This is answered in the article. Chunks of R are written in Fortran 90, which can’t be converted to C easily right now. You might ask why it’s written in Fortr

This is answered in the article. Chunks of R are written in Fortran 90, which can’t be converted to C easily right now. You might ask why it’s written in Fortran at all. Probably has something to do with its history coming out of the S language at Bell labs in the 70s and 80s.