C++ (Qt)
typedef type_list< double, int, std::string, float > list_of_types;
 
struct cals_sum : public any_visitor< double, list_of_types >
{
    double m_sum;
 
    cals_sum () : m_sum() {}
 
    double operator()( const std::string & str ) { return m_sum += std::stod(str); }
    template <class T>
    double operator()( const T & val ) { return m_sum += double( val ); }
};
 
 
struct to_string : public any_visitor< std::string, list_of_types >
{
    std::string operator()( const std::string & str ) const { return str; }
 
    template <class T>
    std::string operator()(const T & val) const { return std::to_string(val); }
};
 
int main()
{
    std::list< boost::any > many = {123, 3.14, 5.6f, std::string("2.71")};
 
    cals_sum visitor;
    for ( const auto & x : many )
        apply_any_visitor( visitor, x );
 
    std::cout << visitor.m_sum << std::endl;
    return 0;
}
 

C++ (Qt)
template <class Visitor, class TypeList>
struct any_cast_helper
{
    static typename Visitor::result_type get(const boost::any & any, Visitor & visitor)
    {
        if (any.type() == typeid(typename TypeList::first_type))
            return visitor(boost::any_cast<typename TypeList::first_type >(any));
 
        return any_cast_helper<Visitor, typename TypeList::next_type_list>::get(any, visitor);
    }
    static typename Visitor::result_type get(const boost::any & any, const Visitor & visitor)
    {
        if (any.type() == typeid(typename TypeList::first_type))
            return visitor(boost::any_cast<typename TypeList::first_type>(any));
 
        return any_cast_helper<Visitor, typename TypeList::next_type_list>::get(any, visitor);
    }
};
 
 
template <class Visitor>
struct any_cast_helper<Visitor, null_type>
{
    static typename Visitor::result_type get(const boost::any &, Visitor &) throw(std::bad_cast)
    {
        throw std::bad_cast();
    }
    static typename Visitor::result_type get(const boost::any &, const Visitor &) throw(std::bad_cast)
    {
        throw std::bad_cast();
    }
};
 
 
template <class Visitor>
typename Visitor::result_type apply_any_visitor(const Visitor & visitor, const boost::any & any)
{
    return any_cast_helper<Visitor, typename Visitor::type_list>::get(any, visitor);
}
 
template <class Visitor>
typename Visitor::result_type apply_any_visitor( Visitor & visitor, const boost::any & any)
{
    return any_cast_helper<Visitor, typename Visitor::type_list>::get(any, visitor);
}
 

C++ (Qt)
class serializator
{
public:
    serializator(std::ofstream & out) : m_out(out) {}
 
    template <class T>
    friend serializator & operator<<(serializator &, const T &);
 
    friend serializator & operator<<(serializator &, bool);
 
private:
    int bool_packet; 
    std::ofstream & m_out;
};
 

C++ (Qt)
struct editor : public any_visitor<void, type_list<int, double, std::string>>
{
    void operator()(std::string & s) { s += " Qt5"; }
 
    void operator()(int & i) { i += 100500; }
 
    void operator()(double & d) { d = 3.14159; }
};
 
struct printer : public any_visitor<void, type_list<int, double, std::string>>
{
    template <class T>
    void operator()(const T & val) const { std::cout << val << std::endl; }
};
 
int main()
{
    std::list<boost::any> many = {13, 1.34834657, std::string("hello")};
 
    std::cout << "before:" << std::endl;
    for (auto & x : many)
        apply_any_visitor(printer(), x);
 
    for (auto & x : many)
        apply_any_visitor(editor(), x); // Editor изменяет значения элементов. 
 
    std::cout << "after:" << std::endl;
    for (auto & x : many)
        apply_any_visitor(printer(), x);
 
    return 0;
}