[Rcpp-devel] split the c++ code in several files

[Romain Francois]

Le 16/09/10 15:24, baptiste auguie a écrit :
> Dear list,
>
>
> This is probably not specific to Rcpp but I couldn't find any advice
> in the R-exts manual. I am using RcppArmadillo in a package to do some
> linear algebra. The C++ code is getting a bit too large to manage in
> one file only, I would like to split its content in several files.
> It seems possible, but I'm not sure how to deal with the scoping
> rules: if a function requires a subroutine defined in another file it
> seems to have a scoping problem (the compilation fails with message
> "error: ‘xxxx’ was not declared in this scope)". Currently my cpp file
> looks like this,
>
> ///////////////////////////////////////////////////
> #include "cda.h"
> #include<RcppArmadillo.h>
> #include<iostream>
>
> using namespace Rcpp ;
> using namespace RcppArmadillo ;
>
> using namespace std;
>
> extern "C" {
>
>    arma::mat foo(const arma::mat&  R) {
>      return(R);
>     }
>
>    // R wrapper
>    RCPP_FUNCTION_1(NumericMatrix, test, NumericMatrix IR)
>    {
>     arma::mat R = Rcpp::as<  arma::mat>(IR);
>     return wrap( foo(R) );
>    }
>   // other routines
> }
> ///////////////////////////////////////////////////
>
> (The actual file is here:
> https://r-forge.r-project.org/scm/viewvc.php/pkg/cda/src/cda.cpp?diff_format=h&root=photonics&view=log)
>
>
> Are there workarounds / rules to split the content in several files?
>
> Best regards,
>
> baptiste

Hello,

The usual thing is to declare functions in header files, and include 
these headers from each .cpp file. You then define the functions in .cpp 
files in any order you like. As long as it is declared, the compiler 
knows it is coming.

I think you should use RCPP_FUNCTION_* outside of the extern "C" block.



However, I believe modules now do a better job than the RCPP_* macros, 
and for example I think you don't need this wrapper:

  // R level wrapper
   RCPP_FUNCTION_3(NumericMatrix, rotation, double phi,
                   double theta, double psi) {
     return wrap(euler(phi, theta, psi));
   }

You would simply make a module liks this:

RCPP_MODULE(aladdin){
	using namespace Rcpp ;

	function( "rotation", &euler ) ;
	function( "interaction_matrix", &interactionA ) ;
}

and then on the R side, you grab the module :

jasmine <- Module( "aladdin" )
jasmine$rotation( 1, 2, 3 )
jasmine$interaction_matrix( ... )




Also note that from the most recent version of RcppArmadillo, you don't 
need the Rcpp::as anymore to convert a NumericMatrix to an arma::mat, 
you can just do (I think):

arma::mat R = IR ;


Romain



-- 
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
|- http://bit.ly/cCmbgg : Rcpp 0.8.6
|- http://bit.ly/bzoWrs : Rcpp svn revision 2000
`- http://bit.ly/b8VNE2 : Rcpp at LondonR, oct 5th