John, Could you test the latest version (ver. 13) of my fpclassify library? It is available in the vault in the directory Math-Numerics. The library is based on a helper class fp_traits<T> that contains information about the binary representation of T. Here T = float, double or long double. The generic version of fp_traits<T> is initialized at run time, and is hence safe but also slow. Then there are fast specializations of fp_traits<T> for different floating point types T, operating systems and processors. The library does not use the limits and boost/endian.hpp headers. The library has been tested on the following platforms: Win / MSVC 7.1 / x86 Mac / GCC 3.3, GCC 4.0 / ppc Linux / GCC 3.3 / x86, x64, ia64, ppc, hppa, mips, m68k Let's see if you can break it! --Johan