c++自定义对象支持按下标遍历

1. #include<iostream>
2. #include<string>
3. using namespace std;
5. class Array
6. {
7. public:
8. Array(){length = 0; num = NULL;};
9. Array(int n);
10. int & operator[]( int );
11. const int & operator[]( int )const;
12. int getlength() const {return length;}
13. private:
14. int length;
15. int * num;
16. };
18. Array::Array(int n)
19. {
20. try
21. {
22. num = new int[n];
23. }
24. catch(bad_alloc)
25. {
26. cerr<<"allocate storage failure!"<<endl;
27. throw;
28. }
29. length = n;
30. }
32. int& Array::operator[](int i)
33. {
34. if(i < 0 || i >= length)
35. throw string("out of bounds");
36. return num[i];
37. }
39. const int & Array::operator[](int i) const
40. {
41. if(i < 0 || i >= length)
42. throw string("out of bounds");
43. return num[i];
44. }
46. int main()
47. {
48. Array A(5);
49. int i;
50. try
51. {
52. for(i = 0; i < A.getlength(); i++)
53. A[i] = i;
54. for(i = 0 ;i < 6; i++ )
55. cout<< A[i] <<endl;
56. }
57. catch(string s)
58. {
59. cerr<< s <<", i = "<< i <<endl;
60. }
62. return 0;
63. }