Method volume

Examples/NoModules/Chapter 17/Ex17_01A/Box.h:10–10

  Box(double l, double w, double h) : m_length{ l }, m_width{ w }, m_height{ h } {}

  double volume() const { return m_length * m_width * m_height; }
private:
  double m_length, m_width, m_height;
};