| Re: Yet again, The Sky is Falling! [message #52963 is a reply to message #52872] |
Fri, 09 March 2007 13:11   |
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Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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David Fanning wrote:
> Paul van Delst writes:
>
>>> 2. Don't pass the same named variable as both an input and output
>>> parameter in a routine call. (Or as two output parameters!)
>> Good lord. Why would anyone do *that*? (In any language) :o)
>
> Well, because it seems "natural", for one thing. Consider
> the POSITION keyword to TVIMAGE when you don't know for
> sure if the user wants to preserve the aspect ratio of the
> image or not, but you are keenly interested in knowing
> where the image ended up.
Well, of course. That's normal and I do that a lot (for the above purpose and also to
prevent memory leaks) in f95 all the time. The syntax would be
real, intent(in out) :: position(:)
> That's, uh, about the only example I can thing of at the
> moment, but it seems a good one. :-)
That's not how I interpreted Mike's post. I meant if given a procedure like:
pro mypro, input_var, output_var
output_var = input_var + 1.0
end
then don't call it thusly,
x = 1.0
mypro, x, x
I don't even know if it's possible in IDL... or f95..or C... or..? Hence my "why on
earth...?"
cheers,
paulv
--
Paul van Delst Ride lots.
CIMSS @ NOAA/NCEP/EMC Eddy Merckx
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