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Re: Structures [message #42917 is a reply to message #23873]

Tue, 01 March 2005 16:21

mperrin+news
Messages: 81
Registered: May 2001

Member

Michael Wallace <mwallace.no.spam@no.spam.swri.edu.invalid> wrote:
> I learned all this the hard way by trying to figure out why I kept
> getting errors when I'd attempt to use a different array size for some
> of my structure variables. I finally ran across this in the IDL
> documentation, but there wasn't any actual reason given for such
> draconian policy, especially when compared to the rest of the language.

I *think* it's something along these lines: We want to be able to
create arrays of structs, which (from a language designer's
viewpoint!) is much, much easier when all the structs are the same
size. If you let array sizes inside of structs vary, then you might
have foo1.somearray with 10 elements, and foo2.somearray with 100.
Then when the user does bar = [foo1,foo2], suddenly you're dealing
with an array of heterogenous data types and memory access becomes a
whole lot uglier and more inefficient. At that point, it's probably
easiest just to switch to Perl. ;-)

> It's really not a big deal since I can create anonymous structs
> everywhere instead of using named structures. Do named structures

You can also create named structures containing pointers to arrays, too.
This very problem is what finally pushed me over the potential barrier
into learning how to do pointers in IDL!

- Marshall

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[Message index]

		Structures: By: Chris Bull on Wed, 21 February 2001 11:15
		Re: Structures By: marc schellens[1] on Wed, 02 March 2005 19:14
		Re: Structures By: David Fanning on Wed, 02 March 2005 09:36
		Re: Structures By: Benjamin Hornberger on Wed, 02 March 2005 09:33
		Re: Structures By: Paul Van Delst[1] on Wed, 02 March 2005 09:31
		Re: Structures By: Michael Wallace on Wed, 02 March 2005 09:04
		Re: Structures By: Michael Wallace on Wed, 02 March 2005 08:59
		Re: Structures By: Paul Van Delst[1] on Wed, 02 March 2005 07:33
		Re: Structures By: marc schellens[1] on Tue, 01 March 2005 19:43
		Re: Structures By: David Fanning on Tue, 01 March 2005 16:49
		Re: Structures By: Michael Wallace on Tue, 01 March 2005 16:40
		Re: Structures By: mperrin+news on Tue, 01 March 2005 16:21
		Re: Structures By: Paul Van Delst[1] on Tue, 01 March 2005 14:39
		Re: Structures By: Michael Wallace on Tue, 01 March 2005 14:38
		Re: Structures By: David Fanning on Tue, 01 March 2005 13:52

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