/**/class Composite;class Component {public:    //...    virtual Composite* GetComposite() { return 0; }};/**/class Composite : public Component {public:    void Add(Component*);    // ...    virtual Composite* GetComposite() { return this; }};/**/class Leaf : public Component {    // ...};/**/void dummy () {/**/Composite* aComposite = new Composite;Leaf* aLeaf = new Leaf;Component* aComponent;Composite* test;/**/aComponent = aComposite;if (test = aComponent->GetComposite()) {    test->Add(new Leaf);}/**/aComponent = aLeaf;if (test = aComponent->GetComposite()) {    test->Add(new Leaf); // will not add leaf}/**/}/**/#include "List.H"#include "iostream.h"typedef int Watt;typedef int Currency;typedef int Power;/**/class Equipment {public:    virtual ~Equipment();    const char* Name() { return _name; }/**/    virtual Watt Power();    virtual Currency NetPrice();    virtual Currency DiscountPrice();/**/    virtual void Add(Equipment*);    virtual void Remove(Equipment*);    virtual Iterator<Equipment*>* CreateIterator();protected:    Equipment(const char*);private:    const char* _name;};/**/class FloppyDisk : public Equipment {public:    FloppyDisk(const char*);    virtual ~FloppyDisk();/**/    virtual Watt Power();    virtual Currency NetPrice();    virtual Currency DiscountPrice();};/**/class CompositeEquipment : public Equipment {public:    virtual ~CompositeEquipment();/**/    virtual Watt Power();    virtual Currency NetPrice();    virtual Currency DiscountPrice();/**/    virtual void Add(Equipment*);    virtual void Remove(Equipment*);    virtual Iterator<Equipment*>* CreateIterator();/**/protected:    CompositeEquipment(const char*);private:    List<Equipment*> _equipment;};/**/Currency CompositeEquipment::NetPrice () {    Iterator<Equipment*>* i = CreateIterator();    Currency total = 0;    for (i->First(); !i->IsDone(); i->Next()) {        total += i->CurrentItem()->NetPrice();    }    delete i;    return total;}/**/class Chassis : public CompositeEquipment {public:    Chassis(const char*);    virtual ~Chassis();/**/    virtual Watt Power();    virtual Currency NetPrice();    virtual Currency DiscountPrice();};/**/class Cabinet  : public CompositeEquipment {public:    Cabinet(const char*);};class Bus  : public CompositeEquipment {public:    Bus(const char*);};class Card  : public Equipment {public:    Card(const char*);};void dummy1 () {/**/Cabinet* cabinet = new Cabinet("PC Cabinet");Chassis* chassis = new Chassis("PC Chassis");/**/cabinet->Add(chassis);/**/Bus* bus = new Bus("MCA Bus");bus->Add(new Card("16Mbs Token Ring"));/**/chassis->Add(bus);chassis->Add(new FloppyDisk("3.5in Floppy"));cout << "The net price is " << chassis->NetPrice() << endl;/**/}/**/