Thanks a lot, again. ;-) This is the working code now. #include <string> #include <sstream> #include <boost/cstdint.hpp> #include <vector> #include <boost/shared_ptr.hpp> #include <boost/bind.hpp> #include <iostream> class Base { public: virtual std::string to_String ( boost::uint32_t indent ) = 0; }; class A : public Base { public: A ( boost::uint32_t value ) : m_value ( value ) {} virtual std::string to_String ( boost::uint32_t indent ) { std::stringstream output; for ( boost::uint32_t i = 0; i < indent; i++ ) { output << " "; } output << m_value; return output.str(); } private: boost::uint32_t m_value; }; class D : public Base { public: D ( boost::uint32_t value ) : m_value ( value ) {} virtual std::string to_String ( boost::uint32_t indent ) { std::stringstream output; for ( boost::uint32_t i = 0; i < indent; i++ ) { output << " "; } output << m_value; return output.str(); } private: boost::uint32_t m_value; }; void print( const std::string& s ) { std::cout << s; } int main ( int, char** ) { typedef boost::shared_ptr<A> A_ptr_t; typedef boost::shared_ptr<D> D_ptr_t; typedef std::vector < boost::shared_ptr<Base> > Data_t; Data_t m_data; A_ptr_t a ( new A ( 50 ) ); D_ptr_t d ( new D ( 30 ) ); m_data.push_back ( a ); m_data.push_back ( d ); boost::uint32_t indent_value = 4; std::for_each ( m_data.begin(), m_data.end(), boost::bind( &print , boost::bind( &Base::to_String , _1 , indent_value ))); return 0; } It's still not quite what we what but we are getting closer. ;-) Christian