https://www.facebook.com/DonMcMillan/photos/a.422597364327.213059.65413379327/10154681541084328

change_bulb_required_engineers.c

typedef int boolean_t;

boolean_t (*status_checker_function)(void);

int change_bulb_required_engineers_recur(status_checker_function);
int change_bulb_required_engineers_recur(status_checker_function testbulb)
{
  return _change_bulb_required_engineers_recur(testbulb, 0);
}

/**
 * We are not at the mercy of a microcontroller or compiler w/o tail-call-O
 */
int _change_bulb_required_engineers_recur(status_checker_function, int);
int _change_bulb_required_engineers_recur(status_checker_function testbulb, int num_engineers_already)
{
  return testbulb() ? num_engineers : _change_bulb_required_engineers(testbulb, num_engineers + 1);
}

int change_bulb_required_engineers(status_checker_function);
int change_bulb_required_engineers(status_checker_function testbulb)
{
  int counter = 0;
  while ( !testbulb() )
    counter++;
  return counter;
}