[Rcpp-devel] Modify R object within C++ function that returns bool to indicate success/failure

[Paul Theodor Pyl]

Hi all,

I have a question concerning the modification of R objects within C++ 
using Rcpp, what I would like to do is shown in this fantasy-R-session:
 > l <- list()
 > while( mycppfunc( l ) ){ print("running!") }
running!
running!
...
 > l
$a
[1] "Something"
$b
...

The corresponding c++ function would look like this:

bool mycppfunc( List l ){
     some_struct x;
     if( some_other_function( x ) ){
         l[x.name] = x.some_member;
         return true;
     }else{
         return false;
     }
}

where some_other_function is a c++ function that takes the struct and 
modifies it returning a bool to indicate success/failure.

Looking at the examples of Rcpp so far I have not found one where an R 
object is handed to a c++ function that modifies it and returns a bool 
to indicate success / failure.

How would I go about this? Could that be done using SEXP's (since they 
are pointers I would suspect they can be modified 'in-place')

Cheers,
Paul