Re: [Rd] :Re: PROTECT and OCaml GC.

From: Laurent Gautier <lgautier_at_gmail.com>
Date: Mon, 30 Nov 2009 16:56:36 +0100

Guillaume Yziquel wrote:
> Laurent Gautier a écrit :

>>
>> It does not have to be a functional language.
>> To see it in use within a some-language-to-R bridge, you can check the
>> source in JRI, rpy2.
>> I can mostly speak for rpy2, and the way it is done there relies on 
>> both R and Python's GC. Creating a anonymous R object presented to the 
>> Python world is first "R_preserved" (from garbage collection from R) 
>> then using Python's reference counting mechanism, calling an 
>> "R_Release" whenever the Python wrapper is available for garbage 
>> collection (in fact there is a twist, but this is roughly the way it 
>> is working). In your case, you'll use the OCaml GC system (and 
>> "R_release" the R object when its OCaml representation is going for 
>> garbage collection).

>
> For now, garbage collection is a secondary issue.
>
> I would have been interested in a binding to a functional language to
> see exactly where you get a closure to closure mapping. That's why I was
> asking since that's what I'm foremost interested in.
>
>>> By low-level, I mean a binding that takes hold of R objects without 
>>> using symbols all over to reference them. (Using symbols in the
>>> formals, the body or the environment of a closure is fine, for
>>> instance, but I'd like to execute a closure directly, and eventually
>>> be able to construct R closure from OCaml functions).
>>
>> Rpy2 can do a lot of that, and probably so can JRI.

>
> An anonymous closure to anonymous closure mapping? Could you point out
> where this is done exactly?
>

Anonymous R objects, that is without an associated symbol in R, can be passed to functions (and in that way makes a binding "take hold of R objects without using symbols").
For example, building R code made of anonymous objects can be achieved by making a LANGSXP object and tweaking it.

Example in R itself:
 > x <- call("round", 2.3)
 > eval(x)
[1] 2
 > x[[1]] <- function(x) x^2
 > eval(x)
[1] 5.29

Getting more complex constructs may need a little more trickery.

...or do you mean something else ?

L.



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