[boost] variant with shrink

Subject: [boost] variant with shrink
From: Niitsuma Hirotaka (hirotaka.niitsuma_at_[hidden])
Date: 2013-03-03 02:13:38

boost::variant should be

variant<int,int>
=> int

variant<int,double>
=> double

variant<int,boost::rational<int> >
=> boost::rational<int>

variant<int,double,std::string>
=> variant<double,std::string>

I wrote such extension

https://github.com/niitsuma/variant_shrink

Default generalize order is
int  < boost::rational<int>  < float  < double   < std::complex<double>

You can use other custom generalize relation by defining function object
is_generalizable_to<Type,TypeTo>