Vincent J. Carey Practical uses of external references ************************************* The externalptr class has recently been introduced to R. A detailed discussion with applications to file handling and regular expression processing is provided by Luke Tierney (http://www.stat.uiowa.edu/~luke/R/regexp.html, http://www.stat.uiowa.edu/~luke/R/simpleref.html). In this paper, a new library for linear algebra using matrix pointers and the RSGB package (R interface to Stanford Graph Base, see bioconductor.org browsable CVS archive) will be discussed with respect to package architecture and applications. Particular attention will be paid to the use of formal classes, memory management, and exception handling.