Listing A

// this will work only for 'char' streams!!!

 class write_key_and_value

 {

 public:

    template< class CharType, class CharTraits, class Key, class Value>

        void operator() (

            std::basic_ostream< CharType, CharTraits> & streamOut,

           const std::pair< const Key, Value> & value)

    {

        streamOut << "key: " << value.first << ", value: " << value.second;

    }

 };


 std::map< std::string, int> collWords;

 collWords.insert( std::make_pair( (std::string)"easily", 3));

 collWords.insert( std::make_pair( (std::string)"write", 5));

 collWords.insert( std::make_pair( (std::string)"collections", 12));

 std::cout << coll_container( collWords, formatter( write_key_and_value()));

 // will print out:

 // key: collections, value: 12

 // key: easily, value: 3

 // key: write, value: 5