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Re: Math Question [message #51109 is a reply to message #51108]

Mon, 30 October 2006 07:29

Foldy Lajos
Messages: 268
Registered: October 2001

Senior Member

On Mon, 30 Oct 2006, edward.s.meinel@aero.org wrote:

>
> Rob wrote:
>> In general, powers of negative numbers are complex so you should start
>> with that assumption in the expression:
>>
>> IDL> print,(dcomplex(-1.0,0.0))^2.01
>> ( 0.99950656, 0.031410729)
>> IDL> print,(dcomplex(-1.0,0.0))^2.0
>> ( 1.0000000, -2.4492127e-016)
>>
>> It would be nice if IDL told you this rather than throwing a NaN at
>> you.
>
> Actually, to be consistent, IDL should just return a complex number.
> One of the reasons that I've been using IDL is that it automatically
> changes the variable TYPE when necessary so that I don't have to keep
> track of whether I'm operating on a BYTE, LONG, DOUBLE, whatever... Now
> I find out that it's "mostly" true (but who can refuse a nice mutton
> sandwich?).
>
> I would consider this a bug.
>
> Ed "to blave" Meinel
>

I think complex results should be returned only if complex input was
given, like in the example above. Otherwise, all your data would easily
become complex. Think of sqrt(-1.0), log(-1.0), asin(-2.0), etc.

regards,
lajos

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[Message index]

		Re: Math Question By: rkombiyil on Wed, 01 November 2006 04:51
		Re: Math Question By: Jo Klein on Tue, 31 October 2006 04:33
		Re: Math Question By: news.qwest.net on Mon, 30 October 2006 13:07
		Re: Math Question By: Jean H. on Mon, 30 October 2006 12:32
		Re: Math Question By: Jean H. on Mon, 30 October 2006 12:35
		Re: Math Question By: Jo Klein on Mon, 30 October 2006 12:17
		Re: Math Question By: Braedley on Mon, 30 October 2006 10:22
		Re: Math Question By: James Kuyper on Mon, 30 October 2006 10:15
		Re: Math Question By: David Fanning on Mon, 30 October 2006 09:19
		Re: Math Question By: James Kuyper on Mon, 30 October 2006 09:04
		Re: Math Question By: news.qwest.net on Mon, 30 October 2006 08:54
		Re: Math Question By: Foldy Lajos on Mon, 30 October 2006 07:29
		Re: Math Question By: edward.s.meinel@aero. on Mon, 30 October 2006 07:19
		Re: Math Question By: Rob Dimeo on Sun, 29 October 2006 16:15
		Re: Math Question By: Robbie on Sun, 29 October 2006 15:40
		Re: Math Question By: Robbie on Sun, 29 October 2006 15:01
		Re: Math Question By: Foldy Lajos on Sun, 29 October 2006 09:59

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