C++ mechanisms for polymorphism

C++ mechanisms for polymorphism

Explicit programmer-specified polymorphism

You can write f() such that it can operate on multiple types in any of the following ways:

• Preprocessing:

  #define f(X)((X)+=2)// (note: in real code, use a longer uppercase name for a macro!)

• Overloading:

  void f(int& x){ x +=2;}void f(double& x){ x +=2;}

• Templates:

  template<typename T>void f(T& x){ x +=2;}

• Virtual dispatch:

  structBase{virtualBase&operator+=(int)=0;};struct X :Base{
      X(int n): n_(n){}
      X&operator+=(int n){ n_ += n;return*this;}int n_;};struct Y :Base{
      Y(double n): n_(n){}
      Y&operator+=(int n){ n_ += n;return*this;}double n_;};void f(Base& x){ x +=2;}// run-time polymorphic dispatch