Douglas M. Bates, Saikat DebRoy C++ Classes for R Objects ******************************* When creating the R Matrix package, which provides access to the Fortran Lapack and BLAS3 routines, we patterned the functions after the corresponding S-PLUS library but chose a completely different implementation. We based the R implementation on the lapack++ classes that provide C++ wrappers for the Lapack code. There are several advantages to using C++ instead of C for code that will be called from R. In particular it is possible to encapsulate some of the S-language class structure in the C++ classes. There are also disadvantages to using C++. We discuss these for the particular example of the Matrix package and also describe a more general approach of reflecting basic R object types in C++ classes.