Function

template <typename R>
class MultiFuncObject
{
    unordered_map<type_index, void(*)()> m_funcs;
public:

    template <typename ...A1>
    MultiFuncObject<R> operator +=(R(*f)(A1...))
    {
        m_funcs[typeid(R(A1...))] = (void(*)()) f;
        return *this;
    }


    template <typename ...A1>
    R operator()(A1... a1) const
    {
        unordered_map<type_index, void(*)()>::const_iterator it = m_funcs.find(typeid(R(A1...)));
        if (it != m_funcs.end())
        {
            R(*f)(A1...) = (R(*)(A1...))(it->second);
            (*f)(a1...);
        }
    }

};