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Re: IDL array subscripting issue [message #90229 is a reply to message #90227]

Thu, 12 February 2015 10:26

Paul Van Delst[1]
Messages: 1157
Registered: April 2002

Senior Member

On 02/12/15 12:29, Fabien wrote:
> On 12.02.2015 18:22, David B wrote:
>> ===============================
>>
>> IDL> a = INDGEN(10)
>> IDL> b = [0,10]
>> IDL> print, a[b]
>> 0 9
>> IDL> b = [0,9]
>> IDL> print, a[b]
>> 0 9
>>
>> ===============================
>> Why?!
>
> This is a strange but documented feature of IDL:
>
> http://www.exelisvis.de/docs/Using_Arrays_as_Array_Su.html
>
> See "Array Subscripts and Clipping".
>
> Depending on what you want, this is a feature of a bug. I learned to
> like it as a feature, personally.

I really like the use of negative indices to reference from the end of
the array. The above url has the following "note" in the section about
clipping:

<quote>
Note: Because of the confusion between the clipping of array subscripts
and the use of negative indices (see the next section), it is best to
avoid using code that relies on this clipping behavior.
</quote>

Just sayin'. Not judging.

cheers,

paulv

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[Message index]

		IDL array subscripting issue By: David B on Thu, 12 February 2015 09:22
		Re: IDL array subscripting issue By: David B on Thu, 12 February 2015 09:23
		Re: IDL array subscripting issue By: Fabzi on Thu, 12 February 2015 09:29
		Re: IDL array subscripting issue By: Paul Van Delst[1] on Thu, 12 February 2015 10:26
		Re: IDL array subscripting issue By: Fabzi on Thu, 12 February 2015 10:36
		Re: IDL array subscripting issue By: David Fanning on Thu, 12 February 2015 10:05
		Re: IDL array subscripting issue By: David B on Fri, 13 February 2015 01:32

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