http://barendgehrels.blogspot.com/2010/10/tag-dispatching-by-type-tag-dispatching.html Tag-dispatch examples.

tag_dispatch.h

#ifndef TAG_DISPATCH_H
#define TAG_DISPATCH_H
struct  apple_tag{};
struct  banana_tag{};
struct orange_tag{};
struct apple
{
	double reduis;
	std::string name;
	apple(std::string const& n): name(n){}
};

struct banana
{
	double length;
	std::string name;
	banana(std::string const& n): name(n){}
};

namespace dispatch{
	
	template <typename Tag> struct eat{};
	
	template<>struct eat<apple_tag>
	{
		static void apply(apple const& a){
			std::cout<<"Apple tag"<<std::endl;
		}
	};
	
	/* void eat(apple const& a, apple_tag){
		std::cout<<"Apple tag"<<std::endl;
	} */
	
	template<>struct eat<banana_tag>
	{
		static void apply(banana const& b){
			std::cout<<"Banana tag"<<std::endl;
		}
	};
	
 /*	void eat(banana const& b, banana_tag){
		std::cout<<"Banana tag"<<std::endl;
	} */
	
}

/* template<typename T>
void eat(T const&  friut){
	typename tag<T>::type the_tag;
	dispatch::eat( friut, the_tag);
} */

template <typename T>
void eat(T const& fruit)
{
    dispatch::eat<typename tag<T>::type>::apply(fruit);
}



#endif