visitor

#include <functional>
#include <boost/mpl/inherit_linearly.hpp>
#include <boost/mpl/inherit.hpp>
#include <boost/mpl/vector.hpp>

template<typename TargetsVector, typename SignatureVector>
struct visit_method;

template<typename TargetType, typename ReturnType, typename ... ArgsTypes>
struct visit_method<TargetType, std::tuple<ReturnType, ArgsTypes ...>> {

	virtual void visit(TargetType, ArgsTypes&& ...) = 0;
	virtual ~visit_method() {

	}
};

template<typename T, typename TargetType, typename Signature>
struct inherit_wrapper: boost::mpl::inherit<T,
		visit_method<TargetType, Signature>> {

};

template<typename TargetsVector, typename SignatureVector>
class basic_visitor;

template<typename ... TargetsTypes, typename SignatureVector>
class basic_visitor<std::tuple<TargetsTypes ...>, SignatureVector> : public boost::mpl::inherit_linearly<
		boost::mpl::vector<TargetsTypes ...>,
		inherit_wrapper<boost::mpl::_1, boost::mpl::_2, SignatureVector>>::type {

};

template<typename SelfType, typename ReturnType>
class visitable {
public:
	template<typename VisitorType, typename ... ArgsTypes>
	ReturnType accept(VisitorType& visitor, ArgsTypes&& ... args) {
		return visitor.visit(static_cast<SelfType&>(*this), args ...);
	}
};