Exercise: Use BOOST_STATIC_ASSERT to add error checking to the binary template presented in section 1.4.1 so that binary<N>::value causes a compilation error if N contains digits other than 0 or 1.

	#include <iostream>
	#include <boost/static_assert.hpp>
	template <unsigned long N>
	struct binary
	{
	BOOST_STATIC_ASSERT(N % 10 < 2);
	static unsigned const value
	= binary<N/10>::value << 1 // prepend higher bits
	| N%10; // to lowest bit
	};
	template <> // specialization
	struct binary<0> // terminates recursion
	{
	static unsigned const value = 0;
	};
	unsigned const one = binary<1>::value;
	unsigned const three = binary<11>::value;
	unsigned const two = binary<10>::value;
	unsigned const five = binary<101>::value;
	unsigned const seven = binary<151>::value;
	unsigned const nine = binary<1001>::value;
	int main()
	{
	std::cout << two << std::endl;
	return 0;
	}

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