Re: [boost] [serialization] How are floating point values handled?

Subject: Re: [boost] [serialization] How are floating point values handled?
From: John Maddock (john_at_[hidden])
Date: 2013-08-08 04:32:49

>> The current
>> default situation is to print just 5 digits, and that certainly
>> doesn't get close!
>
> Hmmm - that surprises me.  I look at the code in the file
> basic_text_oprimitive.hpp and I find:
>
> void save(const float t)
> {
>    // must be a user mistake - can't serialize un-initialized data
>    if(os.fail())
>        boost::serialization::throw_exception(
>        archive_exception(archive_exception::output_stream_error)
>    );
>    os << std::setprecision(std::numeric_limits<float>::digits10 + 2);
>    os << t;
> }
>
> Is this code not correct? Note that I added in 2 extra digits.  Or
> is this code not getting invoked?  Let me know.

Ah... my problem was with a UDT that was marked as a primitive: then it just 
calls the << operator and doesn't attempt to set the stream precision as far 
as I can tell?

The issue would presumably also surface if someone tried to non-intrusively 
support non-standard native floating point types such as GCC's __float128 or 
Intel's _Quad data types, you can write a "serialize" function instead, but 
as you already pointed out, that involves more typing once you you split the 
method into load/save and binary/text variants.

John.