template<typename T, template<typename> typename>
struct crtp
{
  T& underlying()
  {
    return static_cast<T&>(*this);
  }

  T const& underlying() const
  {
    return static_cast<T const&>(*this);
  }
};

template<typename T>
struct Scale : public crtp<T, Scale>
{
  void scale(double multiplicator)
  {
    this->underlying().setValue(this->underlying().getValue() * multiplicator);
  }
};

template<typename T>
struct Square : public crtp<T, Square>
{
  void square()
  {
    this->underlying().setValue(this->underlying().getValue() * this->underlying().getValue());
  }
};


class Sensitivity : public Scale<Sensitivity>, public Square<Sensitivity>
{
public:
  double getValue() const
  {
    return value_;
  }
  void setValue(double value)
  {
    value_ = value;
  }
private:
  double value_ = 0.;
};

int main()
{
  Sensitivity s;

  s.setValue(10.);
  
  s.scale(2.);

  return 0;
}