// Sort a vector into ascending order of id members
#include <iostream>
#include <cassert>
#include <vector>
#include <algorithm>
#include <functional>
using namespace std;

class U : public binary_function<U, U, bool> {
public:
  int id;
  bool operator()(const U& x, const U& y) const { 
     return x.id >= y.id;
  }
  friend ostream& operator<<(ostream& o, const U& x) {
    o << x.id;
    return o;
  }
};

int main()
{
  vector<U> vector1(1000);
  for (int i = 0; i != 1000; ++i)
    vector1[i].id = 1000 - i - 1;
  sort(vector1.begin(), vector1.end(), not2(U()));
  for (int k = 0; k != 1000; ++k)
    assert (vector1[k].id == k);
  cout << " --- Ok." << endl;
  return 0;
}