#include <iostream>
#include <complex>
 
template <typename T>
class Vector
{
  public:
    bool is_complex() { return false; }
};
 
template <typename U>
class ComplexVector : Vector<std::complex<U>>
{
  public:
    bool is_complex() { return true; }
    bool only_for_complex() { return true; }
};
 
// For any type T, value is false.
template <typename T>
struct is_complex_vector
{
    static const bool value = false;
};
 
// We specialize the struct so that, for any type U,
// passing ComplexVector<U> makes value true
template <>
template <typename U>
struct is_complex_vector<ComplexVector<U>>
{
    static const bool value = true;
};
 
int main() {
  Vector<float> float_vec;
  ComplexVector<float> complex_vec;
 
  std::cout << "Is float_vec a ComplexVector type? " << is_complex_vector<typeof(float_vec)>::value << "\n";
  std::cout << "Is complex_vec a ComplexVector type? " << is_complex_vector<typeof(complex_vec)>::value << "\n";
 
  return 0;
}

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