Hi All,
I have some questions regarding the R C API.
Let's assume I have a function which is defined as follows:
R file:
myfunc <- function(a, b, ...) .External(Cfun, a, b, ...)
C file:
SEXP Cfun(SEXP args) {
args = CDR(args);
SEXP a = CAR(args); args = CDR(args);
SEXP b = CAR(args); args = CDR(args);
/* continue to do something with remaining arguments in "..." using the
same logic as above*/
return R_NilValue;
}
1/ Let's suppose that in my c function I change the value of a inside the
function but I want to reset it to what it was when I did SEXP a =
CAR(args); . How can I do that?
2/Is there a method to set "args" at a specific position so I can access a
specific value of my choice? If yes, do you have an simple example?
3/ Let's suppose now, I call the function in R. Is there a way to avoid the
function to evaluate its arguments before going to the C call? Do I have to
do it at the R level or can it be done at the C level?
Thank you very much in advance.
Best regards
Morgan
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