Returning multidimensional array from function

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A two-dimensional array does not decay to a pointer to pointer to ints. It decays to a pointer to arrays of ints – that is, only the first dimension decays to a pointer. The pointer does not point to int pointers, which when incremented advance by the size of a pointer, but to arrays of 5 integers.

class Myclass {
private:
    int myarray[5][5];
public:
    typedef int (*pointer_to_arrays)[5]; //typedefs can make things more readable with such awkward types

    pointer_to_arrays get_array() {return myarray;}
};

int main()
{
    Myclass o;
    int (*a)[5] = o.get_array();
    //or
    Myclass::pointer_to_arrays b = o.get_array();
}

A pointer to pointer (int**) is used when each subarray is allocated separately (that is, you originally have an array of pointers)

int* p[5];
for (int i = 0; i != 5; ++i) {
    p[i] = new int[5];
}

Here we have an array of five pointers, each pointing to the first item in a separate memory block, altogether 6 distinct memory blocks.

In a two-dimensional array you get a single contiguous block of memory:

int arr[5][5]; //a single block of 5 * 5 * sizeof(int) bytes

You should see that the memory layout of these things are completely different, and therefore these things cannot be returned and passed the same way.

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