[Rcpp-devel] Problem exposing constructor taking std::vector of user defined class to R using Rcpp-attributes and Rcpp-modules

Hi All,

I running into some problems using a combination of Rcpp-attributes and
Rcpp-modules to expose a C++ class library, and would appreciate your help.

I am trying to expose to R the constructor of a C++ class template which
accepts a std vector of the template parameter T as input, as shown in
the following toy class A used to replicate the problem:

template <class T> class A {

     public:

         std::vector<T> vec_of_T;

         A( std::vector<T> in_vec );

};

The class and constructor will only be exposed to R as a specific
instantiation of the class A with template parameter T=class B, i.e.
A<B>, where B is implemented in both C++ and R, and the C++
implementation of B has a constructor B::B(SEXP):

#include <RcppCommon.h>

class B {

     public:

         int id;

         B (SEXP b);

         B (int id=-1);

};

/*** R

# Reference Class of B

B_R <- setRefClass( "B_R",

     fields = list(id="numeric")

)

*/

template <class T> class A {

     public:

         std::vector<T> vec_of_T;

         A( std::vector<T> in_vec );

};

#include <Rcpp.h>

B::B(SEXP b){

     Rcpp::Reference in_b(b);

     id=in_b.field("id");

}

B::B(int id){

     this->id=id;

}

The idea is to allow an R vector of Reference Class objects B_R to be
passed to the C++ class A<B> constructor. To achieve this I have used
the following Rcpp-modules directly after the preceding code:

using namespace Rcpp;

RCPP_MODULE(testing) {

     class_< A<B> >("A")

     .constructor< std::vector<B> >()

     ;

}

I then use Rcpp-attributed sourceCpp() to compile the code from the R
prompt, and generate the R bindings to the C++ class A<B>.

sourceCpp(file="test.cpp", verbose=TRUE)

 From my understand of  section 3.2 in Rcpp-introduction.pdf, and what I
could glean about the handling of RCPP_MODULE declarations within
Rcpp-attribute (e.g. help(sourceCpp)), the conversion of ?STL vectors of
[?] arbitrary types that offer a constructor that takes a SEXP? should
be supported by Rcpp, and Rcpp-attributes should automatically generate
wrappers/bindings which utilize them.

However, when I run the above sourceCpp command I get the following
error which is stretching my understanding on both C++ and Rcpp:

C:/PROGRA~1/R/R-30~1.1/bin/i386/R CMD SHLIB -o "sourceCpp_42052.dll"
"test.cpp"

g++ -m32 -I"C:/PROGRA~1/R/R-30~1.1/include" -DNDEBUG
-I"C:/Users/me/Documents/R/win-library/3.0/Rcpp/include"
-I"d:/RCompile/CRANpkg/extralibs64/local/include"     -O2 -Wall
-mtune=core2 -c test.cpp -o test.o

In file included from
C:/Users/me/Documents/R/win-library/3.0/Rcpp/include/RcppCommon.h:110:0,

                  from test.cpp:1:

C:/Users/me/Documents/R/win-library/3.0/Rcpp/include/Rcpp/internal/export.h:
In function 'void Rcpp::internal::export_range(SEXP, InputIterator)
[with InputIterator = __gnu_cxx::__normal_iterator<B*, std::vector<B> >,
SEXP = SEXPREC*]':

C:/Users/me/Documents/R/win-library/3.0/Rcpp/include/Rcpp/internal/Exporter.h:47:17:
instantiated from 'T Rcpp::traits::RangeExporter<T>::get() [with T =
std::vector<B>]'

C:/Users/me/Documents/R/win-library/3.0/Rcpp/include/Rcpp/as.h:83:33:
instantiated from 'T Rcpp::internal::as(SEXP,
Rcpp::traits::r_type_generic_tag) [with T = std::vector<B>, SEXP =
SEXPREC*]'

C:/Users/me/Documents/R/win-library/3.0/Rcpp/include/Rcpp/as.h:126:89:
instantiated from 'T Rcpp::as(SEXP) [with T = std::vector<B>, SEXP =
SEXPREC*]'

C:/Users/me/Documents/R/win-library/3.0/Rcpp/include/Rcpp/module/Module_generated_Constructor.h:47:43:
instantiated from 'Class* Rcpp::Constructor_1<Class,
U0>::get_new(SEXPREC**, int) [with Class = A<B>, U0 = std::vector<B>,
SEXP = SEXPREC*]'

test.cpp:59:1:   instantiated from here

C:/Users/me/Documents/R/win-library/3.0/Rcpp/include/Rcpp/internal/export.h:90:4:
error: no matching function for call to
'export_range__dispatch(SEXPREC*&, __gnu_cxx::__normal_iterator<B*,
std::vector<B> >&, Rcpp::traits::r_type_traits<B>::r_category)'

C:/Users/me/Documents/R/win-library/3.0/Rcpp/include/Rcpp/internal/export.h:90:4:
note: candidates are:

C:/Users/me/Documents/R/win-library/3.0/Rcpp/include/Rcpp/internal/export.h:71:14:
note: template<class InputIterator, class value_type> void
Rcpp::internal::export_range__dispatch(SEXP, InputIterator,
Rcpp::traits::r_type_primitive_tag)

C:/Users/me/Documents/R/win-library/3.0/Rcpp/include/Rcpp/internal/export.h:80:8:
note: template<class InputIterator, class value_type> void
Rcpp::internal::export_range__dispatch(SEXP, InputIterator,
Rcpp::traits::r_type_string_tag)

make: *** [test.o] Error 1

Error in sourceCpp(file = "test.cpp", verbose = TRUE) :

   Error 1 occurred building shared library.

Am I missing something in my code?

Thanks in advance,

Luke Domanski.