Exercise 3-3 Abrahams & Gurtovoy

Turn T into T**** by using twice twice.

	#include <boost/type_traits/add_pointer.hpp>
	#include <boost/type_traits/is_same.hpp>
	#include <boost/static_assert.hpp>
	template <class UnaryMetaFunctionClass, class Arg>
	struct apply1
	: UnaryMetaFunctionClass::template apply<Arg>
	{};
	template <class F, class X>
	struct twice
	: apply1<F, typename apply1<F,X>::type>
	{};
	struct add_pointer_f
	{
	template <class T>
	struct apply : boost::add_pointer<T> {};
	};
	BOOST_STATIC_ASSERT((
	boost::is_same<
	twice<add_pointer_f,
	twice<add_pointer_f, int>::type>::type
	, int****
	>::value
	));
	int main()
	{
	return 0;
	}

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