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Re: A simple IF statement question [message #42517 is a reply to message #42513]

Mon, 14 February 2005 06:37

Benjamin Luethi
Messages: 22
Registered: December 2004

Junior Member

Excerpt from the IDL help:

The definition of true and false for the different data types is as
follows:
- Byte, integer, and long: odd integers are true, even integers are false.
- Floating-point, and complex: non-zero values are true, zero values are
false.
The imaginary part of a complex number is ignored.
- String: any string with a nonzero length is true, null strings are false.
- Heap variables (pointers and object references): non-null values are
true,
null values are false.

In your case it's integer. So because 0, 2 and 24 are even they are
"false",
1 and 19 are "true" (odd).

Ben

On 14 Feb 2005 05:55:28 -0800, Andry William <andry_william@hotmail.com>
wrote:

> Dear IDL user,
>
> I am using IDL 6.1 on Linux SUSE. I am writing a simple code using the
> IF statement and am wondering about the following result:
>
> IDL> IF 1 THEN PRINT, '1' ELSE PRINT, 'None'
> 1
> IDL> IF 2 THEN PRINT, '2' ELSE PRINT, 'None'
> None
> IDL> IF 19 THEN PRINT, '19' ELSE PRINT, 'None'
> 19
> IDL> IF 24 THEN PRINT, '24' ELSE PRINT, 'None'
> None
> IDL> IF 0 THEN PRINT, '0' ELSE PRINT, 'None'
> None
>
> Am I wrong when I expect the IF statement to return always TRUE if the
> condition is not 0 (I mean something like 1,2,3,4,....)?
>
> Thanks for any comments.
>
> Andry

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[Message index]

		A simple IF statement question By: andry_william on Mon, 14 February 2005 05:55
		Re: A simple IF statement question By: Benjamin Luethi on Mon, 14 February 2005 06:37
		Re: A simple IF statement question By: David Fanning on Mon, 14 February 2005 07:11
		Re: A simple IF statement question By: David Fanning on Mon, 14 February 2005 06:49

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