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Re: wrapper functions [message #50492]

Thu, 05 October 2006 20:04

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Kenneth P. Bowman writes:

> I find that N_PARAMS() with SWITCH is very handy for setting defaults in
> procedures where optional positional parameters make sense.
>
> PRO BLAH, A, B, C
>
> SWITCH N_PARAMS() OF
> 0 : A = ...
> 1 : B = ...
> 2 : C = ...
> ENDSWITCH

In thinking about it, I guess I use N_ELEMENTS for
all my parameters because I can throw better errors
since I know *exactly* which parameter is missing:

IF N_Elements(foo) EQ 0 THEN $
Message, 'Argument FOO must be a 2D array.'

I can also trap the error of the user calling my
routine with an undefined variable, rather than with
a real variable. This happens more often than you would
think in IDL programming courses. N_PARAMS, of course,
can't tell you much of anything about the parameter.

Cheers,

David

P.S. And don't even get me started on the mostly
mis-used KEYWORD_SET. I see that function misused
almost constantly in IDL programs to perform the
function of N_ELEMENTS. Folks, it DOESN'T!! :-)

--
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: wrapper functions By: David Fanning on Thu, 05 October 2006 20:04
		Re: wrapper functions By: Kenneth P. Bowman on Thu, 05 October 2006 19:28
		Re: wrapper functions By: David Fanning on Thu, 05 October 2006 19:11
		Re: wrapper functions By: Robbie on Thu, 05 October 2006 19:01
		Re: wrapper functions By: David Fanning on Thu, 05 October 2006 18:35
		Re: wrapper functions By: David Fanning on Thu, 05 October 2006 18:28
		Re: wrapper functions By: Robbie on Thu, 05 October 2006 18:14
		Re: wrapper functions By: David Fanning on Thu, 05 October 2006 17:52
		Re: wrapper functions By: Robbie on Thu, 05 October 2006 17:13
		Re: wrapper functions By: Dominic Metzger on Thu, 05 October 2006 16:51
		Re: wrapper functions By: David Fanning on Thu, 05 October 2006 16:39
		Re: wrapper functions By: K. Bowman on Fri, 06 October 2006 06:35
		Re: wrapper functions By: Dominic Metzger on Thu, 05 October 2006 22:32

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