| -----Original Message----- | From: boost-bounces@lists.boost.org | [mailto:boost-bounces@lists.boost.org] On Behalf Of Johan Råde | Sent: 12 October 2006 16:40 | To: boost@lists.boost.org | Subject: Re: [boost] Optimized portable isnan, isfinite, | fpclassify etc | | John Maddock wrote: | > Johan Råde wrote: | >> 3. Your <limits> header is a bit funny. | >> numeric_limits<T>::quiet_NaN() returns a NaN with the signbit set. | >> This triggered the assertion. | > | > You need to allow for the possibility that the sign bit is | set anyway. | | I will. | | > | >> (Does it matter? Maybe. According to C99, positive NaN should be | >> written to text files as "nan" or "+nan" and negative | NaN as "-nan". | >> And this will probably be part of C++0x as well.) | > | > C++ doesn't guarentee any particular format for printing | NaN's or Infinities | > :-( | | C99 does. And C99 will become part of C++0X, right? | I have also raised this issue http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2022.pdf and suggest that, with NaNs (like other types), sign bit should be detectable and printed, without implying any mathematical sense. Paul --- Paul A Bristow Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB +44 1539561830 & SMS, Mobile +44 7714 330204 & SMS pbristow@hetp.u-net.com