C++ dependent types array concat

concat.cpp

//g++ -std=c++11 a.cpp
#include <array>

template <typename T, size_t a, size_t b>
std::array<T, a + b> concat(std::array<T, a> const& x, std::array<T, b> const& y) {
      std::array<T, a + b> z;
      std::copy(x.begin(), x.end(), z.begin());
      std::copy(y.begin(), y.end(), z.begin() + x.size());
      return z;
}

#include <cstdio>

int main() {
      for (auto const& x : concat(std::array<int, 3>{{1, 2, 3}},
                                  std::array<int, 2>{{4, 5}}))
                printf("%d\n", x);
}