How Not to Program in C++

Classes with No Class 161

41 data(NULL), next(NULL) {}

42 };

43 //----------------------------------------

44

45 node *first; // First node in the list

46

47 /*

48 * Delete the data for the node.

49 * Because we don't know what type of

50 * data we have,the derived class does

51 * the work of deleting the data

52 * through the delete_data function.

53 */

54 virtual void delete_data(void *data) = 0;

55 public:

56 // Delete all the data in the list

57 void clear(void) {

58 while (first != NULL)

59 {

60 // Pointer to the next node

61 class node *next;

62

63 next = first->next;

64 delete_data(first->data);

65 delete first;

66 first = next;

67 }

68 }

69

70 // Constructor

71 list(void): first(NULL) {};

72

73 // Destructor. Delete all data

74 virtual ~list(void) {

75 clear();

76