// B7.cpp - compute the average of the values of a vector, list, or set.

#pragma warning(disable : 4786)
#include <iostream>
#include <vector>
#include <list>
#include <set>
using namespace std;

/////////////////////////////////////////////////////////////////////
// The function below will fail to compile if the type container
// does not provide every one of the container operations used in
// the body of the function.  These are:
// - declare a const_iterator type
// - declare a value_type type
// - provide an assignment operator accepting a numeric value of 0
// - provide member functions begin() and end(), each returning
//   an iterator on the container
// - provide a size() function, returning a numeric value comparable
//   to the numeric value 0
// For correct operation the value_type type must provide a correct
// copy constructor or have correct compiler generated copy semantics,
// support initialization with zero, and provide operator+=(...).

template <class container> 
container::value_type average(const container &con) {

  container::const_iterator it;
  container::value_type sum = 0;
  for(it = con.begin(); it != con.end(); it++)
    sum += *it;
  if(con.size() > 0)
    return (sum/con.size());
  return 0;
}
////// end of complete answer /////////////////////////////////////////

void main() {

  double array[] = { -1.5, 0.5, 1.5, 2.5, 3.5 };
  int size = sizeof(array)/sizeof(double);

  vector<double> vd(&array[0], &array[size]);
  double vectorAvg = average(vd);
  cout << "\n  average of vector<double> is: " << vectorAvg;

  list<double> ld(&array[0], &array[size]);
  double listAvg = average(ld);
  cout << "\n  average of list<double> is:   " << listAvg;

  set<double> sd(&array[0], &array[size]);
  double setAvg = average(sd);
  cout << "\n  average of set<double> is:    " << setAvg;
  
  cout << "\n\n";
}