[boost] Portable signbit macro/function?

Does anyone have a ***portable*** version of macro signbit (C99) or can we combine versions that work on each compiler/hardware/endian... or an equivalent C++ function, perhaps called is_negative? (This would just test the signbit for the type(s)). There are several places where this would be useful in dealing properly with NaNs and zero and infinity etc. Thanks Paul PS Must be Boost license of course. --- Paul A Bristow Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB +44 1539561830 & SMS, Mobile +44 7714 330204 & SMS pbristow@hetp.u-net.com