C++ how to create double class operator [][] [duplicate]

Question

I am building an type to be able to manage matrixes so i have searched how to make an [][] operator but no luck so any idea how to do that i just need a way to make double operator this the class am building

#include<iostream>
#include<conio.h>

using namespace std;

class ddouble{
private:
unsigned short int  x, y;
public:
ddouble();
ddouble(unsigned short int, unsigned short int);
double **M;
void read();
void print();
};

ddouble::ddouble(unsigned short int m, unsigned short int n){
for (int i = 0; i < m; i++){
    M = new (nothrow) double *[i];
    for (int I = 0; I < n; I++){
        M[i] = new (nothrow) double[I];
    }
}
}
void ddouble::read(){
for (int i = 0; i < x; i++){

    cout << "plz enter line \n";

    for (int I = 0; I < y; I++){
        cin >> M[i][I];
    }
}
}
void ddouble::print(){

cout << "i,j\t|\t";

for (int i = 0; i < y; i++){
    cout << i << "\t";
}

cout << endl;

for (int i = 0; i < x; i++){

    cout << i << "\t|\t";

    for (int I = 0; I < y; I++){
        cout << M[i][I] << "\t";
    }

    cout << endl;
}
} 

void main(){

ddouble a(2, 2);
a.read();
a.print();

_getch();
}

Answer 1

I would recommend using std::vector<std::vector<double>>. That said, given the structure you have now, you can simply define an operator[] that returns a double *, e.g.:

double * ddouble::operator[](int i) {
    return M[i];
}

You can now access your variable in main as a[i][j].

Also, you are missing a destructor that deallocates the memory; without it you have memory leaks. You should define a destructor as:

void ddouble::~ddouble() {
    for(int I = 0; I < y; I++) {
        delete [] M[I];
    }

    delete [] M;
}