Function Return Array C++

Question

I have a function and want to return a 2d array:

int flip[5][5](int input[5][5]);

But it returns an error: no function error allowed (this is a translation)

How can I fix this?

This works:

void flip(int input[5][5]);

Answer 1

In this function declaration

void flip(int input[5][5]);

the parameter is implicitly adjusted to pointer to the first element of the array. So actually the function declaration looks like

void flip(int ( *input )[5] );

You may not return an array because arrays do not have a copy constructor.

You may return an array by reference provided that the array itself is not a local variable of the function.

So for example if your funciotn gets an array by reference then you may return this array from the function.

For example

int ( & flip(int ( &input )[5][5]) )[5][5];

You can wrap your array in a structure and return this structure along with the array.

For example

struct data
{
    int a[5][5];
};

data flip( int input[5][5] );

Answer 2

Use std::array<std::array<int, 5>, 5> instead of a built-in array type.

Answer 3

The syntax for returning an array is ugly. You're better off using a typedef, or auto.

auto flip(int input[5][5]) -> int[5][5];

However the problem you have is, you aren't passing the array to the function as a reference or pointer, which won't work.

typedef int myArray[5][5];

void foo(myArray& arr) {
    //do stuff
}

int main() {
    int arr[5][5];
    foo(arr);
    return 0;
}

As an aside, working with arrays like this is tedious, you're better off using a container from the STL.