reshape.cpp

#include <array>
#include <cstddef>
#include <type_traits>

template <typename T, std::size_t N, std::size_t... Ns>
struct multi_array
{
    using type = std::array<typename multi_array<T, Ns...>::type, N>;
};

template <typename T, std::size_t N>
struct multi_array<T, N>
{
    using type = std::array<T, N>;
};

template <typename T, std::size_t... Ns>
using multi_array_t = typename multi_array<T, Ns...>::type;

template <typename T>
struct array_element
{
  	using type = T;
};

template <typename T, std::size_t N>
struct array_element<std::array<T, N>>
{
  	using type = typename array_element<T>::type;
};

template <typename T>
using array_element_t = typename array_element<T>::type;

template <std::size_t... DestShape>
struct reshape_array
{
    template <typename Src, size_t N1>
    static auto reshape(std::array<Src, N1>& src) -> multi_array_t<array_element_t<Src>, DestShape...>&
    {
      	static_assert(sizeof(std::array<Src, N1>) == sizeof(multi_array_t<array_element_t<Src>, DestShape...>));
    	return *reinterpret_cast<multi_array_t<array_element_t<Src>, DestShape...>*>(&src);
    }
};

int main(int argc, char** argv)
{
    std::array<int, 4> foo {1, 2, 3, 4};
    std::array<std::array<int, 2>, 2>& bar = reshape_array<2, 2>::reshape(foo);
    bar[1][1] = 0;
    for (int f : foo)
    {
        printf("%i\n", f);
    }
}