How Can I Return and Modify Arrays in C Functions?

Returning Arrays in Functions

In C , arrays are not first-class objects, which means that they cannot be directly returned from functions. However, there are two common approaches to working with arrays in functions:

Approach 1: Passing by Reference

As demonstrated in the question, an array can be passed to a function as a reference, allowing the function to modify the original array. The function can then return a void or another data type while still having access to the updated array.

Approach 2: Returning a Pointer

Alternatively, arrays can be returned from functions as pointers to their first element. This is essentially the same as passing by reference, as the function can still access and modify the original array through the pointer.

Implementation Example:

int* fillArray(int arr[], int size) {
  for (int i = 0; i < size; ++i) {
    arr[i] = i + 1;
  }
  return arr;
}

int main() {
  int arr[5];
  int* result = fillArray(arr, 5);

  // Access and print the modified array through the pointer
  for (int i = 0; i < 5; ++i) {
    cout << result[i] << " ";
  }
  cout << endl;
  return 0;
}

In this example, the fillArray function takes an array reference and a size as input and returns a pointer to the first element of the modified array. The main function calls this function and stores the result in a pointer. It then accesses the modified array through this pointer.

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