Sams Teach Yourself C++ in 21 Days

16: void List<Type>::insert(Type value)

17: {

18: ListCell *pt = new ListCell( value, head );

19: assert (pt != 0);

20:

21: // this line added to handle tail

22: if ( head == 0 ) tail = pt;

23:

24: head = pt;

25: theCount++;

26: }

27:

28: template <class Type>

29: void List<Type>::append( Type value )

30: {

31: ListCell *pt = new ListCell( value );

32: if ( head == 0 )

33: head = pt;

34: else

35: tail->next = pt;

36:

37: tail = pt;

38: theCount++;

39: }

40:

41: template <class Type>

42: int List<Type>::is_present( Type value ) const

43: {

44: if ( head == 0 ) return 0;

45: if ( head->val == value || tail->val == value )

46: return 1;

47:

48: ListCell *pt = head->next;

49: for (; pt != tail; pt = pt->next)

50: if ( pt->val == value )

51: return 1;

52:

53: return 0;

54: }

4. The following declare the three objects:
   List string_list;
   List Cat_List;
   List int_List;
   5.Catdoesn’t have operator ==defined; all operations that compare the values in the
   List cells, such as is_present, will result in compiler errors. To reduce the chance
   of this, put copious comments before the template definition stating what opera-
   tions must be defined for the instantiation to compile.

866 Appendix D

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