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Re: pointer question [message #24319 is a reply to message #24316]

Thu, 22 March 2001 06:01

Jaco van Gorkom
Messages: 97
Registered: November 2000

Member

Mark Hadfield wrote:
>
> "Ted Graves" <egraves@socrates.Berkeley.EDU> wrote in message
> news:99blck$ko7$1@agate.berkeley.edu...
...
>> result = TEST(PTR_NEW(value))
>>
>> where value is whatever i want the heap variable to be. What happens toth e
>> heap variable assigned in this statement after TEST returns? I'm assuming
>> from that because of the way it was created, a heap variable now exists that i
>> can't easily get rid of without using HEAP_GC.
>
> Yes.
>
> But if you have access to the code of TEST you could do this:
>
> pro test, a
>
> ; Do something with a
>
> if not arg_present(a) then if ptr_valid(a) then ptr_free, a
>
> end

Very nice! However, what if you pass in 'a' by value, e.g., from an
array of pointers?
If I call test like
for i=0, n_elements(PointerArray)-1 do test(PointerArray[i])
then I lose all the heap variables, right?

I would prefer to avoid the problem altogether by making TEST accept
both pointers and values, something like:

pro test, a
if size(a, /type) ne 10 then begin
a = ptr_new(a, /no_copy)
a2ptr = 1
endif else a2ptr = 0

; Do something with a, pointer-based.

if a2ptr and ptr_valid(a) then begin
a_copy = a
a = temporary(*a)
ptr_free, a_copy
endif
end

If TEST is not your own code, this could easily be done in a wrapper
routine as well. The flexibility of not having to bother about
pointers-or-not is great for command-line use. But then again, using
heap_gc on the command line every once in a while is not a big problem
either...

Jaco

----------------
Jaco van Gorkom gorkom@rijnh.nl
FOM-Instituut voor Plasmafysica "Rijnhuizen", The Netherlands

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[Message index]

		Re: pointer question By: Martin Schultz on Mon, 26 March 2001 01:05
		Re: pointer question By: Mark Hadfield on Sun, 25 March 2001 14:16
		Re: pointer question By: Mark Hadfield on Sun, 25 March 2001 14:07
		Re: pointer question By: R.Bauer on Sun, 25 March 2001 09:24
		Re: pointer question By: Craig Markwardt on Thu, 22 March 2001 20:15
		Re: pointer question By: Paul van Delst on Thu, 22 March 2001 10:00
		Re: pointer question By: Pavel A. Romashkin on Thu, 22 March 2001 09:21
		Re: pointer question By: John-David T. Smith on Thu, 22 March 2001 08:56
		Re: pointer question By: Pavel A. Romashkin on Thu, 22 March 2001 08:24
		Re: pointer question By: Paul van Delst on Thu, 22 March 2001 06:52
		Re: pointer question By: Jaco van Gorkom on Thu, 22 March 2001 06:01
		Re: pointer question By: Mark Hadfield on Wed, 21 March 2001 19:47
		Re: pointer question By: Craig Markwardt on Mon, 26 March 2001 04:56
		Re: pointer question By: egraves on Mon, 26 March 2001 17:06

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