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Re: Inheritance query [message #17770 is a reply to message #17640]

Thu, 11 November 1999 00:00

Struan Gray
Messages: 178
Registered: December 1995

Senior Member

Martin Schultz, m218003@modell3.dkrz.de writes:

> why do you use _REF_EXTRA in the procedure header
> but then pass it on to SuperClass via _EXTRA?

I freely admit that I don't understand the help files for _EXTRA
and _REF_EXTRA. I found by trial and error that the way I do it in my
SLFoWid examples allows extra keywords to be passed through to
procedures *and* for the results to be passed back to the main program
level. That is, if you have three procedures:

pro level3, result3=result3, _ref_extra=extra
result3=3
end

pro level2, result2=result2, _ref_extra=extra
result2=2
level3, _extra=extra
end

pro level1, result1=result1, _ref_extra=extra
result1=1
level1, _extra=extra
end

and call: level1, result1=result1, result2=result2, result3=result3
you end up with the expected numbers in result1,2,3.

The downside is that the intermediate procedures have no access to
keywords other than their own (ie, in level2, the variable result3 is
undefined, even after the call to level3). In object programming this
enforces a tidy programming style, where parameters are only dealt
with at the object level where they are declared, but in general that
might be too strong a restriction and then the only cure (that I
found) is to add the wanted keywords to the intermediate procedures
explicitly.

Struan

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[Message index]

		Inheritance query By: Bernard Puc on Thu, 04 November 1999 00:00
		Re: Inheritance query By: Struan Gray on Thu, 11 November 1999 00:00
		Re: Inheritance query By: m218003 on Thu, 11 November 1999 00:00
		Re: Inheritance query By: J.D. Smith on Wed, 10 November 1999 00:00
		Re: Inheritance query By: J.D. Smith on Wed, 10 November 1999 00:00
		Re: Inheritance query By: J.D. Smith on Mon, 15 November 1999 00:00

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