Re: Arrays in Structures Question (newbie)

["J.D. Smith" <jdsmith(at)astro.cornell.edu>]

Mike Garrett wrote:
> 
> Hej guys,
> 
> I was writing some structures to hold some data values and I am having a
> hard time determining what is going inside IDL.  Could someone explain why
> I keep gettin two values back when I am just asking for one?  And why the
> values are getting switched down a level?
> 
> IDL> pointdata([1]).distance([[44],[0]]) = 12
> IDL> print, pointdata([1]).distance([[44],[0]])
>       12
>       12
> IDL> pointdata([1]).distance([[44],[1]]) = 3
> IDL> print, pointdata([1]).distance([[44],[1]])
>        3
>        3
> IDL> print, pointdata([1]).distance([[44],[0]])
>        3
>       12
> 
> Thanks for any help,
> 
> Mike

Short answer:

IDL> pointdata[1].distance[44,0]=12
IDL> print, pointdata[1].distance[44,0]

Long answer:

The quantity [[44],[0]] in your statement is really the vector [44,0]. 
If you index an array with a vector, you get all of those elements.  By
the way, don't use () to index an array unless you're using a very old
IDL.  It confuses the compiler in some cases.

If you're really fond of lots and lots of punctuation, you could still
do:

IDL> print, pointdata([1]).distance([[44]],[[0]])

(note carefully the difference) but hopefully I've convinced you not to.

JD

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