id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
9479	polymorphic_get<> for variant	Antony Polukhin	Antony Polukhin	"The original idea was described [http://coliru.stacked-crooked.com/a/3e920faa604fa534 here]:
{{{
#include <iostream>
#include <boost/variant.hpp>
#include <boost/variant/get.hpp>

//------------------------------------------------------------------------------
struct unused
{
    template<class T>
    unused(T&) {}
};

template<class T>
struct Getter
{
    typedef T* result_type;
    
    T* operator()(T& v) const
    {
        return &v;
    }

    T* operator()(unused) const
    {
        return nullptr;
    }
};

template<class U, class T>
U* poly_get(T* v)
{
    return boost::apply_visitor(Getter<U>(), *v);
}
//------------------------------------------------------------------------------

struct O{
};
struct A:O{
};
struct B:O{
};


int main(int argc, char** argv) {
    boost::variant<A, B> v;
    std::cout << ""boost::get-------------------------------\n"";
    std::cout << boost::get<O>(&v) << std::endl;
    std::cout << boost::get<A>(&v) << std::endl;
    std::cout << boost::get<B>(&v) << std::endl;
    std::cout << ""poly_get---------------------------------\n"";
    std::cout << poly_get<O>(&v) << std::endl;
    std::cout << poly_get<A>(&v) << std::endl;
    std::cout << poly_get<B>(&v) << std::endl;
}
}}}"	Feature Requests	closed	Boost 1.56.0	variant	Boost 1.54.0	Problem	fixed