R modules, such as Rcpp (http://rcpp.org/) are not present in portage, but must be installed directly using R commands. a new eclass may be useful to help portage to correctly install these modules. Reproducible: Always Sometimes, R modules are needed for install other packages. For example, sci-physics/root fails to build against R useflag if Rcpp and RInside are not installed. actually, portage does not offer any way to automatically install sci-physics/root. here: https://github.com/cloc3/gentoo/tree/sci-physics_root I prepare a patch for sci-physics/root to solve this problem, which contain Rutils new eclass, but I need developer opinion about my Rutils.eclass before making a pull request.
The bug tracker is not well suited for discussions. Please contact the science project. Ideally members of the maths section https://wiki.gentoo.org/wiki/Project:Science IRC will be a good start: https://www.gentoo.org/get-involved/irc-channels/