Type Generator

More C++ Idioms/Type Generator

Solution and Sample Code

template <class Value>
struct Directory
{
  typedef std::map <std::string, Value, std::less<std::string>, 
                    __gnu_cxx::malloc_allocator<std::string> > type;
};

Directory<int>::type    // gives a map of string to integers.
Directory<float>::type  // gives a map of string to floats.

Directory<int>::type age; // This is a map.
transform(age.begin(), age.end(),
          std::ostream_iterator<string>(std::cout, "\n"),
          _Select1st<std::map<std::string, int>::value_type> ());

template <class Value>
struct Directory
{
  typedef map <string, Value, less<string>, __gnu_cxx::malloc_allocator<std::string> > type;
  typedef _Select1st<typename type::value_type> KeySelector;
  typedef _Select2nd<typename type::value_type> ValueSelector;
};
Directory<int>::type age;    // This is a map.
transform(age.begin(), age.end(),
          std::ostream_iterator<string>(std::cout, "\n"),
          Directory<int>::KeySelector());

Template aliases

C++11的Template aliases能够用于实现type generator。