type_map_2.cpp

#include <iostream>
#include <map>
#include <typeinfo>

struct type_info_cmp{
    bool operator ()(const std::type_info *lhs, const std::type_info *rhs) const{
        return lhs->before(*rhs) != 0;
    }
};

struct a_type{
    virtual ~a_type(){}
};

struct n_type{
    virtual ~n_type(){}
};

struct b_type : a_type, n_type{
    virtual ~b_type(){}
};

int main(){
    a_type a;
    b_type b;
    a_type *a_ptr = &a;
    a_type *b_ptr = &b;
    n_type *n_ptr = &b;
    std::map<const std::type_info*, std::string, type_info_cmp> map;
    map[&typeid(*a_ptr)] = "A";
    map[&typeid(*b_ptr)] = "B";
    map[&typeid(*n_ptr)] = "N"; // !!

    // A, N
    for(auto iter = map.begin(); iter != map.end(); ++iter){
        std::cout << iter->second << std::endl;
    }

    return 0;
}