The R Project SVN R

This suite of C language elementary functions offers support for
not-a-number (NaN) and infinity rules, subnormal numbers, and minus
zero as described by IEEE standard 754 and the Numerical C Extensions
Group (NCEG).  For a variety of reasons, many computers cannot take
advantage of these features.  You can disable any or all of them by
removing the corresponding preprocessor macros.  Check the files
mconf.h and const.c carefully to be sure they are appropriate for your
system.