Sams Teach Yourself C++ in 21 Days

Handling Errors and Exceptions 733

20

21: // friend function

22: friend ostream& operator<< (ostream&, const Array&);

23:

24: // define the exception classes

25: class xBoundary {};

26: class xSize {};

27: class xTooBig : public xSize {};

28: class xTooSmall : public xSize {};

29: class xZero : public xTooSmall {};

30: class xNegative : public xSize {};

31: private:

32: int *pType;

33: int itsSize;

34: };

35:

36:

37: Array::Array(int size):

38: itsSize(size)

39: {

40: if (size == 0)

41: throw xZero();

42: if (size > 30000)

43: throw xTooBig();

44: if (size <1)

45: throw xNegative();

46: if (size < 10)

47: throw xTooSmall();

48:

49: pType = new int[size];

50: for (int i = 0; i < size; i++)

51: pType[i] = 0;

52: }

53:

54: int& Array::operator[](int offSet)

55: {

56: int size = GetitsSize();

57: if (offSet >= 0 && offSet < GetitsSize())

58: return pType[offSet];

59: throw xBoundary();

60: return pType[0]; // appease MFC

61: }

62:

63: const int& Array::operator[](int offSet) const

64: {

65: int mysize = GetitsSize();

66:

67: if (offSet >= 0 && offSet < GetitsSize())

68: return pType[offSet];

69: throw xBoundary();

LISTING20.6 continued