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Re: array handling [message #52113]

Mon, 08 January 2007 09:43

news.qwest.net
Messages: 137
Registered: September 2005

Senior Member

"Brian Larsen" <balarsen@gmail.com> wrote in message
news:1168100109.828745.131590@11g2000cwr.googlegroups.com...
> Something I have always wondered is the difference between using
> finite() and just using ne?
>
> As an example:
> IDL> array = [ 1.0, 2.0, !Values.F_NAN, 4.0, !Values.F_NAN ]
> IDL> Print, Where( NOT Float( Finite(array) ) )
> 2 4
> IDL> print, where(array ne array)
> 2 4
>
> What is the fundamental difference here? Speed? Style? or something
> else entirely?
>
> Cheers,
>
> Brian

while where(array ne array) is clever, short, and possibly fast
one should note (from IDL help):
"On Windows, using relational operators such as EQ and NE
with the values infinity or NaN (Not a Number) causes an "illegal operand"
error"

Programmers will generally avoid depending on a result that flags an error,
and is not strictly defined in the language. The results may change in
different versions
of IDL, and perahps on different operating systems. Who knows, in version 7,
IDL may
decide to make nan eq nan return 1.

Cheers,
bob

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[Message index]

		Re: array handling By: news.qwest.net on Mon, 08 January 2007 09:43
		Re: array handling By: David Fanning on Sat, 06 January 2007 08:51
		Re: array handling By: David Fanning on Sat, 06 January 2007 08:47
		Re: array handling By: Michael Galloy on Sat, 06 January 2007 08:39
		Re: array handling By: Brian Larsen on Sat, 06 January 2007 08:15
		Re: array handling By: David Fanning on Sat, 06 January 2007 07:01
		Re: array handling By: Brian Larsen on Thu, 11 January 2007 07:27

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