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 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
