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Re: Passing optional parameters through a wrapper routine [message #18839 is a reply to message #18830]

Tue, 08 February 2000 00:00

davidf
Messages: 2866
Registered: September 1996

Senior Member

Kenneth P. Bowman (bowman@null.edu) writes:

> The _EXTRA keyword handles passing keyword parameters through a wrapper
> routine, but what about optional parameters?

_Extra (and _Ref_Extra, for that matter) apply only to *KEYWORD*
parameters. Positional parameters do not count.

> If my wrapper for TVRD has
> one of my own (mandatory) parameters, do I have to do the following?
>
> PRO TVRD_WRAPPER, my_arg, x0, y0, nx, ny, channel, _EXTRA = tvrd_keywords
>
> CASE N_PARAMS() OF
> 1 : image = TVRD( _EXTRA = tvrd_keywords)
> 2 : image = TVRD(x0, _EXTRA = tvrd_keywords)
> 3 : image = TVRD(x0, y0, _EXTRA = tvrd_keywords)
> 4 : image = TVRD(x0, y0, nx, _EXTRA = tvrd_keywords)
> 5 : image = TVRD(x0, y0, nx, _EXTRA = tvrd_keywords)
> 6 : image = TVRD(x0, y0, nx, ny, channel, _EXTRA = tvrd_keywords)
> ELSE : MESSAGE, 'Incorrect number of arguments.'
> ENDCASE
> ...

That's one way to do it. :-)

Another way is to define any parameter that is NOT passed
in. That might make more sense, since this is standard
operating procedure for any optional parameter.

IF N_Elements(y0) EQ 0 THEN y0 = 0
IF N_Elements(nx) EQ 0 THEN nx = 100
etc.

> (Is TVRD just counting the number of passed
> parameters and not checking to see if they are defined?)

Hard to know what TVRD is doing, but what *you*
better be doing is making sure any variable you
plan to use is defined. :-)

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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[Message index]

		Re: Passing optional parameters through a wrapper routine By: Mark Hadfield on Wed, 09 February 2000 00:00
		Re: Passing optional parameters through a wrapper routine By: bowman on Tue, 08 February 2000 00:00
		Re: Passing optional parameters through a wrapper routine By: davidf on Tue, 08 February 2000 00:00
		Re: Passing optional parameters through a wrapper routine By: bowman on Tue, 08 February 2000 00:00
		Re: Passing optional parameters through a wrapper routine By: Liam E. Gumley on Tue, 08 February 2000 00:00
		Re: Passing optional parameters through a wrapper routine By: davidf on Tue, 08 February 2000 00:00

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