For a while now I've been meaning to clean up my floating-point classification code to provide a more reliable way of testing for Nan's and infinities. The new TR1 complex number code could really use this to improved it's reliability. I believe Robert Ramey was looking for this functionality for serialisation, and frankly it's hard to write any serious floating point code without it. So... attached is a first version of an fpclassify implementation for Boost (if there's interest). As long as this one works (not a given unfortunately) then it's obviously trivial to sit isnan, isinfinity etc on top of it. So.... I'm looking for testers to run the attached program on as many different platforms/compilers as possible, basically I want to see if there's any mileage in this or if I'm on to a looser with this code! Please build the test program with optimisations turned on: many compilers make non-IEEE arithmetic assumptions once you tell them to optimise the code. Tested so far: Win32: VC6: Can't detect signaling NaN's (_isnan is broken). VC7, 7.1, 8: OK Intel 7, 8, 9: OK provided you're not using the VC6 runtime. GCC cygwin: OK. Borland 5.6.4: So broken I don't know where to begin :-( HP-UX: gcc-3.4.2: OK. aCC: OK (native fpclassify broken for long doubles, but portable version works). Tru64: cxx : OK (but can't test infinities/NaN's as they're not supported? Suse Linux: gcc-3.3.3 : OK. Many thanks, John.