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Re: array subscripting problem [message #43424 is a reply to message #43423]

Mon, 11 April 2005 07:34

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Martin writes:

> Thanks David, could you expand on that a bit?
>
> I realise it's still only breakfast time over there!

I really need to fix my coffee before I look at the newsgroup. :-(

You wanted to know how to keep array subscripts from going
negative. If you compare the subscript with 0 and choose
the larger of the two with the "greater than" operator,
you will have achieved your goal. I'm not saying it will
be *correct*, but I am saying it will *not be negative*. :-)

Similarly, you can fix problems on the other end by using
the "less than" operator and checking that the index is
smaller than the size of the array.

array = indgen(100)
s = Size(array, /Dimensions)
print, array[0 > j < (s[0]-1)]

This will keep your index between the allowed indices of
the array. Be *sure* to include those parentheses! Leaving
them off is one of the classic gotchas.

Cheers,

David

--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/

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[Message index]

		Re: array subscripting problem By: Benjamin Luethi on Mon, 11 April 2005 08:11
		Re: array subscripting problem By: Martin[1] on Mon, 11 April 2005 06:56
		Re: array subscripting problem By: David Fanning on Mon, 11 April 2005 07:34
		Re: array subscripting problem By: David Fanning on Mon, 11 April 2005 06:38

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