template <typename T>
void stack<T>::push(const T& el)
{
  stackNode<T> *newNode = new stackNode<T>(el);
  newNode->ptr = topPtr;
  topPtr = newNode;
}

template <typename T>
void stack<T>::pop()
{
  if(topPtr != nullptr) {
    stackNode<T> *toDelete = topPtr;
    topPtr = topPtr->ptr;
    delete toDelete;
  }
}