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Re: pointer to structures [message #19558 is a reply to message #19540]

Tue, 04 April 2000 00:00

John-David T. Smith is currently offline

John-David T. Smith
Messages: 384
Registered: January 2000

Senior Member

"Liam E.Gumley" wrote:
>
> "J.D. Smith" wrote:
>> With time, you will get used to these semantics. They seem arcane, but
>> eventually it becomes somewhat readable to the experienced eye. Of course, I've
>> struggled with statements like:
>>
>> HEADER=*(*(*self.DR)[sel[i]].HEADER)
>
> I neglected to provide an example of why simplified pointer and
> structure referencing is desirable. Thanks for the help JD!
>
> ;-)
>
> Cheers,
> Liam.

But then you have to ask yourself which is worse, the confusing string above, or
the explicit:

drs_ptr=self.DR
drs=*drs_ptr
this=drs[sel[i]]
hd_arr_ptr=*this
hd=*hd_arr_ptr

repeat this about 5000 times throughout your application, and you begin to
appreciate the terse form above. Especially if you're passing some part of the
nested data to a routine by reference... intermediate variables require you to
remember to assign them after use (everybody remember
widget_control,stash,set_uvalue=state,/NO_COPY?).

Maybe we need a lexical parser like cdecl, to check on these for you? A fine
programming project for an aspiring IDL programmer out there.

JD

--
J.D. Smith |*| WORK: (607) 255-5842
Cornell University Dept. of Astronomy |*| (607) 255-6263
304 Space Sciences Bldg. |*| FAX: (607) 255-5875
Ithaca, NY 14853 |*|

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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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