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Re: Array indexing problem [message #37866 is a reply to message #37858]

Wed, 28 January 2004 14:11

Liam Gumley
Messages: 473
Registered: November 1994

Senior Member

"Roy" <roberson_1@yahoo.com> wrote in message
news:c0a9aee5.0401281200.400888f1@posting.google.com...
> Is there any existing code that will catch the below IDL simple
> example? Input a and b must be an array.
>
> Input is an array:
> IDL> b=[4]
> IDL> a=[0,1,2]
> IDL> print,a[b]
> 2
> This should give me an error.

This is how array subscripting works in IDL, when the subscript is an array.
To quote the IDL Manual "Building IDL Applications", Chapter 5, "Using
Arrays as Subscripts":

"If an element of the subscript array is less than or equal to zero, the
first element of the subscripted variable is selected. If an element of the
subscript is greater than or equal to the last subscript in the subscripted
variable (N, above), the last element is selected."

If the subscript variable has just one elements, then you can do this
instead

IDL> print, a[b[0]]
% Attempt to subscript A with <LONG ( 4)> is out of range.
% Execution halted at: $MAIN$

since b[0] is a scalar. You can do this even if b is a scalar.

Cheers,
Liam.
Practical IDL Programming
http://www.gumley.com/

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[Message index]

		Re: Array indexing problem By: kashyap on Thu, 29 January 2004 15:21
		Re: Array indexing problem By: David Fanning on Thu, 29 January 2004 09:58
		Re: Array indexing problem By: Liam Gumley on Thu, 29 January 2004 09:43
		Re: Array indexing problem By: roberson_1 on Thu, 29 January 2004 09:03
		Re: Array indexing problem By: hunter on Wed, 28 January 2004 13:43
		Re: Array indexing problem By: Mark Hadfield on Wed, 28 January 2004 16:55
		Re: Array indexing problem By: David Fanning on Wed, 28 January 2004 14:40
		Re: Array indexing problem By: Paul Van Delst[1] on Wed, 28 January 2004 14:28
		Re: Array indexing problem By: Michael Wallace on Wed, 28 January 2004 14:23
		Re: Array indexing problem By: Liam Gumley on Wed, 28 January 2004 14:11
		Re: Array indexing problem By: David Fanning on Wed, 28 January 2004 13:34

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