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Subscripting arrays. [message #84150]

Thu, 02 May 2013 12:40

Russell Ryan
Messages: 122
Registered: May 2012

Senior Member

So someone showed me this and I'm trying to wrap my head around it. Sorry if it's already posted, I didn't know how to begin to search The Group for it...

Create an array:

a = intarr(3)

Using IDL 8, subscript with 4 (ie. an index that's too large and should be out of bounds)

a[4]=3

Obviously, this crashes.

Conversely subscript with a negative index:

a[-1]=2

does what you expect.

But, now subscript the array, WITH an array:

a[[4]]=2

voila. It works, and simply truncates to the last element of the array... Spooky. Now do that with a negative index:

a[[-1]]=4

Like before, it works. But now, it doesn't wrap the index, but rather truncates to the first element of the array.

Hmm.. I can't tell if this is the designed behavior, because I have a hard time describing it --- it's easier to show it.

All the best,
Russell

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		Subscripting arrays. By: Russell Ryan on Thu, 02 May 2013 12:40
		Re: Subscripting arrays. By: Jeremy Bailin on Mon, 06 May 2013 06:37

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