Calling R functions with multiple arguments from C

Hi,
I'm writing a C function that has to call a R function with multiple
arguments. I've read the relevant section in  Writing R Extensions, and
searched the R site, mailing lists as well as rseek. I managed to call
the function, but I'm now having trouble creating the argument list.
I tried to create a pairlist of the arguments and send it to the R
function. The R function however only recieves one argument as a list. I
can change the R function to use this argument, but would like to know
what I'm doing wrong. I copied the C and R code below. It is code
submitted by Timur Elzhov on the the R mailing list under the discussion
Calling R function from within C code that I've modified. I've read that
discussion, but still got stuck. Could anybody point me in the right
direction?


SEXP foo(SEXP fn, SEXP elmt1, SEXP elmt2, SEXP rho)
{
   SEXP R_fcall, args, ans,s;
   PROTECT( args = s = allocList(2));
   PROTECT( R_fcall = lang2(fn, R_NilValue) );
   SETCAR(s,elmt1);
   SET_TAG(s,install("x"));
   s = CDR(s);
   SETCAR(s,elmt2);
   SET_TAG(s,install("y"));
   SETCADR( R_fcall, args);
   PROTECT( ans = eval(R_fcall, rho) );
   UNPROTECT(3);
   return ans;

}

foo.func <- function(x,y)match.call()

.Call("foo",foo.func,x=10,y=12,new.env())

function(x,y)match.call()
(x = list(x = 10, y = 12))

sessionInfo()

R version 2.7.0 (2008-04-22)
i386-pc-mingw32

locale:
LC_COLLATE=English_South Africa.1252;LC_CTYPE=English_South
Africa.1252;LC_MONETARY=English_South
Africa.1252;LC_NUMERIC=C;LC_TIME=English_South Africa.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

Regards,

Ruan Rossouw
Sasol Technology R&D
Reaction Technology and Industrial Statistics
Tel: +27 16 960 4717
Fax: +27 11 522 4465
Cell: +27 83 724 4163
e-mail: Ruan.Rossouw at Sasol.Com

[All views expressed are my own and not necessarily that of my
employer.]




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