Среднее арифметическое элементов массива

double foo2(int * a , size_t size, int key)
{
     int S = 0 ;
     for(int i = 0 ; i < size ; ++i  ) 
     {
         S += a[i]; 
     }
     return  S / (double) size ;
}

#include <cstdlib>
#include <cstring>
#include <iostream>
#include <stdexcept>
 
template <class Iterator, class T>
int getIndexOf(Iterator begin, Iterator end, const T &value) {
  for (Iterator i = begin; i != end; ++i)
    if (value == *begin)
      return i - begin;
  return -1;
};
 
template <class Iterator, class T>
T getAverageOf(Iterator begin, Iterator end, const T &initialValue = 0) {
  T result = initialValue;
  int count = 0;
  for (; begin != end; ++count, ++begin)
    result += *begin;
  return result / count;
}
 
int main(int argc, char **argv) { 
  srand(time(0));
 
  int aSize = 10 + rand() % 5;
  double *a = new double[aSize];
  for (int i = 0; i < aSize; ++i)
    std::cout << (a[i] = (100 + rand() % 100) / 10.0) << " ";
  std::cout << std::endl;
 
  double value = (100 + rand() % 100) / 10.0;
  std::cout << "Index of " << value << " is " << getIndexOf(a, a + aSize, value) << std::endl;
  
  std::cout << "Average is " << getAverageOf(a, a + aSize, 0.0) << std::endl;
 
  delete [] a;
  return 0;
};

if (value == *i)