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Re: Return UNDEFINED from a function [message #50688]

Thu, 12 October 2006 19:52

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Mark Hadfield writes:

> Spoken like a true IEP!
>
> For what purpose have you used this feature, David?

I use it with text widgets when I want to know if the
user actually typed something into the text widget.
Maybe they cleared the text that was there, but
didn't type anything else. This is hard to check for
because the text isn't really *there*, if you know
what I mean.

Here, for example, is code from FSC_INPUTFIELD:

IF String(testValue) EQ "NULLVALUE" THEN BEGIN
Ptr_Free, self.theValue
self.theValue = Ptr_New(/Allocate_Heap)
ENDIF ELSE *self.theValue = testValue

I return self.theValue, which I guess technically
is NOT an undefined variable, but is a pointer to
an undefined variable. But I can test it to see if
it is undefined.

Humm. Maybe this isn't *exactly* what Ed was complaining
about, but I still don't think it is a bug. :-)

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Re: Return UNDEFINED from a function By: David Fanning on Thu, 12 October 2006 19:52
		Re: Return UNDEFINED from a function By: badjelly.witch on Thu, 12 October 2006 14:27
		Re: Return UNDEFINED from a function By: JD Smith on Thu, 12 October 2006 12:54
		Re: Return UNDEFINED from a function By: Jean H. on Thu, 12 October 2006 11:21
		Re: Return UNDEFINED from a function By: JD Smith on Thu, 12 October 2006 10:53
		Re: Return UNDEFINED from a function By: MarioIncandenza on Thu, 12 October 2006 01:04
		Re: Return UNDEFINED from a function By: MarioIncandenza on Wed, 11 October 2006 16:28
		Re: Return UNDEFINED from a function By: MarioIncandenza on Wed, 11 October 2006 16:09
		Re: Return UNDEFINED from a function By: David Fanning on Wed, 11 October 2006 16:04

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