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Re: negative array index in IDL8 [message #86375 is a reply to message #86374]

Fri, 01 November 2013 11:55

suicidaleggroll
Messages: 14
Registered: September 2013

Junior Member

On Friday, November 1, 2013 11:38:03 AM UTC-6, chu xiangning wrote:
> Hi All,
>
> My first noobie post here. I wanted to turn off negative index in the following commands. New IDL return error for x[[-1,-2]], but not for x[-1]. Is there anyway that I can turn off the negative indexing completely?
>
> Thank you in advance!
>
>
>
>
>
> pro test_negative_index
>
> COMPILE_OPT STRICTARRSUBS
>
> x=INDGEN(10)
>
> print,x[-1]
>
> print,x[[-1,-2]]
>
> end
>
>
>
> Here is the result I got:
>
> % Compiled module: TEST_NEGATIVE_INDEX.
>
> 9
>
> % Array used to subscript array contains out of range subscript: X.
>
> % Execution halted at: TEST_NEGATIVE_INDEX 6

I'm following this thread with hopeful anticipation.

A lot of my colleagues (who are no longer here) used to write IDL code assuming that a negative index would cause an error. So for example if they used a where statement to find some match, rather than checking the number of matches and erroring if there were none, they would just directly subscript the array with the output, counting on the fact that IDL would crash with the negative subscript.

Bad programming practices aside, all of these programs now result in unpredictable behaviour in IDL8. Rather than combing through all of our old programs line by line to find these problems, it would be nice to add an option to turn off negative subscripting, since we never use it anyway for backwards compatibility.

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[Message index]

		negative array index in IDL8 By: chuxiangning on Fri, 01 November 2013 10:38
		Re: negative array index in IDL8 By: suicidaleggroll on Fri, 01 November 2013 11:55
		Re: negative array index in IDL8 By: David Fanning on Fri, 01 November 2013 12:03
		Re: negative array index in IDL8 By: chuxiangning on Fri, 01 November 2013 13:05
		Re: negative array index in IDL8 By: David Fanning on Fri, 01 November 2013 13:31
		Re: negative array index in IDL8 By: wlandsman on Fri, 01 November 2013 15:18
		Re: negative array index in IDL8 By: chuxiangning on Fri, 01 November 2013 19:38
		Re: negative array index in IDL8 By: wlandsman on Sat, 02 November 2013 06:42
		Re: negative array index in IDL8 By: David Fanning on Sat, 02 November 2013 07:43
		Re: negative array index in IDL8 By: chuxiangning on Tue, 12 November 2013 12:21

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