| -----Original Message----- | From: boost-bounces@lists.boost.org | [mailto:boost-bounces@lists.boost.org] On Behalf Of Jeff Garland | Sent: 20 April 2006 04:01 | To: boost@lists.boost.org | Subject: Re: [boost] Report from Berlin C++ Standards | Committee meeting | | On Wed, 19 Apr 2006 18:31:14 +0100, Paul A Bristow wrote | | > So a) is in principle fixed IMO. | > | > As to b), I had understood that we had agreed that all NaNs | could reasonably | > be treated as identical and one would get a NaN (unspecified) back. | > Similarly infinities. | > | > | http://article.gmane.org/gmane.comp.lib.boost.devel/134569/mat | ch=serializati | > on+nan | > | > But simple | > | > stream << output_value; // write out. | > double read_value; | > stream >> read_value; // read back. | > | > doesn't work for | > | > double output_value = numeric_limits<double>::quiet_NaN(); | // output_value | > 1.#QNAN != read_value 1 | > double output_value = numeric_limits<double>::infinity(); | // output_value | > 1.#INF != read_value 1 | > | > So some special flag would be needed to hold the Nan or Inf nature. | > | > If only there was a Standard representation of Nan and Infs. VERY | > shortsighted, making NaNs and infs hardly useable. | | Agreed. The types in date_time have the ability to serialize | and deserilize | NADT (not a date time), -infinity and +infinity. Why | couldn't there be a | simple extension to the numpunct<charT> facet to define an | appropriate output | string? Basically something like: | | //see Langer and Kreft p 414... | template<class charT> | class numpunct : public locale::facet { | | //new functions for nan and infinity | string_type not_a_number_name() const; | string_type infinity_name() const; | | And you'd have to fix num_get as well. Looks a good idea - but these facets look complicated to my inexpert eye. Should we ALSO press to get a 'proper' C++0x Standard solution to this? Paul -- Paul A Bristow Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB Phone and SMS text +44 1539 561830, Mobile and SMS text +44 7714 330204 mailto: pbristow@hetp.u-net.com http://www.hetp.u-net.com/index.html http://www.hetp.u-net.com/Paul%20A%20Bristow%20info.html