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Re: pointer to structures [message #19561 is a reply to message #19558]

Tue, 04 April 2000 00:00

Ben Tupper
Messages: 186
Registered: August 1999

Senior Member

David Fanning wrote:

> eeeyler@my-deja.com (eeeyler@my-deja.com) writes:
>
>> 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
>
> The problem here is that a pointer dereference has the lowest
> order of precedence. Lower, even, than a structure dereference.
> So, you must first dereference the structure (by using
> parentheses), and *then* dereference the pointer, like this:
>
> filter=ptr_new({points:['a','b'],pt1_value:200, pt2_value:'X_WHYLOG'})
> Print, *(filter.points)
>

David,

Caution! Bikes all over the road ahead!

I have always hoped that I'm not the only one who has driven a perfectly
nice bike into a parked car! Ouch!

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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