Как запрограммировать в рекурсивной форме алгоритм бинарного поиска

#include <iostream>
 
const int* FindFirstElem(const int* arr, unsigned size, int value)
{
  if (arr == 0 || size == 0)
    return 0;
 
  if (size == 1)
    return arr[0] == value ? arr : 0;
 
  const unsigned halfArrSize = size / 2;
 
  if (arr[halfArrSize - 1] < value)
    return FindFirstElem(arr + halfArrSize, size - halfArrSize, value);
 
  return FindFirstElem(arr, halfArrSize, value);
}
 
int FindFirstIndex(const int* arr, unsigned size, int value)
{
  const int* result = FindFirstElem(arr, size, value);
  return result == 0 ? -1 : static_cast<int>(result - arr);
}
 
int main()
{
  const int arr[] = {0, 1, 2, 3, 4, 5, 5, 6, 7};
  const int searchValue = 5;
  const int* result = FindFirstElem(arr, sizeof(arr) / sizeof(*arr), searchValue);
  if (result != 0)
  {
    std::cout << "The '" << searchValue << "' is found." << std::endl;
    std::cout << "First value index = " << result - arr << std::endl;
  }
  else
  {
    std::cout << "The '" << searchValue << "' is not found." << std::endl;
  }
 
  const int index = FindFirstIndex(arr, sizeof(arr) / sizeof(*arr), searchValue);
  std::cout << "Index = " << index << std::endl;
 
  return 0;
}

  const int arr[] = {0, 0, 0, 0, 2, 2, 2, 2, 4, 5};
  const int searchValue = 2;