Why does this make my R session abort?

Question

I'm trying to implement named-list calling in Rcpp

in R

b<-list("bgroups"=c(1,1,1,1,0,0,0,0))
> b$bgroups
[1] 1 1 1 1 0 0 0 0

cppFunction(
  "
NumericVector split(Rcpp::List & b){
  Rcpp::NumericVector c= b['bgroups'];
  return c;
}")

split(b)

But this causes my R session to abort.

I'm trying to implement this procedure as illustrated in one of Dirk's presentations, but I'm missing something.

This is an extension of my question

You need double quote `"` in the C++ code. – Qiang Kou Jul 11 '18 at 17:59 — Qiang Kou, Jul 11 '18 at 17:59

Ralf Stubner · Accepted Answer · 2018-07-11T18:17:18.230

The following works:

b<-list("bgroups"=c(1,1,1,1,0,0,0,0))
b$bgroups
#[1] 1 1 1 1 0 0 0 0

Rcpp::cppFunction(
  '
NumericVector split(Rcpp::List & b){
  Rcpp::NumericVector c = b["bgroups"];
  return c;
}')

split(b)
#[1] 1 1 1 1 0 0 0 0

In C++, ' is used to quote a character, while " is used to quote strings. My compiler warns me about this:

warning: character constant too long for its type
   Rcpp::NumericVector c= b['bgroups'];
                            ^~~~~~~~~

Generally it is a good idea to take compiler warnings seriously.

Why does this make my R session abort?

1 Answers1