How to return pointers to arrays from functions?

Question

I want a function to return a pointer to an array of size 10. What is the prototype for such a function?

I have tried 3 different prototypes and it doesn't work:

int(*)[10] returnPtrArray(int (*arr)[10])
{
    return arr;
}
//The return type doesn't seem to work

int(*)[10] returnPtrArray(int[][10]);
int (returnPtrArray(int[][10])(*)[10];
int(*)(returnPtrArray(int[][10])[10];
//none of these prototypes seem to work

//calling
int main()
{
    int a[5][10];
    int (*ptr)[10] = returnPtrArray(&a);
    //How do I make this work?
}

Answer 1

The correct definition of the function would be:

int (*returnPtrArray(int (*arr)[10]))[10]
{
    return arr;
}

Breaking this down: returnPtrArray is a function:

returnPtrArray()

That takes a pointer to an array of 10 int:

returnPtrArray(int (*arr)[10])

And returns a pointer:

*returnPtrArray(int (*arr)[10])

To an array of size 10:

(*returnPtrArray(int (*arr)[10]))[10]

Of int:

int (*returnPtrArray(int (*arr)[10]))[10]

And you would call it like this:

int a[5][10];
int (*ptr)[10] = returnPtrArray(a);