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Re: pointer to structures [message #19568 is a reply to message #19567]

Tue, 04 April 2000 00:00

Ben Tupper
Messages: 186
Registered: August 1999

Senior Member

eeeyler@my-deja.com wrote:

> suppose I wish to create a structure and wish to reference that
> structure and its contents via a pointer:
> filter=ptr_new({points:['a','b'],pt1_value:200, pt2_value:'X_WHYLOG'})
> how do I reference the points array? I thought it would be as:
> print, *filter.points
> but I get the message
> %Expression must be a structure in this context: Filter
> Thank you for your help!
>
>

Hello,

You must first derefence the pointer before derefencing the structure.

IDL> print,(*filter).points
a b

This is the exact problem I bump into all the time when I have structures
of pointers or pointers of structures of pointers. I always have to slow
down and noodle it out. Unfortunately, for me, it has been just like
riding a bike... I seem to always forget.

Good luck,

Ben

--
Ben Tupper

Bigelow Laboratory for Ocean Science
tupper@seadas.bigelow.org

pemaquidriver@tidewater.net

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[Message index]

		Re: pointer to structures By: John-David T. Smith on Wed, 05 April 2000 00:00
		Re: pointer to structures By: Liam E. Gumley on Wed, 05 April 2000 00:00
		Re: pointer to structures By: John-David T. Smith on Tue, 04 April 2000 00:00
		Re: pointer to structures By: Liam E. Gumley on Tue, 04 April 2000 00:00
		Re: pointer to structures By: davidf on Tue, 04 April 2000 00:00
		Re: pointer to structures By: Ben Tupper on Tue, 04 April 2000 00:00
		Re: pointer to structures By: John-David T. Smith on Tue, 04 April 2000 00:00
		Re: pointer to structures By: John-David T. Smith on Tue, 04 April 2000 00:00
		Re: pointer to structures By: davidf on Tue, 04 April 2000 00:00
		Re: pointer to structures By: wbiagiot on Tue, 04 April 2000 00:00
		Re: pointer to structures By: Liam E. Gumley on Tue, 04 April 2000 00:00
		Re: pointer to structures By: Ben Tupper on Tue, 04 April 2000 00:00

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