In this case, Rcpp was internally converting (already-existing) LISTSXPs to LANGSXPs using SET_TYPEOF in some places; the goal was to allow Rcpp to continue doing this without using SET_TYPEOF just to preserve existing behavior in an API-compliant way. I ended up doing exactly what you suggested; thanks.
On Sat, Jul 6, 2024 at 8:09 PM Ivan Krylov <ikry...@disroot.org> wrote: > > On Fri, 5 Jul 2024 15:27:50 +0800 > Kevin Ushey <kevinus...@gmail.com> wrote: > > > A common idiom in the R sources is to convert objects between LANGSXP > > and LISTSXP by using SET_TYPEOF. However, this is soon going to be > > disallowed in packages. > > Would you mind providing an example where a package needs to take an > existing LISTSXP and convert it to a LANGSXP (or vice versa)? I think > that Luke Tierney intended to replace the uses of > SET_TYPEOF(allocList(...), LANGSXP) with allocLang(...). > > At least it's easy to manually convert between the two by replacing the > head of the list using LCONS(CAR(list), CDR(list)) or CONS(CAR(lang), > CDR(lang)): in a call, the rest of the arguments are ordinary LISTSXPs. > > -- > Best regards, > Ivan ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
