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Re: Still missing features in IDL 8 [message #73212 is a reply to message #72898]

Mon, 01 November 2010 08:30

chris_torrence@NOSPAM is currently offline

chris_torrence@NOSPAM
Messages: 528
Registered: March 2007

Senior Member

On Oct 31, 6:00 pm, Paulo Penteado <pp.pente...@gmail.com> wrote:
> On Oct 13, 2:38 pm, Chris Torrence <gorth...@gmail.com> wrote:
>
>
>
>> Regarding #2, what if you could use additional indices to access array
>> elements within lists?
>
>> For example:
>
>> IDL> a = LIST(FINDGEN(10), BYTARR(5,3))
>> IDL> help, a[0]
>> <Expression> FLOAT = Array[10]
>> IDL> help, a[0,3] ; currently throws an error in IDL8.0
>> <Expression> FLOAT = 3.00000
>> IDL> a[0,3] = !pi ; currently throws an error in IDL8.0
>
>> IDL> help, a[1]
>> <Expression> BYTE = Array[5, 3]
>> IDL> help, a[1,4,2] ; currently throws an error in IDL8.0
>> <Expression> BYTE = 0
>> IDL> a[1,4,2] = 255 ; currently throws an error in IDL8.0
>
>> So the first index would give the list element, and the remaining
>> indices would index into the array itself. Obviously you could only
>> have up to 7 dimensions in your contained array, but that probably
>> isn't a huge limitation.
>
> I was writing a class like that, inheriting from list, and that
> brought me a question: Should the extra dimension (of the list index)
> be on the left, as above, or on the right?
>
> The notation (already valid for retrieving values) (a[1])[0] suggests
> that the array index should come on the left. However, writing a[1,0]
> suggests array dimensions, in which case the list index would make
> more sense on the right, as the list dimension is the slowest-varying
> one.
>
> Tough it would be a bit incoherent with the array dimension order, it
> seems to me that it is better to have the list index on the left. That
> way,
>
> print,(a[1])[0] ;already valid
>
> would be the same as
>
> print,a[1,0]
>
> instead of the more confusing
>
> print,a[0,1]
>
> Any thoughts on that?

Yes, that is exactly what I was thinking.

Back to your original thread - if we added this way of subscripting,
does that eliminate the need to convert a list to/from a pointer
array? I'd rather not add more functionality if we don't have to.

-Chris
ITTVIS

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[Message index]

		Still missing features in IDL 8 By: penteado on Tue, 12 October 2010 14:35
		Re: Still missing features in IDL 8 By: chris_torrence@NOSPAM on Mon, 01 November 2010 08:30
		Re: Still missing features in IDL 8 By: penteado on Mon, 01 November 2010 10:17
		Re: Still missing features in IDL 8 By: Bob[4] on Thu, 04 November 2010 11:29
		Re: Still missing features in IDL 8 By: penteado on Tue, 02 November 2010 17:05
		Re: Still missing features in IDL 8 By: penteado on Thu, 04 November 2010 16:40
		Re: Still missing features in IDL 8 By: JDS on Sat, 06 November 2010 12:03
		Re: Still missing features in IDL 8 By: JDS on Thu, 04 November 2010 16:29
		Re: Still missing features in IDL 8 By: penteado on Thu, 04 November 2010 15:28
		Re: Still missing features in IDL 8 By: penteado on Sat, 06 November 2010 14:51
		Re: Still missing features in IDL 8 By: penteado on Tue, 09 November 2010 17:41

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