[Rcpp-devel] Not able to convert from Rcpp::NumericVector to Teuchos::ArrayRCP<size_t>

[Romain François]

Hello, 

From what I understand of ArrayRCP, having read the documentation for a few minutes. (http://trilinos.sandia.gov/packages/docs/r9.0/packages/teuchos/doc/html/classTeuchos_1_1ArrayRCP.html)
This looks like a vector and therefore it is likely that the default Exporter<T> will not be useful as it tries to use the constructor taking a SEXP : 

		template <typename T>
		class Exporter{
		public:
		    Exporter( SEXP x ) : t(x){}
		    inline T get(){ return t ; }

		private:
		    T t ;
		} ;

you can use a RangeExporter instead which looks more compatible to what ArrayRCP looks like: 

		template <typename T> class RangeExporter {
		public:
		    typedef typename T::value_type r_export_type ;

		    RangeExporter( SEXP x ) : object(x){}
		    ~RangeExporter(){}

		    T get(){
		        T vec( ::Rf_length(object) );
		        ::Rcpp::internal::export_range( object, vec.begin() ) ;
		        return vec ;
		    }

		private:
		    SEXP object ;
		} ;


You can probably do this by having something like this early enough (after RcppCommon.h but before Rcpp.h). 

namespace Rcpp {
namespace traits {

  template <typename T> class Exporter<  Teuchos::ArrayRCP<T> > : public RangeExporter< Teuchos::ArrayRCP<T> >{
  public:
    Exporter( SEXP x) : RangeExporter< Teuchos::ArrayRCP<T> >(x){}  
  }

}
}


Romain

Le 23 mai 2014 à 00:42, Chaomei Lo <chaomeilo at gmail.com> a écrit :

> Sorry to confuse you, Dirk, I had my previous message title wrong.  Here below was the message with the correct title and content.
>  
> ////////////////////////////////
> I have created R packages using Makevars and it works pretty good for me. I am able to convert from a Rcpp::NumericVector to std::vector as in below.
>  
> NumericVector col_cts = buildMatrix(Xr);
> 
> vector<long unsigned int> col_counts = Rcpp::as<vector<long unsigned int>>(col_cts);
>   
> Now I am having a problem with an application involves the Trilinos library. Here below I am trying to convert a Rcpp::NumericVector to Teuchos::ArrayRCP<size_t> in the following line, it gave me errors as shown below in red.  Would you please help me with this ?
>  
> Teuchos::ArrayRCP<size_t> col_counts=Rcpp::as<Teuchos::ArrayRCP<size_t>>(col_cts);
>  
> Thanks a lot.
>  
> In file included from /share/apps/R/3.0.2/lib64/R/library/Rcpp/include/Rcpp/as.h:25:0,
>                  from /share/apps/R/3.0.2/lib64/R/library/Rcpp/include/RcppCommon.h:169,
>                  from /share/apps/R/3.0.2/lib64/R/library/Rcpp/include/Rcpp.h:27,
>                  from buildMatrix.cpp:4:
> /share/apps/R/3.0.2/lib64/R/library/Rcpp/include/Rcpp/internal/Exporter.h: In constructor 'Rcpp::traits::Exporter<T>::Exporter(SEXP) [with T = Teuchos::Array
> RCP<long unsigned int>, SEXP = SEXPREC*]':
> /share/apps/R/3.0.2/lib64/R/library/Rcpp/include/Rcpp/as.h:79:51:   instantiated from 'T Rcpp::internal::as(SEXP, Rcpp::traits::r_type_generic_tag) [with T =
>  Teuchos::ArrayRCP<long unsigned int>, SEXP = SEXPREC*]'
> /share/apps/R/3.0.2/lib64/R/library/Rcpp/include/Rcpp/as.h:144:84:   instantiated from 'T Rcpp::as(SEXP) [with T = Teuchos::ArrayRCP<long unsigned int>, SEXP
>  = SEXPREC*]'
> buildMatrix.cpp:84:87:   instantiated from here
> /share/apps/R/3.0.2/lib64/R/library/Rcpp/include/Rcpp/internal/Exporter.h:31:31: error: invalid conversion from 'SEXP' to 'long int' [-fpermissive]
> /people/d3j508/trilinos-11.6.1/trilinos-11.6.1_Install/include/Teuchos_ArrayRCP.hpp:129:1: error:   initializing argument 1 of 'Teuchos::ArrayRCP<T>::ArrayRC
> P(Teuchos::ArrayRCP<T>::size_type, const T&) [with T = long unsigned int, Teuchos::ArrayRCP<T>::size_type = long int]' [-fpermissive]
> make: *** [buildMatrix.o] Error 1
> ERROR: compilation failed for package 'Tpkg'
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