// Sign of an integer
template<bool b> struct SIGN {static const int value = ( b * 2 ) - 1; };

// Positive powers of two (fast exponentiation)
template<unsigned int N> struct POW2_POS {
    static const float value =
      POW2_POS<N%2>::value
    * POW2_POS<N/2>::value
    * POW2_POS<N/2>::value;
};
template<> struct POW2_POS <1> { static const float value = 2.0f; };
template<> struct POW2_POS <0> { static const float value = 1.0f; };

// Negative powers of two
template<unsigned int N> struct POW2_NEG {static const float value = 1.0f / POW2_POS<N>::value; };

// Calls POW2_POS or POW2_NEG depending on boolean parameter
template<bool b, int N> struct POW2_SIGNED;
template<int N> struct POW2_SIGNED<true, N> { static const float value = POW2_POS<N>::value;};
template<int N> struct POW2_SIGNED<false, N> { static const float value = POW2_NEG<N>::value;};

// Integer power of two
template<int N> struct POW2 {
    static const float value = POW2_SIGNED<(N>=0), SIGN<(N>=0)>::value * N>::value;
};

#include <iostream>
int main()
{
    std::cout<<POW2<0>::value <<"n";
    std::cout<<POW2<1>::value <<"n";
    std::cout<<POW2<4>::value <<"n";
    std::cout<<POW2<7>::value <<"n";
    std::cout<<POW2<-4>::value <<"n";
}

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