C++ () operator overloading하기

#include <iostream>

using namespace std;

class A
{
    private:
    double m_i[10][10];

    public:
    A()
    {
        for (int i = 0 ; i < 10; i++)
            for (int j = 0; j< 10; j++)
                m_i[i][j] = 0.0;
    }
    double &operator () (int i, int j=1)
    {
        return m_i[i][j];
    }
};

int main()
{
    A a;
    a(1,3) = 40.3;

//    cout << a.m_i[1][3] << endl; // m_i가 public일때 가능
    cout << a(1,3) << endl;

    return 0;
}

$ g++ a.cpp -W -Wall
$ ./a.out
20