Hi First of all I want to say how impressed I am with Rcpp. I think it is going to be very useful for some of the packages I am developing. Thank you very much for developing it.
I have a question regarding writing custom as and wrap functions for my own classes. Following the example in: http://gallery.rcpp.org/articles/custom-as-and-wrap-example/ I can get my own minimal example to work with a very simple class, and using the sourceCpp() function. The cpp code saved as a *.cpp file: #include <RcppCommon.h> class DummyClass { public: double value; }; namespace Rcpp { // non-intrusive extension via template specialisation template <> DummyClass as(SEXP dt); // non-intrusive extension via template specialisation template <> SEXP wrap(const DummyClass &d); } #include <Rcpp.h> // define template specialisations for as and wrap namespace Rcpp { template <> DummyClass as(SEXP dtsexp) { S4 dc_s4 = Rcpp::as<S4>(dtsexp); DummyClass dc; dc.value = dc_s4.slot("value"); return dc; } template <> SEXP wrap(const DummyClass &d) { Rcpp::S4 dc_s4("DummyClass"); dc_s4.slot("value") = d.value; return Rcpp::wrap(dc_s4); } } // [[Rcpp::export]] DummyClass test_as_wrap(DummyClass dc, double multiplier){ DummyClass dc_out; dc_out.value = dc.value * multiplier; return dc_out; } And the following R code compiles and calls the function: library(Rcpp) sourceCpp("DummyClass_example.cpp") setClass("DummyClass", representation(value = "numeric")) dc <- new("DummyClass") dc@value <- 23 test_as_wrap(dc, 4) This works just fine (like magic!) and the test_as_wrap() function is happily called from R and returns an object of type DummyClass. I want to use a similar approach in a package, so I made a minimal package using: Rcpp.package.skeleton("asWrapExample",attributes=TRUE) I then split my original cpp file above into header and source code files. In the /inst/include directory I placed a file 'DummyClass_example.h' which has: #include <RcppCommon.h> class DummyClass { public: double value; }; namespace Rcpp { // non-intrusive extension via template specialisation template <> DummyClass as(SEXP dt); // non-intrusive extension via template specialisation template <> SEXP wrap(const DummyClass &d); } In the /src directory I placed a file 'DummyClass_example.cpp' which has: #include "../inst/include/DummyClass_example.h" #include <Rcpp.h> // define template specialisations for as and wrap namespace Rcpp { template <> DummyClass as(SEXP dtsexp) { S4 dc_s4 = Rcpp::as<S4>(dtsexp); DummyClass dc; dc.value = dc_s4.slot("value"); return dc; } template <> SEXP wrap(const DummyClass &d) { Rcpp::S4 dc_s4("DummyClass"); dc_s4.slot("value") = d.value; return Rcpp::wrap(dc_s4); } } // [[Rcpp::export]] DummyClass test_as_wrap(DummyClass dc, double multiplier){ DummyClass dc_out; dc_out.value = dc.value * multiplier; return dc_out; } When I try to compile the package I get this error message: RcppExports.cpp:9:1: error: 'DummyClass' does not name a type This is probably caused by the RcppExports.cpp not having an #include for my DummyClass_example.h. I understand the RcppExports.cpp file is automatically generated by the magic of Rcpp so there is no point in adding it there by hand. I've looked at the documentation but it is not clear to me how I can tell RcppExports to also include my header file (if this is the source of the problem). Have I missed something in the documentation, or is there an example I can follow? Any help is appreciated. Yours Finlay
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