#include <iostream>

// NOTHING
struct Nothing { };

// define states
struct UndefinedState { };

// define actions
struct UndefinedAction { };

// define base fsm transitioner
template <typename State, typename Action>
struct FSMTransitioner
{
    typedef UndefinedState Next;
};

// define cons cells
template <typename Car_, typename Cdr_>
struct Cons {
    typedef Car_ Car;
    typedef Cdr_ Cdr;
};

// define dog st--SQUIRREL!--uff
struct PantingState { };
struct BarkingState { };

struct SquirrelAction { };
struct PetAction { };

// the fsm transitioner
template <typename State, typename Action>
struct DogFSMTransitioner : public FSMTransitioner <State, Action> { };

template <>
struct DogFSMTransitioner <PantingState, SquirrelAction>
{
    typedef BarkingState Next;
};

template <>
struct DogFSMTransitioner <PantingState, PetAction>
{
    typedef PantingState Next;
};

template <>
struct DogFSMTransitioner <BarkingState, SquirrelAction>
{
    typedef BarkingState Next;
};

template <>
struct DogFSMTransitioner <BarkingState, PetAction>
{
    typedef PantingState Next;
};

// define some steps in a linked list
typedef Cons <PantingState, Nothing> dogFSMCons1;
typedef Cons <DogFSMTransitioner <dogFSMCons1::Car, SquirrelAction>::Next, dogFSMCons1> dogFSMCons2;
typedef Cons <DogFSMTransitioner <dogFSMCons2::Car, PetAction>::Next, dogFSMCons2> dogFSMCons3;
typedef Cons <DogFSMTransitioner <dogFSMCons3::Car, PetAction>::Next, dogFSMCons3> dogFSMCons4;
typedef Cons <DogFSMTransitioner <dogFSMCons4::Car, PetAction>::Next, dogFSMCons4> dogFSMLinkedList;

// define reprs
template <typename State>
struct DogFSMStateRepr
{
    static const char *repr()
    {
        return "in an undefined state";
    }
};

template <>
struct DogFSMStateRepr <BarkingState>
{
    static const char *repr()
    {
        return "barking";
    }
};

template <>
struct DogFSMStateRepr <PantingState>
{
    static const char *repr()
    {
        return "panting";
    }
};

// define FSM iterator
template <typename Cons_>
struct DogFSMIterator
{
    typedef DogFSMIterator <typename Cons_::Cdr> Next;
    typedef DogFSMStateRepr <typename Cons_::Car> Repr;

    static void execute()
    {
        Next::execute();
        std::cout << "Dog is currently: " << Repr::repr() << std::endl;
    }
};

template <>
struct DogFSMIterator <Nothing>
{
    static void execute()
    {
    }
};

typedef DogFSMIterator<dogFSMLinkedList> dogFSMIterator;

int main()
{
    dogFSMIterator::Next::execute();
    return 0;
}