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Re: Calling data from a structure of pointers? [message #43028 is a reply to message #43020]

Thu, 10 March 2005 22:57

Antonio Santiago
Messages: 201
Registered: February 2004

Senior Member

Jonathan Greenberg wrote:

> How do I retrieve the data the pointers are referring to?

pStr is pointer to a structure variable. This strucutre has 2 pointer
fields.

pStr = PTR_NEW(
{
a: PTR_NEW(10),
b: PTR_NEW(INDGEN(3))
})

pStr - Pointer variable to structure stored in HEAP memory.
IDL> help, pStr
PSTR POINTER = <PtrHeapVar6>

*pStr - The content that pStr points to, that is, the structure
stored in HEAP memory.l
IDL> help, *pStr, /STRUCT
** Structure <1f06f8>, 2 tags, length=8, data length=8, refs=1:
A POINTER <PtrHeapVar4>
B POINTER <PtrHeapVar5>

(*pStr).a - First "get" the strucutre and then access to the firts
pointer field 'a'.
IDL> help, (*pStr).a
<Expression> POINTER = <PtrHeapVar4>

(*(*pStr).a) - The same as above but obtain the content that 'a'
points (10).
IDL> help, (*(*pStr).a)
<PtrHeapVar4> INT = 10

And the same for 'b' field:
IDL> help, (*pStr).b
<Expression> POINTER = <PtrHeapVar5>
IDL> help, (*(*pStr).b)
<PtrHeapVar5> INT = Array[3]

IDL> arr = *(*pStr).b
IDL> print, arr
0 1 2

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[Message index]

		Re: Calling data from a structure of pointers? By: Jonathan Greenberg on Fri, 11 March 2005 09:16
		Re: Calling data from a structure of pointers? By: Antonio Santiago on Thu, 10 March 2005 22:57
		Re: Calling data from a structure of pointers? By: R.G.Stockwell on Thu, 10 March 2005 15:09
		Re: Calling data from a structure of pointers? By: David Fanning on Thu, 10 March 2005 14:46

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