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Re: string definition question [message #33607 is a reply to message #33606]

Tue, 14 January 2003 10:13

btupper
Messages: 55
Registered: January 2002

Member

On Tue, 14 Jan 2003 10:55:24 -0500, Paul van Delst
<paul.vandelst@noaa.gov> wrote:

> Hello there,
>
> Although I should probably know the answer to this, since all my IDL reference books have
> been borrowed, hope you don't mind me asking here.
>
> I'm a bit anal about argument checking in IDL. After establishing that the correct number
> of arguments has been passed using:
>
> n_arguments = 1
> IF ( N_PARAMS() LT n_arguments ) THEN $
> MESSAGE, 'Invalid number of arguments.', $
> /NONAME, /NOPRINT
>
>
> My standard method for checking string arguments (like filenames to read) is something
> like:
>
> IF ( N_ELEMENTS( FileNAME ) EQ 0 ) THEN BEGIN
> MESSAGE, 'Input FileNAME argument not defined!', $
> /NONAME, /NOPRINT
>
> IF ( STRLEN( FileNAME ) EQ 0 ) THEN $
> MESSAGE, 'Input FileNAME argument not defined!', $
> /NONAME, /NOPRINT
>
> If I pass a zero-length string, e.g. FileNAME='', the N_ELEMENTS() test passes so I always
> test for a non-zero string length (it's happened). If I combine the two tests using AND,
> then if the variable is undefined, the STRLEN() function generates an errors (since its
> argument must be defined).
>
Hi Paul,

I can't think how to get away from the two step test. Usually the
ARG_PRESENT() test is reserved for optional output keywords. I would
stick to N_ELEMENTS() and N_PARAMS()

You could squish the two statements into one - but there are still two
tests involved.

If (n_elements(FileName) NE 0) Then $
If (StrLen(FileName[0]) EQ 0) Then $
Print, "Ain't nuttin here, Paul" Else $
Print, "Here's the string" + fileNAME[0] Else $
Print, "fileNAME argument is required, ya' know"

Ben

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[Message index]

		Re: string definition question By: thompson on Wed, 15 January 2003 07:31
		Re: string definition question By: sheryn.gillin on Tue, 14 January 2003 14:12
		Re: string definition question By: Paul Van Delst[1] on Tue, 14 January 2003 13:27
		Re: string definition question By: Mark Hadfield on Tue, 14 January 2003 12:39
		Re: string definition question By: Mark Hadfield on Tue, 14 January 2003 12:32
		Re: string definition question By: JD Smith on Tue, 14 January 2003 11:36
		Re: string definition question By: Paul Van Delst[1] on Tue, 14 January 2003 11:28
		Re: string definition question By: thompson on Tue, 14 January 2003 10:45
		Re: string definition question By: btupper on Tue, 14 January 2003 10:13
		Re: string definition question By: Paul Van Delst[1] on Tue, 14 January 2003 10:04

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