From: Paul A Bristow (pbristow_at_[hidden])
Date: 2006-10-13 13:26:09
| -----Original Message-----
| From: boost-bounces_at_[hidden]
| [mailto:boost-bounces_at_[hidden]] On Behalf Of Johan Råde
| Sent: 12 October 2006 16:40
| To: boost_at_[hidden]
| 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_at_[hidden]