Binary search (recursive)

def recursive_binary_search(array, target):
    return bs_helper(array, target, 0, len(array)-1)

def bs_helper(array, target, left, right):
    if left > right:
        return -1
    middle = (left+right) // 2
    potential_match = array[middle]
    if target == potential_match:
            return middle
    elif target < potential_match:
        return binary_search_helper(array, target, left, middle - 1)
    else:
        return binary_search_helper(array, target, middle + 1, right)

# Example usage
arr = [1, 2, 3, 10, 40]
print(recursive_binary_search(arr, 10))  # Output: 3
print(recursive_binary_search(arr, 0))  # Output: -1