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Re: Invalid indices? [message #68414 is a reply to message #68413]

Tue, 27 October 2009 11:02

Foldy Lajos
Messages: 268
Registered: October 2001

Senior Member

On Tue, 27 Oct 2009, Y.T. wrote:

> So I'm kinda living under a rock:
> IDL Version 6.3, Microsoft Windows (Win32 x86 m32)
>
> so I'm curious whether this is intended/expected behaviour or a bug or
> what (and whether it has change in recent years):
>
> IDL> t = lindgen(7)
> IDL> print,t
> 0 1 2 3 4
> 5 6
>
> IDL> n=5*indgen(5)
> IDL> print,n
> 0 5 10 15 20
>
> IDL> t[n] = 100
> IDL> print,t
> 100 1 2 3 4
> 100 100
>
> So element number 0 got set to 100 (OK), element number 5 got set to
> 100 and ... element number 6 also got set to 100?
>
> Why is that? I understand that I'm specifying elements "out of
> range" (number 10 and 15 etc) - is that the reason? Is this
> documented? It took me by surprise...
>

There is no out of range error for array subscripts, they are always
clipped. From the docs:

Elements of the subscript array that are negative or larger than the
highest subscript are clipped to the target array boundaries. Note that a
common error is to use a negative scalar subscript (e.g., A[-1]). Using
this type of subscript causes an error. Negative array subscripts (e.g.,
A[[-1]]) do not cause errors.

regards,
lajos

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[Message index]

		Re: Invalid indices? By: Michael Galloy on Wed, 28 October 2009 19:55
		Re: Invalid indices? By: Brian Larsen on Wed, 28 October 2009 16:02
		Re: Invalid indices? By: Michael Galloy on Tue, 27 October 2009 11:48
		Re: Invalid indices? By: David Fanning on Tue, 27 October 2009 11:27
		Re: Invalid indices? By: Foldy Lajos on Tue, 27 October 2009 11:02
		Re: Invalid indices? By: David Fanning on Tue, 27 October 2009 11:00

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