Tests cpp interface

[Nowosad]

adds line // [[Rcpp::interfaces(r, cpp)]] in src/dist_matrix.cpp and then run devtools::document() -- this adds the rest of the files exporting all cpp functions in the cpp file

[brownag]

This looks good to me!

[Nowosad]

Hi @brownag -- could you take one more look at the new changes? In relation to your comment at #46 (comment), I moved distance_cpp from dist_matrix.cpp to utils.h, and also stopped exporting utils in C++. What do you think? An alternative to this could be to create a new file (e.g., distance_cpp.h) just for the distance_cpp and related functions.

[brownag]

Ya, this is essentially what I had in mind, as far as moving some things out of dist_matrix.cpp
Te organization into multiple files I guess depends on how often utils.h may need to be used more generically without the distance functions. So distance_cpp.h or similar would good organization since that is a bit more specialized?

[Nowosad]

@brownag Ok -- I made it even cleaner. Now:

• the distance_cpp (and related) is in src/distance_cpp.cpp
• the utils.h is now split into utils.h and utils.cpp
• the dist_matrix.cpp is now renamed to dist_functions.cpp

I think it is ready for review (and merge)

CC: @HajkD