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Re: Return UNDEFINED from a function [message #50699 is a reply to message #50697]

Thu, 12 October 2006 10:53

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Thu, 12 Oct 2006 01:04:44 -0700, Ed Hyer wrote:

>> [quoted text muted]
>
> I fail to see how this "feature" could be used. If you call a function as
> value = FUNCTION(args)
> and FUNCTION() returns an <UNDEFINED>, this will cause an error.
>
> Of course, I'm not using my imagination enough. If you have a procedure,
> and you're not feeling like using any normal error-handling mechanism, you
> can simply define it as a function and execute it using HELP, and use a
> HELP-parsing routine to determine if it ran correctly or not. Is there an
> obfuscated IDL contest?

I think it's a shame IDL doesn't have undef() for creating a real,
undefined anonymous variable (you can fake it just by mentioning an
undeclared variable). And, analogously, defined() to test if a
variable is defined (which reads better than 'n_elements(var) ne 0').
But in any case, you could always have something like:

if n_elements(function(args,OTHER=other)) ne 0 then do_something_with,other

Not exactly a standard paradigm, but it might come in useful
somewhere. In particular, if FUNCTION passes an argument through, and
that argument is undefined, it would be nice to keep it undefined.

JD

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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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