[Rd] Is there any way to check the class of an ALTREP?

[Jiefei Wang]

Thank Denes for the clarification, glad to see my package got one citation
from my own question:) Also, thank Benjamin
for sending many useful documents.

Actually, the question is related to the SharedObject package that Benjamin
has pointed to. I wanna
avoid sharing an object that has already been shared, so I need to check
whether an object is an ALTREP
that is defined in my package. Since the ALTREP definition involves an `
R_altrep_class_t` object and a
 class name, I will expect to see a method defined in R to retrieve such
information. I hope this can clarify my question.

Best,
Jiefei

On Mon, Oct 19, 2020 at 5:38 PM Benjamin Christoffersen <boennecd using gmail.com>
wrote:

> > You happened to send a link which points to the OP's own package :) I
> > think Jiefei would like to know how one can "officially" determine if an
> > arbitrary ALTERP object belongs to a class that he owns.
> Argh, I am sorry! I did not notice that. My best bet for what I
> thought the question was is section 1.1.2 of R Internals where they
> note that: `unsigned int alt : 1; /* is this an ALTREP object? */`
>
> This is also what the ALTREP macro checks. However, I also did not
> notice the "... if an ALTREP object is from my package" part. I am
> sorry.
>
> Sincerely Yours,
> Benjamin
>
> Den man. 19. okt. 2020 kl. 11.25 skrev Dénes Tóth <toth.denes using kogentum.hu
> >:
> >
> > Benjamin,
> >
> > You happened to send a link which points to the OP's own package :) I
> > think Jiefei would like to know how one can "officially" determine if an
> > arbitrary ALTERP object belongs to a class that he owns.
> >
> > Regards,
> > Denes
> >
> >
> > On 10/19/20 10:22 AM, Benjamin Christoffersen wrote:
> > > It seems as if you can you use the ALTREP macro as done in this
> > > package:
> https://github.com/Jiefei-Wang/SharedObject/blob/804b6ac58c63a4bae95343ab43e8b1547b07ee6b/src/C_interface.cpp#L185
> > >
> > > and in base R:
> https://github.com/wch/r-source/blob/54fbdca9d3fc63437d9e697f442d32732fb4f443/src/include/Rinlinedfuns.h#L118
> > >
> > > The macro is defined here in Rinternals.h:
> > >
> https://github.com/wch/r-source/blob/abb550c99b3927e5fc03d12f1a8e7593fddc04d2/src/include/Rinternals.h#L325
> > >
> > > Den man. 19. okt. 2020 kl. 10.13 skrev Jiefei Wang <szwjf08 using gmail.com
> >:
> > >>
> > >> Hi all,
> > >>
> > >> I would like to determine if an ALTREP object is from my package, I
> see
> > >> there is a function `ALTREP_CLASS` defined in RInternal.h but its
> return
> > >> value is neither a `R_altrep_class_t` object nor an STRSXP
> representing a
> > >> class name. I do not know how to correctly use it. Any suggestions?
> > >>
> > >> Thanks,
> > >> Jiefei
> > >>
> > >>          [[alternative HTML version deleted]]
> > >>
> > >> ______________________________________________
> > >> R-devel using r-project.org mailing list
> > >> https://stat.ethz.ch/mailman/listinfo/r-devel
> > >
> > > ______________________________________________
> > > R-devel using r-project.org mailing list
> > > https://stat.ethz.ch/mailman/listinfo/r-devel
> > >
>

	[[alternative HTML version deleted]]