How to serialize boost::rational

Question

I cannot serialize boost::rational. I searched for a boost/serialize/rational.h header but it does not exist.

 /usr/include/boost/seriali         


        

Answer 1

Just serialize the numerator and denominator.

Here's the legwork, in semi-generic form (supports archives with named nodes, like XML serialization, too): Live On Coliru

#include 
#include 
#include 
#include 
#include 

namespace boost { namespace serialization {

    template 
        void save(Archive& ar, ::boost::rational const& r, unsigned /*version*/)
        {
            int n = r.numerator(), d = r.denominator();
            ar & boost::serialization::make_nvp("numerator", n);
            ar & boost::serialization::make_nvp("denominator", d);
        }

    template 
        void load(Archive& ar, ::boost::rational& r, unsigned /*version*/)
        {
            int n, d;
            ar & boost::serialization::make_nvp("numerator", n);
            ar & boost::serialization::make_nvp("denominator", d);

            r = ::boost::rational(n, d);
        }

} }

BOOST_SERIALIZATION_SPLIT_FREE(boost::rational);

using namespace boost;
#include 
#include 

int main()
{
    rational number(2, 3), other;

    std::stringstream ss;
    {
        archive::xml_oarchive oa(ss);
        oa << serialization::make_nvp("rational", number);
    }

    std::cout << "Serialized: '" << ss.str() << "'\n";

    {
        archive::xml_iarchive ia(ss);
        ia >> serialization::make_nvp("rational", other);
    }

    std::cout << "Deserialized: " << other;
}

Prints

Serialized: '



    2
    3



'
Deserialized: 2/3