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Re: Creating Variables in Programs [message #12301 is a reply to message #12195]

Tue, 14 July 1998 00:00

davidf
Messages: 2866
Registered: September 1996

Senior Member

Riemar Bauer (r.bauer@fz-juelich.de) writes:

> An other way to get an undefined
> variabel is b=n_elements(a)
> Yes b is well defined by 0 but a is defined as undefined.
>
> help
> % At $MAIN$
> B LONG = 0
> A UNDEFINED = <Undefined>

Uh, this *only* happens if A is undefined to start with
and is perfectly normal behavior. In fact, it is the only
way to know if keywords are undefined in an IDL procedure or
function:

IF N_Elements(keyword) EQ 0 THEN keyword = 5

This construction NEVER makes A undefined (or there is
something seriously wrong with your version of IDL):

A = 5
B = N_Elements(A)
HELP, A, B

A INT = 5
B LONG = 1

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting
E-Mail: davidf@dfanning.com
Phone: 970-221-0438
Coyote's Guide to IDL Programming: http://www.dfanning.com/

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[Message index]

		Creating Variables in Programs By: p.phillips on Fri, 10 July 1998 00:00
		Re: Creating Variables in Programs By: davidf on Tue, 14 July 1998 00:00
		Re: Creating Variables in Programs By: R. Bauer on Tue, 14 July 1998 00:00
		Re: Creating Variables in Programs By: R. Bauer on Tue, 14 July 1998 00:00

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