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Re: Accessing 2D array from pointer array within structure [message #31753 is a reply to message #31733]

Thu, 15 August 2002 09:25

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Brandon Jones (bjones8@yahoo.com) writes:

> I have a structure called "info" with an item called "img" which is a
> pointer array. Each of these pointers point to an image (2D array).
>
> IMG POINTER Array[5]
>
> I want to be able to access the image via subscripts. Is it possible?
> What is the syntax?
>
> So something like
> value=*info.img[3][130,453]
>
> I know this is invalid....but something along those lines. Right now
> my code does this, which is sloppy:
>
> tmp=*info.img[3]
> value=tmp[130,453]
>
> I can't really find any info about doing this in the docs....

The correct syntax is:

value=(*(info.img[3]))[130,453]

The problem you have here is that pointer de-referencing
has the very lowest order of precedence, lower than
array subscripting. The parentheses have the highest order
of precedence, so we throw them around pretty liberally
when we want to get things like this to work. :-)

Cheers,

David
--
David W. Fanning, Ph.D.
Fanning Software Consulting, Inc.
Phone: 970-221-0438, E-mail: david@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155

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[Message index]

		Re: Accessing 2D array from pointer array within structure By: JD Smith on Fri, 16 August 2002 13:24
		Re: Accessing 2D array from pointer array within structure By: bjones8 on Thu, 15 August 2002 15:46
		Re: Accessing 2D array from pointer array within structure By: David Fanning on Thu, 15 August 2002 09:25

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