Hi all, By looking at the implementation of R's wrapper. I found a function ` R_altrep_inherits` that can check whether an object belongs to an ALTREP class. Even though it is a little different from what I am looking for, but it should be satisfactory for my purpose. I will suspect there is no such function in R to get the class of an ALTREP object for the SEXP struct is very compact and this less-important information might not be stored when an ALTREP object is created.
Best, Jiefei On Mon, Oct 19, 2020 at 8:37 PM Jiefei Wang <szwj...@gmail.com> wrote: > 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 < > boenn...@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.de...@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 <szwj...@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@r-project.org mailing list >> > >> https://stat.ethz.ch/mailman/listinfo/r-devel >> > > >> > > ______________________________________________ >> > > R-devel@r-project.org mailing list >> > > https://stat.ethz.ch/mailman/listinfo/r-devel >> > > >> > [[alternative HTML version deleted]] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel