[Rcpp-devel] sugar: x+y and y+x gives different results when there are NA's in y

[Søren Højsgaard]

Dear all,
Came across this:

#include <Rcpp.h>
using namespace Rcpp;

//[[Rcpp::export]]
List  sumxy(NumericVector x, NumericVector y){
  NumericVector xy = x+y;
  NumericVector yx = y+x;
  return List::create(xy, yx);
}

/*** R
x <- c(1,3,5,7)
y <- c(NA,2,4,6,8)
x+y
y+x
sumxy(x, y)
 */

> x <- c(1,3,5,7)
> y <- c(NA,2,4,6,8)
> x+y
[1] NA  5  9 13  9
> y+x
[1] NA  5  9 13  9
> sumxy(x, y)
[[1]]
[1] NA  5  9 13
[[2]]
[1] NA  5  9 13  8

Is this intentional? Apologies if this has been documented anywhere; was unable to find it.

Regards
Søren