I've just added changesign function and nonfinite facets to Boost.Math in boost-trunk. These functions were part of the original floating-point collection written by Johan Rade but were previously only available from Spirit in boost-sandbox. Making them First Class citizens in Boost.Math will allow portable input/output of infinity and NaN, including use of lexical cast, archiving and serialization. Multiplatform testing of these new features should start soon. I hope this will not have any unwanted side effects - I'm sure you'll shout if it does. Paul --- Paul A. Bristow, Prizet Farmhouse, Kendal LA8 8AB UK +44 1539 561830 07714330204 pbristow@hetp.u-net.com