Thank yiou On Tue, Jun 25, 2024, 3:57 PM Duncan Murdoch <murdoch.dun...@gmail.com> wrote:
> On 2024-06-25 5:25 a.m., Matthew Fidler wrote: > > Hi, > > > > I have adapted code to run R from within C from the writing R extensions > > here > > > > > https://colinfay.me/writing-r-extensions/system-and-foreign-language-interfaces.html > > That was written in 2017. You should use the one that came with R, or > even better, the one that comes with the development version of R. > > Duncan Murdoch > > > > > As a more comprehensive example of constructing an R call in C code and > > evaluating, consider the following fragment of printAttributes in > > src/main/print.c. > > > > /* Need to construct a call to > > > > print(CAR(a), digits=digits) > > > > based on the R_print structure, then eval(call, env). > > > > See do_docall for the template for this sort of thing. > > > > */ > > > > SEXP s, t; > > > > t = s = PROTECT(allocList(3)); > > > > SET_TYPEOF(s, LANGSXP); > > > > SETCAR(t, install("print")); t = CDR(t); > > > > SETCAR(t, CAR(a)); t = CDR(t); > > > > SETCAR(t, ScalarInteger(digits)); > > > > SET_TAG(t, install("digits")); > > > > eval(s, env); > > > > UNPROTECT(1); > > > > At this point CAR(a) is the R object to be printed, the current > attribute. > > There are three steps: the call is constructed as a pairlist of length 3, > > the list is filled in, and the expression represented by the pairlist is > > evaluated. > > > > A pairlist is quite distinct from a generic vector list, the only > > user-visible form of list in R. A pairlist is a linked list (with CDR(t) > > computing the next entry), with items (accessed by CAR(t)) and names or > > tags (set by SET_TAG). In this call there are to be three items, a symbol > > (pointing to the function to be called) and two argument values, the > first > > unnamed and the second named. Setting the type to LANGSXP makes this a > call > > which can be evaluated. > > > > > > > > New checks tells me that this is no longer allowed since it was not part > > of the public api any longer. > > > > > > So, how does one call R from C then? > > > > Also should the writing R extensions be updated with the new approved > > approach? > > > > > > Thanks in advance. > > > > Matt > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > 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
