| Re: Passing optional parameters through a wrapper routine [message #18920 is a reply to message #18840] |
Wed, 09 February 2000 00:00   |
Craig Markwardt
Messages: 1869
Registered: November 1996
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Senior Member |
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bowman@null.edu (Kenneth P. Bowman) writes:
> The _EXTRA keyword handles passing keyword parameters through a wrapper
> routine, but what about optional parameters? 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
I have a wrapper procedure in XFWINDOW.PRO which looks remarkably
similar to this one. To counter David, I find that it's usually the
cleanest and safest bet to mess with as *few* parameters and keywords
as possible when wrapping another function. You can get into too much
trouble trying to second-guess what the defaults should be.
The ugliness above could be solved if there would be a
variable-parameter feature to the language. This might work the same
way that _EXTRA passes keywords through. For example, in
PRO TVRD_WRAPPER, my_arg, $EXTRA_ARGS$, _EXTRA = tvrd_keywords
image = TVRD($EXTRA_ARGS$, _EXTRA = tvrd_keywords)
end
the black box variable $EXTRA_ARGS$ would somehow contain any
additional arguments, and could be passed directly through to the
wrapped function. The use of $'s is syntactic sugar to be sure, but
it's just an example.
Craig
--
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Craig B. Markwardt, Ph.D. EMAIL: craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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