#include <iostream>
#include <boost/mpl/fold.hpp>
#include <boost/mpl/list.hpp>
#include <boost/static_assert.hpp>
#include <boost/type_traits.hpp>

class a;
class b;

struct test_failure
{
        template< class Previous_State, class T >
	struct apply
	{
		BOOST_STATIC_ASSERT( (boost::is_same< T, a >::value) );
		class type {};
	};
};

class initial_state {};

template< class List >
struct test_failure2;

template<>
struct test_failure2< boost::mpl::null_node >
{
	class result {};
};

template< class Head, class Tail >
struct test_failure2< boost::mpl::list_node< Head, Tail > >
{
	BOOST_STATIC_ASSERT( (boost::is_same< Head, a >::value) );
	typedef typename test_failure2< Tail >::result result;
};

int main()
{
	using boost::mpl::fold;
	using boost::mpl::list;
	
#ifndef TEST2
	typedef fold< list< a, a, b >::type,
	  initial_state, test_failure >::type result;
#else
	using boost::mpl::list_node;
	using boost::mpl::null_node;
        typedef test_failure2< list_node< a, list_node< a, list_node< b, null_node > > > >::result result;
#endif
	
	std::cout << typeid( result ).name() << std::endl;

	return 0;
}