[Rcpp-devel] Using complex numbers in a C program called by R

[Pierre Lafaye de Micheaux]

Dear all,

This email comes after a discussion on the R-pkg-devel mailing list:
https://stat.ethz.ch/pipermail/r-package-devel/2016q1/000627.html

My purpose was to be able, in two of my packages, to use complex numbers 
(create some, addition, multiplication, division, modulus, etc)
directly in a C code that is called from R (using the .C interface).
Note that these complex numbers might not come from R but could be 
created and used directly in my C code, that will then output (via 
pointers)
real (I mean double) values back to R (via the .C interface). I could 
also send from R these complex numbers via the .C interface.

A very simple example of such a function called from R via the .C 
interface could be the following:

#include <R.h>
#include "Rmath.h"
extern "C" {
void Cfunc(complex double *var) {
     double _Complex z = 1.0 + 2.0 * _Complex_I;
     var[0] = z + exp(var[0]);
return;
}}

I could call this function from R as follows:
.C(1i)

No problem so far when I use such a function in a package that is 
compiled under Linux. But this will not work under windows (see the 
discussion
on the R-pkg-devel list). So what I did to make everything work under 
Windows also was to include in the src/ directory of my package the 
source files
from the RcppFaddeeva package. Then I would modify the function above as 
follows:

#include <R.h>
#include "Rmath.h"
#include "libraries/callFaddeeva.cpp"
#include "libraries/Faddeeva.cpp"
#include "libraries/RcppExports.cpp"
extern "C" {
void Cfunc(complex double *var) {
     cmplx z = C(1.0, 2.0);
     var[0] = z + cexp(var[0]);
return;
}}

Maybe there is a way not to include all the Faddeeva source files in my 
packages? But I do not know how to do it.

Best regards,

Pierre L.



-- 
Pierre Lafaye de Micheaux

Adresse courrier:
Université de Montréal
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lafaye at dms.umontreal.ca
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