c++自定义对象支持按下标遍历*

#include <iostream>

#include <string>

using namespace std;

class Array {

   public:

    Array() {

        length = 0;

        num = NULL;

    };

    Array(int n);

    int& operator[](int) const;

    int getlength() const { return length; }

   private:

    int length;

    int* num;

};

Array::Array(int n) {

    try {

        num = new int[n];

        for (int i = 0; i < n; i++) num[i] = i;

    } catch (bad_alloc) {

        cerr << "allocate storage failure!" << endl;

        throw;

    }

    length = n;

}

int& Array::operator[](int i) const {

    if (i < 0 || i >= length) throw string("out of bounds");

    return num[i];

}

int main() {

    Array A(5);

    int i;

    try {

        for (i = 0; i < 6; i++) cout << A[i] << " ";

    } catch (string s) {

        cout << endl;

        cerr << s << ", i = " << i << endl;

    }

    cout << endl << "+++++++++++++" << endl << endl << endl;

    int aa = A[0];

    return 0;

}