// Function object - functor - taking cosine of 
// elementes and summing them up
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
using namespace std;

class TakeCos{
  double sum;
public:
  //function object
  double operator()(double& x){ 
    x = cos(x); // must change element x!
    sum += x;
    return x; 
  } 
  TakeCos() : sum(0.0){} // zero sum at construction
  double getsum() {
    return sum;
  }
};


void doubleout(double& x) { cout<< x<<" ";}
void vector_out(vector<double> & x){
  for_each (x.begin(), x.end(), doubleout);
  cout<<endl;
}
int main () {
  vector<double> x;
  x.push_back(1.1); x.push_back(2.2);  x.push_back(3.3);
  cout << "vector x      : ";
  vector_out(x);
  // for_each works with a copy of Cos, 
  // so I need to store that copy to Cosx to get out the sum as Cosx.sum
  TakeCos Cos; 
  TakeCos Cosx = for_each(x.begin(), x.end(), Cos); 
  cout << "vector cos(x) : ";
  vector_out(x);
  cout<<"sum = "<<Cosx.getsum()<<endl;
  return 0;
}