The document discusses different types of polymorphism in C++, including runtime polymorphism using virtual methods and compile-time polymorphism using templates. It notes that templates can provide polymorphism without the performance overhead of virtual methods, but may increase compile times. Both techniques have advantages and can be combined effectively in some cases to leverage their respective benefits.

1. Polymorphism in C++ 24th Aug 2007

4. Any of them works – example // Using virtual method based polymorphism // lock is a virtual method. SingleThreading and Multi-threading are 2 derived classes which define lock() differently void func(BaseThreadingPolicy * pThreadingPolicy) { pThreadingPolicy->lock(); }; // Using template based polymorphism SingleThreading and Multi-threading both implement a lock() method, but the needn’t have any virtual methods, nor do they need to derive from a common base class template <class T> func(T* pThreadingPolicy) { pThreadingPolicy->lock(); };

9. Design of reusable data structures – Inheritance or Templates? Value or Reference semantics, both allowed Reference semantics only (leaks, crashes..) 4 Non-Intrusive Intrusive (put an int/char inside a class and derive from base) 3 Type safe Non type-safe (Crash!) 2 Faster Slower (virtuals) 1 Template based approach Inheritance based approach Index

17. Illustration Class Base { public: Base(); virtual void func1(); virtual void func2(); virtual ~Base(): }; Class Derived { public: Derived(); virtual void func1(); virtual ~Derived(); };

18. Illustration (Contd) vtable for the Derived class vtable for the Base class Pointer to Base::~Base Pointer to Base::func2 Pointer to Base::func1 Pointer to Derived::~Derived Pointer to Base::func2 Pointer to Derived::func1

19. Illustration (Contd)