Error while writing State Design Pattern Code

Hi All

i am getting Error while writing following code for state design
Pattern
kindly let me know How to Correct this Error ??

Thanks
Pallav Singh

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#include<iostream.h>
using namespace std;

class state;

class Machine
{
 class state * current;
 public :
 Machine();

 void setcurrentstate(state * s)
   { current = s ; }

 void on();
 void off();
};

class state
{
   public :
   virtual void on(Machine * m)
     {cout<< " Already On \n"; }

   virtual void off(Machine * m)
     {cout<<"Already Off \n"; }
};

 void Machine::on()
   { current->on(this); }

 void Machine::off()
   { current->off(this); }

class ON : public state
{
   public :
   ON() {cout<<"Destructor invoked \n ";}
  ~ON() {cout<<"Constructor invoked \n ";}
   void off(Machine * m);
};

class OFF : public state
{
   public :
   OFF() {cout<<"Destructor invoked \n ";}
  ~OFF() {cout<<"Constructor invoked \n ";}
   void on(Machine * m)
    {cout<<"Going from OFF to ON";
     m->setcurrentstate( new ON() );
     delete this;
    }
};

 Machine::Machine()
   {
     current = new OFF();
     cout<<"Machine constructor Called "<<endl;
   }

 void ON::off(Machine * m)
   {
     cout<<"Going from ON to OFF";
     m->setcurrentstate( new OFF() );
     delete this;
   }

int main()
{

 void (Machine::*ptrs[] )() = { Machine::off, Machine::on }; // Error
Point
  Machine FSM;
  int num;
  while(1)
   { cout <<"Enter 0 / 1 : ";
     cin >> num;
     (FSM.*ptrs[num])();
   }

   return 0;
}

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