Thread: Fun with templates.

Just messing around with templates. It works, just wondering if anyone could see any use for what I'm doing.

Code:

class Human { /* No Implementation, yet */ };

class Male : public Human {
  public:
    void Speak() { cout << "I am a man." << endl; }
};
class Female : public Human {
  public:
    void Speak() { cout << "I am a woman." << endl; }
};
class Adult : public Human {
  public:
    void Speak() { cout << "I am an adult." << endl; }
};
class Child : public Human {
  public:
    void Speak() { cout << "I am a child." << endl; }
};

template <class Gender, class Age>
class Individual : public Gender, public Age {
  public:
    void Speak() {
      Gender::Speak();
      Age::Speak();
    }
};

int main() {
   Individual<Male, Adult> man;
   Individual<Female, Adult> woman;
   Individual<Female, Child> girl;

   man.Speak();
   cout << endl;
   woman.Speak();
   cout << endl;
   girl.Speak();

   return 0;
}

Originally Posted by SlyMaelstrom

J

Code:

template <class Gender, class Age>
class Individual : public Gender, public Age

this is often referred to as the Curiously Recurring Template Pattern and has lots of uses.

an easy one off the top of my head is a Singleton template

Code:

template <typename SINGLETON_TYPE>
class Singleton
{
    static SINGLETON_TYPE* pInstance;
public:
    static inline SINGLETON_TYPE* Instance()
    {
         if (!pInstance)
         {
              pInstance = new SINGLETON_TYPE();
         }
         return pInstance;
     }
};

class x : public Singleton<x>
{
private:
     friend class Singleton;
     x()
    {}
};

that's obviously not complete, but you get the idea.

Templates are real fun when you get into specializations and template meta programming (ow, my brain hurts!)

If you're interested, have a read of
C++ Templates: The Complete Guide by Josuttis and Vandevoorde.

Then buy Modern C++ Design by Alexandrescu to learn where the language is going. It will fry your brain!