Paul A Bristow wrote:
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(),
As far as I'm concerned it not simple enough. Once you admit Inf then someone is going to insist on -Inf (rightly so in my opinion). The whole idea of trying to overload a floating point number with non-floating pointing values is the idea that has to go. I'm sure someone is going to chime in that this has legitimate uses but it causes lots of problems. I'm sure its the source of a lot of software bugs. So I would propose only one thing other than a float - a NaN. Actually, taking the idea to its logical conclusion, the best would be just to say that serialization of a NaN is undefined. The serialization library could implement this by trapping all attempts to serialize a NaN() as errors. If a user wants to save/load other stuff he could define a "rich float" which would parse the float into a flag + an optional floating point value. This would "reduce" the problem to making a portable implementation of "rich float" which your proposal would address. I doubt your proposal will be acceptable though. Those who think overloading floats with non-numeric indicators is a good idea will want more not less variety on the types. If the "rich float" were to be implemented, people would want to start adding their own overloads - like special indicators for pi and e . I think we should go in the opposite direction. A float is a a legitmate floating point value. A union of float and some other special non-floating point values is something else. Robert Ramey