Multidimentional array wrapper

ndarray.cpp

#include <iostream>
#include <cassert>

template <typename T, size_t dim>
class NDArray: protected NDArray<T, dim - 1> {
public:
  template <typename T1, typename... D>
  NDArray (T1* data, size_t size, D...sizes): NDArray<T, dim - 1>(data, sizes...), size(size) {}
  NDArray<T, dim - 1> operator [] (size_t i) {
    assert(i >= 0 && i < size);
    NDArray<T, dim> that = *this;
    that.data += that.parent_elements() * i;
    return static_cast<NDArray<T, dim-1>>(that);
  }

protected:
  size_t parent_elements() { return NDArray<T, dim - 1>::nelements(); }
  size_t nelements() { return size * NDArray<T, dim - 1>::nelements(); }
  size_t size;
};

template <typename T>
class NDArray<T, 1> {
public:
  NDArray(T* data, size_t size): data(data), size(size) {}
  T& operator [] (size_t i) {
    assert(i >= 0 && i < size);
    return data[i];
  }

protected:
  size_t nelements() { return size; }
  T* data;
  size_t size;
};

int main() {
	int x[2*3*5*7];
	for (int i=0; i<sizeof(x)/sizeof(int);i++) x[i] = i+1;
	
	NDArray<int, 4> arr(x, 2, 3, 5, 7);
	
	for(int i=0, n=0; i<2; i++)
		for(int j=0; j<3; j++)
			for(int k=0; k<5; k++)
				for(int l=0; l<7; l++, n++)
					std::cout << arr[i][j][k][l] << (arr[i][j][k][l] == x[n] ? "" : "ERROR") << " ";
	
	return 0;
}