How Do I Pass and Return Arrays in Functions?

Passing and Returning Arrays in Functions

When passing an array to a function as an argument, it can be treated implicitly as a pointer to the beginning of the array's memory block. This means that the function can directly access and manipulate the array's elements. However, when attempting to return an array from a function, a different approach is necessary.

Returning an Array

To return an array from a function, you actually return a pointer to the first element of the array. Here's an example:

int* fillArr(int arr[]) {
    // Do some operations on the array
    return arr;  // Returns a pointer to the first element of arr
}

Using the Returned Array

After you return a pointer to the array, you can use it in your code just like a normal array. For instance:

int main() {
    int y[10];
    int *a = fillArr(y);  // Call the function and store the returned pointer
    cout << a[0] << endl;  // Access the first element of the array through the pointer
}

In this example, the fillArr function returns a pointer to the first element of the y array, which is stored in the a pointer. You can then access the elements of the array through this pointer.

Implicit Conversion from Array to Pointer

It's worth noting that in the above examples, we have used the following syntax for the function argument:

int* fillArr(int arr[])

However, this is functionally equivalent to:

int* fillArr(int *arr)

This is because an array variable can be implicitly converted to a pointer to its first element. Therefore, you can pass and return arrays using either syntax.

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