- Solution

// templateClassTemplateMethods.cpp
#include <type_traits>
#include <algorithm>
#include <iostream>
#include <vector>
template <typename T, int N>
class Array{
public:
  Array()= default;
  template <typename T2>
  Array<T,N>& operator=(const Array<T2, N>& arr){
	  static_assert(std::is_convertible<T2, T>::value, "Cannot convert source type to destination type!");
    elem.clear();
	  elem.insert(elem.begin(), arr.elem.begin(), arr.elem.end());
	  return *this;
  }
  int getSize() const;
  std::vector<T> elem;
};
template <typename T, int N>
int Array<T, N>::getSize() const {
  return N;
}
int main(){
  Array<double, 10> doubleArray{};
  Array<int, 10> intArray{};
  doubleArray= intArray;
  Array<std::string, 10> strArray{};
  Array<int, 100> bigIntArray{};
  // doubleArray= strArray;            // ERROR: cannot convert ‘const std::basic_string<char>’ to ‘double’
  // doubleArray= bigIntArray;         // ERROR: no match for ‘operator=’ in ‘doubleArray = bigIntArray
}