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Re: Keyword checking [message #31011 is a reply to message #31009]

Wed, 29 May 2002 07:15

Paul Van Delst[1]
Messages: 1157
Registered: April 2002

Senior Member

Randall Skelton wrote:
>
> I have run into a great deal of trouble checking keywords in IDL and I
> thought I would relay my thoughts and frustrations. I am trying to
> prevent a user from passing an undefined variable in a keyword...
>
> Imagine,
>
> pro test, A=a, B=b
> print, n_params()
> print, arg_present(a), keyword_set(a), n_elements(a), size(a,/type)
> print, arg_present(b), keyword_set(b), n_elements(b), size(b,/type)
> end
>
> If I call this routine as:
>
> IDL> .reset
> IDL> test, a=1, b=undefvar
> % Compiled module: TEST.
> 0
> 0 1 1 2
> 1 0 0 0
>
> So, in order to prevent a user from passing junk in a keyword, I have:
>
> pro test, B=b
> if n_elements(b) eq 0 and arg_present(b) eq 1 then $
> message, 'You passed an undefined variable as a keyword'
> if n_elements(b) gt 0 then b = 'passed'
> end
>
> Now,
>
> IDL> .reset
> IDL> test, b=junk
> % Compiled module: TEST.
> % TEST: You passed an undefined variable as a keyword
>
> Surely there must be something simpiler than my 2-step approach ;)

Why the arg_present? Do you specifically want to tell the user that what they passed was
undefined? I thought arg_present was for using when you wanted to return something in the
variable? If the data is for input only, won't n_elements() suffice?

me confused.

paulv

--
Paul van Delst Religious and cultural
CIMSS @ NOAA/NCEP/EMC purity is a fundamentalist
Ph: (301)763-8000 x7274 fantasy
Fax:(301)763-8545 V.S.Naipaul

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[Message index]

		Re: Keyword checking By: R.Bauer on Wed, 29 May 2002 09:02
		Re: Keyword checking By: Liam E. Gumley on Wed, 29 May 2002 08:22
		Re: Keyword checking By: thompson on Wed, 29 May 2002 07:55
		Re: Keyword checking By: Paul Van Delst[1] on Wed, 29 May 2002 07:15
		Re: Keyword checking By: Jaco van Gorkom on Wed, 29 May 2002 07:04
		Re: Keyword checking By: Jaco van Gorkom on Wed, 29 May 2002 06:52
		Re: Keyword checking By: David Fanning on Wed, 29 May 2002 06:43

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