Re: Newbie Questions

[Craig Markwardt <craigmnet(at)cow.physics.wisc.edu>]

Geoff Herbynchuk <gherbyn@irus.rri.on.ca> writes:

> Hi,
> 
> Was just wondering if IDL can have pointers to structures.  I'm trying to
> access a variable in the structure with:
> 
> 	if (*info).active_cursor EQ 1) then .....
> 
> And I keep getting an error which says "Expression must be a structure in
> this context: <PtrHeapVar57>."
> 
> Does anyone know what I'm doing wrong?

Umm, are you sure that INFO points to a structure?  I tried it and it
worked fine.  (see below).  Why not put a "HELP, *INFO, /STRUCT" right
before this statement and see what pops up?

IDL> struct = {active_cursor: 1}
IDL> info = ptr_new(struct)
IDL> help, (*info).active_cursor
<Expression>    INT       =        1
IDL> help, info
INFO            POINTER   = <PtrHeapVar1>

Craig

-- 
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Craig B. Markwardt, Ph.D.         EMAIL:    craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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