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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

Senior Member

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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		Re: Everything I always wanted to know about IDL * but were afraid to ask. Chapter1 By: Nuno Oliveira on Fri, 14 November 2003 05:38
		Re: Everything I always wanted to know about IDL * but were afraid to ask. Chapter1 By: David Fanning on Fri, 14 November 2003 04:44

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