[Rcpp-devel] advice on sharing C++ code across R and Python

[Simon Barthelmé]

Dear list,

I have an R package that's mostly C++ code (using Eigen, but no other 
dependencies) and some glue. We wish to re-use the C++ code for a Python 
package. Most of the external-facing C++ functions are pretty simple: 
essentially they're all variants of:

NumericVector some_matrix_calculation(NumericMatrix a_matrix);

and all the stuff coming in or out are dense vectors and matrices. Note 
that I wrote all this with the idea that the C++ would only be called 
from R, so the C++ bits don't amount to a proper library.

I haven't used Python in years but from what I read there's about a 
dozen different ways now of interfacing Python and C/C++. Obviously none 
of them know about Rcpp objects like NumericVector so I'm guessing it'll 
have to be std::vector<double> in and out, unless there's a better way?

So: does anyone have any experience or advice on sharing C++ code 
between R and Python, short of spinning off the C++ as a stand-alone 
library and writing entirely separate interfaces?

Also, I know you can call R from Python and vice-versa, but we don't 
want to require Python users to install R+dependencies and vice-versa.

Many thanks for any advice!

Best regards

Simon Barthelme