| Re: Everything I always wanted to know about IDL * but were afraid to ask. Chapter1 [message #36937] |
Fri, 14 November 2003 05:38 |
Nuno Oliveira
Messages: 75
Registered: October 2003
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Member |
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Hi, David, thanks again for your tip. It is clear to me that IDL is NOT C
language. But also it is clear to me that I'm trying to be a good boy
searching the tutorials (still the tutorials!). And again the information
was not enough. Because I noticed some similar syntax between IDL and C
language, I confess, I tried a C-like solution before I come to this
newsgroup. :)
Cheers,
Nuno.
"David Fanning" <davidf@dfanning.com> wrote in message
news:MPG.1a1e7c32da522d9a989684@news.frii.com...
> df23775@hotmail.com writes:
>
>
> Forget what you learned about C pointers. IDL pointers
> are NOT C pointers. Think of them as regular IDL variables
> that live in global memory space and you will be MUCH
> further ahead. :-)
>
> Cheers,
>
> David
>
> --
> David W. Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming: http:/www.dfanning.com/
> Phone: 970-221-0438, IDL Book Orders: 1-888-461-0155
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| Re: Everything I always wanted to know about IDL * but were afraid to ask. Chapter1 [message #36938 is a reply to message #36937] |
Fri, 14 November 2003 04:44  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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df23775@hotmail.com writes:
> *A=[*A, next_value]
> As many times as the values I want to add to the pointer.
>
> I can print the whole pointer with PRINT, *A. But how can I get intermediate
> positions??.
You subscript like any normal IDL variable. The only
trick is knowing that pointer dereferencing has (generally)
lower precedence than almost everything else. So we throw
a lot of parentheses around when we are working with pointers.
values = (*A)[4:6]
*A = [(*A)[0:6], new_Value, (*A)[7:*]]
> As far as I can recall from my C classes I do believe that in C, A means the
> memory position pointed by A, in what we could call the first pointer
> positions and you could use a counter to get further position with a syntax
> like *(A+counter) In IDL *A means not only the memory position pointed by A
> but also the full contents of the pointer?
Forget what you learned about C pointers. IDL pointers
are NOT C pointers. Think of them as regular IDL variables
that live in global memory space and you will be MUCH
further ahead. :-)
Cheers,
David
--
David W. Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http:/www.dfanning.com/
Phone: 970-221-0438, IDL Book Orders: 1-888-461-0155
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