templates.cpp

#include <iostream>
#include <vector>

template <size_t N, class ElementType>
class Tensor
{
  std::vector<Tensor<N - 1, ElementType>> data_;

 public:
  Tensor<N - 1, ElementType>& operator[](size_t index)
  {
    return data_[index];
  }

  const Tensor<N - 1, ElementType>& operator[](size_t index) const
  {
    return data_[index];
  }

  Tensor(const std::initializer_list<Tensor<N - 1, ElementType>>& list) :
    data_(list)
  { }

  template <class...Arg2> Tensor(size_t size, Arg2...list) :
    data_(size, Tensor<N - 1, ElementType>(list...))
  { }
};

template <class ElementType>
class Tensor<0, ElementType>
{
  ElementType element_;

 public:
  Tensor()
  { }

  Tensor(const ElementType& element) : element_(element)
  { }

  operator ElementType() { return element_; }
};

int main()
{
  Tensor<2, int> q({{1, 2, 3}});
  Tensor<5, int> haha(1, 2, 3, 4, 5);
  Tensor<0, int> v(0);
  Tensor<3, int> cube =
  {
    {
      { 1, 2, 3 },
      { 4, 5, 6 },
      { 7, 8, 9 }
    }, {
      { 1, 2, 3 },
      { 4, 5, 6 },
      { 7, 8, 9 }
    }, {
      { 1, 2, 3 },
      { 4, 5, 6 },
      { 7, 8, 9 }
    }
  };
  v = 10;
  std::cout << cube[0][1][2] << std::endl;
  q[0] = { 100, 100, 100 };
  std::cout << q[0][1] + v << ' ' << haha[0][1][2][3][4] << std::endl;
}