R-alpha: unif_rand() again

Kurt Hornik Kurt.Hornik@ci.tuwien.ac.at
Mon, 9 Jun 1997 08:02:18 +0200

>>>>> Peter Dalgaard BSA writes:

> Kurt Hornik <Kurt.Hornik@ci.tuwien.ac.at> writes:
>> >> What I need is to call runif() (more precisely, `runif(1, 0, 1)') from
>> >> inside a C function.  Is this possible using call_S?  If so, how?
>> > Hmm ... Stupid counter-question: Did you study the zfun() function in
>> > $RHOME/demos/dynload/zero.c ? Looks pretty straightforward to me,
>> > except that I have no offhand guess what the 0L argument to call_S is
>> > good for. Peeking at the source should cure that.
>> I did.  I hoped that something like
>> static char *func = "runif";
>> double unif_rand() {
> ...
>> return(result[0]);
>> }
>> might work, but it does not ...

> Aha. I see, call_R seems to want an SEXP parameter, not a character
> pointer. So some way of converting "runif" into the relevant SEXPREC
> seems to be needed. Something like mkChar() <um, no, that doesn't seem
> to be the way to make a "SEXPsymbol"..> followed by findFun(). Or just
> pass it as a parameter to .C

I see.

Thanks to all who helped.  I now have a working example of unif_rand(),
but I still hope for Ross to come up with something cleaner ...

Trying to map a function name to the function in call_R would be very
nice, in any case.

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