#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>

using namespace std;

class gt{
public:
	bool operator()(int a, int b){
		return(b < a);
	}
};

class average{
private:
   int count;
   int sum;
   // keep initializer list in order declared
   // do NOT do :sum(0),count(0)
public:
   average():count(0),sum(0){}
   int ave(){return sum/count;};
   void operator()(int x){sum += x; count++;}
};

void main(){

    average avg, a2;
	/*
	avg(3);
	avg(6);
	avg(17);
	cout << avg.ave() << endl;
	*/
	vector<int> v;
	v.push_back(3);v.push_back(6);v.push_back(17);
    //cout << (for_each(v.begin(),v.end(),avg)).ave() << endl;
    a2 = for_each(v.begin(),v.end(),avg);
	
	cout << a2.ave() << endl;
	gt great;
	//greater<int> great; using built in function object
	sort(v.begin(),v.end(),great);
	ostream_iterator<int> out(cout, "...\n");
    copy(v.begin(), v.end(), out);

}