#include <ptlib.h>#include "abstract.h"class MyConcreteClass : public MyAbstractClass{  public:    PString Function()    { return "Concrete"; }};PFactory<MyAbstractClass>::Worker<MyConcreteClass> concreteFactory("concrete", false);PFactory<MyAbstractClass, unsigned>::Worker<MyConcreteClass> intConcreteFactory(1, false);class MyConcrete2Class : public MyAbstractClass{  public:    PString Function()    { return "Concrete2"; }};PFactory<MyAbstractClass>::Worker<MyConcrete2Class> concrete2Factory("concrete2", false);PFactory<MyAbstractClass, unsigned>::Worker<MyConcrete2Class> intConcrete2Factory(2, false);