How to return R NULL to Rcpp code?

Question

Suppose I have C ++ code to compile with Rcpp and is invoked in R.

// [[Rcpp::export]] SEXP to_env(List x) { if(x.hasAttribute("names")) { return x; } else { return NULL; } } 

What NULL should return R NULL instead of failing?

Answer 1

Use this code:

 return R_NilValue;