Beispiellösung

#ifndef ARRAY_HPP
#define ARRAY_HPP

#include <algorithm>
#include <cassert>
#include <cstdlib>
#include <new>
#include <utility>

template<typename T>
class Array {
   private:
      using Tag = enum {AllocateStorage};
      Array(Tag tag, std::size_t size) :
	 size(size),
	 data(size > 0?
	       static_cast<T*>(operator new(sizeof(T) * size))
	    :
	       nullptr) {
      }
   public:
      Array() : size(0), data(nullptr) {
      }
      Array(std::size_t size) : Array(AllocateStorage, size) {
	 for (std::size_t index = 0; index < size; ++index) {
	    new (data + index) T();
	 }
      }
      Array(std::size_t size, const T& t) : Array(AllocateStorage, size) {
	 for (std::size_t index = 0; index < size; ++index) {
	    new (data + index) T(t);
	 }
      }
      Array(const Array& other) : Array(AllocateStorage, other.size) {
	 for (std::size_t index = 0; index < size; ++index) {
	    new (data + index) T(other.data[index]);
	 }
      }
      friend void swap(Array& a1, Array& a2) {
	 using std::swap;
	 swap(a1.size, a2.size);
	 swap(a1.data, a2.data);
      }
      Array(Array&& other) : Array() {
	 swap(*this, other);
      }
      ~Array() {
	 for (std::size_t index = 0; index < size; ++index) {
	    data[index].~T();
	 }
	 operator delete(data);
      }
      Array& operator=(Array other) {
	 swap(*this, other);
	 return *this;
      }
      std::size_t get_size() const {
	 return size;
      }
      T& operator()(std::size_t index) {
	 assert(index < size);
	 return data[index];
      }
      const T& operator()(std::size_t index) const {
	 assert(index < size);
	 return data[index];
      }
   private:
      std::size_t size;
      T* data;
};

#endif

#include <iostream>
#include "array.hpp"

int main() {
   Array<Array<double>> m(8);
   for (std::size_t i = 0; i < m.get_size(); ++i) {
      m(i) = Array<double>(m.get_size());
      for (std::size_t j = 0; j < m(i).get_size(); ++j) {
	 m(i)(j) = i + j;
      }
   }
   for (std::size_t i = 0; i < m.get_size(); ++i) {
      for (std::size_t j = 0; j < m(i).get_size(); ++j) {
	 std::cout << " " << m(i)(j);
      }
      std::cout << std::endl;
   }
}