[Rcpp-devel] Access Rcpp::List element

[Simon Zehnder]

Dear Rcpp::Devels and Rcpp::Users,

I have maybe some trivial questions. 

1. If I use 

	Rcpp::NumericVector A(someVector),
    
    does it reuse memory from someVector for A? From http://cran.r-project.org/web/packages/Rcpp/vignettes/Rcpp-quickref.pdf I would say it does, whereas 
	
	Rcpp::NumerixVector A(clone(someVector)) 

    does not.

2. Let us assume I am right in point 1, then my next question would arise towards reusing memory from R: Does it make a difference in C++ if I create a NumericVector with own memory and fill it in a loop or if I reuse memory from R and fill it in a loop? Again, I would say no, as if memory is reused, we usually pass a pointer to the memory tom the Rcpp Object, that has now direct access to this memory (of course this will be different when using parallel code, where memory allocation is essential). 

3. Imagine I use now an S4 Object from R:

	Rcpp::Export SEXP fName (SEXP& data_S4) {
	
		Rcpp::S4 dataS4O (data_S4);

	}

   If data_S4 contains a list, has the command Rcpp::S4 dataS4(data_S4) already created an Rcpp::List Object from it? If not, how do I proceed to get such a Rcpp::List Object? 



Best

Simon