// Use a functor to change the sorting order of a container.
//
// Why doesn’t 1.0 show up?

#include <iostream>
#include <set>
#include <cmath>

using namespace std;

// Sort doubles according to how close they are to 5.0.
class Proximity {
  public:
    bool operator()(double a, double b) const {
	return fabs(a-5.0) < fabs(b-5.0);
    }
};

int main() {
    set<double, Proximity> s;
    s.insert(1.2);
    s.insert(3.4);
    s.insert(5.6);
    s.insert(7.8);
    s.insert(9.0);
    s.insert(1.0);

    for (set<double>::iterator it=s.begin(); it!=s.end(); ++it)
	cout << *it << ' ';
    cout << '\n';
}