boost mpl vector demonstration

Consider the following code copied from Polukhin's book:

	#include <boost/mpl/aux_/na.hpp>
	// boost::mpl::na == n.a. == not available
	template <
	class T0 = boost::mpl::na,
	class T1 = boost::mpl::na,
	class T2 = boost::mpl::na,
	class T3 = boost::mpl::na,
	class T4 = boost::mpl::na,
	class T5 = boost::mpl::na,
	class T6 = boost::mpl::na,
	class T7 = boost::mpl::na,
	class T8 = boost::mpl::na,
	class T9 = boost::mpl::na
	>
	struct variant;
	#include <boost/mpl/vector.hpp>
	template <
	class T0
	, class T1
	, class T2
	, class T3
	, class T4
	, class T5
	, class T6
	, class T7
	, class T8
	, class T9
	>
	struct variant {
	typedef boost::mpl::vector<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9> types;
	};
	#include <string>
	struct declared{ unsigned char data[4096]; };
	struct non_defined;
	typedef variant<
	volatile int,
	const int,
	const long,
	declared,
	non_defined,
	std::string
	>::types types;
	#include <boost/static_assert.hpp>
	#include <boost/mpl/empty.hpp>
	BOOST_STATIC_ASSERT((!boost::mpl::empty<types>::value));
	#include <boost/mpl/at.hpp>
	#include <boost/type_traits/is_same.hpp>
	BOOST_STATIC_ASSERT((boost::is_same<
	non_defined
	, boost::mpl::at_c<types, 4>::type>::value));
	#include <boost/mpl/back.hpp>
	BOOST_STATIC_ASSERT((boost::is_same<
	std::string
	, boost::mpl::back<types>::type>::value));
	#include <boost/mpl/transform.hpp>
	#include <boost/type_traits/remove_cv.hpp>
	typedef boost::mpl::transform<
	types,
	boost::remove_cv<boost::mpl::_1>
	>::type noncv_types;
	#include <boost/mpl/unique.hpp>
	typedef boost::mpl::unique<
	noncv_types,
	boost::is_same<boost::mpl::_1, boost::mpl::_2>
	>::type unique_types;
	#include <boost/mpl/size.hpp>
	BOOST_STATIC_ASSERT((boost::mpl::size<unique_types>::value == 5));
	// Without this we'll get an error:
	// use of undefined type 'non_defined'
	struct non_defined{};
	#include <boost/mpl/sizeof.hpp>
	typedef boost::mpl::transform<
	unique_types,
	boost::mpl::sizeof_<boost::mpl::_1>
	>::type sizes_types;
	#include <boost/mpl/max_element.hpp>
	typedef boost::mpl::max_element<sizes_types>::type max_size_type;
	BOOST_STATIC_ASSERT(max_size_type::type::value == sizeof(declared));
	int main()
	{
	return 0;
	}

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When run, this code prints nothing. All checking is done at compile time.