TMP Prime

#include <iostream>
#include <type_traits>

template<bool I,typename T1,typename T2>
struct If
{
	typedef T1 type;
};

template<typename T1, typename T2>
struct If<false,T1,T2>
{
	typedef T2 type;
};

template<int N,int I=0>
struct Sqrt
{
	typedef typename If < (I*I >= N), std::integral_constant<int, I>, Sqrt<N, I + 1>>::type type;
	static constexpr int value = type::value;
};

template<int N,int I>
struct Seive
{
	typedef typename If<N % I, Seive<N, I + 1>, std::integral_constant<bool, false>>::type type;
	typedef typename If<(I > Sqrt<N>::value || I==N), std::integral_constant<bool, true>, type > ::type temptype;
	static constexpr bool value = temptype::value;
};

template<int N,int I,int C>
struct Process
{
	typedef typename If<Seive<N, 2>::value, Process<N + 1, I + 1, C>, Process<N + 1, I, C>>::type type;
	static constexpr int result = type::result;
};

template<int N,int C>
struct Process<N,C,C>
{
	static constexpr int result = N-1;
};
template<int N>
struct Primes
{
	static constexpr int result = Process<2,0,N>::result;
};

int main()
{
	std::cout << Sqrt<5>::value;
	std::cout << Primes<20>::result;
	system("pause");
}