invalid use of non-static member function

Projects Programming
1

Hello Guys!!!
I'm having a trouble compiling the following code.
Actually it works fine on my desktop computer.
But the avr-g++ gives me the following error messages.
Can anybody help me out? Please.....
Thanks in advance....

class Machine {
  class State *current;
public:
  Machine();
  void setCurrent(State *s){
    current = s;
  }
  void on();
  void off();
  void red();
};

class State {
public:
  virtual void  on(Machine *m){ Serial.println(" already ON"  );}
  virtual void off(Machine *m){ Serial.println(" already OFF" );}
  virtual void red(Machine *m){ Serial.println(" already RED" );}
};

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

class ON: public State {
public:
  void red(Machine *m);
};

class OFF: public State {
public:
  void on(Machine *m){
    m->setCurrent(new ON());
    delete this;
  }
};

class RED: public State {
public:
  void off(Machine *m){
    m->setCurrent(new OFF());
    delete this;
  }
};

void ON::red(Machine *m){
  m->setCurrent(new RED());
  delete this;
}

Machine::Machine(){
  current = new OFF();
}

const char btn[3]={22,23,24};

void (Machine::*ptrs[])()= {
  Machine::off,
  Machine::on,
  Machine::red
};

Machine fsm;

char num[3];

void setup(){
  for (int i=0; i<3; i++)
    pinMode(btn[i], INPUT);
  pinMode(13, OUTPUT);
}

void loop() {
  for (int i=0; i<3; i++)
    num[i] = digitalRead(btn[i]);
  if(num == 1 || num == 0 || num == 2)
    (fsm.*ptrs[num])();
}

statePattern:57: error: invalid use of non-static member function 'void Machine::off()'

Machine::off,

^

statePattern:58: error: invalid use of non-static member function 'void Machine::on()'

Machine::on,

^

statePattern:59: error: invalid use of non-static member function 'void Machine::red()'

Machine::red

2

I found the solution by myself.
Below is the Solution.

void (Machine::*ptrs[])()= {
&Machine::off,
&Machine::on,
&Machine::red};