R-alpha: unif_rand() again

Peter Dalgaard BSA p.dalgaard@kubism.ku.dk
03 Jun 1997 18:23:24 +0200

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

This looks like a bug in the S compatibility, doesn't it? Nothing in
the Splus examples indicate that the first argument should be a
string, but I seem to recall seeing something to that effect in the
blue book (?) 

   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
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