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Re: Basic Math: I _hope_ this is a stupid question [message #43792 is a reply to message #43789]

Sun, 24 April 2005 14:48

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Ed Hyer writes:

> IDL> print,288*180
> -13696
> IDL> print,long(288*180)
> -13696
> IDL> print,ulong64(288*180)
> 18446744073709537920
> IDL> print,288.*180
> 51840.0
>
> I just want to multiply two integers! Is that so wrong?

Here are a couple of articles for you:

http://www.dfanning.com/math_tips/sky_is_falling.html
http://www.dfanning.com/math_tips/double.html

Where you see "double" you should read "long integer", and where
you see "float" you should read "integer".

Basically, casting a short multiplication (288*180) to a
long *after* you do the arithmetic, doesn't gain you
anything. You have to do it *before* you to the arithmetic. :-)

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]

		Re: Basic Math: I _hope_ this is a stupid question By: MarioIncandenza on Wed, 27 April 2005 16:14
		Re: Basic Math: I _hope_ this is a stupid question By: Geoff Cureton on Wed, 27 April 2005 09:26
		Re: Basic Math: I _hope_ this is a stupid question By: btt on Mon, 25 April 2005 05:44
		Re: Basic Math: I _hope_ this is a stupid question By: David Fanning on Sun, 24 April 2005 14:48
		Re: Basic Math: I _hope_ this is a stupid question By: K. Bowman on Thu, 28 April 2005 06:15

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