, a ne a
0 0 1 0 1
% Program caused arithmetic error: Floating illegal operand
IDL> print, a eq a
1 1 0 1 0
% Program caused arithmetic error: Floating illegal operand

Consistent, anyway. :-)

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/

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[Message index]

		NaN problems By: David Lopez Pons on Thu, 21 April 2005 06:37
		Re: NaN problems By: R.Bauer on Sat, 23 April 2005 12:48
		Re: NaN problems By: David Fanning on Fri, 22 April 2005 20:38
		Re: NaN problems By: yp on Mon, 25 April 2005 16:51
		Re: NaN problems By: yp on Mon, 25 April 2005 16:49
		Re: NAN Problem By: R.Bauer on Thu, 14 January 2010 00:49
		Re: NAN Problem By: penteado on Wed, 13 January 2010 16:15
		Re: NAN Problem By: R.G.Stockwell on Wed, 13 January 2010 16:00
		Re: NAN Problem By: Foldy Lajos on Wed, 13 January 2010 13:00
		Re: NAN Problem By: penteado on Wed, 13 January 2010 12:59
		Re: NAN Problem By: David Fanning on Wed, 13 January 2010 12:39
		Re: NAN Problem By: jeanh on Wed, 13 January 2010 12:28

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