Jeff Garland proposed a solution the problem of serialization of NaN and infinity which had beed discussed http://article.gmane.org/gmane.comp.lib.boost.devel/141006/match=langer+nan Although this is probably the right expendient solution which could be done now (if anyone has the time and skill - SoC?), I also feel this is a general problem that needs a Standard solution (some impect on lexical_cast) so I have drafted a proposal for TR2 which is attached for comment. Briefly, it is a KISS solution. All infinities are output (and input) as one string like "Inf", And all the various NaNs are also a single string "NaN", And on input you get the numeric_limits<FPtype>::quiet_NaN() or infinity(), Is the same for ALL FP types (including UDTs) and layouts. Paul --- Paul A Bristow Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB +44 1539561830 & SMS, Mobile +44 7714 330204 & SMS