Re: [Boost-users] [serialization]Nans and infinity in wide xml archive

Subject: Re: [Boost-users] [serialization]Nans and infinity in wide xml archive
From: Robert Ramey (ramey_at_[hidden])
Date: 2017-07-04 17:38:55

On 7/4/17 10:01 AM, Paul A. Bristow via Boost-users wrote:

>> I would wonder though.  I'm not sure that the Nan literals are standard.
>>    I also don't trust them to be portable.  Also to me it's a problem
>> with stream i/o rather than serialization itself.  So my instinct would
>> have been to maybe make a custom manipulator or something like that. But
>> still, you've got a solution which looks like it will work well for your
>> needs so good luck with this.
> 
> http://www.boost.org/doc/libs/1_64_0/libs/math/doc/html/math_toolkit/fp_facets/facets_intro.html
> 
> has some info on this:
> 
> "C99 standard for output of infinity and NaN
> 
> The C99 standard does specify how infinity and NaN are formatted by printf and similar output functions, and parsed by scanf and
> similar input functions.
> 
> The following string representations are used:
> 
> Table 2.1. C99 Representation of Infinity and NaN
> 
> number
> 
> string
> Positive infinity
> "inf" or "infinity"
> Positive NaN
> "nan" or "nan(...)"
> Negative infinity
> "-inf" or "-infinity"
> Negative NaN
> "-nan" or "-nan(...)"
> 
> So following C99 provides a sensible 'standard' way of handling input and output of nonfinites in C++, and this implementation
> follows most of these formats."
> 
> And Elizabeta's solution is close to this.  Using lower case might become more 'Standard'.
> 
> I don't know of any progress in a 'Standard' representation in C++14, 17 ....
> 
> HTH
> 

This is all very interesting!  I know some time ago when this problem 
first came up (I'm always getting the blame for this!)  There was some 
work in addressing it.  I didn't take part because I was sort of burned 
out on working on the serialization library.  But I would think it would 
be a good thing if this could be "resolved" via a combination of 
documentation and code so provide a canonical C++ solution which would 
be compatible with just C++ stream i/o and hence automatically apply to 
the the serialization library.

Robert Ramey