Function testBox

Exercises/Modules/Chapter 13/Soln13_05/Soln13_05.cpp:8–16

import box;

void testBox(const Box& box)
{
  std::cout << "The box's volume is " << box.volume() << ".\n";
  if (box)
	  std::cout << "This volume is non-zero.";
  if (!box)
	  std::cout << "This volume is zero.";
  std::cout << std::endl;
}

int main()
{