#include <iostream>
#include <stdexcept>

// Function declarations
int main();
void intermediate( int k );
void innermost( int k );

// Function definitions
int main() {
  std::cout << "Entering main()" << std::endl;

  for ( int k{ 0 }; k <= 2; ++k ) {
    std::cout << std::endl
              << "Beginning loop body with k == " << k
              << std::endl;

    try {
      std::cout << "  Calling intermediate(" << k << "):"
                << std::endl;

      intermediate( k );

      std::cout << "  Returned normally to main()"
                << std::endl;
    } catch ( std::invalid_argument const &e ) {
      std::cout << "  >> Caught an exception in main(): "
                << e.what() << std::endl;
    }

    std::cout << "Ending loop body with k == " << k
              << std::endl;
  }

  std::cout << std::endl
            << "Leaving main()" << std::endl;

  return 0;
}

// Call innermost() and report when it returns.
void intermediate( int k ) {
  std::cout << "    Entering intermediate(" << k << ") and "
               "calling innermost(" << k << "):"
            << std::endl;

  innermost( k );

  std::cout << "    Back in intermediate(...) and returning"
            << std::endl;
}

// Throw an exception if k is odd.
void innermost( int k ) {
  std::cout << "      Entering innermost(" << k << ")"
            << std::endl;

  if ( k%2 == 1 ) {
    std::cout << "      >> k is odd: throwing an exception"
              << std::endl;

    throw std::invalid_argument{ "k must be even" };
  }

  std::cout << "      k == " << k
	    << " and returning from innermost(...)" << std::endl;
}

/***********************************************************
 * Output:
 *
 * Entering main()
 *
 * Beginning loop body with k == 0
 *   Calling intermediate(0):
 *     Entering intermediate(0) and calling innermost(0):
 *       Entering innermost(0)
 *       k == 0 and leaving innermost(...)
 *     Back in intermediate(...) and returning
 *   Returned normally to main()
 * Ending loop body with k == 0
 * 
 * Beginning loop body with k == 1
 *   Calling intermediate(1):
 *     Entering intermediate(1) and calling innermost(1):
 *       Entering innermost(1)
 *       >> k is odd: throwing an exception
 *   >> Caught an exception in main(): k must be even
 * Ending loop body with k == 1
 * 
 * Beginning loop body with k == 2
 *   Calling intermediate(2):
 *     Entering intermediate(2) and calling innermost(2):
 *       Entering innermost(2)
 *       k == 2 and leaving innermost(...)
 *     Back in intermediate(...) and returning
 *   Returned normally to main()
 * Ending loop body with k == 2
 * 
 * Leaving main()
 *
 ***********************************************************/